Methods for Measuring the Acute

Toxicity of Effluents and Receiving

Waters to Freshwater and Marine

Organisms 

Fifth Edition

October 2002
U.S. Environmental Protection Agency

Office of Water (4303T)

1200 Pennsylvania Avenue, NW

Washington, DC 20460

EPA-821-R-02-012
ii

DISCLAIMER

The Engineering and Analysis Division, of the Office of Science and Technology, has reviewed and

approved this report for publication. Neither the United States Government nor any of its employees, contractors,

or their employees make any warranty, expressed or implied, or assumes any legal liability or responsibility for any

third party’s use of or the results of such use of any information, apparatus, product, or process discussed in this

report, or represents that its use by such party would not infringe on privately owned rights.
CONTENTS

Page

iii

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

1. Introduction ......................................................................... 1

2. Types of Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3. Health and Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

General Precautions ............................................................... 5

Safety Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

General Laboratory and Field Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Disease Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Safety Manuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Waste Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4. Quality Assurance .................................................................... 7

Introduction ..................................................................... 7

Facilities, Equipment, and Test Chambers .............................................. 7

 Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Laboratory Water Used for Culturing and Test Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Effluent Sampling and Sample Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Test Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Quality of Test Organisms .......................................................... 8

 Food Quality ..................................................................... 8

Acceptability of Acute Toxicity Test Results ........................................... 9

Analytical Methods ............................................................... 9

Calibration and Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Replication and Test Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Variability in Toxicity Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Demonstrating Acceptable Laboratory Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Documenting Ongoing Laboratory Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Reference Toxicants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Record Keeping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5. Facilities and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Cleaning Test Chambers and Laboratory Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Apparatus and Equipment for Culturing and Toxicity Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Reagents and Consumable Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

6. Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Test Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Sources of Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Life Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Laboratory Culturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Holding and Handling Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Transportation to the Test Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Test Organism Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

7. Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Types of Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Standard, Synthetic Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
CONTENTS (CONTINUED)

iv

Use of Receiving Water as Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Use of Tap Water as Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Dilution Water Holding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

8. Effluent and Receiving Water Sampling and Sample Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Effluent Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Effluent Sample Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Effluent Sampling Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Receiving Water Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Effluent and Receiving Water Sample Handling, Preservation, and Shipping . . . . . . . . . . . . . . . . . 39

Sample Receiving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Persistence of Effluent Toxicity During Sample Shipment and Holding . . . . . . . . . . . . . . . . . . . . . 40

9. Acute Toxicity Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Preparation of Effluent and Receiving Water Samples for Toxicity Tests . . . . . . . . . . . . . . . . . . . . 41

Preliminary Toxicity Range-finding Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Multi-Concentration (Definitive) Effluent Toxicity Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Receiving Water Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Static Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Flow-Through Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Number of Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Replicate Test Chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Loading of Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Illumination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Test Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Dissolved Oxygen Concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Test Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Acceptability of Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Summary of Test Conditions for the Principal Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

10. Test Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Biological Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Chemical and Physical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

11. Acute Toxicity Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Determination of the LC50 from Definitive, Multi-Effluent-Concentration

 Acute Toxicity Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

The Graphical Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

The Spearman-Karber Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

The Trimmed Spearman-Karber Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

The Probit Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Determination of No-Observed-Adverse-Effect Concentration (NOAEC)

 from Multi-Concentration Tests, and Determination of Pass or Fail (Pass/Fail)

 for Single-Concentration (Paired) Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

General Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Single Concentration Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Multi-Concentration Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

12. Report Preparation and Test Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Report Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Plant Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
CONTENTS (CONTINUED)

v

Source of Effluent, Receiving Water, and Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Test Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Conclusions and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Test Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Sampling and Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Test Acceptability Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Test Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Statistical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Concentration-Response Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Reference Toxicant Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Test Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Cited References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

A. Distribution, Life Cycle, Taxonomy, and Culture Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

A.1. Ceriodaphnia dubia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

A.2. Daphnia (D. magna and D. pulex) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

A.3. Mysids (Mysidopsis bahia and Holmesimysis costata) ............................... 159

A.4. Brine Shrimp (Artemia salina) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

A.5. Fathead Minnow (Pimephales promelas) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

A.6. Rainbow Trout, Oncorhynchus mykiss and Brook Trout, Salvelinus fontinalis . . . . . . . . . . . . 201

A.7. Sheepshead minnow (Cyprinodon variegatus) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

A.8. Silversides: Inland Silverside (Mendia beryllina), 

Atlantic Silverside (M. menidia), and Tidewater 

Silverside (M. peninsulae) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

B. Supplemental List of Acute Toxicity Test Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

C. Dilutor Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

D. Plans for Mobile Toxicity Test Laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

D.1. Tandem-Axle Trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

D.2. Fifth Wheel Trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

E. Check Lists and Information Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

E.1. Toxicity Test Field Equipment List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

E.2. Information Check List for On-Site Industrial or Municipal Toxicity Test . . . . . . . . . . . . . . . 259

E.3. Daily Events Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

E.4. Dilutor Calibration Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

E.5. Daily Dilutor Calibration Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
FIGURES

Number Page

vi

 1. Control (cusum) charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

 2. Approximate times required to replace water in test chambers in flow-through tests . . . . . . . . . . . . . . . 47

 3. Rawson's nomograph for obtaining oxygen saturation values in freshwater at

different temperatures at sea level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

 4. Example of data sheet for effluent toxicity tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

 5. Check list on back of effluent toxicity data sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

 6. Flowchart for determination of the LC50 for multi-effluent-concentration acute

toxicity tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

 7. Plotted data and fitted line for graphical method, using all-or-nothing data . . . . . . . . . . . . . . . . . . . . . . . 75

 8. Example of input for computer program for Trimmed Spearman-Karber Method . . . . . . . . . . . . . . . . . . 80

 9. Example of output from computer program for Trimmed Spearman-Karber Method . . . . . . . . . . . . . . . 82

10. Example of input for computer program for Probit Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

11. Example of output for computer program for Probit Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

12. Flowchart for analysis of single-effluent-concentration test data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

13. Flowchart for analysis of multi-effluent-concentration test data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

14. Plot of mean survival proportion data in Table 29 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
TABLES

Number Page

vii

 1. Intra-laboratory precision of LC50s from static acute toxicity tests with

aquatic organisms using reference toxicants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

 2. Intra- and inter-laboratory precision of acute toxicity tests with

Daphnia magna, using a standard effluent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

 3. Inter-laboratory precision of acute toxicity tests with aquatic organisms,

using reference toxicants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 4. Interlaboratory study of acute toxicity test precision, 1990: Summary of

responses using KCL as the reference toxicant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

 5. National inter-laboratory study of acute toxicity test precision, 1991:

Summary of responses using reference toxicants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

 6. National interlaboratory study of acute toxicity test precision, 2000: Precision of 

LC50 point estimates for reference toxicant, effluent, and receiving water sample types . . . . . . . . . . . . 16

 7. Preparation of synthetic freshwater using reagent grade chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

 8. Preparation of synthetic freshwater using mineral water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

 9. Preparation of synthetic seawater using reagent grade chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

10. Percent unionized NH3 in aqueous ammonia solutions: Temperatures between

15-26EC and pH's 6.0-8.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

11. Oxygen solubility (mg/L) in water at equilibrium with air at 760 mm Hg . . . . . . . . . . . . . . . . . . . . . . . . 48

12. Summary of test conditions and test acceptability criteria for Ceriodaphnia dubia

acute toxicity tests with effluents and receiving waters (Test Method 2002.0) . . . . . . . . . . . . . . . . . . . . 51

13. Summary of test conditions and test acceptability criteria for Daphnia pulex and

D. magna acute toxicity tests with effluents and receiving waters (Test Method 2021.0) . . . . . . . . . . . . 53

14. Summary of test conditions and test acceptability criteria for fathead minnow,

Pimephales promelas, acute toxicity tests with effluents and receiving waters (Test Method 2000.0) . . 55

15. Summary of test conditions and test acceptability criteria for rainbow trout,

Oncorhynchus mykiss, and brook trout, Salvelinus fontinalis, acute toxicity tests

with effluents and receiving waters (Test Method 2019.0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

16. Summary of test conditions and test acceptability criteria for mysid, Mysidopsis

bahia, acute toxicity tests with effluents and receiving waters (Test Method 2007.0) . . . . . . . . . . . . . . . 59

17. Summary of test conditions and test acceptability criteria for sheepshead minnow,

Cyprinodon variegatus, acute toxicity tests with effluents and receiving waters (Test Method 2004.0) . 61
TABLES (CONTINUED)

Number Page

viii

18. Summary of test conditions and test acceptability criteria for silverside, Menidia

beryllina, M. menidia, and M. peninsulae, acute toxicity tests with effluents and

receiving waters (Test Method 2006.0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

19. Summary of test conditions and test acceptability criteria for west coast mysid, 

Holmesimysis costata, acute toxicity tests with effluents and receiving waters . . . . . . . . . . . . . . . . . . . . 65

20. Mortality data (number of dead organisms) from acute toxicity tests used in

examples of LC50 determinations (20 organisms in the control and all test

concentrations) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

21. Coefficients for the Shapiro Wilk's test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

22. Quantiles of the Shapiro Wilk's test statistic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

23. Critical values for Wilcoxon's rank sum test five percent significance level . . . . . . . . . . . . . . . . . . . . . . 95

24. Data from an acute single-concentration toxicity test with Ceriodaphnia . . . . . . . . . . . . . . . . . . . . . . . . 95

25. Example of Shapiro Wilk's test: Centered observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

26. Example of Shapiro Wilk's test: Ordered observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

27. Example of Shapiro Wilk's test: Table of coefficients and differences . . . . . . . . . . . . . . . . . . . . . . . . . . 97

28. Example of Wilcoxon's rank sum test: Assigning ranks to the control and 100%

effluent concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

29. Fathead minnow survival data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

30. Centered observations for Shapiro Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

31. Ordered centered observations for the Shapiro Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

32. Coefficients and differences for the Shapiro Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

33. ANOVA table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

34. ANOVA table for Dunnett's Procedure example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

35. Calculated t values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

36. Dunnett's "t" values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
1

SECTION 1

INTRODUCTION

1.1 This manual describes acute toxicity tests for use in the National Pollutant Discharge Elimination System

(NPDES) Permits Program to identify effluents and receiving waters containing toxic materials in acutely toxic

concentrations. With the exception of the Holmesimysis costata Acute Test (Table 19), the methods included in this

manual are referenced in Table IA, 40 CFR Part 136 regulations and, therefore, constitute approved methods for

acute toxicity tests. They are also suitable for determining the toxicity of specific compounds contained in

discharges. The tests may be conducted in a central laboratory or on-site, by the regulatory agency or the permittee. 

The Holmesimysis costata Acute Test (Table 19) is specific to Pacific Coast waters and is not listed at 40 CFR Part

136 for nationwide use. This method has been proposed but not yet approved at 40 CFR Part 136.

1.2 The data are used for NPDES permits development and to determine compliance with permit toxicity limits. 

Data can also be used to predict potential acute and chronic toxicity in the receiving water, based on the LC50 and

appropriate dilution, application, and persistence factors. The tests are performed as a part of self-monitoring

permit requirements, compliance biomonitoring inspections, toxics sampling inspections, and special investigations. 

Data from acute toxicity tests performed as part of permit requirements are evaluated during compliance evaluation

inspections and performance audit inspections. 

1.3 Modifications of these tests are also used in toxicity reduction evaluations and toxicity identification

evaluations to identify the toxic components of an effluent, to aid in the development and implementation of toxicity

reduction plans, and to compare and control the effectiveness of various treatment technologies for a given type of

industry, irrespective of the receiving water (USEPA, 1988a; USEPA, 1988b; USEPA, 1989a; USEPA, 1989b;

USEPA, 1991a).

1.4 This methods manual serves as a companion to the short-term chronic toxicity test methods manuals for

freshwater and marine organisms (USEPA, 2002a; USEPA, 2002b), the NPDES compliance inspection manual

(USEPA, 1988c), and the manual for evaluation of laboratories performing aquatic toxicity tests (USEPA, 1991b).

In 2002, EPA revised previous editions of each of the three methods manuals (USEPA, 1993a; USEPA, 1994a;

USEPA, 1994b).

1.5 Guidance for the implementation of toxicity tests in the NPDES program is provided in the Technical Support

Document for Water Quality-based Toxics Control (USEPA, 1991c).

1.6 The use of any test species or test conditions other than those described in Tables 12-18 in this manual and

referenced in Table 1A, 40 CFR 136.3, shall be considered a major modification to the method and subject to

application and approval of alternate test procedures under 40 CFR 136.4 and 40 CFR 136.5. 

1.7 These methods are restricted to use by, or under the supervision of, analysts experience in the use or conduct

of, and interpretation of data from, aquatic toxicity tests. Each analyst must demonstrate the ability to generate

acceptable test results with the methods using the procedures described in this methods manual.

1.8 This manual was prepared in the established EMSL-Cincinnati format (USEPA, 1983a).
2

SECTION 2

TYPES OF TESTS

2.1 The selection of the test type will depend on the NPDES permit requirements, the objectives of the test, the

available resources, the requirements of the test organisms, and effluent characteristics such as fluctuations in

effluent toxicity.

2.2 Effluent acute toxicity is generally measured using a multi-concentration, or definitive test, consisting of a

control and a minimum of five effluent concentrations. The tests are designed to provide dose-response

information, expressed as the percent effluent concentration that is lethal to 50% of the test organisms (LC50)

within the prescribed period of time (24-96 h), or the highest effluent concentration in which survival is not

statistically significantly different from the control.

2.3 Use of pass/fail tests consisting of a single effluent concentration (e.g., the receiving water concentration or

RWC) and a control is not recommended. If the NPDES permit has a whole effluent toxicity limit for acute toxicity

at the RWC, it is prudent to use that permit limit as the midpoint of a series of five effluent concentrations. This

will ensure that there is sufficient information on the dose-response relationship. For example, the effluent

concentrations utilized in a test may be: (1) 100% effluent, (2) (RWC + 100)/2, (3) RWC, (4) RWC/2, and (5)

RWC/4. More specifically, if the RWC = 50%, appropriate effluent concentrations may be 100%, 75%, 50%, 25%,

and 12.5%. 

2.4 Receiving (ambient) water toxicity tests commonly employ two treatments, a control and the undiluted

receiving water, but may also consist of a series of receiving water dilutions.

2.5 A negative result from an acute toxicity test does not preclude the presence of chronic toxicity. Also, because

of the potential temporal variability in the toxicity of effluents, a negative test result with a particular sample does

not preclude the possibility that samples collected at some other time might exhibit acute (or chronic) toxicity. 

2.6 The frequency with which acute toxicity tests are conducted under a given NPDES permit is determined by the

regulatory agency on the basis of factors such as the variability and degree of toxicity of the waste, production

schedules, and process changes. 

2.7 Tests may be static (static non-renewal or static renewal), or flow-through. 

2.7.1 STATIC TESTS

2.7.1.1 Static non-renewal tests - The test organisms are exposed to the same test solution for the duration of the

test. 

2.7.1.2 Static-renewal tests - The test organisms are exposed to a fresh solution of the same concentration of

sample every 24 h or other prescribed interval, either by transferring the test organisms from one test chamber to

another, or by replacing all or a portion of solution in the test chambers.

2.7.2 FLOW-THROUGH TESTS 

2.7.2.1 Two types of flow-through tests are in common use: (1) sample is pumped continuously from the sampling

point directly to the dilutor system; and (2) grab or composite samples are collected periodically, placed in a tank

adjacent to the test laboratory, and pumped continuously from the tank to the dilutor system. The flow-through

method employing continuous sampling is the preferred method for on-site tests. Because of the large volume (often

400 L/day) of effluent normally required for flow-through tests, it is generally considered too costly and impractical

to conduct these tests off-site at a central laboratory. 
3

2.8 Advantages and disadvantages of the types of tests are as follows: 

2.8.1 STATIC NON-RENEWAL TESTS

2.8.1.1 Advantages:

1. Simple and inexpensive.

2. Very cost effective in determining compliance with permit conditions. 

3. Limited resources (space, manpower, equipment) required; would permit staff to perform many

more tests in the same amount of time.

4. Smaller volume of effluent required than for static renewal or flow-through tests.

2.8.1.2 Disadvantages:

1. Dissolved oxygen (DO) depletion may result from high chemical oxygen demand (COD),

biological oxygen demand (BOD), or metabolic wastes. 

2. Possible loss of toxicants through volatilization and/or adsorption to the exposure vessels. 

3. Generally less sensitive than static renewal or flow-through tests, because the toxic substances

may degrade or be adsorbed, thereby reducing the apparent toxicity. Also, there is less chance of

detecting slugs of toxic wastes, or other temporal variations in waste properties. 

2.8.2 STATIC-RENEWAL, ACUTE TOXICITY TESTS

2.8.2.1 Advantages:

1. Reduced possibility of dissolved oxygen (DO) depletion from high chemical oxygen demand

(COD) and/or biological oxygen demand (BOD), or ill effects from metabolic wastes from

organisms in the test solutions.

2. Reduced possibility of loss of toxicants through volatilization and/or adsorption to the exposure

vessels. 

3. Test organisms that rapidly deplete energy reserves are fed when the test solutions are renewed,

and are maintained in a healthier state.

2.8.2.2 Disadvantages:

1. Require greater volume of effluent that non-renewal tests.

2. Generally less sensitive than flow-through tests, because the toxic substances may degrade or be

adsorbed, thereby reducing the apparent toxicity. Also, there is less chance of detecting slugs of

toxic wastes, or other temporal variations in waste properties. 

2.8.3 FLOW-THROUGH TESTS

2.8.3.1 Advantages:

1. Provide a more representative evaluation of the acute toxicity of the source, especially if sample is

pumped continuously directly from the source and its toxicity varies with time. 

 2. DO concentrations are more easily maintained in the test chambers. 

 3. A higher loading factor (biomass) may be used. 

 4. The possibility of loss of toxicant due to volatilization, adsorption, degradation, and uptake is

reduced. 
4

2.8.3.2 Disadvantages:

1. Large volumes of sample and dilution water are required. 

2. Test equipment is more complex and expensive, and requires more maintenance and attention. 

3. More space is required to conduct tests. 

4. Because of the resources required, it would be very difficult to perform multiple or overlapping

sequential tests. 
5

SECTION 3

HEALTH AND SAFETY

3.1 GENERAL PRECAUTIONS

3.1.1 Development and maintenance of an effective health and safety program in the laboratory requires an

ongoing commitment by laboratory management, and includes (1) the appointment of a laboratory health and safety

officer with the responsibility and authority to develop and maintain a safety program, (2) the preparation of a

formal, written, health and safety plan, which is provided to each laboratory staff member, (3) an ongoing training

program on laboratory safety, and (4) regularly scheduled, documented, safety inspections.

3.1.2 Collection and use of effluents in toxicity tests may involve significant risks to personal safety and health. 

Personnel collecting effluent samples and conducting toxicity tests should take all safety precautions necessary for

the prevention of bodily injury and illness which might result from ingestion or invasion of infectious agents,

inhalation or absorption of corrosive or toxic substances through skin contact, and asphyxiation due to lack of

oxygen or presence of noxious gases. 

3.1.3 Prior to sample collection and laboratory work, personnel must determine that all required safety equipment

and materials have been obtained and are in good condition. 

3.1.4 Guidelines for the handling and disposal of hazardous materials must be strictly followed. 

3.2 SAFETY EQUIPMENT

3.2.1 PERSONAL SAFETY GEAR 

3.2.1.1 Personnel must use safety equipment, as required, such as rubber aprons, laboratory coats, respirators,

gloves, safety glasses, hard hats, and safety shoes. 

3.2.2 LABORATORY SAFETY EQUIPMENT 

3.2.2.1 Each laboratory (including mobile laboratories) must be provided with safety equipment such as first aid

kits, fire extinguishers, fire blankets, emergency showers, and eye fountains. 

3.2.2.2 Mobile laboratories should be equipped with a telephone to enable personnel to summon help in case of

emergency.

3.3 GENERAL LABORATORY AND FIELD OPERATIONS

3.3.1 Guidance in Material Safety Data Sheets should be followed for reagents and other chemicals purchased

from supply houses. Incompatible materials should not be stored together.

3.3.2 Work with effluents must be performed in compliance with accepted rules pertaining to the handling of

hazardous materials (see Safety Manuals, Subsection 3.5). Personnel collecting samples and performing toxicity

tests should not work alone.

3.3.3 Because the chemical composition of effluents is usually only poorly known, they must be considered as

potential health hazards, and exposure to them should be minimized. Fume and canopy hoods over the test areas

must be used whenever necessary. 

3.3.4 It is advisable to cleanse exposed parts of the body immediately after collecting effluent samples. 
6

3.3.5 All containers must be adequately labeled to indicate their contents. 

3.3.6 Strong acids and volatile organic solvents employed in glassware cleaning must be used in a fume hood or

under an exhaust canopy over the work area.

3.3.7 Good housekeeping contributes to safety and reliable results. 

3.3.8 Electrical equipment or extension cords not bearing the approval of Underwriter Laboratories must not be

used. Ground-fault interrupters must be installed in all "wet" laboratories where electrical equipment is used. 

3.3.9 Mobile laboratories must be properly grounded to protect against electrical shock.

3.4 DISEASE PREVENTION

3.4.1 Personnel handling samples which are known or suspected to contain human wastes should be immunized

against hepatitis B, tetanus, typhoid fever, and polio. 

3.5 SAFETY MANUALS 

3.5.1 For further guidance on safe practices when collecting effluent samples and conducting toxicity tests, check

with the permittee and consult general industrial safety manuals, including USEPA (1986) and Walters and Jameson

(1984). 

3.6 WASTE DISPOSAL

3.6.1 Wastes generated during toxicity testing must be properly handled and disposed of in an appropriate manner. 

Each testing facility will have its own waste disposal requirements based on local, state, and Federal rules and

regulations. It is extremely important that these rules and regulations be known, understood, and complied with by

all persons responsible for, or otherwise involved in, performing testing activities. Local fire officials should be

notified of any potentially hazardous conditions.
7

SECTION 4

QUALITY ASSURANCE

4.1 INTRODUCTION

4.1.1 Development and maintenance of a toxicity test laboratory quality assurance (QA) program requires an

ongoing commitment by laboratory management, and includes the following: (1) appointment of a laboratory

quality assurance officer with the responsibility and authority to develop and maintain a QA program;

(2) preparation of a quality assurance plan with data quality objectives; (3) preparation of written descriptions of

laboratory standard operating procedures (SOP's) for test organism culturing, toxicity testing, instrument calibration,

sample chain-of-custody, laboratory sample tracking system, etc.; and (4) provision of adequate, qualified technical

staff and suitable space and equipment to assure reliable data.

4.1.2 QA practices within an aquatic toxicology laboratory must address all activities that affect the quality of the

final effluent toxicity data, such as: (1) effluent sampling and handling; (2) the source and condition of the test

organisms; (3) condition and operation of equipment; (4) test conditions; (5) instrument calibration; (6) replication;

(7) use of reference toxicants; (8) record keeping; and (9) data evaluation.

4.1.3 Quality control practices, on the other hand, consist of the more focused, routine, day-to-day activities carried

out within the scope of the overall QA program. For more detailed discussion of quality assurance, and general

guidance on good laboratory practices related to toxicity testing, see: FDA, 1978; USEPA, 1975; USEPA, 1979a;

USEPA, 1980a; USEPA, 1980b; USEPA, 1991b; DeWoskin, 1984; and Taylor, 1987.

4.1.4 Guidance for the evaluation of laboratories performing toxicity tests and laboratory evaluation criteria may

be found in USEPA 1991b.

4.2 FACILITIES, EQUIPMENT, AND TEST CHAMBERS

4.2.1 Separate test organism culturing and toxicity testing areas should be provided to avoid possible loss of

cultures due to cross-contamination. Ventilation systems should be designed and operated to prevent recirculation

or leakage of air from chemical analysis laboratories or sample storage and preparation areas into organism

culturing or toxicity testing areas, and from toxicity test laboratories and sample preparation areas into culture

rooms.

4.2.2 Laboratory and toxicity test temperature control equipment must be adequate to maintain recommended test

water temperatures. Recommended materials must be used in the fabrication of the test equipment which comes in

contact with the effluent (see Section 5, Facilities and Equipment).

4.3 TEST ORGANISMS

4.3.1 The test organisms used in the procedures described in this manual are listed in Section 6, Test Organisms. 

The organisms should appear healthy, behave normally, feed well, and have low mortality in cultures, during

holding, and in test controls. Test organisms should be positively identified to species.

4.4 LABORATORY WATER USED FOR CULTURING AND TEST DILUTION WATER

4.4.1 The quality of water used for test organism culturing and for dilution water used in toxicity tests is extremely

important. Water for these two uses should come from the same source. The dilution water used in effluent toxicity

tests will depend in part on the objectives of the study and logistical constraints, as discussed in detail in Section 7,

Dilution Water. The dilution water used for internal quality assurance tests with organisms, food, and reference

toxicants should be the water routinely used with success in the laboratory. Types of water are discussed in Section
8

5, Facilities and Equipment. Water used for culturing and test dilution should be analyzed for toxic metals and

organics at least annually or whenever difficulty is encountered in meeting minimum acceptability criteria for

control survival and reproduction or growth. The concentration of the metals, Al, As, Cr, Co, Cu, Fe, Pb, Ni, and

Zn, expressed as total metal, should not exceed 1 μg/L each, and Cd, Hg, and Ag, expressed as total metal, should

not exceed 100 ng/L each. Total organochlorine pesticides plus PCBs should be less than 50 ng/L (APHA, 1992). 

Pesticide concentrations should not exceed USEPA's Ambient Water Quality chronic criteria values where

available. 

4.5 EFFLUENT SAMPLING AND SAMPLE HANDLING

4.5.1 Sample holding times and temperatures must conform to conditions described in Section 8, Effluent and

Receiving Water Sampling and Sample Handling. 

4.6 TEST CONDITIONS

4.6.1 The temperature of test solutions must be measured by placing the thermometer or probe directly into the test

solutions, or by placing the thermometer in equivalent volumes of water in surrogate vessels positioned at

appropriate locations among the test vessels. Temperature should be recorded continuously in at least one vessel

during the duration of each test. Test solution temperatures should be maintained within the limits specified for

each test. DO concentration and pH in test chambers should be checked daily throughout the test period, as

prescribed in Section 9, Acute Toxicity Test Procedures. 

4.7 QUALITY OF TEST ORGANISMS

4.7.1 The health of test organisms is primarily assessed by the performance (survival, growth, and/or reproduction)

of organisms in control treatments of individual tests. The health and sensitivity of test organisms is also assessed

by reference toxicant testing. In addition to documenting the sensitivity and health of test organisms, reference

toxicant testing is used to initially demonstrate acceptable laboratory performance (Subsection 4.14) and to

document ongoing laboratory performance (Subsection 4.15). 

4.7.2 Regardless of the source of test organisms (in-house cultures or purchased from external suppliers), the

testing laboratory must perform at least one acceptable reference toxicant test per month for each toxicity test

method conducted in that month (Subsection 4.15). If a test method is conducted only monthly, or less frequently, a

reference toxicant test must be performed concurrently with each effluent toxicity test.

4.7.3 When acute or short-term chronic toxicity tests are performed with effluents or receiving waters using test

organisms obtained from outside the test laboratory, concurrent toxicity tests of the same type must be preformed

with a reference toxicant, unless the test organism supplier provides control chart data from at least the last five

monthly acute toxicity tests using the same reference toxicant and test conditions.

4.7.4 The supplier should also certify the species identification of the test organisms, and provide the taxonomic

reference (citation and page) or name(s) of the taxonomic expert(s) consulted. 

4.7.5 If a routine reference toxicant test fails to meet test acceptability criteria, then the reference toxicant test must

be immediately repeated.

4.8 FOOD QUALITY

4.8.1 The nutritional quality of the food used in culturing and testing fish and invertebrates is an important factor

in the quality of the toxicity test data. This is especially true for the unsaturated fatty acid content of brine shrimp

nauplii, Artemia. Suitable trout chow, Artemia, and other foods must be obtained as described in this manual.
9

4.8.2 Problems with the nutritional suitability of the food will be reflected in the survival, growth, and

reproduction of the test organisms in cultures and toxicity tests. If a batch of food is suspected to be defective, the

performance of organisms fed with the new food can be compared with the performance of organisms fed with a

food of known quality in side-by-side tests. If the food is used for culturing, its suitability should be determined

using a short-term chronic test which will determine the effect of food quality on growth or reproduction of each of

the relevant test species in culture, using four replicates with each food source. Where applicable, foods used only

in acute toxicity tests can be compared with a food of known quality in side-by-side, multi-concentration acute tests,

using the reference toxicant regularly employed in the laboratory QA program.

4.8.3 New batches of food used in culturing and testing should be analyzed for toxic organics and metals or

whenever difficulty is encountered in meeting minimum test acceptability criteria for control survival and

reproduction or growth. If the concentration of total organochlorine pesticides exceeds 0.l5 μg/g wet weight, or the

concentration of the total organochlorine pesticides plus PCBs exceeds 0.30 μg/g wet weight, or toxic metals (Al,

As, Cr, Co, Cu, Pb, Ni, Zn, expressed as total metal) exceed 20 μg/g wet weight, the food should not be used (for

analytical methods see AOAC, 1990 and USDA, 1989). For foods (e.g., such as YCT) which are used to culture

and test organisms, the quality of food should meet the requirements for the laboratory water used for culturing and

test dilution water as described in Section 4.4 above.

4.9 ACCEPTABILITY OF ACUTE TOXICITY TEST RESULTS

4.9.1 For the test results to be acceptable, control survival must equal or exceed 90%.

4.9.2 An individual test may be conditionally acceptable if temperature, DO, and other specified conditions fall

outside specifications, depending on the degree of the departure and the objectives of the tests (see test condition

summaries). The acceptability of the test will depend on the experience and professional judgment of the laboratory

analyst and the reviewing staff of the regulatory authority. Any deviation from test specifications must be noted

when reporting data from a test.

4.10 ANALYTICAL METHODS 

4.10.1 Routine chemical and physical analyses for culture and dilution water, food, and test solutions, must include

established quality assurance practices outlined in Agency methods manuals (USEPA, 1979a; USEPA, 1993b).

4.10.2 Reagent containers should be dated when received from the supplier, and the shelf life should not be

exceeded. Also, working solutions should be dated when prepared, and the recommended shelf life should be

observed.

4.11 CALIBRATION AND STANDARDIZATION

4.11.1 Instruments used for routine measurements of chemical and physical parameters such as pH, DO,

temperature, conductivity, salinity, alkalinity, and hardness must be calibrated and standardized prior to use each

day according to the instrument manufacturer's procedures as indicated in the general section on quality assurance

(see EPA Methods 150.1, 360.1, 170.1, and 120.1; USEPA, 1979b). Calibration data are recorded in a permanent

log.

4.11.2 Wet chemical methods used to measure hardness, alkalinity, and total residual chlorine must be

standardized prior to use each day according to the procedures for those specific EPA methods (see EPA Methods

130.2 and 310.1; USEPA 1979b). 
10

4.12 REPLICATION AND TEST SENSITIVITY

4.12.1 The sensitivity of toxicity tests will depend in part on the number of replicates per concentration, the

significance level selected, and the type of statistical analysis. If the variability remains constant, the sensitivity of

the test will increase as the number of replicates is increased. The minimum recommended number of replicates

varies with the objectives of the test and the statistical method used for analysis of the data.

4.13 VARIABILITY IN TOXICITY TEST RESULTS 

4.13.1 Factors which can affect test success and precision include: the experience and skill of the laboratory

analyst; test organism age, condition, and sensitivity; dilution water quality; temperature control; and the quality and

quantity of food provided. The results will depend upon the species used and the strain or source of the test

organisms, and test conditions such as temperature, DO, food, and water quality. The repeatability or precision of

toxicity tests is also a function of the number of test organisms used at each toxicant concentration. Jensen (1972)

discussed the relationship between sample size (numbers of fish) and the standard error of the test, and considered

20 fish per concentration as optimum for Probit Analysis. 

4.13.2 Test precision can be estimated by using the same strain of organisms under the same test conditions, and

employing a known toxicant, such as a reference toxicant. The single-laboratory (intra-laboratory) and

multi-laboratory (inter-laboratory) precision of acute toxicity tests with several common test species and reference

toxicants are listed in Tables 1-4. Intra- and inter-laboratory precision are described by the mean, standard

deviation, and relative standard deviation (percent coefficient of variation, or CV) of the calculated endpoints from

the replicated tests. 

4.13.3 Intra-laboratory precision data from 268 acute toxicity tests with four species and five reference toxicants

are listed in Tables 1 and 2. The precision, expressed as CV%, ranged from 3% to 86%. More recent CV values

reported by Jop et al. (1986), Dorn and Rogers (1989), Hall et al. (1989), and Cowgill et al. (1990), fell in a

somewhat lower range (8% to 41%).

4.13.4 Inter-laboratory precision of acute toxicity tests from 253 reference toxicant tests with seven species, listed

in Tables 2, 3, 4, and 5 (expressed as CV% for LC50s), ranged from 11% to 167%. Table 6 shows interlaboratory

precision data from a study of acute toxicity test methods using reference toxicant, effluent, and receiving water

sample types (USEPA, 2001a; USEPA, 2001b). Averaged across sample types, total interlaboratory precision

(expressed as CV% for LC50s) ranged from 13% to 38.5% for the acute methods. 

4.13.5 No clear pattern of differences were noted in the intra- or inter-laboratory test precision with the species

listed, although the test results with some toxicants, such as cadmium, appear to more variable than those with other

reference toxicants. 

4.13.6 Additional information on toxicity test precision is provided in the Technical Support Document for Water

Quality-Based Toxics Control (see pp. 2-4, and 11-15; USEPA, 1991c).
11

TABLE 1. INTRA-LABORATORY PRECISION OF LC50S FROM STATIC ACUTE TOXICITY TESTS

WITH AQUATIC ORGANISMS USING REFERENCE TOXICANTS1

 REFERENCE TOXICANT 2 

 SDS NAPCP CD 

TEST ORGANISM N LC50 CV (%) N LC50 CV (%) N LC50 CV (%)

Pimephales promelas (96 h, 21EC)3 9 8.6 20 12 0.14 40 9 0.15 120

Daphnia magna (24 h, 20EC)4 8 20.9 28 10 0.69 14 11 0.121 49

Daphnia magna (24 h, 26EC)4 10 12.9 48 9 0.67 25 9 0.026 77

Daphnia magna (48 h, 20EC)4 10 13.5 29 10 0.42 21 9 0.038 58

Daphnia magna (48 h, 26EC)4 9 10.8 33 9 0.48 23 8 0.009 35

Daphnia pulex (24 h, 20EC)4 9 18.4 23 9 0.64 15 5 0.147 30

Daphnia pulex (24 h, 26EC)4 10 13.9 25 9 0.62 25 10 0.063 45

Daphnia pulex (48 h, 20EC)4 10 12.6 32 9 0.48 16 10 0.042 45

Daphnia pulex (48 h, 26EC)4 9 10.2 36 8 0.47 32 6 0.006 14

Mysidopsis bahia (96 h, 25EC)5 13 0.346 9

1

 Precision expressed as percent coefficient of variation, where CV% = (standard deviation X 100)/mean. 2

 SDS = Sodium dodecyl (lauryl) sulfate; NAPCP = Sodium pentachlorophenate; CD = Cadmium; N = Number

 of tests; toxicant concentration in mg/L. 

3

 Pimephales promelas tests were performed in soft, synthetic freshwater; total hardness, 40-48 mg/L as CaCO3,

 by J. Dryer, Aquatic Biology Section, EMSL-Cincinnati.

4

 Daphnia data from Lewis and Horning, 1991. Tests with D. magna used hard reconstituted water (total

 hardness, 180-200 mg/L as CaCO3); tests with D. pulex used moderately-hard reconstituted water (total

 hardness, 80-100 mg/L as CaCO3). 5

 Mysid tests were performed in 25 ppt salinity, natural seawater. Data were provided by Steve Ward,

 Environmental Services Division, U.S. Environmental Protection Agency, Edison, New Jersey. Personal

 communication, November 14, 1990.
12

TABLE 2. INTRA- AND INTER-LABORATORY PRECISION OF ACUTE TOXICITY TESTS WITH

DAPHNIA MAGNA, USING A STANDARD EFFLUENT1,2

LABORATORY

 INTER-LABORATORY PRECISION:

 LC50s FROM REPLICATE TESTS 

INTRA-LABORATORY

PRECISION3

 24 H 48 H

INDUSTRY

1 14.4 4.2

11.4 4.9 ---

2 13.9 6.8

16.6 6.1

13.7 6.1 6.4

3 11.7 3.5

17.4 7.1 ---

GOVERNMENT

1 14.0 4.4

10.0 4.4

10.8 4.1 4.0

2 13.2 4.5

14.1 4.5 ---

3 11.6 4.2 ---

COMMERCIAL

1 20.1 4.9

20.1 4.7 ---

2 8.9 3.7

12.3 5.6 ---

3 14.8 9.0

25.4 9.1

26.4 8.6 3.0

 N 20 20 3

 MEAN 15.0 5.52 4.47

 SD 4.75 1.75 1.75

 CV% 31.6 31.6 39.1

1

 From Table 2, p. 191, Grothe and Kimerle, 1985. Tests performed at 20EC ±2EC; dilution water hardness, 

 100mg/L as CaCO3; dilution water alkalinity, 76 mg/L as CaCO3; effluent hardness, approx. 1000 mg/L as 

 CaCO3; effluent alkalinity, 310 mg/L as CaCO3; effluent dilutions - 56%, 32%, 18%, 10%, 5.6%, 3.1%, 1.7%. 2

 LC50 expressed in percent effluent. 

3

 Intra-laboratory precision expressed as the weighted mean CV(%).
13

TABLE 3. INTER-LABORATORY PRECISION OF ACUTE TOXICITY TESTS WITH AQUATIC

ORGANISMS, USING REFERENCE TOXICANTS1

REFERENCE TOXICANT

SILVER ENDOSULFAN

TEST ORGANISM N LC50 CV (%) N LC50 CV (%)

1. Pimephales promelas (96 h, 22EC)

96-h static test (Meas) 10 14.0 53 12 2.03 38

96-h flow-through test (Meas) 9 7.49 40 12 0.96 46

2. Oncorhyncus mykiss (96 h, 12EC)

96-h static test (Meas) 10 34.5 88 12 1.15 50

96-h flow-through test (Meas) 9 11.5 33 12 0.40 42

3. Daphnia magna (48 h, 20EC)

48-h static (Meas) 12 10.6 166 11 328 51

4. Mysidopsis bahia (96 h, 22EC) 

96-h static test (Nom) 6 210 27 5 0.84 62

96-h flow-through test (Nom) 6 251 22 6 1.02 58

96-h flow-through test (Meas) 6 192 58 5 0.94 167

5. Cyprinodon variegatus (96 h, 22EC)

96-h static test (Nom) 4 1122 35 6 2.41 37

96-h flow-through test (Nom) 5 1573 50 6 1.69 46

96-h flow-through test (Meas) 5 1216 50 6 0.81 46

1

 Data for Pimephales promelas (fathead minnow), Oncorhyncus mykiss (rainbow trout), and Daphnia magna 

 were taken from USEPA, 1983b. 

 Data for, Mysidopsis bahia, and Cyprinodon variegatus (sheepshead minnow) were taken from USEPA, 1981. 

 Six laboratories participated in each study. Test salinity was 28‰.

 LC50s expressed in μg/L. 

 In the studies with the freshwater organisms, the water hardness for five of the six laboratories ranged between 

 36 and 75 mg/L. However, the water hardness for the sixth laboratory was 255 mg/L, resulting in LC50 values 

 for silver more than an order of magnitude larger than for the other five. These values were rejected in 

 calculating the CV%. The mean weights of test fish were from 0.05-0.26 g for fathead minnows, and 

 0.22-1.32 g for rainbow trout. Daphnia were #24-h old.

 In studies with the marine organisms, only one LC50 (presumably the combined LC50 from duplicate tests) was 

 reported for each toxicity test. LC50s for flow-through tests with Mysidopsis bahia and Cyprinodon variegatus 

 were calculated two different ways -- (1) on the basis of the nominal toxicant concentrations (Nom), and (2) on 

 the basis of measured (Meas) toxicant concentrations. Test organism age was #2 days for Mysidopsis bahia, and 

 28 days for Cyprinodon variegatus. The salinity of test solutions was 28‰. 

 N, the total number of LC50 values used in calculating the CV(%) varied with organism and toxicant because 

 some data were rejected due to water hardness, lack of concentration measurements, and/or because some of the 

 LC50s were not calculable.

2 CV% = Percent coefficient of variation = (standard deviation x 100)/mean. 
14

TABLE 4. INTER-LABORATORY STUDY OF ACUTE TOXICITY TEST PRECISION, 1990: 

SUMMARY OF RESPONSES USING KCL AS THE REFERENCE TOXICANT1

NO. LABS

SUBMITTING

VALID DATA

TEST PRECISION (CV%)2

GRAPH3

 METHOD 

STAT4

 METHOD TOTAL5 

TEST TYPE N LC50 CV% N LC50 CV% N LC50 CV%

Pimephales promelas (96 h, 22EC)6 17 6 944 28.8 13 832 27.8 17 864 29.6

Pimephales promelas (24 h, 25EC)7 6 6 832 11.5 6 832 11.5 – – –

Ceriodaphnia dubia (48 h, 25EC)7 11 11 256 53.1 11 264 48.5 – – –

Mysidopsis bahia (96 h, 22EC)8 14 7 292 32.9 11 250 36.0 14 268 37.3

1

 Interlaboratory study of toxicity test precision conducted in 1990 by the Environmental Monitoring Systems 

 Laboratory - Cincinnati, U.S. Environmental Protection Agency, Cincinnati, Ohio 45268, in cooperation with the 

 states of New Jersey and North Carolina, and the Office of Water Enforcement and Permits, U.S. Environmental 

 Protection Agency, Washington, DC.

2

 Percent coefficient of variation = (standard deviation X 100)/mean. Calculated for LC50 from acute tests. LC50s 

 expressed as mg/L KCl added to the dilution water.

3

 LC50 estimated by the Graphical Method.

4

 LC50 estimated by Probit, Litchfield-Wilcoxon, or Trimmed Spearman-Karber method. 5

 LC50 usually reported for only one method of analysis for each test. Where more than one LC50 was reported 

 for a test, the lowest value was used to calculate the statistics for "Total." 6

 Data from the New Jersey Department of Environmental Protection: static daily-renewal tests, using moderately- 

 hard synthetic freshwater.

7

 Data from North Carolina certified laboratories: static non-renewal tests, using moderately-hard reconstituted 

 freshwater.

8

 Data from the New Jersey Department of Environmental Protection: static daily-renewal tests, using 25 ppt 

 salinity, FORTY FATHOMS® synthetic seawater.
15

TABLE 5. NATIONAL INTERLABORATORY STUDY OF ACUTE TOXICITY TEST PRECISION,

1991: SUMMARY OF RESPONSES USING REFERENCE TOXICANTS1

Test Type

No. Labs

Submitting Data LC50 CV%2

Pimephales promelas (48 h, 25EC)3 203 8964 28.6

Ceriodaphnia dubia (48 h, 25EC)3 171 4324 39.8

Mysidopsis bahia (48 h, 25EC)5 61 5324 30.1

Menidia beryllina (48 h, 25EC)5 39 1646 42.2

1

 From a national study of interlaboratory precision of toxicity test data performed in 1991 by the Environmental 

 Monitoring Systems Laboratory - Cincinnati, U.S. Environmental Protection Agency, Cincinnati, OH 45268. 

 Participants included Federal, state, and private laboratories engaged in NPDES permit compliance monitoring. 

 LC50s were estimated by the graphical or Spearman-Karber method.

2

 Percent coefficient of variation = (standard deviation X 100)/mean. 3

 Static non-renewal tests, using moderately-hard synthetic freshwater (total hardness = 80-100 mg/L as CaCO3). 4

 Expressed as mg KCl added per liter of dilution water.

5

 Static non-renewal tests, using 30 ppt modified GP2 artificial seawater. 6

 Expressed as Fg Cu++ added per liter of dilution water.
16

TABLE 6. NATIONAL INTERLABORATORY STUDY OF ACUTE TOXICITY TEST PRECISION,

2000: PRECISION OF LC50 POINT ESTIMATES FOR REFERENCE TOXICANT,

EFFLUENT, AND RECEIVING WATER SAMPLE TYPES1

.

Method Sample Type

CV (%)2

Within-lab3 Between-lab4 Total5

Pimephales promelas KCl 7.62 19.7 21.1

Municipal effluent 10.3 19.2 21.8

Receiving water - - 17.2

Average 8.96 19.4 20.0

Ceriodaphnia dubia KCl 14.6 15.2 21.1

Municipal effluent 9.68 32.8 34.2

Receiving water - - 31.8

Average 12.1 24.0 29.0

Cyprinodon variegatus KCl - - 26.0

Municipal effluent - - 19.4

Receiving water - - 32.5

Average - - 26.0

Menidia beryllina CuSO4

6 - --

Industrial effluent 9.91 49.7 50.7

Receiving water - - 26.3

Average 9.91 49.7 38.5

Holmesimysis costata7 Zn (48 h test) 19 -

Zn (96 h test) 23 -

Zn (interlaboratory trial 1) - - 24

Zn (interlaboratory trial 2) - - 1

Average 21 13

1 From EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b). 2 CVs were calculated based on the within-laboratory component of variability, the between-laboratory component

of variability, and total interlaboratory variability (including both within-laboratory and between-laboratory

components). For the receiving water sample type, within-laboratory and between-laboratory components of

variability could not be calculated since the study design did not provide within-laboratory replication for this

sample type. The study design also did not provide within-laboratory replication for the Cyprinodon variegatus

Acute Method. 
17

3 The within-laboratory (intralaboratory) component of variability for duplicate samples tested at the same time in

the same laboratory. 4 The between-laboratory component of variability for duplicate samples tested at different laboratories. 5 The total interlaboratory variability, including within-laboratory and between-laboratory components of

variability. The total interlaboratory variability is synonymous with interlaboratory variability reported from other

studies where individual variability components are not separated. 6 Precision estimates were not calculated for the reference toxicant sample type since the majority of results for this

sample type were outside of the test concentration range (ie., >100). 7 Holmesimysis costata Acute Test data were from Martin et al. (1989). Zn was tested in two intralaboratory trials

and in two interlaboratory trials. Data from this study was only reported to two significant figures.
18

4.14 DEMONSTRATING ACCEPTABLE LABORATORY PERFORMANCE

4.14.1 It is a laboratory's responsibility to demonstrate its ability to obtain consistent, precise results with reference

toxicants before it performs toxicity tests with effluents for permit compliance purposes. To meet this requirement,

the intra-laboratory precision, expressed as percent coefficient of variation (CV%), of each type of test to be used in

a laboratory should be determined by performing five or more tests with different batches of test organisms, using

the same reference toxicant, at the same concentrations, with the same test conditions (i.e., the same test duration,

type of dilution water, age of test organisms, feeding, etc.), and same data analysis methods. A reference toxicant

concentration series (0.5 or higher) should be selected that will consistently provide partial mortalities at two or

more concentrations. 

4.15 DOCUMENTING ONGOING LABORATORY PERFORMANCE

4.15.1 Satisfactory laboratory performance is demonstrated by performing at least one acceptable test per month

with a reference toxicant for each toxicity test method conducted in the laboratory during that month. For a given

test method, successive tests must be performed with the same reference toxicant, at the same concentrations, in the

same dilution water, using the same data analysis methods. Precision may vary with the test species, reference

toxicant, and type of test. Each laboratory’s reference toxicity data will reflect conditions unique to that facility,

including dilution water, culturing, and other variables; however, each laboratory’s reference toxicity results should

reflect good repeatability. 

4.15.2 A control chart should be prepared for each combination of reference toxicant, test species, test condition,

and endpoint. Toxicity endpoints from five or six tests are adequate for establishing the control charts. In this

technique, a running plot is maintained for the toxicity values (Xi

) from successive tests with a given reference

toxicant (Figure 1), and endpoints (LC50s) are examined to determine if they are within prescribed limits. The

types of control charts illustrated (see USEPA, 1979a) are used to evaluate the cumulative trend of results from a

series of samples, thus reference toxicant test results should not be used as a de facto criterion for rejection of

individual effluent or receiving water tests. The mean ( ) and upper and lower control limits (±2S) are re-  ̄

X

calculated with each successive test result. After two years of data collection, or a minimum of 20 data points, the

control chart should be maintained using only the 20 most recent data points. 

4.15.3 Laboratories should compare the calculated CV (i.e., standard deviation / mean) of the LC50 for the 20

most recent data points to the distribution of laboratory CVs reported nationally for reference toxicant testing (Table

3-3 in USEPA, 2000b). If the calculated CV exceeds the 75th percentile of CVs reported nationally, the laboratory

should use the 75th and 90th percentiles to calculate warning and control limits, respectively, and the laboratory

should investigate options for reducing variability.

4.15.4 The outliers, which are values falling outside the upper and lower control limits, and trends of increasing or

decreasing sensitivity, are readily identified. At the P0.05 probability level, one in 20 tests would be expected to fall

outside of the control limits by chance alone. If more than one out of 20 reference toxicant tests fall outside the

control limits, the laboratory should investigate sources of variability, take corrective actions to reduce identified

sources of variability, and perform an additional reference toxicant test during the same month. In those instances

when the laboratory can document the cause for the outlier (e.g., operator error, culture health or test system

failure), the outlier should be excluded from the future calculations of the control limits. If two or more

consecutive tests do not fall within the control limits, the results must be explained and the reference toxicant test

must be immediately repeated. Actions taken to correct the problem must be reported. 

4.15.5 If the toxicity value from a given test with the reference toxicant falls well outside the expected range for

the test organisms when using the standard dilution water, the laboratory should investigate sources of variability,

take corrective actions to reduce identified sources of variability, and perform an additional reference toxicant test

during the same month. Performance should improve with experience, and the control limits for point estimates

should gradually narrow. However, control limits of ±2S, by definition, will be exceeded 5% of the time, regardless

of how well a laboratory performs. Highly proficient laboratories which develop a very narrow control limit may be

unfairly penalized if a test which falls just outside the control limits is rejected de facto. For this reason, the width
19

of the control limits should be considered in determining whether or not a reference toxicant test result falls “well”

outside the expected range. The width of the control limits may be evaluated by comparing the calculated CV (i.e.,

standard deviation / mean) of the LC50 for the 20 most recent data points to the distribution of laboratory CVs

reported nationally for reference toxicant testing (Table 3-3 in USEPA, 2000b). In determining whether or not a

reference toxicant test result falls “well” outside the expected range, the result also may be compared with upper

and lower bounds for ±3S, as any result outside these control limits would be expected to occur by chance only 1

out of 100 tests (Environment Canada, 1990). When a result from a reference toxicant test is outside the 99%

confidence intervals, the laboratory must conduct an immediate investigation to assess the possible causes for the

outlier. 

4.15.6 Reference toxicant test results should not be used as a de facto criterion for rejection of individual effluent

or receiving water tests. Reference toxicant testing is used for evaluating the health and sensitivity of organisms

over time and for documenting initial and ongoing laboratory performance. While reference toxicant test results

should not be used as a de facto criterion for test rejection, effluent and receiving water test results should be

reviewed and interpreted in the light of reference toxicant test results. The reviewer should consider the degree to

which the reference toxicant test result fell outside of control chart limits, the width of the limits, the direction of the

deviation (toward increased test organism sensitivity or toward decreased test organism sensitivity), the test

conditions of both the effluent test and the reference toxicant test, and the objective of the test.
20
21

4.16 REFERENCE TOXICANTS

4.16.1 Reference toxicants such as sodium chloride (NaCl), potassium chloride (KCl), cadmium chloride (CdCl2),

copper sulfate (CuSO4), sodium dodecyl sulfate (SDS), and potassium dichromate (K2Cr2O7), are suitable for use in

the NPDES and other Agency programs requiring aquatic toxicity tests. EMSL-Cincinnati hopes to release EPAcertified solutions of cadmium and copper, with accompanying toxicity data for the recommended test species, for

use as reference toxicants through cooperative research and development agreements with commercial suppliers,

and will continue to develop additional reference toxicants for future release. Standard reference materials can be

obtained from commercial supply houses, or can be prepared inhouse using reagent grade chemicals. The

regulatory agency should be consulted before reference toxicant(s) are selected and used. 

4.17 RECORD KEEPING

4.17.1 Proper record keeping is important. A complete file should be maintained for each individual toxicity test

or group of tests on closely related samples. This file should contain a record of the sample chain-of-custody; a

copy of the sample log sheet; the original bench sheets for the test organism responses during the toxicity test(s);

chemical analysis data on the sample(s); detailed records of the test organisms used in the test(s), such as species,

source, age, date of receipt, and other pertinent information relating to their history and health; information on the

calibration of equipment and instruments; test conditions employed; and results of reference toxicant tests. 

Laboratory data should be recorded on a real-time basis to prevent the loss of information or inadvertent

introduction of errors into the record. Original data sheets should be signed and dated by the laboratory personnel

performing the tests.

4.17.2 The regulatory authority should retain records pertaining to discharge permits. Permittees are required to

retain records pertaining to permit applications and compliance for a minimum of 3 years [40 CFR 122.41(j)(2)].
22

SECTION 5 

FACILITIES AND EQUIPMENT

5.1 GENERAL REQUIREMENTS 

5.1.1 Effluent toxicity tests may be performed in a fixed or mobile laboratory. Facilities should include equipment

for rearing and/or holding organisms. 

5.1.2 The facilities must be well ventilated and free of toxic fumes. Sample preparation, culturing, and toxicity

testing areas should be separated to avoid cross contamination of cultures or toxicity test solutions with toxic fumes. 

Laboratory ventilation systems should be checked to ensure that return air from chemistry laboratories and/or

sample handling areas is not circulated to test organism culture rooms or toxicity test rooms, or that air from toxicity

test rooms does not contaminate culture areas. Air pressure differentials between such rooms should not result in a

net flow of potentially contaminated air to sensitive areas through open or loosely-fitting doors. 

5.1.3 Control of test solution temperature can best be achieved using circulating water baths, heat exchangers, or

environmental chambers. Photoperiod can be controlled using automatic timers in the laboratory or environmental

chambers.

5.1.4 Water used for rearing, holding, and testing organisms may be reconstituted synthetic water, ground water,

surface water, or dechlorinated tap water. Dechlorination can be accomplished by carbon filtration, laboratory

water conditioning units, or the use of sodium thiosulfate. After dechlorination, total residual chlorine should be

non-detectable. Sodium thiosulfate may be toxic to the test organisms, and if used for dechlorination, paired

controls with and without sodium thiosulfate should be incorporated in effluent toxicity tests. Use of 3.6 mg

(anhydrous) sodium thiosulfate/L will reduce l.0 mg chlorine/L. After dechlorination, total residual chlorine should

be non-detectable.

5.1.4.1 A good quality, laboratory grade deionized water, providing a resistance of 18 megaohm-cm, must be

available in the laboratory and in sufficient quantity for laboratory needs. Deionized water may be obtained from

MILLIPORE®, Milli-Q®, MILLIPORE QPAKTM

2 or equivalent system. If large quantities of high quality deionized

water are needed, it may be advisable to supply the laboratory grade water deionizer with preconditioned water from

a CULLIGAN®, CONTINENTAL®, or equivalent, mixed-bed water treatment system.

5.1.5 Air used for aeration must be free of oil and fumes. Oil-free air pumps should be used where possible. 

Particulates can be removed from the air using BALSTON® Grade BX or equivalent filters (Balston, Inc.,

Lexington, MA), and oil and other organic vapors can be removed using activated carbon filters (BALSTON®, C-1

filter, or equivalent).

5.1.6 During rearing, holding, and testing, test organisms should be shielded from external disturbances such as

rapidly changing light conditions (especially salmonids) and pedestrian traffic. 

5.1.7 Materials used for exposure chambers, tubing, etc., that come in contact with the effluent and dilution water

should be carefully chosen. Tempered glass and perfluorocarbon plastics (TEFLON®) should be used whenever

possible to minimize sorption and leaching of toxic substances, and may be reused after cleaning. Containers made

of plastics, such as polyethylene, polypropylene, polyvinyl chloride, TYGON®, etc., may be used to ship, store, and

transfer effluents and receiving waters, but they should not be reused unless absolutely necessary, because they

could carry over adsorbed toxicants from one test to another. However, these containers may be repeatedly reused

for storing uncontaminated waters such as deionized or laboratory-prepared dilution waters and receiving waters. 

Glass or disposable polystyrene containers can be used as test chambers. The use of large ($20 L) glass carboys is

discouraged for safety reasons.
23

5.1.8 New plastic products should be tested for toxicity before general use by exposing organisms to them under

ordinary test conditions. 

5.1.9 Equipment which cannot be discarded after each use because of cost, must be decontaminated according to

the cleaning procedures listed below. Fiberglass, in addition to the previously mentioned materials, can be used for

holding and dilution water storage tanks, and in the water delivery system. All material should be flushed or rinsed

thoroughly with dilution water before using in the test.

5.1.10 Copper, galvanized material, rubber, brass, and lead must not come in contact with holding or dilution

water, or with effluent samples and test solutions. Some materials, such as neoprene rubber (commonly used for

stoppers), may be toxic and should be tested before use. 

5.1.11 Silicone adhesive used to construct glass test chambers absorbs some organochlorine and organophosphorus

pesticides, which are difficult to remove. Therefore, as little of the adhesive as possible should be in contact with

water. Extra beads of adhesive inside the containers should be removed. 

5.2 CLEANING TEST CHAMBERS AND LABORATORY APPARATUS

5.2.1 New plasticware used for effluent or dilution water collection or organism test chambers does not require

thorough cleaning before use. It is sufficient to rinse new sample containers once with sample dilution water before

use. New glassware must be soaked overnight in 10% acid (see below) and rinsed well in deionized water and

dilution water.

5.2.2 All non-disposable sample containers, test vessels, tanks, and other equipment that has come in contact with

effluent must be washed after use in the manner described below to remove surface contaminants as described

below:

1. Soak 15 min in tap water, and scrub with detergent, or clean in an automatic dishwasher. 

2. Rinse twice with tap water. 

3. Carefully rinse once with fresh, dilute (10%, V:V) hydrochloric or nitric acid to remove scale, metals,

and bases. To prepare a 10% solution of acid, add 10 mL of concentrated acid to 90 mL of deionized

water. 

4. Rinse twice with deionized water. 

5. Rinse once with full-strength, pesticide-grade acetone to remove organic compounds (use a fume

hood or canopy). 

6. Rinse three times with deionized water. 

5.2.3 All test chambers and equipment should be thoroughly rinsed with the dilution water immediately prior to use

in each test. 

5.3 APPARATUS AND EQUIPMENT FOR CULTURING AND TOXICITY TESTS 

5.3.1 Culture units -- see Appendix. It is preferable to obtain test organisms from in-house culture units. If it is

not feasible to maintain cultures in-house, test organisms can be obtained from commercial sources, and should be

shipped to the laboratory in well oxygenated water in insulated containers to minimize excursions in water

temperature during shipment. The temperature of the water in the shipping containers should be measured on

arrival, to determine if the organisms were subjected to obvious undue thermal stress.

5.3.2 Samplers -- automatic samplers, preferably with sample cooling capability, that can collect a 24-h composite

sample of 2 L or more. 

5.3.3 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water Sampling

and Sample Handling). 
24

5.3.4 Environmental chamber or equivalent facility with temperature control (20EC or 25EC)

5.3.5 Water purification system -- MILLIPORE® MILLI-Q®, MILLIPORE® QPAKTM2, or equivalent. Depending

on the quantity of high grade water needed, a first-stage pre-conditioner deionizer, such as a Culligan® or

Continental® System, or equivalent, may be needed to provide feed water to the high-purity system.

5.3.6 Balance -- analytical, capable of accurately weighing to 0.0001 g. 

5.3.7 Reference weights, Class S -- for documenting the performance of the analytical balance(s). The balance(s)

should be checked with reference weights which are at the upper and lower ends of the range of the weighings made

when the balance is used. A balance should be checked at the beginning of each series of weighings, periodically

(such as every tenth weight) during a long series of weighings, and after the last weight of a series is taken. 

5.3.8 Test chambers -- borosilicate glass or non-toxic disposable plastic test chambers are suitable. Test chamber

volumes are indicated in the method summaries. To avoid potential contamination from the air and excessive

evaporation of test solutions during the test, the chambers should be covered with safety glass plates or sheet plastic,

6 mm (1⁄4 in) thick. 

5.3.9 Volumetric flasks and graduated cylinders -- Class A, borosilicate glass or non-toxic plastic labware,

10-1000 mL for making test solutions. 

5.3.10 Volumetric pipets -- Class A, 1-100 mL. 

5.3.11 Serological pipets -- 1-10 mL, graduated. 

5.3.12 Pipet bulbs and fillers -- PROPIPET®, or equivalent. 

5.3.13 Droppers, and glass tubing with fire polished edges, 4 mm ID -- for transferring test organisms. 

5.3.14 Wash bottles -- for rinsing small glassware and instrument electrodes and probes. 

5.3.15 Glass or electronic thermometers -- for measuring water temperature. 

5.3.16 Bulb-thermograph or electronic-chart type thermometers -- for continuously recording temperature. 

5.3.17 National Bureau of Standards Certified thermometer (see USEPA Method 170.1; USEPA 1979b). 

5.3.18 pH, DO, and specific conductivity meters -- for routine physical and chemical measurements. Unless the

test is being conducted to specifically measure the effect of one of the above parameters, a portable, field-grade

instrument is acceptable. 

5.3.19 Refractometer -- for measuring effluent, receiving, and test solution salinity.

5.3.20 Amperometric titrator -- for measuring total residual chlorine.

5.4 REAGENTS AND CONSUMABLE MATERIALS 

5.4.1 Reagent water -- defined as MILLIPORE® MILLI-Q®, MILLIPORE® QPAKTM2 or equivalent water (see

Subsection 5.3.5 above). 

5.4.2 Effluent, dilution water, and receiving water -- see Section 7, Dilution Water, and Section 8, Effluent and

Receiving Water Sampling and Sample Handling. 

5.4.3 Reagents for hardness and alkalinity tests (see USEPA Methods 130.2 and 310.1; USEPA l979b). 
25

5.4.4 Standard pH buffers 4, 7, and 10 (or as per instructions of instrument manufacturer) for instrument

calibration (see USEPA Method 150.1; USEPA 1979b). 

5.4.5 Specific conductivity and salinity standards (see USEPA Method 120.1; USEPA 1979b). 

5.4.6 Laboratory quality control check samples and standards for the above chemistry methods. 

5.4.7 Reference toxicant solutions (see Section 4, Quality Assurance). 

5.4.8 Membranes and filling solutions for dissolved oxygen probe (see USEPA Method 360.1; USEPA 1979b), or

reagents for modified Winkler analysis. 

5.4.9 Sources of Food for Cultures and Toxicity Tests.

5.4.9.1 All food should be tested for nutritional suitability, and chemically analyzed for organic chlorine, PCBs,

and toxic metals (see Section 4, Quality Assurance).

5.4.9.2 Brine Shrimp (Artemia) -- see Appendix A. 

1. Brine Shrimp (Artemia) Cysts.

There are many commercial sources of brine shrimp cysts. The quality of the cysts may vary from one

batch to another, and the cysts in each new batch (can or lot) should be evaluated for nutritional

suitability and chemical contamination. The nutritional suitability (see Leger et al., 1985, 1986) of

each new batch is checked against known suitable reference cysts by performing a side-by-side growth

and/or reproduction tests using the "new" and "reference" cysts. If the results of tests for nutritional

suitability or chemical contamination do not meet standards, the Artemia should not be used. 

2. Frozen Adult Brine Shrimp

Frozen adult brine shrimp are available from pet stores and other commercial sources.

5.4.9.3 Trout Chow

Starter or No. 1 pellets, prepared according to current U.S. Fish and Wildlife Service specifications, are available

from commercial sources. (The flake food, TETRAMIN® or BIORIL®, can be used regularly as a substitute for

trout chow in preparing food for daphnids, and can be used as a short-term substitute for trout chow in feeding

fathead minnows.)

5.4.9.4 Dried, Powdered Leaves (CEROPHYLL®)

Dried, powdered, cereal leaves (e.g., CEROPHYLL® or equivalent) are available from commercial suppliers. Dried,

powdered, alfalfa leaves obtained from health food stores have been found to be a satisfactory substitute for cereal

leaves. 

5.4.9.5 Yeast

Packaged dry yeast, such as Fleischmann's, or equivalent, can be purchased at the local grocery store.

5.4.9.6 Flake Fish Food

The flake foods, TETRAMIN® and BIORIL®, are available at most pet supply shops. 
26

5.5 TEST ORGANISMS

5.5.1 Test organisms are obtained from inhouse cultures or commercial suppliers (see Section 6, Test Organisms).
1

 The genus name of this organism was formally changed to Americamysis (Price et al., 1994); however,

the method manual will continue to refer to Mysidopsis bahia to maintain consistency with previous versions of the

method.

27

SECTION 6

TEST ORGANISMS

6.1 TEST SPECIES

6.1.1 The species used in characterizing the acute toxicity of effluents and/or receiving waters will depend on the

requirements of the regulatory authority and the objectives of the test. It is essential that good quality test organisms

be readily available throughout the year from inhouse or commercial sources to meet NPDES monitoring

requirements. The organisms used in toxicity tests must be identified to species. If there is any doubt as to the

identity of the test organisms, representative specimens should be sent to a taxonomic expert to confirm the

identification. 

6.1.2 Toxicity test conditions and culture methods are provided in this manual for the following principal test

organisms:

Freshwater Organisms:

1. Ceriodaphnia dubia (daphnid) (Table 12). 

2. Daphnia pulex and D. magna (daphnids) (Table 13).

3. Pimephales promelas (fathead minnow) (Table 14). 

4. Oncorhynchus mykiss (rainbow trout) and Salvelinus fontinalis (brook trout) (Table 15).

Estuarine and Marine Organisms:

1. Mysidopsis bahia (mysid) (Table 16).1

2. Cyprinodon variegatus (sheepshead minnow) (Table 17).

3. Menidia beryllina (inland silverside), M. menidia (Atlantic silverside), and M. peninsulae (tidewater

silverside) (Table 18). 

6.1.3 The test species (AFS, 1991) listed in Subsection 6.1.2 are the recommended acute toxicity test organisms. 

They are easily cultured in the laboratory, are sensitive to a variety of pollutants, and are generally available

throughout the year from commercial sources. Summaries of test conditions for these species are provided in

Tables 12-18. Guidelines for culturing and/or holding the organisms are provided in Appendix A. 

6.1.4 Additional species may be suitable for toxicity tests in the NPDES Program. A list of alternative acute

toxicity test species and minimal testing requirements (i.e., temperature, salinity, and life stage) for these species are

provided in Appendix B. Table 19 provides a summary of test conditions for Holmesimysis costata, which should

also be considered an alternative acute toxicity test species. The Holmesimysis costata Acute Test (Table 19) is

specific to Pacific Coast waters and is not listed at 40 CFR Part 136 for nationwide use. It is important to note that

these species may not be as easily cultured or tested as the species on the list in 6.1.2, and may not be available from

commercial sources.

6.1.5 Some states have developed culturing and testing methods for indigenous species that may be as sensitive or

more sensitive than the species recommended in 6.1.2. However, EPA allows the use of indigenous species only

where state regulations require their use or prohibit importation of the species in 6.1.2. Where state regulations

prohibit importation or use of the recommended test species, permission must be requested from the appropriate

state agency prior to their use. 
28

6.1.6 Where states have developed culturing and testing methods for indigenous species other than those

recommended in this manual, data comparing the sensitivity of the substitute species and one or more of the

recommended species must be obtained in side-by-side toxicity tests with reference toxicants and/or effluents, to

ensure that the species selected are at least as sensitive as the recommended species. These data must be submitted

to the permitting authority (State or Region) if required. EPA acknowledges that reference toxicants prepared from

pure chemicals may not always be representative of effluents. However, because of the observed and/or potential

variability in the quality and toxicity of effluents, it is not possible to specify a representative effluent. 

6.1.7 Guidance for the selection of test organisms where the salinity of the effluent and/or receiving water requires

special consideration is provided in the Technical Support Document for Water Quality-Based Toxics Control

(USEPA, 1991c).

1. Where the salinity of the receiving water is <1‰, freshwater organisms are used regardless of the

salinity of the effluent.

2. Where the salinity of the receiving water is $1‰, the choice of organisms depends on state water

quality standards and/or permit requirements.

6.2 SOURCES OF TEST ORGANISMS

6.2.1 INHOUSE CULTURES

6.2.1.1 Inhouse cultures should be established wherever it is cost effective. If inhouse cultures cannot be

maintained, test organisms should be purchased from experienced commercial suppliers (see Appendix for sources).

6.2.2 COMMERCIAL SUPPLIERS

6.2.2.1 All of the principal test organisms listed in Subsection 6.1.2 are available from commercial suppliers.

6.2.3 FERAL (NATURAL OCCURRING, WILD CAUGHT) ORGANISMS

6.2.3.1 The use of test organisms taken from the receiving water has strong appeal, and would seem to be the

logical approach. However, it is impractical for the following reasons: 

1. Sensitive organisms may not be present in the receiving water because of previous exposure to the

effluent or other pollutants.

2. It is often difficult to collect organisms of the required age and quality from the receiving water; 

3. Most states require collection permits, which may be difficult to obtain. Therefore, it is usually more

cost effective to culture the organisms in the laboratory or obtain them from private, state, or Federal

sources. Fish such as fathead minnows, sheepshead minnows, and silversides, and invertebrates such

as daphnids and mysids, are easily reared in the laboratory or purchased. 

4. The required QA/QC records, such as the single laboratory precision data, would not be available.

5. Since it is mandatory that the identity of test organisms is known to the species level, it would

necessary to examine each organism caught in the wild to confirm its identity, which would usually be

impractical or, at the least, very stressful to the organisms.

6. Test organisms obtained from the wild must be observed in the laboratory for a minimum of one week

prior to use, to assure that they are free of signs of parasitic or bacterial infections and other adverse

effects. Fish captured by electroshocking must not be used in toxicity testing.

6.2.3.2 Guidelines for collection of feral organisms are provided in USEPA, 1973; USEPA 1990a.

6.2.4 Regardless of their source, test organisms should be carefully observed to ensure that they are free of signs of

stress and disease, and in good physical condition. Some species of test organisms, such as trout, can be obtained

from stocks certified as "disease-free." 
29

6.3 LIFE STAGE

6.3.1 Young organisms are often more sensitive to toxicants than are adults. For this reason, the use of early life

stages, such as first instars of daphnids and juvenile mysids and fish, is required for all tests. In a given test, all

organisms should be approximately the same age and should be taken from the same source. Since age may affect

the results of the tests, it would enhance the value and comparability of the data if the same species in the same life

stages were used throughout a monitoring program at a given facility. 

6.4 LABORATORY CULTURING

6.4.1 Instructions for culturing and/or holding the recommended test organisms are included in Appendix A. 

6.5 HOLDING AND HANDLING TEST ORGANISMS

6.5.1 Test organisms should not be subjected to changes of more than 3EC in water temperature or 3‰ in salinity

in any 12 h period. 

6.5.2 Organisms should be handled as little as possible. When handling is necessary, it should be done as gently,

carefully, and quickly as possible to minimize stress. Organisms that are dropped or touch dry surfaces or are

injured during handling must be discarded. Dipnets are best for handling larger organisms. These nets are

commercially available or can be made from small-mesh nylon netting, silk bolting cloth, plankton netting, or

similar material. Wide-bore, smooth glass tubes (4 to 8 mm inside diameter) with rubber bulbs or pipettors (such as

a PROPIPETTE® or other pipettor) should be used for transferring smaller organisms such as daphnids, mysids, and

larval fish. 

6.5.3 Holding tanks for fish are supplied with a good quality water (see Section 5, Facilities and Equipment) with a

flow-through rate of at least two tank-volumes per day. Otherwise, use a recirculation system where the water flows

through an activated carbon or undergravel filter to remove dissolved metabolites. Culture water can also be piped

through high intensity ultraviolet light sources for disinfection, and to photodegrade dissolved organics. 

6.5.4 Crowding should be avoided. The DO must be maintained at a minimum of 4.0 mg/L for marine and warm

water, freshwater species, and 6.0 mg/L for cold-water, freshwater species. The solubility of oxygen depends on

temperature, salinity, and altitude. Aerate if necessary. 

6.5.5 Fish should be fed as much as they will eat at least once a day with live or frozen brine shrimp or dry food

(frozen food should be completely thawed before use). Brine shrimp can be supplemented with commercially

prepared food such as Tetramin® or BioRil® flake food, or equivalent. Excess food and fecal material should be

removed from the bottom of the tanks at least twice a week by siphoning.

6.5.6 Fish should be observed carefully each day for signs of disease, stress, physical damage, and mortality. Dead

and abnormal specimens should be removed as soon as observed. It is not uncommon to have some fish (5-10%)

mortality during the first 48 h in a holding tank because of individuals that refuse to feed on artificial food and die

of starvation. 

6.5.7 A daily record of feeding, behavioral observations, and mortality should be maintained.

6.6 TRANSPORTATION TO THE TEST SITE 

6.6.1 Organisms are transported from the base or supply laboratory to a remote test site in culture water or standard

dilution water in plastic bags or large-mouth screw-cap (500 mL) plastic bottles in styrofoam coolers. Adequate DO

is maintained by replacing the air above the water in the bags with oxygen from a compressed gas cylinder, and

sealing the bags. Another method commonly used to maintain sufficient DO during shipment is to aerate with an

airstone which is supplied from a portable pump. The DO concentration must not fall below 4.0 mg/L for marine

and warm-water, freshwater species, and 6.0 mg/L for cold-water, freshwater species.
30

6.6.2 Upon arrival at the test site, organisms are transferred to receiving water if receiving water is to be used as

the test dilution water. All but a small volume of the holding water (approximately 5%) is removed by siphoning,

and replaced slowly over a 10 to 15 min period with dilution water. If receiving water is used as dilution water,

caution must be exercised in exposing the test organisms to it, because of the possibility that it might be toxic. For

this reason, it is recommended that only approximately 10% of the test organisms be exposed initially to the dilution

water. If this group does not show excessive mortality or obvious signs of stress in a few hours, the remainder of

the test organisms are transferred to the dilution water. 

6.6.3 A group of organisms must not be used for a test if they appear to be unhealthy, discolored, or otherwise

stressed, or if mortality appears to exceed 10% preceding the test. If the organisms fail to meet these criteria, the

entire group must be discarded and a new group obtained. The mortality may be due to the presence of toxicity, if

receiving water is used as dilution water, rather than a diseased condition of the test organisms. If the acclimation

process is repeated with a new group of test organisms and excessive mortality occurs, it is recommended that an

alternative source of dilution water be used. 

6.6.4 In static tests, marine organisms can be used at all concentrations of effluent by adjusting the salinity of the

effluent to a standard salinity (such as 25‰) or to the salinity approximating that of the receiving water, by adding

sufficient dry ocean salts, such as Forty Fathoms®, or equivalent, GP2 or hypersaline brine.

6.6.5 Saline dilution water can be prepared with deionized water or a freshwater such as well water or a suitable

surface water. If dry ocean salts are used, care must be taken to ensure that the added salts are completely dissolved

and the solution is aerated 24 h before the test organisms are placed in the solutions. The test organisms should be

acclimated in synthetic saline water prepared with the dry salts. Caution: addition of dry ocean salts to dilution

water may result in an increase in pH. (The pH of estuarine and coastal saline waters is normally 7.5-8.3.)

6.6.6 All effluent concentrations and the control(s) used in a test should have the same salinity. However, if this is

impractical because of the large volumes of water required, such as in flow-through tests, the highest effluent

concentration (lowest salinity) that could be tested would depend upon the salinity of the receiving water and the

tolerance of the test organisms. The required salinities for toxicity tests with estuarine and marine species are listed

in Tables 16-19. However, the tolerances of other candidate test species would have to be determined by the

investigator in advance of the test. 

6.6.7 Because of the circumstances described above, when performing flow-through tests of effluents discharged

to saline waters, it is advisable to acclimate groups of test organisms to each of three different salinities, such as 10,

20, and 30‰, prior to transporting them to the test site. It may also be advisable to maintain cultures of these test

organisms at a series of salinity levels, including at least 10, 20, and 30‰, so that the change in salinity upon

acclimation at the desired test dilutions does not exceed 6‰. 

6.7 TEST ORGANISM DISPOSAL

6.7.1 When the toxicity test is concluded, all test organisms (including controls) should be humanely destroyed and

disposed of in an appropriate manner. 
31

SECTION 7

DILUTION WATER 

7.1 TYPES OF DILUTION WATER

7.1.1 The type of dilution water used in effluent toxicity tests will depend largely on the objectives of the study: 

7.1.1.1 If the objective of the test is to estimate the absolute acute toxicity of the effluent, a synthetic (standard)

dilution water is used. If the test organisms have been cultured in water which is different from the test dilution

water, a second set of controls, using culture water, should be included in the test.

7.1.1.2 If the objective of the test is to estimate the acute toxicity of the effluent in uncontaminated receiving

water, the test may be conducted using dilution water consisting of a single grab sample of receiving water (if

non-toxic), collected either upstream and outside the influence of the outfall, or with other uncontaminated natural

water (ground or surface water) or standard dilution water having approximately the same characteristics (hardness

and/or salinity) as the receiving water. Seasonal variations in the quality of surface waters may affect effluent

toxicity. Therefore, the hardness of fresh receiving water, and the salinity of saline receiving water samples should

be determined before each use. If the test organisms have been cultured in water which is different from the test

dilution water, a second set of controls, using culture water, should be included in the test.

7.1.1.3 If the objective of the test is to determine the additive or mitigating effects of the discharge on already

contaminated receiving water, the test is performed using dilution water consisting of receiving water collected

immediately upstream or outside the influence of the outfall. A second set of controls, using culture water, should

be included in the test.

7.1.2 An acceptable dilution water is one which is appropriate for the objectives of the test; supports adequate

performance of the test organisms with respect to survival, growth, reproduction, or other responses that may be

measured in the test (i.e., consistently meets test acceptability criteria for control responses); is consistent in quality;

and does not contain contaminants that could produce toxicity. Receiving waters, synthetic waters, or synthetic

waters adjusted to approximate receiving water characteristics may be used for dilution provided that the water

meets the above listed qualifications for an acceptable dilution water. USEPA (2000a) provides additional guidance

on selecting appropriate dilution waters.

7.1.3 When dual controls (one control using culture water and one control using dilution water) are used (see

Subsections 7.1.1.1 - 7.1.1.3 above), the dilution water control should be used to determine test acceptability. It is

also the dilution water control that should be compared to effluent treatments in the calculation and reporting of test

results. The culture water control should be used to evaluate the appropriateness of the dilution water source. 

Significant differences between organism responses in culture water and dilution water controls could indicate

toxicity in the dilution water and may suggest an alternative dilution water source. USEPA (2000a) provides

additional guidance on dual controls.

7.2 STANDARD, SYNTHETIC DILUTION WATER 

7.2.1 Standard, synthetic, dilution water is prepared with deionized water and reagent grade chemicals or mineral

water (Tables 7 and 8) and commercial sea salts (FORTY FATHOMS®, HW MARINEMIX®) (Table 9). The

source water for the deionizer can be groundwater, or tap water. 
32

7.2.2 DEIONIZED WATER USED TO PREPARE STANDARD, SYNTHETIC, DILUTION WATER 

7.2.2.1 Deionized water is obtained from a MILLIPORE® MILLI-Q®, MILLIPORE® QPAKTM2, or equivalent

system. It is advisable to provide a preconditioned (deionized) feed water by using a Culligan®, Continental®, or

equivalent, system in front of the MILLIPORE® System to extend the life of the MILLIPORE ® cartridges.

7.2.2.2 The recommended order of the cartridges in a four-cartridge deionizer (i.e., MILLI-Q® System or

equivalent) is: (1) ion exchange, (2) ion exchange, (3) carbon, and (4) organic cleanup (such as ORGANEX-Q®, or

equivalent), followed by a final bacteria filter. The QPAKTM2 water system is a sealed system which does not allow

for the rearranging of the cartridges. However, the final cartridge is an ORGANEX-Q® filter, followed by a final

bacteria filter. Commercial laboratories using this system have not experienced any difficulty in using the water for

culturing or testing. Reference to the MILLI-Q® systems throughout the remainder of the manual includes all

MILLIPORE® or equivalent systems.

7.2.3 STANDARD, SYNTHETIC FRESHWATER

7.2.3.1 To prepare 20 L of standard, synthetic, moderately hard, reconstituted water, use the reagent grade 

chemicals in Table 7 as follows: 

1. Place 19 L of MILLI-Q®, or equivalent, deionized water in a properly cleaned plastic carboy. 

2. Add 1.20 g of MgSO4, 1.92 g NaHCO3, and 0.080g KCl to the carboy. 

3. Aerate overnight. 

4. Add 1.20 g of CaSO4C2 H2O to 1 L of MILLI-Q® or equivalent deionized water in a separate flask. 

Stir on magnetic stirrer until calcium sulfate is dissolved, add to the 19 L above, and mix well. 

5. For Ceriodaphnia culture and testing, add sufficient sodium selenate (Na2SeO4) to provide 2 μg

selenium per liter of final dilution water.

6. Aerate the combined solution vigorously for an additional 24 h to dissolve the added chemicals and

stabilize the medium. 

7. The measured pH, hardness, etc., should be as listed in Table 7. 

7.2.3.2 To prepare 20 L of standard, synthetic, moderately hard, reconstituted water, using 20% mineral water such

as PERRIER® Water, or equivalent (Table 8), follow the instructions below.

1. Place 16 L of MILLI-Q® or equivalent deionized water in a properly cleaned plastic carboy. 

2. Add 4 L of PERRIER® Water, or equivalent. 

3. Aerate vigorously for 24 h to stabilize the medium. 

4. The measured pH, hardness, and alkalinity of the aerated water will be as indicated in Table 8. 

5. This synthetic water is referred to as diluted mineral water (DMW) in the toxicity test methods. 

7.2.4 STANDARD, SYNTHETIC SEAWATER

7.2.4.1 To prepare 20 L of a standard, synthetic, reconstituted seawater (modified GP2), with a salinity of 31‰

(Table 9), follow the instructions below. Other salinities can be prepared by making the appropriate dilutions.

1. Place 20 L of MILLI-Q® or equivalent deionized water in a properly cleaned plastic carboy.

2. Weigh reagent grade salts listed in Table 9 and add, one at a time, to the deionized water. Stir well

after adding each salt.

3. Aerate the final solution at a rate of 1 L/h for 24 h. 

4. Check the pH and salinity. 

Larger or smaller volumes of modified GP2 can be prepared by using proportionately larger or smaller amounts of

salts and dilution water.
33

7.2.4.2 Synthetic seawater can also be prepared by adding commercial sea salts, such as FORTY FATHOMS®,

HW MARINEMIX® or equivalent, to deionized water. For example, thirty-one parts per thousand (31‰) FORTY

FATHOMS® can be prepared by dissolving 31 g of product per liter of deionized water. The salinity of the

resulting solutions should be checked with a refractometer. 

7.3 USE OF RECEIVING WATER AS DILUTION WATER

7.3.1 If the objectives of the test require the use of uncontaminated surface water as dilution water, and the

receiving water is uncontaminated, it may be possible to collect a sample of the receiving water close to the outfall,

but upstream from or beyond the influence of the effluent. However, if the receiving water is contaminated, it may

be necessary to collect the sample in an area "remote" from the discharge site, matching as closely as possible the

physical and chemical characteristics of the receiving water near the outfall. 

7.3.2 The sample should be collected immediately prior to the test, but never more than 96 h before the test begins. 

Except where it is used within 24 h, or in the case where large volumes are required for flow-through tests, the

sample should be chilled to 4°C during or immediately following collection, and maintained at that temperature

prior to use in the test. 

7.3.3 In the case of freshwaters, the regulatory authority may require that the hardness of the dilution water be

comparable to the receiving water at the discharge site. This requirement can be satisfied by collecting an

uncontaminated surface water with a suitable hardness, or adjusting the hardness of an otherwise suitable surface

water by addition of reagents as indicated in Table 7. 

7.3.4 In an estuarine environment, the investigator should collect uncontaminated water having a salinity as near as

possible to the salinity of the receiving water at the discharge site. Water should be collected at slack high tide, or

within one hour after high tide. If there is reason to suspect contamination of the water in the estuary, it is advisable

to collect uncontaminated water from an adjacent estuary. At times it may be necessary to collect water at a

location closer to the open sea, where the salinity is relatively high. In such cases, deionized water or

uncontaminated freshwater is added to the saline water to dilute it to the required test salinity. Where necessary, the

salinity of a surface water can be increased by the addition of artificial sea salts, such as FORTY FATHOMS® or

equivalent, a natural seawater of higher salinity, or hypersaline brine. Instructions for the preparation of hypersaline

brine by concentrating natural seawater are provided below. 

7.3.5 Receiving water containing debris or indigenous organisms, that may be confused with or attack the test

organisms, should be filtered through a sieve having 60 μm mesh openings prior to use.

TABLE 7. PREPARATION OF SYNTHETIC FRESHWATER USING REAGENT GRADE CHEMICALS1

 Reagent Added (mg/L)2 Approximate Final Water Quality 

NaHCO3 CaSO4C2H2O MgSO4 KCl pH3 Hardness4 Alkalinity4

Very soft 12.0 7.5 7.5 0.5 6.4-6.8 10-13 10-13

Soft 48.0 30.0 30.0 2.0 7.2-7.6 40-48 30-35

Moderately Hard 96.0 60.0 60.0 4.0 7.4-7.8 80-100 57-64

Hard 192.0 120.0 120.0 8.0 7.6-8.0 160-180 110-120

Very hard 384.0 240.0 240.0 16.0 8.0-8.4 280-320 225-245

1

Taken in part from Marking and Dawson (1973). 

2

Add reagent grade chemicals to deionized water. 3

Approximate equilibrium pH after 24 h of aeration. 

4

Expressed as mg CaCO3/L. 
34

TABLE 8. PREPARATION OF SYNTHETIC FRESHWATER USING MINERAL WATER1

Water Type

Volume of

Mineral Water

Added (mL/L)2

Proportion

of Mineral

Water (%)

Approximate Final Water Quality

pH3 Hardness4 Alkalinity4

Very Soft 50 2.5 7.2-8.1 10-13 10-13

Soft 100 10.0 7.9-8.3 40-48 30-35

Moderately Hard 200 20.0 7.9-8.3 80-100 57-64

Hard 400 40.0 7.9-8.3 160-180 110-120

Very Hard5 --- --- --- --- ---

1

From Mount et al., 1987; data provided by Philip Lewis, EMSL-Cincinnati. 2

Add mineral water to MILLI-Q® water or equivalent to prepare DMW (Diluted Mineral Water). 3

Approximate equilibrium pH after 24 h of aeration. 

4

Expressed as mg CaCO3/L. 5

Dilutions of PERRIER® Water form a precipitate when concentrations equivalent to "very hard water" are

aerated. 

TABLE 9. PREPARATION OF SYNTHETIC SEAWATER USING REAGENT GRADE 

 CHEMICALS1,2,3

Compound Concentration (g/L) Amount (g) Required for 20 L

NaCl 21.03 420.6

Na2SO4 3.52 70.4

Kcl 0.61 12.2

Kbr 0.088 1.76

Na2B4O7C10 H2O 0.034 0.68

MgCl2C6 H2O 9.50 190.0

CaCl2C2 H2O 1.32 26.4

SrCl2C6 H2O 0.02 0.400

NaHCO3 0.17 3.40

1

Modified GP2.

2

The constituent salts and concentrations were taken from USEPA, 1990b. The salinity is 30.89 G/L. 3

GP2 can be diluted with deionized (DI) water to the desired test salinity.
35

7.3.6 When receiving water is used as dilution water in flow-through tests, it is preferable to pump the dilution

water continuously to the acclimation chamber and/or dilutor. However, where it is not feasible to pump the

dilution water continuously, grab samples of the dilution water are transported to the test site in tanks, and

continuously pumped from the tanks to the acclimation chamber and/or dilutor. 

7.3.7 HYPERSALINE BRINE

7.3.7.1 Hypersaline brine (HSB) has several advantages that make it desirable for use in toxicity testing. It can be

made from any high quality, filtered seawater by evaporation, and can be added to deionized water to prepare

dilution water, or to effluents or surface waters to increase their salinity. 

7.3.7.2 The ideal container for making HSB from natural seawater is one that (1) has a high surface to volume

ratio, (2) is made of a non-corrosive material, and (3) is easily cleaned (fiberglass containers are ideal). Special care

should be used to prevent any toxic materials from coming in contact with the seawater being used to generate the

brine. If a heater is immersed directly into the seawater, ensure that the heater materials do not corrode or leach any

substances that would contaminate the brine. One successful method used is a thermostatically controlled heat

exchanger made from fiberglass. If aeration is used, use only oil-free air compressors to prevent contamination. 

7.3.7.3 Before adding seawater to the brine generator, thoroughly clean the generator, aeration supply tube, heater,

and any other materials that will be in direct contact with the brine. A good quality biodegradable detergent should

be used, followed by several thorough deionized water rinses. High quality (and preferably high salinity) seawater

should be filtered to at least 10 μm before placing into the brine generator. Water should be collected on an

incoming tide to minimize the possibility of contamination. 

7.3.7.4 The temperature of the seawater is increased slowly to 40°C. The water should be aerated to prevent

temperature stratification and to increase water evaporation. The brine should be checked daily (depending on the

volume being generated) to ensure that the salinity does not exceed 100‰ and that the temperature does not exceed

40°C. Additional seawater may be added to the brine to obtain the volume of brine required. 

7.3.7.5 After the required salinity is attained, the HSB should be filtered a second time through a 1-Fm filter and

poured directly into portable containers (20 L CUBITAINERS® or polycarbonate water cooler jugs are suitable). 

The containers should be capped and labeled with the date the brine was generated and its salinity. Containers of

HSB should be stored in the dark and maintained under room temperature until used. 

7.3.7.6 If a source of HSB is available, test solutions can be made by following the directions below. Thoroughly

mix together the deionized water and brine before mixing in the effluent. 

7.3.7.7 Divide the salinity of the HSB by the expected test salinity to determine the proportion of deionized water

to brine. For example, if the salinity of the brine is 100‰ and the test is to be conducted at 25‰, 100‰ divided by

25‰ = 4.0. The proportion of brine is 1 part in 4 (one part brine to three parts deionized water). 

7.3.7.8 To make 1 L of seawater at 25‰ salinity from a hypersaline brine of 100‰, 250 mL of brine and 750 mL

of deionized water are required. 

7.4 USE OF TAP WATER AS DILUTION WATER

7.4.1 The use of tap water as dilution water is discouraged unless it is dechlorinated and fully treated. Tap water

can be dechlorinated by deionization, carbon filtration, or the use of sodium thiosulfate. Use of 3.6 mg/L

(anhydrous) sodium thiosulfate will reduce 1.0 mg chlorine/L (APHA, 1992, p. 4-36). Following dechlorination,

total residual chlorine should not exceed 0.01 mg/L. Because of the possible toxicity of thiosulfate to test

organisms, a control lacking thiosulfate should be included in toxicity tests utilizing thiosulfate-dechlorinated water.
36

7.4.2 To be adequate for general laboratory use following dechlorination, the tap water is passed through a

deionizer and carbon filter to remove toxic metals and organics, and to control hardness and alkalinity.

7.5 DILUTION WATER HOLDING

7.5.1 A given batch of dilution water should not be used for more than 14 days following preparation because of

the possible build-up of bacterial, fungal, or algal slime growth and the problems associated with it. The container

should be kept covered and the contents should be protected from light. 
37

SECTION 8

EFFLUENT AND RECEIVING WATER SAMPLING AND SAMPLE HANDLING

8.1 EFFLUENT SAMPLING 

8.1.1 The effluent sampling point is ordinarily the same as that specified in the NPDES discharge permit (USEPA,

1979c). Conditions for exception would be: (1) better access to a sampling point between the final treatment and

the discharge outfall; (2) if the effluent is chlorinated prior to discharge to the receiving waters, it may also be

desirable to take samples prior to contact with the chlorine to determine toxicity of the unchlorinated effluent; or (3)

in the event there is a desire to evaluate the toxicity of the influent to publicly owned treatment works or separate

process waters in industrial facilities prior to their being combined with other process waters or non-contact cooling

water, additional sampling points may be chosen. 

8.1.2 The decision on whether to collect grab or composite samples is based on the requirements of the NPDES

permit, the objectives of the test, and an understanding of the short and long-term operations and schedules of the

discharger. If the effluent quality varies considerably with time, which can occur where holding times within the

treatment facility are short, grab samples may seem preferable because of the ease of collection and the potential of

observing peaks (spikes) in toxicity. However, the sampling duration of a grab sample is so short that full

characterization of an effluent over a 24-h period would require a prohibitive number of separate samples and tests. 

Collection of a 24-h composite sample, however, may dilute toxicity spikes, and average the quality of the effluent

over the sampling period. Sampling recommendations are provided below. 

8.1.3 Aeration during collection and transfer of effluents should be minimized to reduce the loss of volatile

chemicals.

8.1.4 Details of date, time, location, duration, and procedures used for effluent sample and dilution water

collection should be recorded.

8.2 EFFLUENT SAMPLE TYPES

8.2.1 The advantages and disadvantages of effluent grab and composite samples are listed below: 

8.2.1.1 Grab Samples 

Advantages: 

1. Easy to collect; require a minimum of equipment and on-site time. 

2. Provide a measure of instantaneous toxicity. Toxicity spikes are not masked by dilution. 

Disadvantages: 

1. Samples are collected over a very short period of time and on a relatively infrequent basis. The chances

of detecting a spike in toxicity would depend on the frequency of sampling, and the probability of

missing spikes is high. 
38

8.2.1.2 Composite Samples: 

Advantages: 

1. A single effluent sample is collected over a 24-h period. 

2. The sample is collected over a much longer period of time than grab samples and contains all toxicity

spikes. 

 Disadvantages: 

1. Sampling equipment is more sophisticated and expensive, and must be placed on-site for at least 24 h. 

2. Toxicity spikes may not be detected because they are masked by dilution with less toxic wastes. 

8.3 EFFLUENT SAMPLING RECOMMENDATIONS

8.3.1 When tests are conducted on-site, test solutions can be renewed daily with freshly collected samples.

8.3.2 When tests are conducted off-site, samples are collected once, or daily, and used for test initiation and

renewal. 

8.3.3 Sufficient sample must be collected to perform the required toxicity and chemical tests. A 4-L (1-gal)

CUBITAINER® will provide sufficient sample volume for most tests (see Tables 12-19). 

8.3.4 The following effluent sampling methods are recommended: 

8.3.4.1 Continuous Discharges 

1. If the facility discharge is continuous, but the calculated retention time of the continuously discharged

effluent is less than 14 days and the variability of the effluent toxicity is unknown, at a minimum, four

grab samples or four composite samples are collected over a 24-h period. For example, a grab sample

is taken every 6 h (total of four samples) and each sample is used for a separate toxicity test, or four

successive 6-h composite samples are taken and each is used in a separate test. 

2. If the calculated retention time of a continuously discharged effluent is greater than 14 days, or if it can

be demonstrated that the wastewater does not vary more than 10% in toxicity over a 24-h period,

regardless of retention time, a single grab sample is collected for a single toxicity test. 

3. The retention time of the effluent in the wastewater treatment facility may be estimated from

calculations based on the volume of the retention basin and rate of wastewater inflow. However, the

calculated retention time may be much greater than the actual time because of short-circuiting in the

holding basin. Where short-circuiting is suspected, or sedimentation may have reduced holding basin

capacity, a more accurate estimate of the retention time can be obtained by carrying out a dye study. 

8.3.4.2 Intermittent Discharges 

8.3.4.2.1 If the facility discharge is intermittent, a grab sample is collected midway during each discharge period. 

Examples of intermittent discharges are: 

1. When the effluent is continuously discharged during a single 8-h work shift (one sample is collected),

or two successive 8-h work shifts (two samples are collected). 

2. When the facility retains the wastewater during an 8-h work shift, and then treats and releases the

wastewater as a batch discharge (one sample is collected). 
39

3. When the facility discharges wastewater to an estuary only during an outgoing tide, usually during the 4

h following slack high tide (one sample is collected). 

8.3.4.3 At the end of a shift, clean up activities may result in the discharge of a slug of toxic waste, which may

require sampling and testing. 

8.4 RECEIVING WATER SAMPLING

8.4.1 Logistical problems and difficulty in securing sampling equipment generally preclude the collection of

composite receiving water samples for toxicity tests. Therefore, it is common practice to collect a single grab

sample and use it throughout the test.

8.4.2 The sampling point is determined by the objectives of the test. In rivers, grab samples should be collected at

mid-stream and mid-depth, if accessible. At estuarine and marine sites, samples should be collected at mid-depth.

8.4.3 To determine the extent of the zone of toxicity in the receiving water downstream from the outfall, receiving

water samples are collected at several distances downstream from the discharge. The time required for the effluentreceiving-water mixture to travel to sampling points downstream from the outfall, and the rate and degree of

mixing, may be difficult to ascertain. Therefore, it may not be possible to correlate downstream toxicity with

effluent toxicity at the discharge point unless a dye study is performed. The toxicity of receiving water samples

from five stations downstream from the discharge point can be evaluated using the same number of test vessels and

test organisms as used in one effluent toxicity test with five effluent dilutions. 

8.5 EFFLUENT AND RECEIVING WATER SAMPLE HANDLING, PRESERVATION, AND SHIPPING 

8.5.1 Unless the samples are used in an on-site toxicity test the day of collection (or hand delivered to the testing

laboratory for use on the day of collection), it is recommended that they be held at 0-6°C until used to inhibit

microbial degradation, chemical transformations, and loss of highly volatile toxic substances.

8.5.2 Composite samples should be chilled as they are collected. Grab samples should be chilled immediately

following collection.

8.5.3 If the effluent has been chlorinated, total residual chlorine must be measured immediately following sample

collection.

8.5.4 Sample holding time begins when the last grab sample in a series is taken (i.e., when a series of four grab

samples are taken over a 24-h period), or when a 24-h composite sampling period is completed. If the data from the

samples are to be acceptable for use in the NPDES Program, the lapsed time (holding time) from sample collection

to first use of each grab or composite sample must not exceed 36 h. EPA believes that 36 h is adequate time to

deliver the samples to the laboratories performing the tests in most cases. In the isolated cases, where the permittee

can document that this delivery time cannot be met, the permitting authority can allow an option for on-site testing

or a variance for an extension of shipped sample holding time. The request for a variance in sample holding time,

directed to the USEPA Regional Administrator under 40 CFR 136.3(e) should include supportive data which show

that the toxicity of the effluent sample is not reduced (e.g., because of volatilization and/or sorption of toxics on the

sample container surfaces) by extending the holding time beyond more than 36 h. However, in no case should more

than 72 h elapse between collection and first use of the sample. In static-renewal tests, each grab or composite

sample may also be used to prepare test solutions for renewal at 24 h, 48 h, and/or 72 h after first use, if stored at 0-

6°C, with minimum head space, as described in Subsection 8.5. Guidance for determining the persistence of the

sample is provided in Subsection 8.7.

8.5.5 To minimize the loss of toxicity due to volatilization of toxic constituents, all sample containers should be

"completely" filled, leaving no air space between the contents and the lid. 
40

8.5.6 SAMPLES USED IN ON-SITE TESTS 

8.5.6.1 Samples collected for on-site tests should be used within 24 h. 

8.5.7 SAMPLES SHIPPED TO OFF-SITE FACILITIES 

8.5.7.1 Samples collected for off-site toxicity testing are to be chilled to 0-6°C during or immediately after

collection, and shipped iced to the performing laboratory. Sufficient ice should be placed with the sample in the

shipping container to ensure that ice will still be present when the sample arrives at the laboratory and is unpacked. 

Insulating material should not be placed between the ice and the sample in the shipping container unless required to

prevent breakage of glass sample containers.

8.5.7.2 Samples may be shipped in one or more 4-L (1 gal) CUBITAINERS® or new plastic "milk" jugs. All

sample containers should be rinsed with source water before being filled with sample. After use with receiving

water or effluents, CUBITAINERS® and plastic jugs are punctured to prevent reuse. 

8.5.7.3 Several sample shipping options are available, including Express Mail, air express, bus, and courier

service. Express Mail is delivered seven days a week. Saturday and Sunday shipping and receiving schedules of

private carriers vary with the carrier. 

8.6 SAMPLE RECEIVING 

8.6.1 Upon arrival at the laboratory, samples are logged in and the temperature is measured and recorded. If the

samples are not immediately prepared for testing, they are stored at 0-6°C until used.

8.6.2 Every effort must be made to initiate the test with an effluent sample on the day of arrival in the laboratory,

and the sample holding time should not exceed 36 h before first use unless a variance has been granted by the

NPDES permitting authority.

8.7 PERSISTENCE OF EFFLUENT TOXICITY DURING SAMPLE SHIPMENT AND HOLDING

8.7.1 The persistence of the toxicity of an effluent prior to its use in a toxicity test is of interest in assessing the

validity of toxicity test data, and in determining the possible effects of allowing an extension of the holding time. 

Where a variance in holding time (>36 h, but 72 h) is requested by a permittee (see Subsection 8.5.4 above),

information on the effects of the extension in holding time on the toxicity of the samples must be obtained by

comparing the results of multi-concentration acute toxicity tests performed on effluent samples held 36 h with

toxicity test results using the same samples after they were held for the requested, longer period. The portion of the

sample set aside for the second test must be held under the same conditions as during shipment and holding.
41

SECTION 9

ACUTE TOXICITY TEST PROCEDURES

9.1 PREPARATION OF EFFLUENT AND RECEIVING WATER SAMPLES FOR TOXICITY TESTS

9.1.1 When aliquots are removed from the sample container, the head space above the remaining sample should be

held to a minimum. Air which enters a container upon removal of sample should be expelled by compressing the

container before reclosing, if possible (i.e., where a CUBITAINER® used), or by using an appropriate discharge

valve (spigot). 

9.1.2 It may be necessary to first coarse-filter samples through a sieve having 2-4 mm mesh openings to remove

debris and/or break up large floating or suspended solids. If samples contain indigenous organisms that may attack

or be confused with the test organisms, the samples must be filtered through a sieve with 60 μm mesh openings. 

Caution: filtration may remove some toxicity. 

9.1.3 At a minimum, pH, conductivity or salinity, and total residual chlorine are measured in the undiluted effluent

or receiving water, and pH and conductivity are measured in the dilution water.

9.1.4 It is recommended that total alkalinity and total hardness also be measured in the undiluted test water

(effluent or receiving water) and the dilution water.

9.1.5 Total ammonia is measured in effluent and receiving water samples where toxicity may be contributed by

unionized ammonia (i.e., where total ammonia $5 mg/L). The concentration (mg/L) of unionized (free) ammonia in

a sample is a function of temperature and pH, and is calculated using the percentage value obtained from Table 10,

under the appropriate pH and temperature, and multiplying it by the concentration (mg/L) of total ammonia in the

sample.

9.1.6 Effluents and receiving waters can be dechlorinated using 6.7 mg/L anhydrous sodium thiosulfate to reduce 1

mg/L chlorine (Standard Methods, 18th Edition, APHA, 1992, p. 9-32; note that the amount of thiosulfate required

to dechlorinate effluents is greater than the amount needed to dechlorinate tap water). Since thiosulfate may

contribute to sample toxicity, a thiosulfate control should be used in the test in addition to the normal dilution water

control. 

9.1.7 The DO concentration in the samples should be near saturation prior to use. Aeration may be used to bring

the DO and other gases into equilibrium with air, minimize oxygen demand, and stabilize the pH. However,

aeration during collection, transfer, and preparation of samples should be minimized to reduce the loss of volatile

chemicals. 

9.1.8 If the samples must be warmed to bring them to the prescribed test temperature, supersaturation of the

dissolved oxygen and nitrogen may become a problem. To avoid this problem, samples may be warmed slowly in

open test containers. If DO is still above 100% saturation after warming to test temperature, samples should be

aerated moderately (approximately 500 mL/minimum) for a few minutes using an airstone. If DO is below 4.0

mg/L after warming to test temperature, the solutions must be aerated moderately (approximately 500 mL/min) for a

few minutes, using an airstone, until the DO is within the prescribed range ($4.0 mg/L when using warm water

species, or $6.0 mg/L when using cold water species). Caution: avoid excessive aeration. 

9.1.9 Mortality due to pH alone may occur if the pH of the sample falls outside the range of 6.0-9.0. Thus, the

presence of other forms of toxicity (metals and organics) in the sample may be masked by the toxic effects of low or

high pH. The question about the presence of other toxicants can be answered only by performing two parallel tests,

one with an adjusted pH, and one without an adjusted pH. Freshwater samples are adjusted to pH 7.0, and marine

samples are adjusted to pH 8.0, by adding 1N NaOH or 1N HCl dropwise, as required, being careful to avoid

overadjustment.
42

TABLE 10. PERCENT UNIONIZED NH3 IN AQUEOUS AMMONIA SOLUTIONS: TEMPERATURES 15-26EC AND pH's 6.0-

8.91

pH Temperature (°C)

15 16 17 18 19 20 21 22 23 24 25 26

6.0 0.0274 0.0295 0.0318 0.0343 0.0369 0.0397 0.0427 0.0459 0.0493 0.0530 0.0568 0.06106.1 0.0345 0.0372 0.0400 0.0431 0.0464 0.0500 0.0537 0.0578 0.0621 0.0667 0.0716 0.07686.2 0.0434 0.0468 0.0504 0.0543 0.0584 0.0629 0.0676 0.0727 0.0781 0.0901 0.0901 0.09666.3 0.0546 0.0589 0.0634 0.0683 0.0736 0.0792 0.0851 0.0915 0.0983 0.1134 0.1134 0.12166.4 0.0687 0.0741 0.0799 0.0860 0.0926 0.0996 0.107 0.115 0.124 0.133 0.143 0.1536.5 0.0865 0.0933 0.1005 0.1083 0.1166 0.1254 0.135 0.145 0.156 0.167 0.180 0.1936.6 0.109 0.117 0.127 0.136 0.147 0.158 0.170 0.182 0.196 0.210 0.226 0.2426.7 0.137 0.148 0.159 0.171 0.185 0.199 0.214 0.230 0.247 0.265 0.284 0.3056.8 0.172 0.186 0.200 0.216 0.232 0.250 0.269 0.289 0.310 0.333 0.358 0.3846.9 0.217 0.234 0.252 0.271 0.292 0.314 0.338 0.363 0.390 0.419 0.450 0.4827.0 0.273 0.294 0.317 0.342 0.368 0.396 0.425 0.457 0.491 0.527 0.566 0.6077.1 0.343 0.370 0.399 0.430 0.462 0.497 0.535 0.575 0.617 0.663 0.711 0.7627.2 0.432 0.466 0.502 0.540 0.581 0.625 0.672 0.722 0.776 0.833 0.893 0.9587.3 0.543 0.586 0.631 0.679 0.731 0.786 0.845 0.908 0.975 1.05 1.12 1.207.4 0.683 0.736 0.793 0.854 0.918 0.988 1.061 1.140 1.224 1.31 1.41 1.517.5 0.858 0.925 0.996 1.07 1.15 1.24 1.33 1.43 1.54 1.65 1.77 1.897.6 1.08 1.16 1.25 1.35 1.45 1.56 1.67 1.80 1.93 2.07 2.21 2.377.7 1.35 1.46 1.57 1.69 1.82 1.95 2.10 2.25 2.41 2.59 2.77 2.977.8 1.70 1.83 1.97 2.12 2.28 2.44 2.62 2.82 3.02 3.24 3.46 3.717.9 2.13 2.29 2.46 2.65 2.85 3.06 3.28 3.52 3.77 4.04 4.32 4.628.0 2.66 2.87 3.08 3.31 3.56 3.82 4.10 4.39 4.70 5.03 5.38 5.758.1 3.33 3.58 3.85 4.14 4.44 4.76 5.10 5.46 5.85 6.25 6.68 7.148.2 4.16 4.47 4.80 5.15 5.52 5.92 6.34 6.78 7.25 7.75 8.27 8.828.3 5.18 5.56 5.97 6.40 6.86 7.34 7.85 8.39 8.96 9.56 10.2 10.98.4 6.43 6.90 7.40 7.93 8.48 9.07 9.69 10.3 11.0 11.7 12.5 13.38.5 7.97 8.54 9.14 9.78 10.45 11.16 11.90 12.7 13.5 14.4 15.2 16.28.6 9.83 10.5 11.2 12.0 12.8 13.6 14.5 15.5 16.4 17.4 18.5 19.58.7 12.07 12.9 13.8 14.7 15.6 16.6 17.6 18.7 19.8 21.0 22.2 23.48.8 14.7 15.7 16.7 17.8 18.9 20.0 21.2 22.5 23.7 25.1 26.4 27.88.9 17.9 19.0 20.2 21.4 22.7 24.0 25.3 26.7 28.2 29.6 31.1 32.6

1Table provided by Teresa Norberg-King, Environmental Research Laboratory, Duluth, Minnesota. Also see Emerson, et. al., 1975,

Thurston, et. al, 1974, and USEPA, 1985.
43

9.2 PRELIMINARY TOXICITY RANGE-FINDING TESTS

9.2.1 USEPA Regional and State personnel generally have observed that it is not necessary to conduct a toxicity

range-finding test prior to initiating a static, acute, definitive toxicity test. However, when preparing to perform a

static test with an sample of completely unknown quality, or before initiating a flow-through test, it is advisable to

conduct a preliminary toxicity range-finding test. 

9.2.2 A toxicity range-finding test ordinarily consists of a down-scaled, abbreviated static acute test in which

groups of five organisms are exposed to several widely-spaced sample dilutions in a logarithmic series, such as

100%, 10.0%, 1.00%, and 0.100%, and a control, for 8-24 h. Caution: if the sample must also be used for the fullscale definitive test, the 36-h limit on holding time (Section 8, , Effluent and Receiving Water Sampling and Sample

Handling, Subsection 8.5.4) must not be exceeded before the definitive test is initiated. 

9.2.3 It should be noted that the toxicity (LC50) of a sample observed in a range-finding test may be significantly

different from the toxicity observed in the follow-up definitive test because: (1) the definitive test is usually longer;

and (2) the test may be performed with a sample collected at a different time, and possibly differing significantly in

the level of toxicity.

9.3 MULTI-CONCENTRATION (DEFINITIVE) EFFLUENT TOXICITY TESTS 

9.3.1 The tests recommended for use in determining discharge permit compliance in the NPDES program are

multi-concentration, or definitive, tests which provide (1) a point estimate of effluent toxicity in terms of a LC50, or

(2) a no-observed-adverse-effect concentration (NOAEC) defined in terms of mortality, and obtained by hypothesis

testing. The tests may be static non-renewal, static renewal, or flow-through. 

9.3.2 The tests consist of a control and a minimum of five effluent concentrations. USEPA recommends the use of

a $0.5 dilution factor for selecting effluent test concentrations. Effluent test concentrations of 6.25%, 12.5%, 25%,

50%, and 100% are commonly used, however, test concentrations should be selected independently for each test

based on the objective of the study, the expected range of toxicity, the receiving water concentration, and any

available historical testing information on the effluent. USEPA (2000a) provides additional guidance on choosing

appropriate test concentrations.

9.3.3 When these tests are used in determining compliance with permit limits, effluent test concentrations should

be selected to bracket the receiving water concentration (RWC). This may be achieved by selecting effluent test

concentrations in the following manner: (1) 100% effluent, (2) [RWC + 100]/2, (3) RWC, (4) RWC/2, and

(5) RWC/4. For example, where the RWC = 50%, appropriate effluent concentrations may be 100%, 75%, 50%,

25%, and 12.5%.

9.3.4 If acute/chronic ratios are to be determined by simultaneous acute and short-term chronic tests with a single

species, using the same sample, both types of tests must use the same test conditions, i.e., temperature, water

hardness, salinity, etc.

9.4 RECEIVING WATER TESTS 

9.4.1 Receiving water toxicity tests generally consist of 100% receiving water and a control. The total hardness or

salinity of the control should be comparable to the receiving water.

9.4.2 The data from the two treatments are analyzed by hypothesis testing to determine if test organism survival in

the receiving water differs significantly from the control. A minimum of four replicates and 10 organisms per

replicate are required for each treatment (see Tables 12-19).
44

9.4.3 In cases where the objective of the test is to estimate the degree of toxicity of the receiving water, a

definitive, multi-concentration test is performed by preparing dilutions of the receiving water, using a $0.5 dilution

series, with a suitable control water. 

9.5 STATIC TESTS

9.5.1 Static tests may be non-renewal or renewal.

9.5.2 An excess volume of each dilution is prepared to provide sufficient material for toxicity testing and routine

chemical analyses. The solutions are well mixed with a glass rod, TEFLON® stir bar, or other means. Aliquots of

each sample concentration are delivered to the test chambers, and the chambers are arranged in random order. The

test solutions are brought to the required temperature, and the test organisms are added. The remaining volumes of

each sample concentration are used, as necessary, for the chemical analyses. 

9.5.3 Saline dilution water can be prepared by adding dry salts (FORTY FATHOMS® or equivalent, or modified

GP2) or hypersaline brine to de-ionized water, or a suitable surface freshwater, to adjust the salinity of the entire

dilution series. If saline receiving water is used as the diluent, a salinity control must be prepared using deionized

water and dried sea salts to determine if the addition of sea salts alone has an adverse effect on the test organisms. It

may be desirable to conduct static toxicity tests at several salinities. 

9.5.4 If the effluent has low salinity, but the test is to be conducted with a salt water organism, the test solutions

may be prepared by adding dry ocean salts or hypersaline brine to a sufficient quantity of 100% effluent to raise the

salinity to the required level, which will depend on the objectives of the test and the policy of the regulatory agency. 

After the addition of the dried salts, stir gently for 30 to 60 min, preferably with a magnetic stirrer, to ensure that the

salts are in solution. It is important to check the final salinity with a refractometer. 

9.5.5 Addition of dry salts to effluents and dilution water may change the pH and affect the toxicity of the waste. 

If the objective of the test is to determine the toxicity of the effluent at the original pH, the pH of the

salinity-adjusted solutions can be brought to the required level by dropwise addition of 1N HCl or 1N NaOH. It is

recommended that a concurrent test be conducted with salinity-adjusted effluent in which the pH has not been

altered after adding the salt.

9.5.6 The volume of the effluent used must be sufficient to prepare all percent concentrations of the effluent

needed for the toxicity test and for routine chemical analysis. For example, to conduct tests with Menidia, the use of

200 mL of test solution in each of duplicate exposure vessels and five concentrations of effluent (10 exposure

vessels), would require a total of 1 L of 100% effluent. However, to provide sufficient volumes of test solutions for

routine chemical analysis and for toxicity testing, additional effluent would be required (1.5-2.0 L). 

9.5.7 A standard control lacking thiosulfate should be included in tests where the dilution water was prepared by

dechlorinating tap water with thiosulfate. 

9.5.8 If, within 1 h of the start of the test, 100% mortality has occurred in the higher effluent concentrations (such

as 100% and 50%), additional concentrations of effluents, such as 3.1%, 1.6%, and 0.8%, are added to the test at the

lower end of the concentration series. 

9.5.9 pH drift during acute, static-renewal, or non-renewal toxicity tests may contribute to artifactual toxicity when

ammonia or other pH-dependent toxicants (such as metals) are present. This problem can be minimized by

conducting a test in a static-renewal mode rather than a non-renewal mode, or the problem can be avoided by

conducting the test in a flow-through mode, rather than a static-renewal or non-renewal mode.
45

9.6 FLOW-THROUGH TESTS

9.6.1 Flow-through tests are usually performed with the same effluent concentrations that are used for static tests,

except that where the receiving water is saline and the effluent is not, 100% effluent cannot be tested with a marine

organism. Examples of flow-through test systems are provided in the Appendix. Small organisms, such as mysids

and daphnids, are confined in screened enclosures placed in the flow-through chambers. More than one species

may be used in the same test chamber in a given test, if segregated.

9.6.2 The dilutor system should be operated long enough prior to adding the test organisms to calibrate the dilutor

and make the necessary adjustments in the temperature, flow rate through the test chambers, and aeration. The flow

rate through the proportional dilutor must provide for a minimum of five 90% replacements of water volume in each

test chamber every 24 h (see Figure 2). This replacement rate should provide sufficient flow to maintain an

adequate concentration of dissolved oxygen. The dilutor should also be capable of maintaining the test

concentration at each dilution within 5% of the starting concentration for the duration of the test. The calibration of

the dilutor should be checked carefully before the test begins to determine the volume of effluent and dilution water

used in each portion of the effluent delivery system and the flow rate through each test chamber. The general

operation of the dilutor should be checked at least at the beginning and end of each day during the test. 

9.6.3 The control consists of the same dilution water, test conditions, procedures, and organisms used in testing the

effluent. In the event a test is to be conducted with salt water organisms, where each effluent dilution has a different

salinity, a static control is prepared for the lowest (or highest, in the case of high salinity, e.g. brine wastes) salinity

level used in the flow-through test to determine if salinity alone has any adverse effects on the test organisms.

9.7 NUMBER OF TEST ORGANISMS

9.7.1 A minimum of 20 organisms of a given species are exposed to each effluent concentration (Jensen, 1972). 

Small fish and invertebrates are captured with 4- to 8-mm inside diameter pipettes. Organisms larger than 10 mm

can be captured by dip net. In a typical toxicity test involving five effluent concentrations and a control (six

concentrations x 20 organisms per concentration), fish and other large test organisms are captured from a common

pool and distributed sequentially to the test chambers until the required number of organisms are placed in each. 

The test chambers are then positioned randomly. To avoid carryover of excess culture water in transferring small

organisms to the test chambers, it may be advantageous to distribute small organisms, such as daphnids, mysids, and

larval fish, first to small holding vessels, such as weighing boats, petri dishes, or small beakers. The water in the

intermediary holding vessels is then drawn down to a small volume and the entire lot is transferred to a test

chamber. In the case of daphnids, both excessive handling and carryover of culture water and can be avoided by

placing the tip of the transfer pipettes below the surface of the water in the test chambers and allowing the

organisms to swim out of the pipettes without discharging the contents. 

9.8 REPLICATE TEST CHAMBERS

9.8.1 Two or more test chambers are provided for each effluent concentration and the control. Although the data

from duplicate chambers are usually combined to determine the LC50 and confidence interval, the practice of

dividing the test population for each effluent concentration between two or more replicate chambers has several

advantages and is considered good laboratory practice because it: (1) permits easier viewing and counting of test

organisms; (2) more easily avoids possible violations of loading limits, which might occur if all of the test

organisms are placed in a single test vessel; and (3) ensures against the invalidation of the test which might result

from accidental loss of a test vessel, where all of the test organisms for a given treatment are in a single chamber. 
46

9.9 LOADING OF TEST ORGANISMS

9.9.1 A limit is placed on the loading (weight) of organisms per liter of test solution to minimize the depletion of

dissolved oxygen, the accumulation of injurious concentrations of metabolic waste products, and/or stress induced

by crowding, any of which could significantly affect the test results. However, the probability of exceeding loading

limits is greatly reduced with the use of very young test organisms. 

9.9.2 For both renewal and non-renewal static tests, loading in the test solutions must not exceed the following live

weights: 1.1 g/L at 15°C, 0.65 g/L at 20°C, or 0.40 g/L at 25°C. 

9.9.3 For flow-through tests, the live weight of test organisms in the test chambers must not exceed 7.0 g/L of test

solution at l5°C, or 2.5 g/L at 25°C. 

9.10 ILLUMINATION

9.10.1 Light of the quality and intensity normally obtained in the laboratory during working hours is adequate (10-

20 μE/m2

/s or 50-100 ft-c). A uniform photoperiod of 16 h light and 8 h darkness can be achieved in the laboratory

or environmental chamber, using automatic timers. 

9.11 FEEDING

9.11.1 Where indicated in the test summary tables (Tables 12-19), food is made available to test organisms while

holding before they are placed in the test chambers. The organisms are fed at test renewal, 48 h after the test is

initiated, if Regional or State policy requires a 96-h test duration.

9.11.2 Where Artemia nauplii are fed, the nauplii are first concentrated on a NITEX® screen and then are

resuspended in fresh or salt water, depending on the salinity of the test solutions, using just enough water to form a

slurry that can be transferred by pipette. It should be noted that Artemia nauplii placed in freshwater usually die in

4 h, generally are not eaten after death, and decay rapidly, whereas those placed in saline water remain viable and

can serve as food for the duration of the test.

9.11.3 Problems caused by feeding, such as the possible alteration of the toxicant concentration, the build-up of

food and metabolic wastes and resulting oxygen demand, are common in static test systems. Where feeding is

necessary, excess food should be removed daily by aspirating with a pipette. 

9.11.4 Feeding does not cause the above problems in flow-through systems. However, it is advisable to remove

excess food, fecal material, and any particulate matter that settles from the effluent, from the bottom of the test

vessels daily by aspirating with a pipette. 

9.12 TEST TEMPERATURE

9.12.1 Test temperature will depend on the test species and objectives of the test (see Tables 12-19). Where acute

and short-term chronic toxicity tests are performed simultaneously with the same species to determine acute:chronic

ratios, both tests must be performed at the chronic test temperature. The average daily temperature of the test

solutions should be maintained within ±1°C of the selected test temperature, for the duration of the test. This can be

accomplished for static tests by use of a water bath or environmental chamber, and in flow-through tests by passing

the effluent and/or dilution water through separate coils immersed in a heating or cooling water bath prior to

entering the dilutor system. Coils should be made from materials recommended in Section 5, Facilities and

Equipment.
47

9.13 STRESS

9.13.1 Minimize stress on test organisms by avoiding unnecessary disturbances. 

9.14 DISSOLVED OXYGEN CONCENTRATION

9.14.1 Aeration during the test may alter the results and should be used only as a last resort to maintain the

required DO. Aeration can reduce the apparent toxicity of the test solutions by stripping them of highly volatile

toxic substances, or increase its toxicity by altering the pH. However, the DO in the test solution should not be

permitted to fall below 4.0 mg/L for warm water species and 6.0 mg/L for cold water species. Oxygen saturation

values in fresh and saline waters can be determined from Figure 3 and Table 11, respectively. 
48

TABLE 11. OXYGEN SOLUBILITY (MG/L) IN WATER AT EQUILIBRIUM WITH AIR AT 760 MM HG

(AFTER RICHARDS AND CORWIN, 1956) 

Temp Salinity (‰)

°C 0 5 10 15 20 25 30 35 40 45

0 14.2 13.8 13.4 12.9 12.5 12.1 11.7 11.2 10.8 10.6

1 13.8 13.4 13.0 12.6 12.2 11.8 11.4 11.0 10.6 10.3

2 13.4 13.0 12.6 12.2 11.9 11.5 11.1 10.7 10.3 10.0

3 13.1 12.7 12.3 11.9 11.6 11.2 10.8 10.4 10.0 9.8

4 12.7 12.3 12.0 11.6 11.3 10.9 10.5 10.1 9.8 9.5

5 12.4 12.0 11.7 11.3 11.0 10.6 10.2 9.8 9.5 9.3

6 12.1 11.7 11.4 11.0 10.7 10.3 10.0 9.6 9.3 9.1

8 11.5 11.2 10.8 10.5 10.2 9.8 9.5 9.2 8.9 8.7

10 10.9 10.7 10.3 10.0 9.7 9.4 9.1 8.8 8.5 8.3

12 10.5 10.2 9.9 9.6 9.3 9.0 8.7 8.4 8.1 7.9

14 10.0 9.7 9.5 9.2 8.9 8.6 8.3 8.1 7.8 7.6

16 9.6 9.3 9.1 8.8 8.5 8.3 8.0 7.7 7.5 7.3

18 9.2 9.0 8.7 8.5 8.2 8.0 7.7 7.5 7.2 7.1

20 8.9 8.6 8.4 8.1 7.9 7.7 7.4 7.2 6.9 6.8

22 8.6 8.4 8.1 7.9 7.6 7.4 7.2 6.9 6.7 6.6

24 8.3 8.1 7.8 7.6 7.4 7.2 6.9 6.7 6.5 6.4

26 8.1 7.8 7.6 7.4 7.2 7.0 6.7 6.5 6.3 6.1

28 7.8 7.6 7.4 7.2 7.0 6.8 6.5 6.3 6.1 6.0

30 7.6 7.4 7.1 6.9 6.7 6.5 6.3 6.1 5.9 5.8

32 7.3 7.1 6.9 6.7 6.5 6.3 6.1 5.9 5.7 5.6
49
50

9.14.2 In static tests, low DOs commonly occur in the higher concentrations of wastewater. Aeration is

accomplished by bubbling air through a pipet at the rate of 100 bubbles/min. If aeration is necessary, all test

solutions must be aerated. It is advisable to monitor the DO closely during the first few hours of the test. Samples

with a potential DO problem generally show a downward trend in DO within 4 to 8 h after the test is started. Unless

aeration is initiated during the first 8 h of the test, the DO may be exhausted during an unattended period, thereby

invalidating the test. 

9.14.3 In most flow-through tests, DO depletion is not a problem in the test chambers because aeration occurs as

the liquids pass through the dilutor system. If the DO decreases to a level that would be a source of additional

stress, the turnover rate of the solutions in the test chambers must be increased sufficiently to maintain acceptable

DO levels. If the increased turnover rate does not maintain adequate DO levels, aerate the dilution water prior to the

addition of the effluent, and aerate all test solutions. To reduce the potential for driving off volatile compounds in

the wastewater, aeration may be accomplished by bubbling air through a 1 mL pipet at a rate of no more than 100

bubbles/min, using an air valve to control the flow.

9.14.4 Caution must be exercised to avoid excessive aeration. Turbulence caused by aeration should not result in a

physical stress to the test organisms. When aeration is used, the methodology must be detailed in the report. For

safety reasons, pure oxygen should not be used to aerate test solutions.

9.15 TEST DURATION

9.15.1 Test duration may vary from 24 to 96 h depending on the objectives of the test and the requirements of the

regulatory authority. For specific information on test duration, see the tables summarizing the test conditions

below.

9.16 ACCEPTABILITY OF TEST RESULTS

9.16.1 For the test results to be acceptable, survival in controls must be at least 90%. Tests in which the control

survival is less than 90% are invalid, and must be repeated. In tests with specific chemicals, the concentration of the

test material must not vary more than 20% at any treatment level during the exposure period. 

9.16.2 Upon subsequent completion of a valid test, the results of all tests, valid and invalid, are reported to the

regulatory authority with an explanation of the tests performed and results.

9.17 SUMMARY OF TEST CONDITIONS FOR THE PRINCIPAL TEST ORGANISMS

9.17.1 Summaries of the test conditions for the daphnids, Ceriodaphnia dubia, Daphnia pulex, and D. magna,

fathead minnows, Pimephales promelas, rainbow trout, Oncorhynchus mykiss, brook trout, Salvelinus fontinalis, the

mysids, Mysidopsis bahia and Holmesimysis costata, sheepshead minnows, Cyprinodon variegatus, and silversides,

Menidia beryllina, M. menidia, and M. peninsulae, are provided in Tables 12-19.
51

TABLE 12. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

CERIODAPHNIA DUBIA ACUTE TOXICITY TESTS WITH EFFLUENTS AND

RECEIVING WATERS (TEST METHOD 2002.0)1

 1. Test type: Static non-renewal, static-renewal, or flow-through (available

options)

 2. Test duration: 24, 48, or 96 h (available options)

 3. Temperature:2 20°C ±1°C; or 25°C ±1°C (recommended) 

Test temperatures must not deviate (i.e., maximum minus

minimum temperature) by more than 3°C during the test (required) 

 4. Light quality: Ambient laboratory illumination (recommended) 

 5. Light intensity: 10-20 μE/m2

/s (50-100 ft-c) (recommended)

(ambient laboratory levels) 

 6. Photoperiod: 16 h light, 8 h darkness (recommended) 

 7. Test chamber size: 30 mL (recommended minimum)

 8. Test solution volume: 15 mL (recommended minimum)

 9. Renewal of test 

 solutions: After 48 h (required minimum) 

10. Age of test organisms: Less than 24-h old (required) 

11. No. organisms per

 test chamber: 5 for effluent and receiving water tests (required minimum) 

12. No. replicate chambers 

 per concentration: 4 for effluent and receiving water tests (required minimum) 

13. No. organisms per

 concentration: 20 for effluent and receiving water tests (required minimum) 

14. Feeding regime: Feed YCT and Selenastrum while holding prior to the test; newlyreleased young should have food available a minimum of 2 h prior

to use in a test; add 0.1 mL each of YCT and Selenastrum 2 h prior

to test solution renewal at 48 h (recommended) 

15. Test chamber cleaning:

16. Test chamber aeration:

Cleaning not required 

None (recommended)

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed 

 above is identified as required or recommended (see Subsection 12.2 for more information on test review). 

 Additional requirements may be provided in individual permits, such as specifying a given test condition 

 where several options are given in the method. 

2

 Acute and chronic toxicity tests performed simultaneously to obtain acute/chronic ratios must use the same 

 temperature and dilution water. 
52

TABLE 12. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

CERIODAPHNIA DUBIA ACUTE TOXICITY TESTS WITH EFFLUENTS AND RECEIVING

WATERS (TEST METHOD 2002.0) (CONTINUED)

17. Dilution water: Moderately hard synthetic water prepared using MILLIPORE

MILLI-Q® or equivalent deionized water and reagent grade

chemicals or 20% DMW (see Section 7, Dilution Water), receiving

water, ground water, or synthetic water, modified to reflect

receiving water hardness (available options)

18. Test concentrations: Effluents: 5 and a control (required minimum) 

Receiving Waters: 100% receiving water and a control

(recommended) 

19. Dilution series: Effluents: $0.5 dilution series (recommended) 

Receiving Waters: None, or $0.5 dilution series (recommended) 

20. Endpoint: Effluents: Mortality (required) 

Receiving Waters: Mortality (required)

21. Sampling and sample

 holding requirements:

Effluents: Grab or composite sample first used within 36 h of

completion of the sampling period (required) 

Receiving Waters: Grab or composite sample first used within 36

h of completion of the sampling period (recommended)

22. Sample volume required: 1 L (recommended) 

23. Test acceptability

 criterion:

90% or greater survival in controls (required) 
53

TABLE 13. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

DAPHNIA PULEX AND D. MAGNA ACUTE TOXICITY TESTS WITH EFFLUENTS AND

RECEIVING WATERS (TEST METHOD 2021.0)1

 1. Test type: Static non-renewal, static-renewal, or flow-through (available

options)

 2. Test duration: 24, 48, or 96 h (available options)

 3. Temperature:2 20°C ±1°C; or 25°C ±1°C (recommended)

Test temperatures must not deviate (i.e., maximum minus

minimum temperature) by more than 3°C during the test (required) 

 4. Light quality: Ambient laboratory illumination (recommended) 

 5. Light intensity: 10-20 μE/m2

/s (50-100 ft-c) 

(ambient laboratory levels) (recommended) 

 6. Photoperiod: 16 h light, 8 h darkness (recommended)

 7. Test chamber size: 30 mL (recommended minimum)

 8. Test solution volume: 25 mL (recommended minimum)

 9. Renewal of test 

 solutions: After 48 h (required minimum) 

10. Age of test organisms: Less than 24-h old (required) 

11. No. organisms per

 test chamber: 5 for effluent and receiving water tests (required minimum) 

12. No. replicate chambers

 per concentration: 4 for effluent and receiving water tests (required minimum) 

13. No. organisms per

 concentration: 20 for effluent and receiving water tests (required minimum) 

14. Feeding regime: Feed YCT and Selenastrum while holding prior to the test; newlyreleased young should have food available a minimum of 2 h prior

to use in a test; add 0.1 mL each of YCT and Selenastrum 2 h prior

to test solution renewal at 48 h (recommended) 

15. Test chamber cleaning: Cleaning not required 

16. Test chamber aeration: None (recommended) 

17. Dilution water: Moderately hard synthetic water prepared using MILLIPORE

MILLI-Q® or equivalent deionized water and reagent grade

chemicals or 20% DMW (see Section 7, Dilution Water), receiving

water, ground water, or synthetic water, modified to reflect

receiving water hardness (available options)

1 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed 

 above is identified as required or recommended (see Subsection 12.2 for more information on test review). 

 Additional requirements may be provided in individual permits, such as specifying a given test condition 

 where several options are given in the method.

2

 Acute and chronic toxicity tests performed simultaneously to obtain acute/chronic ratios must use the same 

 temperature and dilution water. 
54

TABLE 13. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

DAPHNIA PULEX AND D. MAGNA ACUTE TOXICITY TESTS WITH EFFLUENTS AND

RECEIVING WATER (TEST METHOD 2021.0) (CONTINUED)

18. Test concentrations: Effluents: 5 and a control (required minimum) 

Receiving Waters: 100% receiving water and a control

(recommended) 

19. Dilution series: Effluents: $0.5 dilution series (recommended) 

Receiving Waters: None, or $0.5 dilution series (recommended) 

20. Endpoint: Effluents: Mortality (required) 

Receiving Waters: Mortality (required)

21. Sampling and sample

 holding requirements:

Effluents: Grab or composite sample first used within 36 h of

completion of the sampling period (required) 

Receiving Waters: Grab or composite sample first used within 36 h

of completion of the sampling period (recommended) 

22. Sample volume required: 1 L (recommended) 

23. Test acceptability 

 criterion: 90% or greater survival in controls (required)
55

TABLE 14. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

FATHEAD MINNOW, PIMEPHALES PROMELAS, ACUTE TOXICITY TESTS WITH

EFFLUENTS AND RECEIVING WATERS (TEST METHOD 2000.0)1,2

 1. Test type: Static non-renewal, static-renewal, or flow-through (available

options)

 2. Test duration: 24, 48, or 96 h (available options) 

 3. Temperature:3 20°C ±1°C; or 25°C ±1°C (recommended) 

Test temperatures must not deviate (i.e., maximum minus minimum

temperature) by more than 3°C during the test (required) 

 4. Light quality: Ambient laboratory illumination (recommended) 

 5. Light intensity: 10-20 μE/m2

/s (50-100 ft-c) 

(ambient laboratory levels) (recommended) 

 6. Photoperiod: 16 h light, 8 h darkness (recommended) 

 7. Test chamber size: 250 mL (recommended minimum) 

 8. Test solution volume: 200 mL (recommended minimum)

 9. Renewal of test 

 solutions: After 48 h (required minimum) 

10. Age of test organisms: 1-14 days; less than or equal to 24-h range in age (required) 

11. No. organisms per

 test chamber: 10 for effluent and receiving water tests (required minimum) 

12. No. replicate chambers

 per concentration:

2 for effluent tests (required minimum) 

4 for receiving water tests (required minimum)

13. No. organisms 

 per concentration:

20 for effluent tests (required minimum) 

40 for receiving water tests (required minimum)

14. Feeding regime: Artemia nauplii are made available while holding prior to the test;

add 0.2 mL Artemia nauplii concentrate 2 h prior to test solution

renewal at 48 h (recommended) 

15. Test chamber cleaning: Cleaning not required 

16. Test solution aeration: None, unless DO concentration falls below 4.0 mg/L; rate should

not exceed 100 bubbles/min (recommended) 

1

 Cyprinella leedsi (Bannerfish shiner, formerly Notropis leedsi; AFS, 1991) can be used with the test 

 conditions in this table, where it is the required test organism in NPDES permits.

2

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed 

 above is identified as required or recommended (see Subsection 12.2 for more information on test review). 

 Additional requirements may be provided in individual permits, such as specifying a given test condition 

 where several options are given in the method.

3

 Acute and chronic toxicity tests performed simultaneously to obtain acute/chronic ratios must use the same 

 temperature and dilution water.
56

TABLE 14. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

FATHEAD MINNOW, PIMEPHALES PROMELAS, ACUTE TOXICITY TESTS WITH

EFFLUENTS AND RECEIVING WATERS1

 (TEST METHOD 2000.0) (CONTINUED)

17. Dilution water: Moderately hard synthetic water prepared using MILLIPORE

MILLI-Q® or equivalent deionized water and reagent grade

chemicals or 20% DMW (see Section 7, Dilution Water), receiving

water, ground water, or synthetic water, modified to reflect

receiving water hardness. (available options) 

18. Test concentrations: Effluents: 5 and a control (required minimum) 

Receiving Waters: 100% receiving water and a control

(recommended) 

19. Dilution series: Effluents: $0.5 dilution series (recommended) 

Receiving Waters: None, or $ 0.5 dilution series (recommended) 

20. Endpoint: Effluents: Mortality (required) 

Receiving Waters: Mortality (required)

21. Sampling and sample

 holding requirements:

Effluents: Grab or composite sample first used within 36 h of

completion of the sampling period (required) 

Receiving Waters: Grab or composite sample first used within 36 h

of completion of the sampling period (recommended) 

22. Sample volume required: 2 L for effluents and receiving waters (recommended) 

23. Test acceptability

 criterion: 90% or greater survival in controls (required) 
57

TABLE 15. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

RAINBOW TROUT, ONCORHYNCHUS MYKISS, AND BROOK TROUT, SALVELINUS

FONTINALIS, ACUTE TOXICITY TESTS WITH EFFLUENTS AND RECEIVING WATERS

(TEST METHOD 2019.0)1

 1. Test type: Static non-renewal, static-renewal, or flow-through (available

options)

 2. Test duration: 24, 48, or 96 h (available options) 

 3. Temperature: 12°C ±1°C (recommended) 

Test temperatures must not deviate (i.e., maximum minus

minimum temperature) by more than 3°C during the test (required) 

 4. Light quality: Ambient laboratory illumination (recommended) 

 5. Light intensity: 10-20 μE/m2

/s (50-100 ft-c)

(ambient laboratory levels) (recommended) 

 6. Photoperiod: 16 h light, 8 h darkness. Light intensity should be raised gradually

over a 15 min period at the beginning of the photoperiod, and

lowered gradually at the end of the photoperiod, using a dimmer

switch or other suitable device. (recommended) 

 7. Test chamber size: 5 L (recommended minimum) (test chambers should be covered to

prevent fish from jumping out) 

 8. Test solution volume: 4 L (recommended minimum)

 9. Renewal of test 

 solutions: After 48 h (required minimum) 

10. Age of test organisms: Rainbow Trout: 15-30 days (after yolk sac absorption to 30 days)

(required)

Brook Trout: 30-60 days (required) 

11. No. organisms per

 test chamber: 10 for effluent and receiving water tests (required minimum) 

12. No. replicate chambers 

 per concentration:

2 for effluent tests (required minimum) 

4 for receiving water tests (required minimum) 

13. No. organisms per

 concentration:

20 for effluent tests (required minimum) 

40 for receiving water tests (required minimum) 

14. Feeding regime: Feeding not required 

15. Test chamber cleaning: Cleaning not required 

16. Test solution aeration: None, unless DO concentration falls below 6.0 mg/L; rate should

not exceed 100 bubbles/min (recommended) 

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed 

 above is identified as required or recommended (see Subsection 12.2 for more information on test review). 

 Additional requirements may be provided in individual permits, such as specifying a given test condition 

 where several options are given in the method.
58

TABLE 15. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

RAINBOW TROUT, ONCORHYNCHUS MYKISS, AND BROOK TROUT, SALVELINUS

FONTINALIS, ACUTE TOXICITY TESTS WITH EFFLUENTS AND RECEIVING WATERS

(TEST METHOD 2019.0) (CONTINUED)

17. Dilution water: Moderately hard synthetic water prepared using MILLIPORE

MILLI-Q® or equivalent deionized water and reagent grade

chemicals or 20% DMW (see Section 7, Dilution Water), receiving

water, ground water, or synthetic water, modified to reflect

receiving water hardness (available options)

18. Test concentrations: Effluents: 5 and a control (required minimum)

Receiving Waters: 100% receiving water and a control

(recommended) 

19. Dilution series: Effluents: $ 0.5 dilution series (recommended) 

Receiving Waters: None, or $ 0.5 dilution series (recommended) 

20. Endpoint: Effluents: Mortality (required) 

Receiving Waters: Mortality (required)

21. Sampling and sample holding

 requirements:

Effluents: Grab or composite sample first used within 36 h of

completion of the sampling period (required) 

Receiving Waters: Grab or composite sample first used within 36 h

of completion of the sampling period (recommended) 

22. Sample volume required: 20 L for effluents (recommended) 

40 L for receiving waters (recommended) 

23. Test acceptability

 criterion: 90% or greater survival in controls (required) 
59

TABLE 16. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

MYSID, MYSIDOPSIS BAHIA, ACUTE TOXICITY TESTS WITH EFFLUENTS AND

RECEIVING WATERS (TEST METHOD 2007.0)1

 1. Test type: Static non-renewal, static-renewal, or flow-through (available

options) 

 2. Test duration: 24, 48, or 96 h (available options) 

 3. Temperature2

: 20°C ±1°C; or 25°C ±1°C (recommended)

Test temperatures must not deviate (i.e., maximum minus minimum

temperature) by more than 3°C during the test (required) 

 4. Light quality: Ambient laboratory illumination (recommended) 

 5. Light intensity: 10-20 μE/m2

/s (50-100 ft-c)

(ambient laboratory levels) (recommended) 

 6. Photoperiod: 16 h light, 8 h darkness (recommended) 

 7. Test chamber size: 250 mL (recommended minimum)

 8. Test solution volume: 200 mL (recommended minimum)

 9. Renewal of test 

 solutions: After 48 h (required minimum) 

10. Age of test organisms: 1-5 days; less than or equal to 24-h range in age (required) 

11. No. organisms per

 test chamber: 10 for effluent and receiving water tests (required minimum) 

12. No. replicate chambers

 per concentration:

2 for effluent tests (required minimum)

4 for receiving water tests (required minimum) 

13. No. organisms per

 concentration:

20 for effluent tests (required minimum) 

40 for receiving water tests (required minimum) 

14. Feeding regime: Artemia nauplii are made available while holding prior to the test;

feed 0.2 mL of concentrated suspension of Artemia nauplii # 24-h

old, daily (approximately 100 nauplii per mysid) (recommended) 

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed 

 above is identified as required or recommended (see Subsection 12.2 for more information on test review). 

 Additional requirements may be provided in individual permits, such as specifying a given test condition 

 where several options are given in the method.

2

 Acute and chronic toxicity tests performed simultaneously to obtain acute/chronic ratios must use the same 

 temperature, salinity, and dilution water. 
60

TABLE 16. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

MYSID, MYSIDOPSIS BAHIA, ACUTE TOXICITY TESTS WITH EFFLUENTS AND

RECEIVING WATERS1

 (TEST METHOD 2007.0) (CONTINUED)

15. Test chamber cleaning: Cleaning not required 

16. Test solution aeration: None, unless DO concentration falls below 4.0 mg/L; rate should

not exceed 100 bubbles/min (recommended) 

17. Dilution water: 5-30‰ ±10%; Uncontaminated source of seawater, deionized

water mixed with hypersaline brine or artificial sea salts (HW

MARINEMIX®, FORTY FATHOMS®, modified GP2, or

equivalent) prepared with MILLI-Q® or equivalent deionized water

(see Section 7, Dilution Water); or receiving water (available

options)

18. Test concentrations: Effluents: 5 and a control (required minimum) 

Receiving Waters: 100% receiving water and a control

(recommended) 

19. Dilution series: Effluents: $0.5 dilution series (recommended) 

Receiving Waters: None, or $0.5 dilution series (recommended) 

20. Endpoint: Effluents: Mortality (required)

Receiving Waters: Mortality (required)

21. Sampling and sample

 holding requirements:

Effluents: Grab or composite sample first used within 36 h of

completion of the sampling period (required) 

Receiving Waters: Grab or composite sample first used within 36 h

of completion of the sampling period (recommended) 

22. Sample volume required: 1 L for effluents (recommended) 

2 L for receiving waters (recommended) 

23. Test acceptability

 criterion: 90% or greater survival in controls (required) 
61

TABLE 17. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

SHEEPSHEAD MINNOW, CYPRINODON VARIEGATUS, ACUTE TOXICITY TESTS WITH

EFFLUENTS AND RECEIVING WATERS (TEST METHOD 2004.0)1

 1. Test type: Static non-renewal, static-renewal, or flow-through (available

options) 

 2. Test duration: 24, 48, or 96 h (available options) 

 3. Temperature:2 20°C ±1°C; or 25°C ±1°C (recommended) 

Test temperatures must not deviate (i.e., maximum minus minimum

temperature) by more than 3°C during the test (required) 

 4. Light quality: Ambient laboratory illumination (recommended) 

 5. Light intensity: 10-20 μE/m2

/s (50-100 ft-c)

(ambient laboratory levels) (recommended) 

 6. Photoperiod: 16 h light, 8 h darkness (recommended) 

 7. Test chamber size: 250 mL (recommended minimum)

 8. Test solution volume: 200 mL (recommended minimum)

 9. Renewal of test 

 solutions: After 48 h (required minimum) 

10. Age of test organisms: 1-14 days; less than or equal to 24-h range in age (required) 

11. No. organisms per

 test chamber:

10 for effluent and receiving water tests (required minimum) 

12. No. replicate chambers

 per concentration:

2 for effluent tests (required minimum) 

4 for receiving water tests (required minimum) 

13. No. organisms per

 concentration:

20 for effluent tests (required minimum) 

40 for receiving water tests (required minimum) 

14. Feeding regime: Artemia nauplii are made available while holding prior to the test;

add 0.2 mL Artemia nauplii concentrate 2 h prior to test solution

renewal at 48 h (recommended) 

15. Test chamber cleaning: Cleaning not required 

16. Test solution aeration: None, unless DO concentration falls below 4.0 mg/L; rate should

not exceed 100 bubbles/min (recommended) 

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed 

 above is identified as required or recommended (see Subsection 12.2 for more information on test review). 

 Additional requirements may be provided in individual permits, such as specifying a given test condition 

 where several options are given in the method.

2

 Acute and chronic toxicity tests performed simultaneously to obtain acute/chronic ratios must use the same 

 temperature, salinity, and dilution water.
62

TABLE 17. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

SHEEPSHEAD MINNOW, CYPRINODON VARIEGATUS, ACUTE TOXICITY TESTS WITH

EFFLUENTS AND RECEIVING WATERS (TEST METHOD 2004.0) (CONTINUED)

17. Dilution water: 5-32‰ ±10%; Uncontaminated source of seawater, deionized

water mixed with hypersaline brine or artificial sea salts (HW

MARINEMIX®, FORTY FATHOMS®, modified GP2, or

equivalent) prepared with MILLI-Q® or equivalent deionized water

(see Section 7, Dilution Water); or receiving water (available

options)

18. Test concentrations: Effluents: 5 and a control (required minimum) 

Receiving Waters: 100% receiving water and a control

(recommended) 

19. Dilution series: Effluents: $0.5 dilution series (recommended) 

Receiving Waters: None, or $ 0.5 dilution series (recommended) 

20. Endpoint: Effluents: Mortality (required) 

Receiving Waters: Mortality (required)

21. Sampling and sample holding

 requirements:

Effluents: Grab or composite sample first used within 36 h of

completion of the sampling period (required) 

Receiving Waters: Grab or composite sample first used within 36 h

of completion of the sampling period (recommended) 

22. Sample volume required: 1 L for effluents (recommended) 

2 L for receiving waters (recommended) 

23. Test acceptability

 criterion: 90% or greater survival in controls (required) 
63

TABLE 18. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

SILVERSIDE, MENIDIA BERYLLINA, M. MENIDIA, AND M. PENINSULAE, ACUTE

TOXICITY TESTS WITH EFFLUENTS AND RECEIVING WATERS (TEST METHOD 2006.0)1

 1. Test type: Static non-renewal, static-renewal, or flow-through (available options)

 2. Test duration: 24, 48, or 96 h (available options)

 3. Temperature:2 20°C ±1°C; or 25°C ±1°C (recommended) 

Test temperatures must not deviate (i.e., maximum minus minimum

temperature) by more than 3°C during the test (required) 

 4. Light quality: Ambient laboratory illumination (recommended) 

 5. Light intensity: 10-20 μE/m2

/s (50-100 ft-c)

(ambient laboratory levels) (recommended) 

 6. Photoperiod: 16 h light, 8 h darkness (recommended) 

 7. Test chamber size: 250 mL (recommended minimum)

 8. Test solution volume: 200 mL (recommended minimum)

 9. Renewal of test 

 solutions: After 48 h (required minimum) 

10. Age of test organisms: 9-14 days; less than or equal to 24-h range in age (required) 

11. No. organisms per

 test chamber: 10 for effluent and receiving water tests (required minimum) 

12. No. replicate chambers

 per concentration:

2 for effluent tests (required minimum) 

4 for receiving water tests (required minimum) 

13. No. organisms per

 concentration:

20 for effluent tests (required minimum) 

40 for receiving water tests (required minimum) 

14. Feeding regime: Artemia nauplii are made available while holding prior to the test; add

0.2 mL Artemia nauplii concentrate 2 h prior to test solution renewal

at 48 h (recommended) 

15. Test chamber cleaning: Cleaning not required

16. Test solution aeration: None, unless DO concentration falls below 4.0 mg/L; rate should not

exceed 100 bubbles/min (recommended) 

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed above is 

 identified as required or recommended (see Subsection 12.2 for more information on test review). Additional 

 requirements may be provided in individual permits, such as specifying a given test condition where several 

 options are given in the method.

2

 Acute and chronic toxicity tests performed simultaneously to obtain acute/chronic ratios must use the same 

 temperature, salinity, and dilution water.
64

TABLE 18. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

SILVERSIDE, MENIDIA BERYLLINA, M. MENIDIA, AND M. PENINSULAE, ACUTE

TOXICITY TESTS WITH EFFLUENTS AND RECEIVING WATERS (TEST METHOD

2006.0) (CONTINUED)

17. Dilution water: 5-32‰ ±10%; Uncontaminated source of seawater, deionized

water mixed with hypersaline brine or artificial sea salts (HW

MARINEMIX®, FORTY FATHOMS®, modified GP2, or

equivalent) prepared with MILLI-Q® or equivalent deionized water

(see Section 7, Dilution Water); or receiving water (available

options)

 1-32‰ ±10% for M. beryllina;

 15-32‰ ±10% for M. menidia; and M. peninsulae

18. Test concentrations: Effluents: 5 and a control (required minimum) 

Receiving Waters: 100% receiving water and a control

(recommended) 

19. Dilution series: Effluents: $0.5 dilution series (recommended) 

Receiving Waters: None, or $0.5 dilution series (recommended) 

20. Endpoint: Effluents: Mortality (required) 

Receiving Waters: Mortality (required)

21. Sampling and sample

 holding requirements:

Effluents: Grab or composite sample first used within 36 h of

completion of the sampling period (required) 

Receiving Waters: Grab or composite sample first used within 36 h

of completion of the sampling period (recommended) 

22. Sample volume required: 1 L for effluents (recommended) 

2 L for receiving waters (recommended) 

23. Test acceptability

 criterion: 90% or greater survival in controls (required) 
65

TABLE 19. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR WEST

COAST MYSID, HOLMESIMYSIS COSTATA, ACUTE TOXICITY TESTS WITH EFFLUENTS

AND RECEIVING WATERS1

NOTE: This method is specific to Pacific Coast waters and is not listed at 40 CFR Part 136

for nationwide use. This method has been proposed but not yet approved at 40 CFR Part 136.

 1. Test type: Static non-renewal or static-renewal 

 2. Test duration: 24, 48, or 96 h 

 3. Temperature: 15°C ± 1°C for organisms collected South of Pt Conception,

CA

13°C ± 1°C for organisms collected North of Pt Conception,

CA

 4. Light quality: Ambient laboratory illumination 

 5. Light intensity: 10-20 μE/m2

/s (50-100 ft-c) (ambient laboratory levels)

 6. Photoperiod: 16 h light, 8 h darkness 

 7. Test chamber size: 1000 mL (minimum)

 8. Test solution volume: 200 mL (minimum)

 9. Renewal of test solutions: Minimum, at 48 h 

10. Age of test organisms: 3 to 4 days post-hatch juveniles

11. No. organisms per

test chamber: Minimum, 5 for effluent and receiving water tests

12. No. replicate chambers 

per concentration: Minimum, 5 for effluent tests and receiving water tests 

13. No. organisms per

concentration: Minimum, 25 for effluent tests and receiving water tests

14. Feeding regime: Artemia nauplii are made available while holding prior to the

test; feed 0.2 mL of concentrated suspension of Artemia nauplii

#24-h old, daily approximately 40 nauplii per mysid)

1 Acute and chronic toxicity tests performed simultaneously to obtain acute/chronic ratios must use the same

temperature and salinity. 
66

TABLE 19. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR WEST

COAST MYSID, HOLMESIMYSIS COSTATA, ACUTE TOXICITY TESTS WITH EFFLUENTS

AND RECEIVING WATERS (CONTINUED)

15. Test chamber cleaning: Cleaning not required 

16. Test solution aeration: None, unless DO concentration falls below 4.0 mg/L; rate

should not exceed 100 bubbles/min 

17. Dilution water: 34 ± 2‰ salinity; Uncontaminated seawater (1 μm filtered) or

hypersaline brine or equivalent (see Section 7, Dilution Water)

18. Test concentrations: Effluents: Minimum of five effluent concentrations and a

control 

Receiving Waters: 100% receiving water and a control 

19. Dilution series: Effluents: $0.5 dilution series 

Receiving Waters: None, or $0.5 dilution series 

20. Endpoint: Effluents: Mortality 

Receiving Waters: Mortality

21. Sampling and sample

holding requirements: Effluents: Grab or composite sample first used within 36 h of

completion of the sampling period 

Receiving Waters: Grab or composite sample first used within

36 h of completion of the sampling period 

22. Sample volume required: 1 L for effluents

2 L for receiving waters 

23. Test acceptability

criterion: 90% or greater survival in controls 
67

SECTION 10

TEST DATA

10.1 BIOLOGICAL DATA

10.1.1 Death is the "effect" used for determining toxicity to aquatic organisms in acute toxicity tests.

10.1.2 Death is not as easily determined for some organisms. The criteria usually employed in establishing death

are: (1) no movement of gills or appendages; and (2) no reaction to gentle prodding. 

10.1.3 The death of some organisms, such as mysids and larval fish, is easily detected because of a change in

appearance from transparent or translucent to opaque. General observations of appearance and behavior, such as

erratic swimming, loss of reflex, discoloration, excessive mucus production, hyperventilation, opaque eyes, curved

spine, hemorrhaging, molting, and cannibalism, should also be noted in the daily record. 

10.1.4 The test chambers should be checked for early mortality during the first few hours of the test. The number

of surviving organisms in each test chamber is recorded at the end of each 24-h period (Figure 4). When

recognizable, dead organisms should be removed during each observation period.

10.1.5 The species, source, and age of the test organisms should be recorded.

10.2 CHEMICAL AND PHYSICAL DATA

10.2.1 In static tests, at a minimum, pH, salinity or conductivity, and total residual chlorine are measured in the

highest concentration of test solution and in the dilution water at the beginning of the test, at test solution renewal,

and at test termination. If total residual chlorine is not detected in effluent or dilution water at test initiation, it is

unnecessary to measure total residual chlorine at test solution renewal or at test termination. It is also unnecessary to

measure total residual chlorine in laboratory prepared synthetic dilution waters. DO, pH, and temperature are

measured in the control and all test concentrations at the beginning of the test, daily thereafter, and at test

termination. 

10.2.1.1 It is recommended that total alkalinity and total hardness also be measured in the control and highest

effluent concentration at the beginning of the test and at test solution renewal.

10.2.1.2 Total ammonia is measured in samples where toxicity may be contributed by unionized ammonia (where

total ammonia might be $5 mg/L). 

10.2.1.3 The DO should be monitored closely (every 2 h) for the first 4 to 8 h, to guard against rapid DO depletion,

and is measured daily thereafter in all effluent concentrations in which there are surviving organisms, and at test

termination. It is recommended that test solution DO be recorded continuously in the test chamber at the highest

test solution concentration or in a surrogate vessel at a comparable test solution concentration and containing the

standard complement of test organisms.

10.2.1.4 At a minimum, test solution temperature is measured at the beginning of the test, and daily thereafter. 

Temperature measurements are made by placing thermometers or other temperature sensing devices directly in test

solutions or in a comparable volumes of water in chambers positioned in several locations among the test vessels to

determine test solution temperatures. It is recommended that test solution temperature be recorded continuously in

at least one test chamber or in a comparable volume of water in a surrogate vessel which is comparable to the test

chambers.
68

10.2.2 In flow-through tests, at a minimum, pH, salinity or conductivity, total alkalinity, total hardness, and total

residual chlorine are measured daily in the highest effluent concentration. DO and temperature are measured at the

beginning of the test, daily thereafter in the control and all test concentrations, and at test termination. 

10.2.3 The measurement of specific conductance is recommended because it is a very useful parameter in detecting

transient fluctuations in the chemical characteristics of effluents, and will indicate errors in test dilutions.

10.2.4 Where acute toxicity test methods are utilized to determine permit limits for toxic chemicals, at a minimum,

the concentration of the test material must be measured in each test concentration at test initiation, daily thereafter,

and at test termination.

10.2.5 Methods used for chemical analysis should be those specified for Section 304(h) of the CWA (USEPA,

1993b). For salinity measurements, a refractometer may be used if calibrated with a sample of known salinity. 
69
70
71

SECTION 11

ACUTE TOXICITY DATA ANALYSIS

11.1 INTRODUCTION

11.1.1 The objective of acute toxicity tests with effluents and receiving waters is to identify discharges of toxic

effluents in acutely toxic amounts. Data are derived from tests designed to determine the adverse effects of

effluents and receiving waters on the survival of the test organisms. The recommended effluent toxicity test

consists of a control and five or more concentrations of effluent (i.e., multi-effluent-concentration, or definitive

tests), in which the endpoint is (1) an estimate of the effluent concentration which is lethal to 50% of the test

organisms in the time period prescribed by the test, expressed as the LC50, or (2) the highest effluent concentration

at which survival is not significantly different from the control (No-Observed-Adverse-Effect Concentration, or

NOAEC). Receiving water tests may be single concentration or multi-concentration tests. The LC50 is determined

by the Graphical, Spearman-Karber, Trimmed Spearman-Karber, or Probit Method. The NOAEC is determined by

hypothesis testing. 

11.1.2 Some states require tests consisting of a control and a single concentration of effluent with a pass/fail

endpoint. Control survival must be 90% or greater for an acceptable test. The test "passes" if survival in the control

and effluent concentration equals or exceeds 90%. The test "fails" if survival in the effluent is less than 90%, and is

significantly different from control survival (which must be 90% or greater), as determined by hypothesis testing. 

11.1.3 The toxicity of receiving (surface) water can be determined with (1) a paired test consisting of four

replicates each of a suitable control and 100% surface water, or (2) a multi-concentration test. The results of the

first type of test (100% receiving water and a control) are analyzed by hypothesis testing. The results of the second

type of test may be analyzed by hypothesis testing or used to determine an LC50. 

11.1.4 The data analysis methods recommended in this manual have been chosen primarily because they are

(1) well-tested and well-documented, (2) applicable to most types of test data sets for which they are recommended,

but still powerful, and (3) most easily understood by non-statisticians. Many other methods were considered in the

selection process, and it is recognized that the methods selected are not the only possible methods of analysis of

acute toxicity data.

11.1.5 ROLE OF THE STATISTICIAN

11.1.5.1 The use of the statistical methods described in this manual for routine data analysis does not require the

assistance of a statistician. However, if the data appear unusual in any way, or fail to meet the necessary

assumptions, a statistician should be consulted. The choice of a statistical method to analyze toxicity test data and

the interpretation of the results of the analysis of the data can become problematic if there are anomalies in the data. 

Analysts who are not proficient in statistics are strongly advised to seek the assistance of a statistician before

selecting alternative methods of analysis and using the results.

11.1.6 INDEPENDENCE, RANDOMIZATION, AND OUTLIERS

11.1.6.1 A critical assumption in the statistical analysis of toxicity data is statistical independence among

observations. Statistical independence means that given knowledge of the true mean for a given concentration or

control, knowledge of the error in any one actual observation would provide no information about the error in any

other observation. One of the best ways to insure independence is to properly follow randomization procedures. 

The purpose of randomization is to avoid situations where test organisms are placed serially, by level of

concentration, into test chambers, or where all replicates for a test concentration are located adjacent to one another,

which could introduce bias into the test results.
72

11.1.6.2 Another area for potential bias of results is the presence of outliers. An outlier is an inconsistent or

questionable data point that appears unrepresentative of the general trend exhibited by the majority of the data. 

Outliers may be detected by tabulation of the data, plotting, and by an analysis of the residuals. An explanation

should be sought for any questionable data points. Without an explanation, data points should be discarded only

with extreme caution. If there is no explanation, the statistical analysis should be performed both with and without

the outlier, and the results of both analyses should be reported. For a discussion of techniques for evaluating

outliers, see Draper and John (1981). 

11.2 DETERMINATION OF THE LC50 FROM DEFINITIVE, MULTI-EFFLUENT-CONCENTRATION

ACUTE TOXICITY TESTS

11.2.1 The method used to estimate the LC50 from multi-concentration acute toxicity tests depends on the shape of

the tolerance distribution, and how well the effluent concentrations chosen characterize the cumulative distribution

function for the tolerance distribution (i.e., the number of partial mortalities). A review of effluent acute toxicity

data from the last 248 tests performed by the Ecological Support Branch, Environmental Services Division, EPA

Region 4, indicated the following pattern in the number of partial mortalities: (1) no partial mortalities (all or

nothing response) - 28%; (2) one partial mortality - 54%; (3) two or more partial mortalities - 16%; (4) LC50

occurring a one of the test concentrations - 2%.

11.2.1.1 Four methods for estimating the LC50 are presented below: the Graphical Method, the Spearman-Karber

Method, the Trimmed Spearman-Karber Method, and the Probit Method. The analysis scheme is shown in Figure

6. Included in the presentation of each method is a description of the method, the requirements for the method, a

description of the calculations involved in the method or a description of the computer program, and an example of

the calculations. 

11.2.1.2 The Probit Method, the Spearman-Karber Method, and the Trimmed Spearman-Karber Method are

designed to produce LC50 values and associated 95% confidence intervals. It should be noted that software used to

calculate point estimates occasionally may not provide associated 95% confidence intervals. This situation may

arise when test data do not meet specific assumptions required by the statistical methods, when point estimates are

outside of the test concentration range, and when specific limitations imposed by the software are encountered. 

USEPA (2000a) provides guidance on confidence intervals under these circumstances.

11.2.2 THE GRAPHICAL METHOD

11.2.2.1 Description

1. The Graphical Method is a mathematical procedure for calculating the LC50.

2. The procedure estimates the LC50 by linearly interpolating between points of a plot of

observed percent mortality versus the base 10 logarithm (log10) of percent effluent

concentration.

3. It does not provide a confidence interval for the LC50 estimate.

4. Use of the Graphical Method is only recommended when there are no partial mortalities.

11.2.2.2 Requirements

1. The only requirement for the Graphical Method is that the observed percent mortalities

bracket the 50%.
73
74

p s

i&1 ' p si ' (pi

%pi&1)/2

p a

i ' (p si &p s0 ) / (1&p s0 )

11.2.2.3 General Procedure

1. Let po, p1, ..., p k denote the observed proportion mortalities for the control and the k effluent

concentrations. The first step is to smooth the pi

 if they do not satisfy p o #... #p k. The

smoothing replaces any adjacent pi

's that do not conform to p o #... #p k, with their average.

For example, if pi

 is less than p i-1, then:

where: = the smoothed observed proporti p on mortality for effluent concentration i. s

i

2. Adjust the smoothed observed proportion mortality in each effluent concentration for mortality in the

control group using Abbott's formula (Finney, 1971). The adjustment takes the form:

where: = the smoothed observed pr p oportion mortality for the control. s

o

3. Plot the smoothed, adjusted data on 2-cycle semi-log graph paper with the logarithmic axis (the y axis)

used for percent effluent concentration and the linear axis (the x axis) used for observed percent mortality.

4. Locate the two points on the graph which bracket 50% mortality and connect them with a

straight line.

5. On the scale for percent effluent concentration, read the value for the point where the plotted

line and the 50% mortality line intersect. This value is the estimated LC50 expressed as a

percent effluent concentration.

11.2.2.4 Example Calculation

1. All-or-nothing data (Graphical Method) in Table 20 are used in the calculations. Note that in this case,

the data must be smoothed and adjusted for mortality in the controls.

2. To smooth the data, the observed proportion mortality for the control and the lower three

effluent concentrations must be averaged. The smoothed observed proportion mortalities

are as follows: 0.0125, 0.0125, 0.0125, 0.0125, 1.0, and 1.0.

3. The smoothed responses are adjusted for control mortality (see 11.2.2.3), where the smoothed response

for the control ( ) = 0.0125. The smoothed, p adjusted response proportions for the effluent s

o

concentrations are as follows: 0.0, 0.0, 0.0, 1.0, and 1.0. 

4. A plot of the smoothed, adjusted data is shown in Figure 7.

5. The two points on the graph which bracket the 50% mortality line (0% mortality at 25%

effluent, and 100% mortality at 50% effluent) are connected with a straight line.

6. The point at which the plotted line intersects the 50% mortality line is the estimated LC50.

The estimated LC50 = 35% effluent. 
75
76

TABLE 20. MORTALITY DATA (NUMBER OF DEAD ORGANISMS) FROM ACUTE TOXICITY TESTS

USED IN EXAMPLES OF LC50 DETERMINATIONS (20 ORGANISMS IN THE CONTROL

AND ALL TEST CONCENTRATIONS) 

Effluent Conc.

(%)

Method of Analysis

Graphical Spearman-Karber

Trimmed

Spearman-Karber Probit

CONTROL 1 1 1 0

6.25% 0 1 0 0

12.5% 0 0 2 3

25.0% 0 0 0 9

50.0% 20 13 0 20

100.0% 20 20 16 20

11.2.3 THE SPEARMAN-KARBER METHOD

11.2.3.1 Description

1. The Spearman-Karber Method is a nonparametric statistical procedure for estimating the

LC50 and the associated 95% confidence interval (Finney, 1978).

2. This procedure estimates the mean of the distribution of the log10 of the tolerance. If the log

tolerance distribution is symmetric, this estimate of the mean is equivalent to an estimate of

the median of the log tolerance distribution.

3. If the response proportions are not monotonically non-decreasing with increasing concentration (constant

or steadily increasing with concentration), the data are smoothed. 

4. Abbott's procedure is used to "adjust" the test results for mortality occurring in the control.

5. Use of the Spearman-Karber Method is recommended when partial mortalities occur in the

test solutions, but the data do not fit the Probit model.

11.2.3.2 Requirements

1. To calculate the LC50 estimate, the following must be true:

a. The smoothed adjusted proportion mortality for the lowest effluent concentration (not including the

control) must be zero.

b. The smoothed adjusted proportion mortality for the highest effluent concentration must be one.

2. To calculate the 95% confidence interval for the LC50 estimate, one or more of the smoothed adjusted

proportion mortalities must be between zero and one.

11.2.3.3 General Procedure

1. The first step in the estimation of the LC50 by the Spearman-Karber Method is to smooth

the observed response proportions, pi, if they do not satisfy p o #... #p k (see 11.2.2.3, Step

1).

2. Adjust the smoothed observed proportion mortality in each effluent concentration for mortality in the

control group using Abbott's formula (see 11.2.2.3, Step 2). 
77

V(m) ' '

k&1

i'2

p a

i (1&p ai ) (Xi%1&Xi&1)

2

4(ni

&1)

3. Plot the smoothed adjusted data on 2-cycle semi-log graph paper with the logarithmic axis (the y axis)

used for percent effluent concentration and the linear axis (the x axis) used for observed percent mortality.

4. Calculate the log10 of the estimated LC50, m, as follows:

m ' '

k&1

i'1

(p a

i%1&p ai ) (Xi

%Xi%1)

2

where: = the smoothed adjusted propor p tion mortality at concentration i a

i

Xi = the log10 of concentration i

k = the number of effluent concentrations tested, not including the control.

5. Calculate the estimated variance of m as follows:

where: Xi = the log10 of concentration i

ni = the number of organisms tested at effluent concentration i

p = the smoothed adjusted observed proportion mortality at effluent concentration i a

i

k = the number of effluent concentrations tested, not including the control.

6. Calculate the 95% confidence interval for m: m ± 2.0 V(m)

7. The estimated LC50 and a 95% confidence interval for the estimated LC50 can be found by

taking base10 antilogs of the above values.

8. With the exclusion of the plot in item 3, the above calculations can be carried out using the

Trimmed Spearman-Karber computer program mentioned in 11.2.4.3 and 11.2.4.4.

11.2.3.4 Example Calculation

1. Mortality data from a definitive, multi-concentration, acute toxicity test are given in Table

20. Note that the data must be smoothed and adjusted for mortality in the controls.

2. To smooth the data, the observed proportion mortality for the control, and the observed

proportion mortality for the 6.25%, 12.5%, and 25% effluent concentrations must be

averaged. The smoothed observed proportion mortalities are as follows: 0.025, 0.025,

0.025, 0.025, 0.65, and 1.00.

3. To adjust the smoothed, observed proportion mortality in each effluent concentration for

mortality in the control group, Abbott's formula must be used. After smoothing and

adjusting, the proportion mortalities for the effluent concentrations are as follows: 0.000,

0.000, 0.000; 0.641, and 1.000.

4. The data will not be plotted for this example. For an example of the plotting procedures, see

11.2.2.4.
78

1.656527 ± 2 0.0010977 ' (1.5902639, 1.7227901)

5. The log10 of the estimated LC50, m, is calculated as follows:

m = [(0.0000 - 0.0000)(0.7959 + 1.0969)]/2 +

[(0.0000 - 0.0000)(1.0969 + 1.3979)]/2 +

[(0.6410 - 0.0000)(1.3979 + 1.6990)]/2 + 

[(1.0000 - 0.6410)(1.6990 + 2.0000)]/2

= 1.656527

6. The estimated variance of m, V(m), is calculated as follows:

V(m) = (0.0000)(1.0000)(1.3979 - 0.7959)2

/4(19) +

(0.0000)(1.0000)(1.6990 - 1.0969)2

/4(19) +

(0.6410)(0.3590)(2.0000 - 1.3979)2

/4(19)

= 0.0010977

7. The 95% confidence interval for m is calculated as follows:

8. The estimated LC50 is as follows: antilog(1.656527) = 45.3%. 

9. The upper limit of the 95% confidence interval for the estimated LC50 is as follows:

antilog(1.7227901) = 52.8% 

10. The lower limit of the 95% confidence interval for the estimated LC50 is as follows:

antilog(1.5902639) = 38.9%

11.2.4 THE TRIMMED SPEARMAN-KARBER METHOD

11.2.4.1 Description

1. The Trimmed Spearman-Karber Method is a modification of the Spearman-Karber nonparametric statistical

procedure for estimating the LC50 and the associated 95% confidence interval (Hamilton, et al, 1977).

2. This procedure estimates the trimmed mean of the distribution of the log10 of the tolerance.

If the log tolerance distribution is symmetric, this estimate of the trimmed mean is

equivalent to an estimate of the median of the log tolerance distribution.

3. Use of the Trimmed Spearman-Karber Method is only appropriate when the requirements

for the Probit Method and the Spearman-Karber Method are not met.

11.2.4.2 Requirements

1. To calculate the LC50 estimate with the Trimmed Spearman-Karber Method, the smoothed, adjusted,

observed proportion mortalities must bracket 0.5.

2. To calculate a confidence interval for the LC50 estimate, one or more of the smoothed,

adjusted, observed proportion mortalities must be between zero and one.
79

Trim ' max(p a

1 , 1 & p ak )

11.2.4.3 General Procedure

1. Smooth the observed proportion mortalities as described in 11.2.2.3, Step 1.

2. Adjust the smoothed observed proportion mortality in each effluent concentration for

mortality in the control group using Abbott's formula (see 11.2.2.3, Step 2).

3. Plot the smoothed, adjusted data as described in 11.2.2.3, Step 3.

4. Calculate the amount of trim to use in the estimation of the LC50 as follows:

where: = the smoothed, adjusted proportion mort p ality for the lowest effluent concentration, a

1

 exclusive of the control.

p = the smoothed, adjusted proportion mortality for the highest effluent concentration. a

k

k = the number of effluent concentrations, exclusive of the control.

5. Due to the intensive nature of the calculation for the estimated LC50 and the calculation for the

associated 95% confidence interval using the Trimmed Spearman-Karber Method, it is recommended

that the data be analyzed by computer.

6. A computer program which estimates the LC50 and associated 95% confidence interval

using the Trimmed-Karber Method, can be obtained through the Environmental Monitoring

and Support Laboratory (EMSL), 26 W. Martin Luther King Drive, Cincinnati, OH 45268.

The program can be obtained from EMSL-Cincinnati by sending a diskette with a written

request to the above address.

7. The modified program automatically performs the following functions:

a. Smoothing.

b. Adjustment for mortality in the control.

c. Calculation of the trim.

d. Calculation of the LC50.

e. Calculation of the associated 95% confidence interval.

11.2.4.4 Example Calculation Using the Computer Program

1. Data from Table 20 are used to illustrate the analysis using the Trimmed Spearman-Karber

program.

2. The program requests the following input (see Figure 8):

a. Output destination (D = disk file or P = printer).

b. Title for output.

c. Control data.

d. Data for each toxicant concentration.
80
81

3. The program output includes the following (see Figure 9):

a. A table of the concentrations tested, number of organisms exposed, and mortalities.

b. The amount of trim used in the calculation.

c. The estimated LC50 and the associated 95% confidence interval.

4. The analysis results for this example are as follows:

a. The observed proportion mortalities smoothed and adjusted for mortality in the control.

b. The amount of trim used to calculate the estimate:

trim = max {0.00, 0.205} = 0.205.

c. The estimate of the LC50 is 77.1% with a 95% confidence interval of (69.7%, 85.3%).

11.2.5 THE PROBIT METHOD

11.2.5.1 Description

1. The Probit Method is a parametric statistical procedure for estimating the LC50 and the associated 95%

confidence interval (Finney, 1978).

2. The analysis consists of transforming the observed proportion mortalities with a probit transformation,

and transforming the effluent concentrations to log10.

 3. Given the assumption of normality for the log10 of the tolerances, the relationship between the

transformed variables mentioned above is approximately linear.

4. This relationship allows estimation of linear regression parameters, using an iterative approach.

5. The estimated LC50 and associated confidence interval are calculated from the estimated linear

regression parameters.

11.2.5.2 Requirements

1. To obtain a reasonably precise estimate of the LC50 with the Probit Method, the observed proportion

mortalities must bracket 0.5.

2. The log10 of the tolerance is assumed to be normally distributed.

3. To calculate the LC50 estimate and associated 95% confidence interval, two or more of the observed

proportion mortalities must be between zero and one.

11.2.5.3 General Procedure

1. Due to the intensive nature of the calculations for the estimated LC50 and associated 95% confidence

interval using the Probit Method, it is recommended that the data be analyzed by a computer program.

2. A machine-readable, compiled, version of a computer program to estimate the LC1 and LC50 and

associated 95% confidence intervals using the Probit Method can be obtained from EMSL-Cincinnati

by sending a diskette with a written request to the Environmental Monitoring Systems Laboratory, 26

W. Martin Luther King Drive, Cincinnati, OH 45268.
82
83

11.2.5.4 Example Using the Computer Program

1. Data from Table 20 are used to illustrate the operation of the Probit program for calculating

the LC50 and the associated 95% confidence interval.

2. The program begins with a request for the following initial input (see Figure 10):

a. Desired output of abbreviated (A) or full (F) output?

b. Output designation (P = printer, D = disk file).

c. Title for the output.

d. Control data.

c. The number of exposure concentrations

d. Data for each toxicant concentration

3. The program output includes the following (see Figure 11):

a. A table of the observed proportion responding, and the proportion responding adjusted for controls.

b. The calculated chi-squared statistic for heterogeneity and the tabular value.

This test is one indicator of how well the data fit the model. The program

will issue a warning when the test indicates that the data do not fit the model.

c. The estimated LC50 and 95% confidence limits.

d. A plot of the fitted regression line with observed data overlaid on the plot.

4. The results of the data analysis for this example are as follows:

a. The observed proportion mortalities were not adjusted for mortality in the control.

b. The test for heterogeneity was not significant (the calculated Chi-square was less than the tabular

value), thus the Probit Method appears to be appropriate for this data.

c. The estimate of the LC50 is 22.9% with a 95% confidence interval of (18.8%, 27.8%).

11.3 DETERMINATION OF NO-OBSERVED-ADVERSE-EFFECT CONCENTRATION (NOAEC) FROM

MULTI-CONCENTRATION TESTS, AND DETERMINATION OF PASS OR FAIL (PASS/FAIL) FOR

SINGLE-CONCENTRATION (PAIRED) TESTS 

11.3.1 Determination of the No-Observed-Adverse-Effect Concentration (NOAEC), for multi-concentration toxicity

tests, and pass or fail (Pass/Fail) for single-concentration toxicity tests is accomplished using hypothesis testing. The

NOAEC is the lowest concentration at which survival is not significantly different from the control. In Pass/Fail tests,

the objective is to determine if the survival in the single treatment (effluent or receiving water) is significantly different

from the control survival. 

11.3.2 The first step in these analyses is to transform the responses, expressed as the proportion surviving, by the arcsine-square-root transformation (Figures 12 and 13). The arc-sine-square-root transformation is commonly used on

proportionality data to stabilize the variance and satisfy the normality requirement. Shapiro Wilk's test may be used to

test the normality assumption.

11.3.3 If the data do not meet the assumption of normality and there are four or more replicates per group, then the

non-parametric test, Wilcoxon Rank Sum Test, can be used to analyze the data.

11.3.4 If the data meet the assumption of normality, the F test for equality of variances is used to test the homogeneity

of variance assumption. Failure of the homogeneity of variance assumption leads to the use of a modified t test, where

the pooled variance estimate is adjusted for unequal variance, and the degrees of freedom for the test are adjusted.
84
85
86

Figure 12. Flowchart for analysis of single-effluent concentration test data.
87

Figure 13. Flowchart for analysis of multi-effluent-concentration test data.
88

Angle(in radians) ' arc sine (RP)

Angle(in radians) ' arc sine 1

4n

Angle ' 1.5708 radians & (radians for RP'0)

D'j

n

i'1

(Xi

&X)

2

11.3.5 GENERAL PROCEDURE

11.3.5.1 Arc Sine Square Root Transformation

11.3.5.1.1 The arc sine square root transformation consists of determining the angle (in radians) represented by a sine

value. In this transformation, the proportion surviving is taken as the sine value, the square root of the sine value is

calculated, and the angle (in radians) for the square root of the sine value is determined. Whenever the proportion

surviving is 0 or 1, a special modification of the transformation must be used (Bartlett, 1937). Illustrations of the arc

sine square root transformation and modification are provided below.

1. Calculate the response proportion (RP) for each replicate within a group, where:

RP = (number of surviving organisms)/(number exposed)

2. Transform each RP to arc sine, as follows.

a. For RPs greater than zero or less than one:

b. Modification of the arc sine when RP = 0.

where n = number animals/treatment rep.

c. Modification of the arc sine when RP = 1.0.

11.3.5.2 Shapiro Wilk's Test

11.3.5.2.1 After the data have been transformed, test the assumption of normality using Shapiro Wilk's test. The test

statistic, W, is obtained by dividing the square of an appropriate linear combination of the sample order statistics by the

usual symmetric estimate of variance (D). The calculated W must be greater than zero and less than or equal to one. 

This test is recommended for a sample size of 50 or less, and there must be more than two replicates per concentration

for the test to be valid.

1. To calculate W, first center the observations by subtracting the mean of all the observations within a

concentration from each observation in that concentration.

2. Calculate the denominator, D, of the test statistic:

where: Xi

 = the ith centered observation

 = the overall mean of the centered observations. X ̄
89

W ' 1

D ['

k

i'1

ai (X (n&i%1) & X (1))]

2

3. Order the centered observations from smallest to largest.

X(1)# X(2) #. . . #X (i)

where: X(i) denotes the ith ordered observation.

4. From Table 21, for the number of observations, n, obtain the coefficients a1, a2, ..., a k, where k is n/2 if n

is even, and (n - 1)/2 if n is odd.

5. Compute the test statistic, W, as follows:

11.3.5.2.2 The decision rule for the test is to compare the critical value from Table 22 to the computed W. If the

computed value is less than the critical value, conclude that the data are not normally distributed.

11.3.5.3 F Test

11.3.5.3.1 The F test for equality of variances is used to test the homogeneity of variance assumption. When

conducting the F test, the alternative hypothesis of interest is that the variances are not equal.

11.3.5.3.2 To make the two-tailed F test at the 0.01 level of significance, put the larger of the two sample variances in

the numerator of F.

F ' S 2

1

S 2

2

where S 2

1 >S 22

11.3.5.3.3 Compare the calculated F with the 0.005 level of a tabulated F value with n1-1 and n2-1 degrees of freedom,

where n1 and n2 are the number of replicates for each of the two groups (Snedecor and Cochran, 1980). If the

calculated F value is less than or equal to the tabulated F, conclude that the variances of the two groups are equal.

11.3.5.4 T Test

11.3.5.4.1 If the variances for the two groups are found to be statistically equivalent, then the equal variance t test is

the appropriate test. 
90

TABLE 21. COEFFICIENTS FOR THE SHAPIRO WILK'S TEST (CONOVER, 1980)

i\n 2 3 4 5 6 7 8 9 10

1 0.7071 0.7071 0.6872 0.6646 0.6431 0.6233 0.6052 0.5888 0.5739

2 - 0.0000 0.1667 0.2413 0.2806 0.3031 0.3164 0.3244 0.3291

3 - - - 0.0000 0.0875 0.1401 0.1743 0.1976 0.2141

4 - - - - - 0.0000 0.0561 0.0947 0.1224

5 - - - - - - - 0.0000 0.0399

i\n 11 12 13 14 15 16 17 18 19 20

1 0.5601 0.5475 0.5359 0.5251 0.5150 0.5056 0.4968 0.4886 0.4808 0.4734

2 0.3315 0.3325 0.3325 0.3318 0.3306 0.3290 0.3273 0.3253 0.3232 0.3211

3 0.2260 0.2347 0.2412 0.2460 0.2495 0.2521 0.2540 0.2553 0.2561 0.2565

4 0.1429 0.1586 0.1707 0.1802 0.1878 0.1939 0.1988 0.2027 0.2059 0.2085

5 0.0695 0.0922 0.1099 0.1240 0.1353 0.1447 0.1524 0.1587 0.1641 0.1686

6 0.0000 0.0303 0.0539 0.0727 0.0880 0.1005 0.1109 0.1197 0.1271 0.1334

7 - - 0.0000 0.0240 0.0433 0.0593 0.0725 0.0837 0.0932 0.1013

8 - - - - 0.0000 0.0196 0.0359 0.0496 0.0612 0.0711

9 - - - - - - 0.0000 0.0163 0.0303 0.0422

10 - - - - - - - - 0.0000 0.0140

i\n 21 22 23 24 25 26 27 28 29 30

1 0.4643 0.4590 0.4542 0.4493 0.4450 0.4407 0.4366 0.4328 0.4291 0.4254

2 0.3185 0.3156 0.3126 0.3098 0.3069 0.3043 0.3018 0.2992 0.2968 0.2944

3 0.2578 0.2571 0.2563 0.2554 0.2543 0.2533 0.2522 0.2510 0.2499 0.2487

4 0.2119 0.2131 0.2139 0.2145 0.2148 0.2151 0.2152 0.2151 0.2150 0.2148

5 0.1736 0.1764 0.1787 0.1807 0.1822 0.1836 0.1848 0.1857 0.1864 0.1870

6 0.1399 0.1443 0.1480 0.1512 0.1539 0.1563 0.1584 0.1601 0.1616 0.1630

7 0.1092 0.1150 0.1201 0.1245 0.1283 0.1316 0.1346 0.1372 0.1395 0.1415

8 0.0804 0.0878 0.0941 0.0997 0.1046 0.1089 0.1128 0.1162 0.1192 0.1219

9 0.0530 0.0618 0.0696 0.0764 0.0823 0.0876 0.0923 0.0965 0.1002 0.1036

10 0.0263 0.0368 0.0459 0.0539 0.0610 0.0672 0.0728 0.0778 0.0822 0.0862

11 0.0000 0.0122 0.0228 0.0321 0.0403 0.0476 0.0540 0.0598 0.0650 0.0697

12 - - 0.0000 0.0107 0.0200 0.0284 0.0358 0.0424 0.0483 0.0537

13 - - - - 0.0000 0.0094 0.0178 0.0253 0.0320 0.0381

14 - - - - - - 0.0000 0.0084 0.0159 0.0227

15 - - - - - - - - 0.0000 0.0076
91

TABLE 21. COEFFICIENTS FOR THE SHAPIRO WILK'S TEST (CONTINUED)

i\n 31 32 33 34 35 36 37 38 39 40

1 0.4220 0.4188 0.4156 0.4127 0.4096 0.4068 0.4040 0.4015 0.3989 0.3964

2 0.2921 0.2898 0.2876 0.2854 0.2834 0.2813 0.2794 0.2774 0.2755 0.2737

3 0.2475 0.2462 0.2451 0.2439 0.2427 0.2415 0.2403 0.2391 0.2380 0.2368

4 0.2145 0.2141 0.2137 0.2132 0.2127 0.2121 0.2116 0.2110 0.2104 0.2098

5 0.1874 0.1878 0.1880 0.1882 0.1883 0.1883 0.1883 0.1881 0.1880 0.1878

6 0.1641 0.1651 0.1660 0.1667 0.1673 0.1678 0.1683 0.1686 0.1689 0.1691

7 0.1433 0.1449 0.1463 0.1475 0.1487 0.1496 0.1505 0.1513 0.1520 0.1526

8 0.1243 0.1265 0.1284 0.1301 0.1317 0.1331 0.1344 0.1356 0.1366 0.1376

9 0.1066 0.1093 0.1118 0.1140 0.1160 0.1179 0.1196 0.1211 0.1225 0.1237

10 0.0899 0.0931 0.0961 0.0988 0.1013 0.1036 0.1056 0.1075 0.1092 0.1108

11 0.0739 0.0777 0.0812 0.0844 0.0873 0.0900 0.0924 0.0947 0.0967 0.0986

12 0.0585 0.0629 0.0669 0.0706 0.0739 0.0770 0.0798 0.0824 0.0848 0.0870

13 0.0435 0.0485 0.0530 0.0572 0.0610 0.0645 0.0677 0.0706 0.0733 0.0759

14 0.0289 0.0344 0.0395 0.0441 0.0484 0.0523 0.0559 0.0592 0.0622 0.0651

15 0.0144 0.0206 0.0262 0.0314 0.0361 0.0404 0.0444 0.0481 0.0515 0.0546

16 0.0000 0.0068 0.0131 0.0187 0.0239 0.0287 0.0331 0.0372 0.0409 0.0444

17 - - 0.0000 0.0062 0.0119 0.0172 0.0220 0.0264 0.0305 0.0343

18 - - - - 0.0000 0.0057 0.0110 0.0158 0.0203 0.0244

19 - - - - - - 0.0000 0.0053 0.0101 0.0146

20 - - - - - - - - 0.0000 0.0049

i\n 41 42 43 44 45 46 47 48 49 50

1 0.3940 0.3917 0.3894 0.3872 0.3850 0.3830 0.3808 0.3789 0.3770 0.3751

2 0.2719 0.2701 0.2684 0.2667 0.2651 0.2635 0.2620 0.2604 0.2589 0.2574

3 0.2357 0.2345 0.2334 0.2323 0.2313 0.2302 0.2291 0.2281 0.2271 0.2260

4 0.2091 0.2085 0.2078 0.2072 0.2065 0.2058 0.2052 0.2045 0.2038 0.2032

5 0.1876 0.1874 0.1871 0.1868 0.1865 0.1862 0.1859 0.1855 0.1851 0.1847

6 0.1693 0.1694 0.1695 0.1695 0.1695 0.1695 0.1695 0.1693 0.1692 0.1691

7 0.1531 0.1535 0.1539 0.1542 0.1545 0.1548 0.1550 0.1551 0.1553 0.1554

8 0.1384 0.1392 0.1398 0.1405 0.1410 0.1415 0.1420 0.1423 0.1427 0.1430

9 0.1249 0.1259 0.1269 0.1278 0.1286 0.1293 0.1300 0.1306 0.1312 0.1317

10 0.1123 0.1136 0.1149 0.1160 0.1170 0.1180 0.1189 0.1197 0.1205 0.1212

11 0.1004 0.1020 0.1035 0.1049 0.1062 0.1073 0.1085 0.1095 0.1105 0.1113

12 0.0891 0.0909 0.0927 0.0943 0.0959 0.0972 0.0986 0.0998 0.1010 0.1020

13 0.0782 0.0804 0.0824 0.0842 0.0860 0.0876 0.0892 0.0906 0.0919 0.0932

14 0.0677 0.0701 0.0724 0.0745 0.0765 0.0783 0.0801 0.0817 0.0832 0.0846

15 0.0575 0.0602 0.0628 0.0651 0.0673 0.0694 0.0713 0.0731 0.0748 0.0764

16 0.0476 0.0506 0.0534 0.0560 0.0584 0.0607 0.0628 0.0648 0.0667 0.0685

17 0.0379 0.0411 0.0442 0.0471 0.0497 0.0522 0.0546 0.0568 0.0588 0.0608

18 0.0283 0.0318 0.0352 0.0383 0.0412 0.0439 0.0465 0.0489 0.0511 0.0532

19 0.0188 0.0227 0.0263 0.0296 0.0328 0.0357 0.0385 0.0411 0.0436 0.0459

20 0.0094 0.0136 0.0175 0.0211 0.0245 0.0277 0.0307 0.0335 0.0361 0.0386

21 0.0000 0.0045 0.0087 0.0126 0.0163 0.0197 0.0229 0.0259 0.0288 0.0314

22 - - 0.0000 0.0042 0.0081 0.0118 0.0153 0.0185 0.0215 0.0244

23 - - - - 0.0000 0.0039 0.0076 0.0111 0.0143 0.0174

24 - - - - - - 0.0000 0.0037 0.0071 0.0104

25 - - - - - - - - 0.0000 0.0035
92

TABLE 22. QUANTILES OF THE SHAPIRO WILK'S TEST STATISTIC1 (CONOVER, 1980)

n 0.01 0.02 0.05 0.10 0.50 0.90 0.95 0.98 0.99

3 0.753 0.756 0.767 0.789 0.959 0.998 0.999 1.000 1.000

4 0.687 0.707 0.748 0.792 0.935 0.987 0.992 0.996 0.997

5 0.686 0.715 0.762 0.806 0.927 0.979 0.986 0.991 0.993

6 0.713 0.743 0.788 0.826 0.927 0.974 0.981 0.986 0.989

7 0.730 0.760 0.803 0.838 0.928 0.972 0.979 0.985 0.988

8 0.749 0.778 0.818 0.851 0.932 0.972 0.978 0.984 0.987

9 0.764 0.791 0.829 0.859 0.935 0.972 0.978 0.984 0.986

10 0.781 0.806 0.842 0.869 0.938 0.972 0.978 0.983 0.986

11 0.792 0.817 0.850 0.876 0.940 0.973 0.979 0.984 0.986

12 0.805 0.828 0.859 0.883 0.943 0.973 0.979 0.984 0.986

13 0.814 0.837 0.866 0.889 0.945 0.974 0.979 0.984 0.986

14 0.825 0.846 0.874 0.895 0.947 0.975 0.980 0.984 0.986

15 0.835 0.855 0.881 0.901 0.950 0.975 0.980 0.984 0.987

16 0.844 0.863 0.887 0.906 0.952 0.976 0.981 0.985 0.987

17 0.851 0.869 0.892 0.910 0.954 0.977 0.981 0.985 0.987

18 0.858 0.874 0.897 0.914 0.956 0.978 0.982 0.986 0.988

19 0.863 0.879 0.901 0.917 0.957 0.978 0.982 0.986 0.988

20 0.868 0.884 0.905 0.920 0.959 0.979 0.983 0.986 0.988

21 0.873 0.888 0.908 0.923 0.960 0.980 0.983 0.987 0.989

22 0.878 0.892 0.911 0.926 0.961 0.980 0.984 0.987 0.989

23 0.881 0.895 0.914 0.928 0.962 0.981 0.984 0.987 0.989

24 0.884 0.898 0.916 0.930 0.963 0.981 0.984 0.987 0.989

25 0.888 0.901 0.918 0.931 0.964 0.981 0.985 0.988 0.989

26 0.891 0.904 0.920 0.933 0.965 0.982 0.985 0.988 0.989

27 0.894 0.906 0.923 0.935 0.965 0.982 0.985 0.988 0.990

28 0.896 0.908 0.924 0.936 0.966 0.982 0.985 0.988 0.990

29 0.898 0.910 0.926 0.937 0.966 0.982 0.985 0.988 0.990

30 0.900 0.912 0.927 0.939 0.967 0.983 0.985 0.988 0.990

31 0.902 0.914 0.929 0.940 0.967 0.983 0.986 0.988 0.990

32 0.904 0.915 0.930 0.941 0.968 0.983 0.986 0.988 0.990

33 0.906 0.917 0.931 0.942 0.968 0.983 0.986 0.989 0.990

34 0.908 0.919 0.933 0.943 0.969 0.983 0.986 0.989 0.990

35 0.910 0.920 0.934 0.944 0.969 0.984 0.986 0.989 0.990

36 0.912 0.922 0.935 0.945 0.970 0.984 0.986 0.989 0.990

37 0.914 0.924 0.936 0.946 0.970 0.984 0.987 0.989 0.990

38 0.916 0.925 0.938 0.947 0.971 0.984 0.987 0.989 0.990

39 0.917 0.927 0.939 0.948 0.971 0.984 0.987 0.989 0.991

40 0.919 0.928 0.940 0.949 0.972 0.985 0.987 0.989 0.991

41 0.920 0.929 0.941 0.950 0.972 0.985 0.987 0.989 0.991

42 0.922 0.930 0.942 0.951 0.972 0.985 0.987 0.989 0.991

43 0.923 0.932 0.943 0.951 0.973 0.985 0.987 0.990 0.991

44 0.924 0.933 0.944 0.952 0.973 0.985 0.987 0.990 0.991

45 0.926 0.934 0.945 0.953 0.973 0.985 0.988 0.990 0.991

46 0.927 0.935 0.945 0.953 0.974 0.985 0.988 0.990 0.991

47 0.928 0.936 0.946 0.954 0.974 0.985 0.988 0.990 0.991

48 0.929 0.937 0.947 0.954 0.974 0.985 0.988 0.990 0.991

49 0.929 0.937 0.947 0.955 0.974 0.985 0.988 0.990 0.991

50 0.930 0.938 0.947 0.955 0.974 0.985 0.988 0.990 0.991
93

t

i ' X ̄

1 & X ̄2

Sp

1

n1

% 1

n2

Sp ' (n1&1)S 2

1 %(n2&1)S 22

n1%n2&2

t ' X ̄

1 & X ̄2

S 2

1

n1

% S 2

2

n2

11.3.5.4.2 Calculate the following test statistic:

where: = Mean for the control X ̄1

X ̄ = Mean for the effluent concentration 2

S1

2

 = Estimate of the variance for the control

S2

2

 = Estimate of the variance for the effluent concentration

n1 = Number of replicates for the control

n2 = Number of replicates for the effluent concentration

11.3.5.4.3 Since we are concerned with a decrease in survival from the control, a one-tailed test is appropriate. Thus,

compare the calculated t with a critical t, where the critical t is at the 5% level of significance with n1+n2-2 degrees of

freedom. If the calculated t exceeds the critical t, the mean responses are declared different.

11.3.5.5 Modified T Test

11.3.5.5.1 If the F test for equality of variance fails, the t test is still a valid test. However, the denominator and the

degrees of freedom for the test are modified.

11.3.5.5.2 The t statistic, with the modification for the denominator, is calculated as follows:

where: = Mean for the control X ̄1

X ̄ = Mean for the effluent concentration 2

S1

2

 = Estimate of the variance for the control

S2

2

 = Estimate of the variance for the effluent concentration

n1 = Number of replicates for the control

n2 = Number of replicates for the effluent concentration
94

df ) ' (n1&1)(n2&1)

(n2&1)C 2 % (1&C)

2 (n1&1)

C '

S 2

1

n1

S 2

1

n1

% S 2

2

n2

11.3.5.5.3 Additionally, the degrees of freedom for the test are adjusted using the following formula:

11.3.5.5.4 The modified degrees of freedom is usually not an integer. Common practice is to round down to the

nearest integer.

11.3.5.5.5 The modified t test is then performed in the same way as the equal variance t test. The calculated t is

compared to the critical t at the 0.05 significance level with modified degrees of freedom. If the calculated t exceeds

the critical t, the mean responses are found to be statistically different.

11.3.5.6 Wilcoxon Rank Sum Test

11.3.5.6.1 If the data fail the test for normality and there are four or more replicates per group, the non-parametric

Wilcoxon Rank Sum Test may be used to analyze the data. If less than four replicates were used, a non-parametric

alternative is not available.

11.3.5.6.2 The Wilcoxon Rank Sum Test consists of jointly ranking the data and calculating the rank sum for the

effluent concentration. The rank sum is then compared to a critical value to determine acceptance or rejection of the

null hypothesis.

11.3.5.6.3 To carry out the test, combine the data for the control and the effluent concentration and arrange the values

in order of size from smallest to largest. Assign ranks to the ordered observations, a rank of 1 to the smallest, 2 to the

next smallest, etc. If ties in rank occur, assign the average rank to each tied observation. Sum the ranks for the effluent

concentration.

11.3.5.6.4 If the survival in the effluent concentration is significantly less than that of the control, the rank sum for the

effluent concentration would be lower than the rank sum of the control. Thus, we are only concerned with comparing

the rank sum for the effluent concentration with some "minimum" or critical rank sum, at or below which the effluent

concentration survival would be considered to be significantly lower than the mortality in the control. For a test at the

5% level of significance, the critical rank sum can be found in Table 23.
95

TABLE 23. CRITICAL VALUES FOR WILCOXON'S RANK SUM TEST FIVE PERCENT CRITICAL

LEVEL

No. of Replicates

in Control

No. of Replicates per Effluent Concentration

3 4 5 6 7 8 9 10

3 10 16 23 30 39 49 59

4 6 11 17 24 32 41 51 62

5 7 12 19 26 34 44 54 66

6 8 13 20 28 36 46 57 69

7 8 14 21 29 39 49 60 72

8 9 15 23 31 41 51 63 72

9 10 16 24 33 43 54 66 79

10 10 17 26 35 45 56 69 82

11.3.6 SINGLE CONCENTRATION TEST

11.3.6.1 Data from an acute effluent toxicity test with Ceriodaphnia are provided in Table 24. The proportion surviving

in each replicate is transformed by the arc sine square root transformation prior to statistical analysis of the data (Figure 12).

TABLE 24. DATA FROM AN ACUTE SINGLE-CONCENTRATION TOXICITY TEST WITH

CERIODAPHNIA

Proportion Surviving

Replicate Control

100% Effluent

Concentration

A 1.00 0.40

RAW B 1.00 0.30

DATA C 0.90 0.40

D 0.90 0.20

ARC SINE A 1.412 0.685

TRANSFORMED B 1.412 0.580

DATA C 1.249 0.685

D 1.249 0.464

X ̄ 1.330 0.604

S2 0.0088 0.0111
96

D ' j

8

i'1

(Xi & X ̄)

2

W ' 1

0.060 @(0.2200)2 ' 0.0807

TABLE 25. EXAMPLE OF SHAPIRO WILK'S TEST: CENTERED OBSERVATIONS

Treatment

Replicate

 A B C D

Control 0.082 0.082 -0.081 -0.081

100% Effluent 0.081 -0.024 0.081 -0.140

11.3.6.2 After the data have been transformed, test the assumption of normality via the Shapiro Wilk's test.

11.3.6.2.1 The first step in the test for normality is to center the observations by subtracting the mean of all observations

within a concentration from each observation in that concentration. The centered observations are listed in Table 25.

11.3.6.2.2 Calculate the denominator, D, of the test statistic:

For this set of data, = 0 and D = 0.060. X ̄

11.3.6.2.3 Order the centered observations from smallest to largest. The ordered observations are listed in Table 26.

11.3.6.2.4 From Table 21, for n = 8 and k = n/2 = 4, obtain the coefficients a1, a2, ..., ak. The ai

 values are listed in

Table 27.

11.3.6.2.5 Compute the test statistic, W, as follows:

The differences, X(n-i+1)-X(i), are listed in Table 27.

11.3.6.2.6 From Table 22, the critical W value for n = 8 and a significance level of 0.01, is 0.749. Since the calculated

W, 0.807, is not less than the critical value the conclusion of the test is that the data are normally distributed.

TABLE 26. EXAMPLE OF SHAPIRO WILK'S TEST: ORDERED 

 OBSERVATIONS

i X(i)

1 -0.140

2 -0.081

3 -0.081

4 -0.024

5 0.081

6 0.081

7 0.082

8 0.082
97

F ' 0.0111

0.0088 ' 1.2614

t ' 1.330 & 0.604

0.0997 1

4 % 14

Sp' (4&1)0.0088%(4&1)(0.0111)

4%4&2

TABLE 27. EXAMPLE OF SHAPIRO WILK'S TEST: TABLE OF COEFFICIENTS AND DIFFERENCES

i ai X(n-i+1) - X(i)

1 0.6052 0.222 X(8) - X(1)

2 0.3164 0.163 X(7) - X(2)

3 0.1743 0.162 X(6) - X(3)

4 0.0561 0.105 X(5) - X(4)

11.3.6.3 The F test for equality of variances is used to test the homogeneity of variance assumption.

11.3.6.3.1 From Table 24, obtain the sample variances for the control and the 100% effluent. Since the variability of

the 100% effluent is greater than the variability of the control, S2

 for the 100% effluent concentration is placed in the

numerator of the F statistic and S2

 for the control is placed in the denominator.

11.3.6.3.2 There are four replicates for the control and four replicates for the 100% effluent concentration. Thus there

are three degrees of freedom for the numerator and the denominator. For a two-tailed test at the 0.01 level of

significance, the critical F value is 47.467. The calculated F, 1.2614, is less than the critical F, 47.467, thus the

conclusion is that the variances of the control and 100% effluent are equal.

11.3.6.4 The assumptions of normality and homogeneity of variance have been met for this data set. An equal

variance t test will be used to compare the mean responses of the control and 100% effluent.

11.3.6.4.1 To perform the t test, obtain the values for X1, X2, S1

2

, and S 2

2

 from Table 24. Calculate the t statistic as

follows:

where: 

11.3.6.4.2 For a one-tailed test at the 0.05 level of significance with 6 degrees of freedom, the critical t value is

1.9432. Since the calculated t, 10.298, is greater than the critical t, the conclusion is that the survival in the 100%

effluent concentration is significantly less than the survival in the control.

11.3.6.5 If the data had failed the normality assumption, the appropriate analysis would have been the Wilcoxon Rank

Sum Test. To provide an example of this test, the survival data from the t test example will be reanalyzed by the

nonparametric procedure.

11.3.6.5.1 The first step in the Wilcoxon Rank Sum Test is to combine the data from the control and the 100% effluent

concentration and arrange the values in order of size, from smallest to largest.

11.3.6.5.2 Assign ranks to the ordered observations, a rank of 1 to the smallest, 2 to the next smallest, etc. The

combined data with ranks assigned is presented in Table 28.
98

TABLE 28. EXAMPLE OF WILCOXON'S RANK SUM TEST: ASSIGNING RANKS TO THE

CONTROL AND 100% EFFLUENT CONCENTRATIONS

Rank Proportion Surviving Control or 100% Effluent

1 0.20 100% EFFLUENT

2 0.30 100% EFFLUENT

3.5 0.40 100% EFFLUENT

3.5 0.40 100% EFFLUENT

5.5 0.90 CONTROL

5.5 0.90 CONTROL

7.5 1.00 CONTROL

7.5 1.00 CONTROL

11.3.6.5.3 Sum the ranks for the 100% effluent concentration. 

11.3.6.5.4 For this set of data, the test is for a significant reduction in survival in the 100% effluent concentration as

compared to the control. The critical value, from Table 23, for four replicates in each group and a significance level of

0.05 is 11. The rank sum for the 100% effluent concentration is 10 which is less than the critical value of 11. Thus the

conclusion is that survival in the effluent concentration is significantly less than the control survival.

11.3.7 MULTI-CONCENTRATION TEST

11.3.7.1 Formal statistical analysis of the survival data is outlined in Figure 13. The response used in the analysis is

the proportion of animals surviving in each test or control chamber. Concentrations at which there is no survival in any

of the test chambers are excluded from statistical determination of the NOAEC. 

11.3.7.2 For the case of equal numbers of replicates across all concentrations and the control, the determination of the

NOAEC endpoint is made via a parametric test, Dunnett's Procedure, or a nonparametric test, Steel's Many-one Rank

Test, on the arc sine transformed data. Underlying assumptions of Dunnett's Procedure, normality and homogeneity of

variance, are formally tested. The test for normality is the Shapiro Wilk's Test, and Bartlett's Test is used to test for the

homogeneity of variance. If either of these tests fail, the nonparametric test, Steel's Many-one Rank Test, is used to

determine the NOAEC endpoints. If the assumptions of Dunnett's Procedure are met, the endpoints are estimated by

the parametric procedure. 

11.3.7.3 If unequal numbers of replicates occur among the concentration levels tested, there are parametric and

nonparametric alternative analyses. The parametric analysis is a t-test with a Bonferroni adjustment. The Wilcoxon

Rank Sum Test with the Bonferroni adjustment is the nonparametric alternative. 

11.3.7.4 Example of Analysis of Survival Data 

11.3.7.4.1 This example uses survival data from a fathead minnow test. The proportion surviving in each replicate

must first be transformed by the arc sine square root transformation procedure. The raw and transformed data, means

and standard deviations of the transformed observations at each toxicant concentration and control are listed in Table

29. A plot of the survival proportions is provided in Figure 14. 
99

Figure 14. Plot of mean survival proportion data in Table 29.
100

D'j

n

i'1

(Xi

&X)

2

11.3.7.4.2 Test for Normality 

1. The first step of the test for normality is to center the observations by subtracting the mean of all

observations within a concentration from each observation in that concentration. The centered

observations are summarized in Table 30. 

TABLE 29. FATHEAD MINNOW SURVIVAL DATA

Replicate Control

Toxicant Concentration (μg/L)

32 64 128 256 512

A 1.0 0.8 0.9 0.9 0.7 0.4

RAW B 1.0 0.8 1.0 0.9 0.9 0.3

C 0.9 1.0 1.0 0.8 1.0 0.4

D 0.9 0.8 1.0 1.0 0.5 0.2

ARC SINE A 1.412 1.107 1.249 1.249 0.991 0.685

TRANS- B 1.412 1.107 1.412 1.249 1.249 0.580

FORMED C 1.249 1.412 1.412 1.107 1.412 0.685

D 1.249 1.107 1.412 1.412 0.785 0.464

MEAN( ) Y ̄ 1.330 1.183 1.371 1.254 1.109 0.604 i

Si

2 0.0088 0.0232 0.0066 0.0155 0.0768 0.0111

i 12345 6

TABLE 30. CENTERED OBSERVATIONS FOR SHAPIRO WILK'S EXAMPLE

Toxicant Concentration (μg/L)

Replicate Control 32 64 128 256 512

A 0.082 -0.076 -0.122 -0.005 -0.118 0.081

B 0.082 -0.076 0.041 -0.005 0.140 -0.024

C -0.081 0.229 0.041 -0.147 0.303 0.081

D -0.081 -0.076 0.041 0.158 -0.324 -0.140

2. Calculate the denominator, D, of the statistic: 

where: Xi

 = the ith centered observation

 = the overall mean of the centered observations X ̄

 n = the total number of centered observations 

3. For this set of data: n = 24 (number of observations) 
101

X ̄ ' 1

24 (0.000) ' 0.000

W ' 1

D ['

k

i'1

ai (X (n&i%1) & X (1))]

2

W ' 1

0.4265 (0.6444)2 ' 0.974

D = 0.4265 

4. Order the centered observations from smallest to largest 

X(1)# X(2)# ... # X(n)

where: X(i) denotes the ith ordered observation. 

The ordered observations for this example are listed in Table 31.

TABLE 31. ORDERED CENTERED OBSERVATIONS FOR THE SHAPIRO WILK'S EXAMPLE 

i X(i) i X(i)

1 -0.324 13 -0.005

2 -0.147 14 0.041

3 -0.140 15 0.041

4 -0.122 16 0.041

5 -0.118 17 0.081

6 -0.081 18 0.081

7 -0.081 19 0.082

8 -0.076 20 0.082

9 -0.076 21 0.140

10 -0.076 22 0.158

11 -0.024 23 0.229

12 -0.005 24 0.303

5. From Table 21, for the number of observations, n, obtain the coefficients a1, a2, . . . ak, where k is

approximately n/2 if n is even; (n-1)/2 if n is odd. For the data in this example, n=24 and k=12. The ai

values are listed in Table 32. 

6. Compute the test statistic, W, as follows: 

The differences X(n-i+1)-X(i) are listed in Table 32. For the data in this example, 

7. The decision rule for this test is to compare W as calculated in #6 to a critical value found in Table 23. If the

computed W is less than the critical value, conclude that the data are not normally distributed. For the data in

this example, the critical value at a significance level of 0.01 and n = 24 observations is 0.884. Since W =

0.974 is greater than the critical value, conclude that the data are normally distributed.
102

B '

[('

P

i'1

Vi) ln S ̄2 & '

P

i'1

Vi ln S 2

i ]

C

S ̄2

'

('

P

i'1

ViS 2

i )

'

P

i'1

Vi

C'1%[3(p&1)]&1['

P

i'1

1/Vi

&('

P

i'1

Vi)

&1

]

TABLE 32. COEFFICIENTS AND DIFFERENCES FOR SHAPIRO WILK'S EXAMPLE 

i ai X(n-i+1) - X(i)

1 0.4493 0.627 X(24) - X(1)

2 0.3098 0.376 X(23) - X(2)

3 0.2554 0.298 X(22) - X(3)

4 0.2145 0.262 X(21) - X(4)

5 0.1807 0.200 X(20) - X(5)

6 0.1512 0.163 X(19) - X(6)

7 0.1245 0.162 X(18) - X(7)

8 0.0997 0.157 X(17) - X(8)

9 0.0764 0.117 X(16) - X(9)

10 0.0539 0.117 X(15) - X(10)

11 0.0321 0.065 X(14) - X(11)

12 0.0107 0.0 X(13) - X(12)

11.3.7.4.3 Test for Homogeneity of Variance 

1. The test used to examine whether the variation in mean proportion surviving is the same across all

toxicant concentrations including the control, is Bartlett's Test (Snedecor and Cochran, 1980). The test

statistic is as follows: 

where: Vi

 = degrees of freedom for each toxicant concentration and control, Vi = (ni - 1)

ni

 = the number of replicates for concentration i. 

1n = loge

i = 1, 2, ..., p where p is the number of concentrations including the control 

2. For the data in this example, (See Table 29) all toxicant concentrations including the control have the

same number of replicates (ni

 = 4 for all i). Thus, Vi = 3 for all i.
103

3. Bartlett's statistic is therefore: 

B ' [(18)1n(0.0236) & 3'

P

i'1

1n(S 2

i )]/1.1296

 = [18(-3.7465) - 3(-24.7516)]/1.1296

 = 6.8178/1.1296

 = 6.036

4. B is approximately distributed as chi square with p - 1 degrees of freedom, when the variances are in fact

the same. Therefore, the appropriate critical value for this test, at a significance level of 0.01 with five

degrees of freedom, is 15.086. Since B = 6.036 is less than the critical value of 15.086, conclude that the

variances are not different. 

11.3.7.4.4 Dunnett's Procedure 

1. To obtain an estimate of the pooled variance for the Dunnett's Procedure, construct an ANOVA table

(Table 33).

TABLE 33. ANOVA TABLE 

Source DF

Sum of Squares

(SS)

Mean Square (MS)

(SS/DF)

BETWEEN P - 1 SSB SB

2

 = SSB/(P-1) 

WITHIN N - P SSW SW

2

 = SSW/(N-P) 

Total N - 1 SST

where: p = number toxicant concentrations including the control 

 N = total number of observations n1 + n2 ... + nP

 ni = number of observations in concentration i 

SSB' ' Between Sum of Squares 

P

i'1

T 2

i /ni

&G 2

/N

SST' ' Total Sum of Squares 

P

i'1

'

ni

j'1

Y 2

ij &G 2

/N

SSW = SST - SSB Within Sum of Squares 
104

SSB' '

P

i'1

T 2

i /ni

&G 2

/N

SST' '

P

i'1

'

ni

j'1

Y 2

ij &G 2

/N

G = the grand total of all sample observations, G''

P

i'1

Ti

Ti = the total of the replicate measurements for concentration "i" 

Yij = the jth observation for concentration "i" (represents the proportion surviving for

 toxicant concentration i in test chamber j)

2. For the data in this example: 

n 1 = n 2 = n 3 = n 4 = n 5 = n 6 = 4 

N = 24

T1 = Y11 + Y12 + Y13 + Y 14 = 5.322 

T2 = Y21 + Y22 + Y23 + Y 24 = 4.733 

T3 = Y31 + Y32 + Y33 + Y 34 = 5.485 

T4 = Y41 + Y42 + Y43 + Y 44 = 5.017 

T5 = Y51 + Y52 + Y53 + Y 54 = 4.437 

T6 = Y61 + Y62 + Y63 + Y 64 = 2.414 

G= T1 + T2 + T 3 + T 4 + T 5 + T 6 = 27.408 

 

' 1

4

(131.495) & (27.408)2

24 ' 1.574

' 33.300 & (27.408)2

24 ' 2.000

 SSW = SST - SSB = 2.000 - 1.574 = 0.4260 

 SB2 = SSB/(p - 1) = 1.574/(6 - 1) = 0.3150 

 SW

2

 = SSW/(N - p) = 0.426/(24 - 6) = 0.024 

3. Summarize these calculations in the ANOVA table (Table 34). 
105

t

i

' (Y1&Yi

)

Sw (1/n1)%(1/ni

)

t

2 ' (1.330 & 1.183)

[0.155 (1/4) % (1/4)]

' 1.341

TABLE 34. ANOVA TABLE FOR DUNNETT'S PROCEDURE EXAMPLE 

Source DF

Sum of Squares

(SS)

Mean Square (MS)

(SS/DF)

BETWEEN 5 1.574 0.315

WITHIN 18 0.426 0.024

Total 23 2.002

4. To perform the individual comparisons, calculate the t statistic for each concentration, and control

combination as follows: 

where: = mean proportion surviving for concentration i Y ̄ i

Y ̄ = mean proportion surviving for the control 1

SW = square root of within mean square 

n1 = number of replicates for control 

ni

 = number of replicates for concentration i. 

 

5. Table 35 includes the calculated t values for each concentration and control combination. In this example,

comparing the 32 μg/L concentration with the control the calculation is as follows: 

6. Since the purpose of this test is to detect a significant reduction in proportion surviving, a one-sided test is

appropriate. The critical value for this one-sided test is found in Table 36. For an overall alpha level of

0.05, 18 degrees of freedom for error and five concentrations (excluding the control) the critical value is

2.41. The mean proportion surviving for concentration "i" is considered significantly less than the mean

proportion surviving for the control if ti

 is greater than the critical value. Since t is greater than 2.41, the

512 μg/L concentration has significantly lower survival than the control. Hence the NOAEC for survival is

256 μg/L. 
106

TABLE 35. CALCULATED T VALUES

Toxicant Concentration (μg/L) i ti

32 2 1.341

64 3 -0.374

128 4 0.693

256 5 2.016

512 6 6.624

7. To quantify the sensitivity of the test, the minimum significant difference (MSD) that can be detected

statistically may be calculated. 

MSD ' d Sw (1/n1) % (1/n)

where: d = the critical value for the Dunnett's procedure 

SW = the square root of the within mean square 

n = the common number of replicates at each concentration (this assumes equal replication 

at each concentration) 

ni

 = the number of replicates in the control. 

8. In this example: 

MSD ' 2.41(0.155) (1/4) % (1/4)

= 2.41 (0.155)(0.707) 

= 0.264 

9. The MSD (0.264) is in transformed units. To determine the MSD in terms of percent survival, carry out the

following conversion. 

(1) Subtract the MSD from the transformed control mean. 

1.330 - 0.264 = 1.066 

 (2) Obtain the untransformed values for the control mean and the difference calculated in 1. 

[Sine ( 1.330) ]2

 = 0.943

[Sine ( 1.066) ]2

 = 0.766

(3) The untransformed MSD (MSDu) is determined by subtracting the untransformed values from 2. 

MSDu = 0.943 - 0.766 = 0.177 

10. Therefore, for this set of data, the minimum difference in mean proportion surviving between the control and

any toxicant concentration that can be detected as statistically significant is 0.177. 

11. This represents a decrease in survival of 19% from the control. 
107

TABLE 36. DUNNETT'S "T" VALUES (MILLER, 1981)

(One-tailed)dαk

α = .05

123456789

5 2.02 2.44 2.58 2.85 2.98 3.08 3.16 3.24 3.306 1.94 2.34 2.56 2.71 2.83 2.92 3.00 3.07 3.127 1.89 2.27 2.48 2.62 2.73 2.82 2.89 2.95 3.018 1.86 2.22 2.42 2.55 2.66 2.74 2.81 2.87 2.929 1.83 2.18 2.37 2.50 2.60 2.68 2.75 2.81 2.86

10 1.81 2.15 2.34 2.47 2.56 2.64 2.70 2.76 2.8111 1.80 2.13 2.31 2.44 2.53 2.60 2.67 2.72 2.7712 1.78 2.11 2.29 2.41 2.50 2.58 2.64 2.69 2.7413 1.77 2.09 2.27 2.39 2.48 2.55 2.61 2.68 2.7114 1.76 2.08 2.25 2.37 2.46 2.53 2.59 2.64 2.6915 1.75 2.07 2.24 2.36 2.44 2.51 2.57 2.62 2.6716 1.75 2.06 2.23 2.34 2.43 2.50 2.56 2.61 2.6517 1.74 2.05 2.22 2.33 2.42 2.49 2.54 2.59 2.6418 1.73 2.04 2.21 2.32 2.41 2.48 2.53 2.58 2.6219 1.73 2.03 2.20 2.31 2.40 2.47 2.52 2.57 2.6120 1.72 2.03 2.19 2.30 2.38 2.46 2.51 2.56 2.6024 1.71 2.01 2.17 2.28 2.36 2.43 2.48 2.53 2.5730 1.70 1.99 2.15 2.25 2.33 2.40 2.45 2.50 2.5440 1.68 1.97 2.13 2.23 2.31 2.37 2.42 2.47 2.5160 1.67 1.95 2.10 2.21 2.28 2.35 2.39 2.44 2.48

120 1.86 1.93 2.08 2.18 2.26 2.32 2.37 2.41 2.45

α 1.64 1.92 2.06 2.16 2.23 2.29 2.34 2.33 2.42
108

TABLE 36. DUNNETT'S "T" VALUES (MILLER, 1981) (CONTINUED)

(One-tailed)dαk

α = 0.1

123456789

5 3.37 3.90 4.21 4.43 4.50 4.73 4.85 4.94 5.036 3.14 3.61 4.88 4.07 4.21 4.33 4.43 4.51 4.397 3.00 3.42 3.56 3.83 3.96 4.07 4.15 4.23 4.308 2.90 3.20 3.51 3.67 3.79 3.88 3.96 4.03 4.099 2.82 3.19 3.40 3.55 3.64 3.75 3.82 3.89 3.94

10 2.76 3.11 3.31 3.45 3.56 3.64 3.71 3.78 3.8311 2.72 3.06 3.25 3.38 3.46 3.56 3.63 3.69 3.7412 2.68 3.01 3.19 3.32 3.42 3.50 3.56 3.62 3.6713 2.65 2.97 3.15 3.27 3.37 3.44 3.91 3.56 3.6114 2.62 2.94 3.11 3.23 3.32 3.40 3.46 3.51 3.5615 2.60 2.91 3.08 3.20 3.29 3.36 3.42 3.47 3.5216 2.58 2.38 3.05 3.17 3.28 3.33 3.39 3.44 3.4817 2.57 2.86 3.03 3.14 3.23 3.30 3.36 3.41 3.4518 2.55 2.84 3.01 3.12 3.21 3.27 3.33 3.38 3.4219 2.54 2.83 2.99 3.10 3.18 3.25 3.31 3.36 3.4020 2.53 2.81 2.97 3.08 3.17 3.23 3.29 3.34 3.3824 2.40 2.77 2.92 3.03 3.11 3.17 3.22 3.27 3.3130 2.46 2.72 2.87 2.97 3.05 3.11 3.16 3.21 3.2440 2.42 2.68 2.82 2.92 2.99 3.06 3.10 3.14 3.1860 2.39 2.64 2.78 2.87 2.94 3.08 3.04 3.06 3.12

120 2.36 2.60 2.73 2.82 2.90 2.94 2.90 3.03 3.06

α 2.33 2.56 2.68 2.77 2.34 2.90 2.83 2.97 3.00
109

SECTION 12

REPORT PREPARATION AND TEST REVIEW

12.1 REPORT PREPARATION

The following general format and content are recommended for the report: 

12.1.1 INTRODUCTION

1. Permit number

2. Toxicity testing requirements of permit

3. Plant location

4. Name of receiving water body

5. Contractor (if contracted)

a. Name of firm

b. Phone number

c. Address

6. Objective of test

12.1.2 PLANT OPERATIONS 

1. Product(s)

2. Raw materials 

3. Operating schedule 

4. Description of waste treatment 

5. Schematic of waste treatment 

6. Retention time (if applicable) 

7. Volume of discharge (MGD, CFS, GPM) 

8. Design flow of treatment facility at time of sampling 

12.1.3 SOURCE OF EFFLUENT, RECEIVING WATER, AND DILUTION WATER 

1. Effluent Samples 

a. Sampling point (including latitude and longitude)

b. Sample collection method 

c. Collection dates and times

d. Mean daily discharge on sample collection date

e. Lapsed time from sample collection to delivery

f. Sample temperature when received at the laboratory

g. Physical and chemical data 

2. Receiving Water Samples 

a. Sampling point (including latitude and longitude)

b. Sample collection method

c. Collection dates and times

d. Streamflow (at time of sampling)

e. Lapsed time from sample collection to delivery

f. Sample temperature when received at the laboratory

g. Physical and chemical data
110

3. Dilution Water Samples 

a. Source

b. Collection date(s) and time(s) (where applicable) 

c. Pretreatment

d. Physical and chemical characteristics (pH, hardness, salinity, etc.)

12.1.4 TEST CONDITIONS 

1. Toxicity test method used (title, number, source)

2. Endpoint(s) of test

3. Deviations from reference method, if any, and reason(s) 

4. Date and time test started

5. Date and time test terminated

6. Type and volume of test chambers

7. Volume of solution used per chamber

8. Number of organisms per test chamber

9. Number of replicate test chambers per treatment

10. Feeding frequency, and amount and type of food

11. Acclimation temperature of test organisms (mean and range) 

12. Test temperature (mean and range) 

12.1.5 TEST ORGANISMS 

1. Scientific name

2. Age

3. Life stage

4. Mean length and weight (where applicable) 

5. Source

6. Diseases and treatment (where applicable) 

12.1.6 QUALITY ASSURANCE 

1. Reference toxicant used routinely; source; date received; lot no.

2. Date and time of most recent reference toxicant test; test results and current cusum chart

3. Dilution water used in reference toxicant test 

4. Physical and chemical methods used 

12.1.7 RESULTS 

1. Provide raw toxicity data in tabular form, including daily records of affected organisms in each concentration

(including controls) and replicate, and in graphical form (plots of toxicity data)

2. Provide table of endpoints: LC50, NOAEC, Pass/Fail (as required in the applicable NPDES permit)

3. Indicate statistical methods used to calculate endpoints 

4. Provide summary table of physical and chemical data 

5. Tabulate QA data

12.1.8 CONCLUSIONS AND RECOMMENDATIONS

1. Relationship between test endpoints and permit limits.

2. Action to be taken.
111

12.2 TEST REVIEW

12.2.1 Test review is an important part of an overall quality assurance program (Section 4) and is necessary for

ensuring that all test results are reported accurately. Test review should be conducted on each test by both the testing

laboratory and the regulatory authority. 

12.2.2 SAMPLING AND HANDLING 

12.2.2.1 The collection and handling of samples are reviewed to verify that the sampling and handling procedures

given in Section 8 were followed. Chain-of-custody forms are reviewed to verify that samples were tested within

allowable sample holding times (Subsection 8.5.4). Any deviations from the procedures given in Section 8 should be

documented and described in the data report (Subsection 12.1). 

12.2.3 TEST ACCEPTABILITY CRITERIA

12.2.3.1 Test data are reviewed to verify that test acceptability criteria (TAC) requirements for a valid test have been

met. Any test not meeting the minimum test acceptability criteria is considered invalid. All invalid tests must be

repeated with a newly collected sample. 

12.2.4 TEST CONDITIONS

12.2.4.1 Test conditions are reviewed and compared to the specifications listed in the summary of test condition tables

provided for each method. Physical and chemical measurements taken during the test (e.g., temperature, pH, and DO)

also are reviewed and compared to specified ranges. Any deviations from specifications should be documented and

described in the data report (Subsection 12.1).

12.2.4.2 The summary of test condition tables presented for each method identify test conditions as required or

recommended. For WET test data submitted under NPDES permits, all required test conditions must be met or the test

is considered invalid and must be repeated with a newly collected sample. Deviations from recommended test

conditions must be evaluated on a case-by-case basis to determine the validity of test results. Deviations from

recommended test conditions may or may not invalidate a test result depending on the degree of the departure and the

objective of the test. The reviewer should consider the degree of the deviation and the potential or observed impact of

the deviation on the test result before rejecting or accepting a test result as valid. For example, if dissolved oxygen is

measured below 4.0 mg/L in one test chamber, the reviewer should consider whether any observed mortality in that test

chamber corresponded with the drop in dissolved oxygen.

12.2.4.3 Whereas slight deviations in test conditions may not invalidate an individual test result, test condition

deviations that continue to occur frequently in a given laboratory may indicate the need for improved quality control in

that laboratory. 

12.2.5 STATISTICAL METHODS

12.2.5.1 The statistical methods used for analyzing test data are reviewed to verify that the recommended flowcharts

for statistical analysis were followed. Any deviation from the recommended flowcharts for selection of statistical

methods should be noted in the data report. Statistical methods other than those recommended in the statistical

flowcharts may be appropriate (see Subsection 11.1.4), however, the laboratory must document the use of and provide

the rationale for the use of any alternate statistical method. In all cases (flowchart recommended methods or alternate

methods), reviewers should verify that the necessary assumptions are met for the statistical method used. 
112

12.2.6 CONCENTRATION-RESPONSE RELATIONSHIPS

12.2.6.1 The concept of a concentration-response, or more classically, a dose-response relationship is “the most

fundamental and pervasive one in toxicology” (Casarett and Doull, 1975). This concept assumes that there is a causal

relationship between the dose of a toxicant (or concentration for toxicants in solution) and a measured response. A

response may be any measurable biochemical or biological parameter that is correlated with exposure to the toxicant. 

The classical concentration-response relationship is depicted as a sigmoidal shaped curve, however, the particular shape

of the concentration-response curve may differ for each coupled toxicant and response pair. In general, more severe

responses (such as acute effects) occur at higher concentrations of the toxicant, and less severe responses (such as

chronic effects) occur at lower concentrations. A single toxicant also may produce multiple responses, each

characterized by a concentration-response relationship. A corollary of the concentration-response concept is that every

toxicant should exhibit a concentration-response relationship, given that the appropriate response is measured and given

that the concentration range evaluated is appropriate. Use of this concept can be helpful in determining whether an

effluent possesses toxicity and in identifying anomalous test results.

12.2.6.2 The concentration-response relationship generated for each multi-concentration test must be reviewed to

ensure that calculated test results are interpreted appropriately. USEPA (2000a) provides guidance on evaluating

concentration-response relationships to assist in determining the validity of WET test results. All WET test results (from

multi-concentration tests) reported under the NPDES program should be reviewed and reported according to USEPA

guidance on the evaluation of concentration-response relationships (USEPA, 2000a). This guidance provides review

steps for 10 different concentration-response patterns that may be encountered in WET test data. Based on the review,

the guidance provides one of three determinations: that calculated effect concentrations are reliable and should be

reported, that calculated effect concentrations are anomalous and should be explained, or that the test was inconclusive

and the test should be repeated with a newly collected sample. It should be noted that the determination of a valid

concentration-response relationship is not always clear cut. Data from some tests may suggest consultation with

professional toxicologists and/or regulatory officials. Tests that exhibit unexpected concentration-response relationships

also may indicate a need for further investigation and possible retesting. 

12.2.7 REFERENCE TOXICANT TESTING

12.2.7.1 Test review of a given effluent or receiving water test should include review of the associated reference

toxicant test and current control chart. Reference toxicant testing and control charting is required for documenting the

quality of test organisms (Subsection 4.7) and ongoing laboratory performance (Subsection 4.15). The reviewer should

verify that a quality control reference toxicant test was conducted according to the specified frequency required by the

permitting authority or recommended by the method (e.g., monthly). The test acceptability criteria, test conditions,

concentration-response relationship, and test sensitivity of the reference toxicant test are reviewed to verify that the

reference toxicant test conducted was a valid test. The results of the reference toxicant test are then plotted on a control

chart (see Subsection 4.15) and compared to the current control chart limits (± 2 standard deviations).

12.2.7.2 Reference toxicant tests that fall outside of recommended control chart limits are evaluated to determine the

validity of associated effluent and receiving water tests (see Subsection 4.15). An out of control reference toxicant test

result does not necessarily invalidate associated test results. The reviewer should consider the degree to which the

reference toxicant test result fell outside of control chart limits, the width of the limits, the direction of the deviation

(toward increasing test organism sensitivity or toward decreasing test organism sensitivity), the test conditions of both

the effluent test and the reference toxicant test, and the objective of the test. More frequent and/or concurrent reference

toxicant testing may be advantageous if recent problems (e.g., invalid tests, reference toxicant test results outside of

control chart limits, reduced health of organism cultures, or increased within-test variability) have been identified in

testing. 
113

12.2.8 TEST VARIABILITY

12.2.8.1 The within-test variability of individual tests should be reviewed. Excessive within-test variability may

invalidate a test result and warrant retesting. For evaluating within-test variability, reviewers should consult EPA

guidance on upper and lower percent minimum significant difference (PMSD) bounds (USEPA, 2000b).

12.2.8.2 USEPA guidance on WET variability recommends incorporating upper and lower bounds using the PMSD to

control and minimize within-test method variability and increase test sensitivity (USEPA, 2000b). The minimum

significant difference (MSD) is the smallest difference between the control and another test treatment that can be

determined as statistically significant in a given test, and the PMSD is the MSD represented as a percentage of the

control response. The equation and examples of MSD calculations are shown in Subsection 11.3.7.4.4.

12.2.8.3 To assist in reviewing within-test variability, EPA recommends maintaining control charts of PMSDs

calculated for successive effluent tests (USEPA, 2000b). A control chart of PMSD values characterizes the range of

variability observed within a given laboratory, and allows comparison of individual test PMSDs with the laboratory’s

typical range of variability. Control charts of other variability and test performance measures, such as the MSD,

standard deviation or CV of control responses, or average control response, also may be useful for reviewing tests and

minimizing variability.
114

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USEPA. 1991b. Manual for evaluation of laboratories performing aquatic toxicity tests. D.J. Klemm, L.B. Lobring,

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USEPA. 1991c. Technical support document for water quality-based toxic control. Office of Water, U.S.

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USEPA. 1993a. Methods for measuring the acute toxicity of effluents to freshwater and marine organisms. Weber, C.I.

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USEPA. 1993b. Table 1. In: Guidelines establishing test procedures for the analysis of pollutants. Code of Federal

Regulations, Vol. 40, Part 136. U.S. Environmental Protection Agency, Washington, DC.
118

USEPA. 1994a. Short-term methods For estimating the chronic toxicity of effluents and receiving waters to freshwater

organisms. 3rd edition. Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency,

Cincinnati, Ohio. EPA-600/4-91/002. 

USEPA. 1994b. Short-term methods For estimating the chronic toxicity of effluents and receiving waters to marine and

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USEPA. 2000b. Understanding and accounting for method variability in whole effluent toxicity applications under the

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USEPA. 2001a. Final report: interlaboratory variability study of EPA short-term chronic and acute whole effluent

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USEPA. 2001b. Final report: interlaboratory variability study of EPA short-term chronic and acute whole effluent

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USEPA. 2002a. Short-term methods for estimating the chronic toxicity of effluents and receiving waters to freshwater

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USEPA. 2002b. Short-term methods for estimating the chronic toxicity of effluents and receiving waters to marine and

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Walters, D.B. and C.W. Jameson. 1984. Health and safety for toxicity testing. Butterworth Publ., Woburn, MA.

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124

APPENDICES 

A. Distribution, Life Cycle, Taxonomy, and Culture Methods . . . . . . . . . . . . . . . . . . . . . . . . . . 125

A.1. Ceriodaphnia dubia–Prepared by Philip A. Lewis and James M. Lazorchak . . 125

A.2. Daphnia (Daphnia magna and D. pulex)–Prepared by Philip A. Lewis and 

James M. Lazorchak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

A.3. Mysids (Mysidopsis bahia and Holmesimysis costata)–Prepared by 

Stephen H. Ward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

A.4. Brine Shrimp (Artemia salina)–Prepared by Philip A. Lewis and 

David A. Bengtson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

A.5. Fathead Minnow (Pimephales promelas)–Prepared by Donald J. Klemm, 

Quentin H. Pickering, and Mark E. Smith . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

A.6. Rainbow Trout (Oncorhynchus mykiss) and Brook Trout 

(Salvelinus fontinalis)–Prepared by Donald J. Klemm . . . . . . . . . . . . . . . . . . . 201

A.7. Sheepshead Minnow (Cyprinodon variegatus)–Prepared by Donald J. Klemm 209

A.8. Silversides: Inland Silverside (Menidia beryllina), 

Atlantic Silverside, (M. menidia, and Tidewater Silverside 

(M. peninsulae)–Prepared by Douglas P. Middaugh and Donald J. Klemm . . . 224

B. Supplemental List of Acute Toxicity Test Species–Prepared by Margarete A. Heber . . . . . . 238

C. Dilutor Systems–Prepared by William H. Peltier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

D. Plans for Mobile Toxicity Test Laboratory–Prepared by William H. Peltier . . . . . . . . . . . . . 253

D.1. Tandem-Axle Trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

D.2. Fifth Wheel Trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

E. Check Lists and Information Sheets–Prepared by William H. Peltier . . . . . . . . . . . . . . . . . . 257

E.1. Toxicity Test Field Equipment List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

E.2. Information Check List for On-Site Industrial or Municipal Toxicity Test . . . 259

E.3. Daily Event Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

E.4. Dilutor Calibration Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

E.5. Daily Dilutor Calibration Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
125

APPENDIX A

DISTRIBUTION, LIFE CYCLE, TAXONOMY, AND CULTURE METHODS

A.1. CERIODAPHNIA DUBIA

1. SYSTEMATICS

1.1 MORPHOLOGY AND TAXONOMY

1.1.1 Ceriodaphnia are closely related and morphologically similar to Daphnia, but are smaller and have a shorter

generation time (USEPA, 1986). They are generally more rotund, lack the prominent rostral projection typical of

Daphnia, and do not develop the dorsal helmets and long posterior spines often observed in Daphnia.

1.1.2 With Ceriodaphnia dubia, the female has a heavy, setulated pecten on the postabdominal claw (Figure 1A),

and the male was long antennules (Figure 1C), in contrast to the closely related C. reticulata, where the female has

heavy, triangular denticles in the pecten of the postabdominal claw (Figure 2A), and the male has very short

antennules (Figure 2C). Some clones having intermediate characters may be hybrids or phenotypic variants of C.

dubia (USEPA, 1986). Detailed descriptions of the males and females of both species and the variant were given

by USEPA (1986).

1.1.3 Although males are very similar to females, they can be recognized by their rapid, erratic swimming habit,

smaller size, denser coloration, extended antennules and claspers, and rostrum morphology. 

2. ECOLOGY AND LIFE HISTORY

2.1 DISTRIBUTION

2.1.1 C. dubia, has been reported from littoral areas of lakes, ponds, and marshes throughout most of the world,

but it is difficult to ascertain its true distribution because it has been reported in the literature under several other

names (C. affinis, C. quadrangula, and C. reticulata). It has also been suggested that reports of C. dubia in New

Zealand and parts of Asia may be yet another unnamed species (Berner, personal communication). 

2.2 ECOLOGY

2.2.1 Ceriodaphnia ecology and life history are very similar to those of other daphnids. Specific information on

the ecology and life history of Ceriodaphnia dubia is either not available or is widely scattered throughout the

literature. However, it is known to be a pond and lake dwelling species that is usually common among the

vegetation in littoral areas (Fairchild, 1981). In the Lake of Velence, Hungary, C. dubia was most common in

regions where "grey" and "dark brown" waters merged (Pal, 1980). In Par Pond (Savannah River Plant, Aiken, SC)

the Ceriodaphnia were much more abundant in the heated water (effluent from the nuclear reactor) than in the

ambient area (Vigerstad and Tilly, 1977), and in a reservoir in Russia, animals from the heated water were larger

and heavier than those living under normal water temperatures (Kititsyna and Sergeeva, 1976). In Iran they are

common in warmer, montane, oligotrophic lakes (Smagowicz, 1976). 

2.2.2 In Lake Kinneret, Israel, Ceriodaphnia reticulata are abundant only between March and June, with a peak in

May when the temperature ranges between 20 and 22°C. When summer temperatures reached 27-28°C, the

Ceriodaphnia were reduced in size and egg production became significantly less, leading to a progressive decline of

the population (Gophen, 1976). In Lake Parvin, France, the period of development was from June to September

(Devaux, 1980).
126

Figure 1. Ceriodaphnia dubia. A. (1) parthenogenetic female, (2) postabdomen, and (3) claw;

B. ephippial female; C. Male. (From USEPA, 1986)
127

Figure 2. Ceriodaphnia reticulata. A. (1) parthenogenetic female, (2) postabdomen, (3) and claw;

B. ephippial female; C. Male. (From USEPA, 1986)
128

2.2.3 Ceriodaphnia typically swim with an erratic, jerking motion for a period of time, and hang motionless in the

water between swimming bouts. This swimming behavior results in a mean speed of 1.5-2.5 mm/s. When

approached by a predator, however, it flees by swimming away quickly along a straight path (Wong, 1981). 

2.2.4 During most of the year, populations of Ceriodaphnia consist almost entirely of females; the males appearing

principally in autumn. Production of males appears to be induced primarily by low water temperatures, high

population densities, and/or a decrease in available food. As far as is presently known, C. dubia reproduce only by

cyclic parthenogenesis in which the males contribute to the genetic makeup of the young during the sexual stage of

reproduction. 

2.2.5 The females tend to aggregate during sexual reproductive activity, when ephippia are produced (Brandl and

Fernando, 1971). Ephippia are embryos encased in a tough covering, and are resistent to drying. They can be stored

for long periods and shipped through the mail in envelopes, like seeds. When placed in water at the proper

temperature, ephippia hatch in a few days producing a new parthenogenetic population. 

2.2.6 Ceriodaphnia have many predators, including fish, the mysid Mysis relicta, Chaoborus larvae, and copepods. 

As with Daphnia, it also reacts to intense predation with defensive strategies. Ceriodaphnia reticulata (possibly

C.dubia) in a Minnesota lake, reacted to the copepod, Cyclops vernalis, by producing large offspring and growing

to a large size at the expense of early reproduction (Lynch, 1979). They reacted to fish predators by producing

smaller offspring in larger numbers.

2.3 FOOD AND FEEDING

2.3.1 Cladocera are polyphagous feeders and find their food in the seston. Daphnids, including the Ceriodaphnia,

are classified as fine mesh filter feeders by Geller and Mueller (1981). These fine mesh filter feeders are most

abundant in eutrophic lakes during summer phytoplankton blooms when suspended bacteria are available as food

only for filter-feeding species with fine mesh. 

2.3.2 Lynch (1978) examined the gut contents of Ceriodaphnia reticulata (possibly C. dubia) from a Minnesota

pond and found bacteria, detritus and partially digested algae. In this pond, Ceriodaphnia and Daphnia pulex

shared the same resource base and had very similar diets, but the Ceriodaphnia fed more intensively on diatoms. 

The Ceriodaphnia were considered to be less sensitive to low food levels than Daphnia, because of their high rate

of population growth during periods of low food levels in late summer.

2.4 LIFE CYCLE

2.4.1 Four distinct periods may be recognized in the life cycle of Ceriodaphnia: (1) egg, (2) juvenile, (3)

adolescent, and (4) adult. The life span of Ceriodaphnia, from the release of the egg into the brood chamber until

the death of the adult, is highly variable depending on the temperature and other environmental conditions. 

Generally the life span increases as temperature decreases, due to lowered metabolic activity. For example, the

average life span of Ceriodaphnia dubia is about 30 days at 25°C, and 50 days at 20°C. One female was reported to

have lived 125 days and produced 29 broods at 20°C (Cowgill et al., 1985).

2.4.2 Typically, a clutch of 4 to 10 eggs is released into the brood chamber, but clutches with as many as 20 eggs

are common. The eggs hatch in the brood chamber and the juveniles, which are already similar in form to the

adults, are released in approximately 38 h, when the female molts (casts off her exoskeleton or carapace). The total

number of young produced per female varies with temperature and other environmental conditions. The most young

are produced in the range of 18-25°C (124 young per female in a 28-day life span at 24°C) (113 young per female in

a 77-day life span at 18°C) but production falls off sharply below 18°C (13 young per female in a 24-day life span

at 12°C) (McNaught and Mount, 1985).
129

2.4.3 The time required to reach maturity (produce their first offspring) in C.dubia varies from three to five days

and appears to be dependent on body size and environmental conditions. A study of the growth and development of

parthenogenetic eggs by Shuba and Costa (1972) revealed that at 24°C the embryos matured to free-swimming

juveniles in approximately 38 h. The eggs that did not develop fully usually were aborted after 12 hours.

2.4.4 The growth rate of the organism is greatest during its juvenile stages (early instars), and the body size may

double during each of these stages. Each instar stage is terminated by a molt. Growth occurs immediately after

each molt while the new carapace is still elastic. 

2.4.5 Following the juvenile stages, the adolescent period is very short, and consists of a single instar. It is during

the adolescent instar that the first clutch of eggs reaches full development in the ovary. Generally, eggs are

deposited in the brood chamber within minutes after molting, and the young which develop are released just before

the next molt. 

2.4.6 In general, the duration of instars increases with age, but also depends on environmental conditions. A given

instar usually lasts approximately 24 h under favorable conditions. However, when conditions are unfavorable, it

may last as long as a week. Four events take place in a matter of a few minutes at the end of each adult instar: (1)

release of young from the brood chamber to the outside, (2) molting, (3) increase in size, and (4) release of a new

clutch of eggs into the brood chamber. The number of young per brood is highly variable, depending primarily on

food availability and environmental conditions. C. dubia may produce as many as 25 young in a single brood, but

more commonly the number is six to ten. The number of young released during the adult instars reaches a

maximum at about the fourth instar, after which there is a gradual decrease. 

3. CULTURING METHODS

3.1 Ceriodaphnia are available from commercial biological supply houses. Guidance on the source of culture

animals to be used by a permittee for self-monitoring effluent toxicity tests should be obtained from the permitting

authority. Only a small number of organisms (20-30) are needed to start a culture. Before test organisms are taken

from a culture, the culture should be maintained for at least two generations using the same food, water, and

temperature as will be used in the toxicity tests. 

3.2 Cultures of test organisms should be started at least three weeks before the brood animals are needed, to ensure

an adequate supply of neonates for the test. Only a few individuals are needed to start a culture because of their

prolific reproduction. 

3.3 Starter animals may be obtained from an outside source by shipping in polyethylene bottles. Approximately

20-30 animals and 3 mL of food (see below) are placed in a l-L bottle filled full with culture water. Animals

received from an outside source should be transferred to new culture media gradually over a period of 1-2 days to

avoid mass mortality. 

3.4 It is best to start the cultures with one animal, which is sacrificed after producing young, embedded, and

retained as a permanent microscope slide mount to facilitate identification and permit future reference. The species

identification of the stock culture should be verified by a taxonomic authority. The following procedure is

recommended for making slide mounts of Ceriodaphnia (Beckett and Lewis, 1982):

 1. Pipet the animal onto a watch glass. 

 2. Reduce the water volume by withdrawing excess water with the pipet.

 3. Add a few drops of carbonated water (club soda or seltzer water) or 70% ethanol to relax the specimen so

that the post-abdomen is extended. (Optional: with practice, extension of the postabdomen may be

accomplished by putting pressure on the cover slip). 

 4. Place a small amount (one to three drops) of mounting medium on a glass microscope slide. The

recommended mounting medium is CMCP-9/9AF Medium, prepared by mixing two parts of CMCP-9 with
130

one part of CMCP-9AF. For more viscosity and faster drying, CMC-10 stained with acid fuchsin may be

used.

 5. Using a forceps or a pipet, transfer the animal to the drop of mounting medium on the microscope slide. 

 6. Cover with a cover slip and exert minimum pressure to remove any air bubbles trapped under the cover

slip. Slightly more pressure will extend the postabdomen.

 7. Allow mounting medium to dry.

 8. Make slide permanent by placing CMC-10 around the edges of the coverslip. 

 9. Identify to species (see Pennak, 1989, and USEPA, 1986).

10. Label with waterproof ink or diamond pencil. 

11. Store for permanent record.

3.5 CULTURE MEDIA

3.5.1 Although Ceriodaphnia stock cultures can be successfully maintained in some tap waters, well waters, and

surface waters, use of synthetic water as the culture medium is recommended because (1) it is easily prepared, (2) it

is of known quality, (3) it yields reproducible results, and (4) allows adequate growth and reproduction. Culturing

may be successfully done in hard, moderately hard or soft reconstituted water, depending on the hardness of the

water in which the test will be conducted. The quality of the dilution water is extremely important in Ceriodaphnia

culture. The use of MILLIPORE MILLI-Q® or SUPER-Q®, or equivalent, to prepare reconstituted water is highly

recommended. The use of diluted mineral water (DMW) for culturing and testing is widespread due to the ease of

preparation.

3.5.2 The chemicals used and instructions for preparation of reconstituted water are given in Section 7, Dilution

Water. The compounds are dissolved in distilled or deionized water and the media are vigorously aerated for

several hours before using. The initial pH of the media is between 7.0 and 8.0, but it will rise as much as 0.5 unit

after the test is underway. 

3.6 MASS CULTURE

3.6.1 Mass cultures are used only as a "backup" reservoir of organisms. Neonates from mass cultures are not to be

used directly in toxicity tests. 

3.6.2 One-liter or 2L glass beakers, crystallization dishes, "battery jars," or aquaria may be used as culture vessels. 

Vessels are commonly filled to three-fourths capacity. Cultures are fed daily. Four or more cultures are maintained

in separate vessels and with overlapping ages to serve as back-up in case one culture is lost due to accident or other

unanticipated problems, such as low DO concentrations or poor quality of food or laboratory water.

3.6.3 Mass cultures which will serve as a source of brood organisms for individual culture should be maintained in

good condition by frequent renewal of the medium and brood organisms. Cultures are started by adding 40-50

neonates per liter of medium. The stocked organisms should be transferred to new culture medium at least twice a

week for two weeks. After two weeks, the culture is discarded and re-started with neonates in fresh medium. Using

this schedule, 1-L cultures will produce 500 to 1000 neonate Ceriodaphnia each week. 

3.6.6 Reserve cultures also may be maintained in large (80-L) aquaria or other large tanks.

3.7 INDIVIDUAL CULTURE 

3.7.1 Individual cultures are used as the immediate source of neonates for toxicity tests. 

3.7.2 Individual organisms are cultured in 15 mL of culture medium in 30-mL (1 oz) plastic cups or 30-mL glass

beakers. One neonate is placed in each cup. It is convenient to place the cups in the same type of board used for

toxicity tests.
131

3.7.3 Organisms are fed daily and are transferred to fresh medium a minimum of three times a week, typically on

Monday, Wednesday, and Friday. On the transfer days, food is added to the new medium immediately before or

after the organisms are transferred. 

3.7.4 To provide cultures of overlapping ages, new boards are started weekly, using neonates from adults which

produce at least eight young in their third or fourth brood. These adults can be used as sources of neonates until

14 days of age. A minimum of two boards are maintained concurrently to provide backup supplies of organisms in

case of problems. 

3.7.5 Cultures which are properly maintained should produce at least 20 young per adult in three broods (seven

days or less at 25°C). Typically, 60 adult females (one board) will produce more than the minimum number of

neonates (120) required for two tests. 

3.7.6 Records should be maintained on the survival of brood organisms and number of offspring at each renewal. 

Greater than 20% mortality of adults or less than an average of 20 young per adult on a board at 25°C during a

one-week period would indicate problems, such as poor quality of culture media or food. Organisms on that board

should not be used as a source of test organisms.

3.8 CULTURE MEDIUM 

3.8.1 Moderately hard synthetic water prepared using MILLIPORE MILLI-Q® or equivalent deionized water and

reagent grade chemicals or 20% DMW is recommended as a standard culture medium (see Section 7, Dilution

Water). 

3.9 CULTURE CONDITIONS 

3.9.1 Ceriodaphnia should be cultured at the temperature at which they will be used in the toxicity tests (20°C or

25°C + 2°C). 

3.9.2 Day/night cycles prevailing in most laboratories will provide adequate illumination for normal growth and

reproduction. A 16-h/8-h day/night cycle is recommended. 

3.9.3 Clear, double-strength safety glass or 6 mm plastic panels are placed on the culture vessels to exclude dust

and dirt, and reduce evaporation.

3.9.4 The organisms are delicate and should be handled as carefully and as little as possible so that they are not

unnecessarily stressed. They are transferred with a pipet of approximately 2-mm bore, taking care to release the

animals under the surface of the water. Any organism that is injured during handling should be discarded. 

3.10 FOOD PREPARATION AND FEEDING 

3.10.1 Feeding the proper amount of the right food is extremely important in Ceriodaphnia culturing. The key is

to provide sufficient nutrition to support normal reproduction without adding excess food which may reduce the

toxicity of the test solutions, clog the animal's filtering apparatus, or greatly decrease the DO concentration and

increase mortality. A combination of Yeast, CEROPHYLL®, and Trout chow (YCT) or flake food, along with the

unicellular green alga, Selenastrum capricornutum, will provide suitable nutrition if fed daily.

3.10.2 The YCT and algae are prepared as follows: 

3.10.2.1 Digested trout chow (or flake food): 

1. Preparation of trout chow requires one week. Use starter or No. 1 pellets prepared according to
132

current U.S. Fish and Wildlife Service specifications, or flake food. 

 2. Add 5.0 g of trout chow pellets or flake food to 1 L of MILLI-Q® water. Mix well in a blender and

pour into a 2-L separatory funnel. Digest prior to use by aerating continuously from the bottom of

the vessel for one week at ambient laboratory temperature. Water lost due to evaporation is

replaced during digestion. Because of the offensive odor usually produced during digestion, the

vessel should be placed in a fume hood or other isolated, ventilated area.

3. At the end of digestion period, place in a refrigerator and allow to settle for a minimum of 1 h. 

Filter the supernatant through a fine mesh screen (i.e., NITEX® 110 mesh). Combine with equal

volumes of supernatant from CEROPHYLL® and yeast preparations (below). The supernatant

can be used fresh, or frozen until use. Discard the sediment.

3.10.2.2 Yeast: 

1. Add 5.0 g of dry yeast, such as FLEISCHMANN'S® to 1 L of MILLI-Q ® water.

2. Stir with a magnetic stirrer, shake vigorously by hand, or mix with a blender at low speed, until

the yeast is well dispersed. 

3. Combine the yeast suspension immediately (do not allow to settle) with equal volumes of

supernatant from the trout chow (above) and CEROPHYLL® preparations (below). Discard

excess material. 

3.10.2.3 CEROPHYLL® (Dried, Powdered, Cereal Leaves): 

1. Place 5.0 g of dried, powdered, cereal leaves in a blender. Dried, powdered, alfalfa leaves

obtained from health food stores have been found to be a satisfactory substitute for cereal leaves. 

2. Add 1 L of MILLI-Q® water. 

3. Mix in a blender at high speed for 5 min, or stir overnight at medium speed on a magnetic stir

plate. 

4. If a blender is used to suspend the material, place in a refrigerator overnight to settle. If a

magnetic stirrer is used, allow to settle for 1 h. Decant the supernatant and combine with equal

volumes of supernatant from trout chow and yeast preparations (above). Discard excess material.

3.10.2.4 Combined YCT Food: 

1. Mix equal (approximately 300 mL) volumes of the three foods as described above. 

2. Place aliquots of the mixture in small (50-mL to 100-mL) screw-cap plastic bottles and freeze

until needed. 

3. Freshly prepared food can be used immediately, or it can be frozen until needed. Thawed food is

stored in the refrigerator between feedings, and is used for a maximum of two weeks. 

4. It is advisable to measure the dry weight of solids (dry 24 h at 105°C) in each batch of YCT

before use. The food should contain 1.7 - 1.9 g solids/L. Cultures or test solutions should contain

12-13 mg solids/L. 

3.10.3 Algal (Selenastrum) Food 

3.10.3.1 Algal Culture Medium 

 1. Prepare (five) stock nutrient solutions using reagent grade chemicals as described in Table 1. 

2. Add 1 mL of each stock solution, in the order listed in Table 1, to approximately 900 mL of

MILLI-Q® water. Mix well after the addition of each solution. Dilute to 1 L and mix well. The

final concentration of macronutrients and micronutrients in the culture medium is given in

Table 2.
133

TABLE 1. NUTRIENT STOCK SOLUTIONS FOR MAINTAINING ALGAL STOCK CULTURES AND TEST

CONTROL CULTURES

STOCK COMPOUND AMOUNT DISSOLVED IN 

SOLUTION 500 ML MILLI-Q® WATER 

1. MACRONUTRIENTS

 A. MgCl2•6H2O 6.08 g 

 CaCl2•2H2O 2.20 g 

 NaNO3 12.75 g 

 B. MgSO4•7H2O 7.35 g 

 C. K2HPO4 0.522 g 

 D. NaHCO3 7.50 g 

2. MICRONUTRIENTS:

H3BO3 92.8 mg 

MnCl2•4H2O 208.0 mg 

ZnCl2 1.64 mga

 FeCl3•6H2O 79.9 mg 

 CoCl2•6H2O 0.714 mgb

 Na2MoO4•2H2O 3.63 mgc

 CuCl2•2H2O 0.006 mgd

 Na2EDTA•2H2O 150.0 mg 

 Na2SeO4 1.196 mge

a

ZnCl2 - Weigh out 164 mg and dilute to 100 mL. Add 1 mL of this 

 solution to Stock #2. 

b

CoCl2•6H2O - Weigh out 71.4 mg and dilute to 100 mL. Add 1 mL of 

 this solution to Stock #2. 

c

Na2MoO4•2H2O - Weigh out 36.6 mg and dilute to 10 mL. Add 1 mL 

 of this solution to Stock #2. 

d

CuCl2•2H2O - Weigh out 60.0 mg and dilute to 1000 mL. Take 1 mL of 

 this solution and dilute to 10 mL. Take 1 mL of the second dilution and 

 add to Stock #2. 

e

Na2SeO4 - Weigh out 119.6 mg and dilute to 100 mL. Add 1 mL of this solution to Stock #2. 
134

TABLE 2. FINAL CONCENTRATION OF MACRONUTRIENTS AND MICRONUTRIENTS IN THE

CULTURE MEDIUM 

CONCENTRATION ELEMENT CONCENTRATION 

MACRONUTRIENT (MG/L) (MG/L) 

NaNO3 25.5 N 4.20 

MgCl2•6H2O 12.2 Mg 2.90 

CaCl2•2H2O 4.41 Ca 1.20 

MgSO4•7H2O 14.7 S 1.91 

K2HPO4 1.04 P 0.186 

NaHCO3 15.0 Na 11.0 

K 0.469 

C 2.14 

CONCENTRATION ELEMENT CONCENTRATION 

MICRONUTRIENT (μG/L) (μG/L) 

H3BO3 185 B 32.5 

MnCl2•4H2O 416 Mn 115 

ZnCl2 3.27 Zn 1.57 

CoCl2•6H2O 1.43 Co 0.354 

CuCl2•2H2O 0.012 Cu 0.004 

Na2MoO4•2H2O 7.26 Mo 2.88 

FeCl3•6H2O 160 Fe 33.1 

Na2EDTA•2H2O 300 -- ---- 

Na2SeO4 2.39 Se 1.00 

 
135

3. Immediately filter the medium through a 0.45 μm pore diameter membrane at a vacuum of not

more than 380 mm (15 in.) mercury, or at a pressure of not more than one-half atmosphere (8 psi). 

Wash the filter with 500 mL deionized water prior to use.

4. If the filtration is carried out with sterile apparatus, filtered medium can be used immediately, and

no further sterilization steps are required before the inoculation of the medium. The medium can

also be sterilized by autoclaving after it is placed in the culture vessels.

5. Unused sterile medium should not be stored more than one week prior to use, because there may

be substantial loss of water by evaporation.

3.10.3.2 Algal Cultures

3.10.3.2.1 Two types of algal cultures are maintained: (1) stock cultures, and, (2) "food" cultures. 

3.10.3.2.2 Establishing and Maintaining Stock Cultures of Algae 

1. Upon receipt of the "starter" culture (usually about 10 mL), a stock culture is initiated by

aseptically transferring one milliliter to each of several 250-mL culture flasks containing 100 mL

algal culture medium (prepared as described above). The remainder of the starter culture can be

held in reserve for up to six months in a refrigerator (in the dark) at 4°C. 

2. The stock cultures are used as a source of algae to initiate "food" cultures for Ceriodaphnia

toxicity tests. The volume of stock culture maintained at any one time will depend on the amount

of algal food required for the Ceriodaphnia cultures and tests. Stock culture volume may be

rapidly "scaled up" to several liters, if necessary, using 4-L serum bottles or similar vessels, each

containing 3 L of growth medium. 

3. Culture temperature is not critical. Stock cultures may be maintained in environmental chambers

with cultures of other organisms if the illumination is adequate (continuous "cool-white"

fluorescent lighting of approximately 86 ± 8.6 μE/m2

/s, or 400 ft-c). 

4. Cultures are mixed twice daily by hand or stirred continuously. 

5. Stock cultures can be held in the refrigerator until used to start "food" cultures, or can be

transferred to new medium weekly. One-to-three milliliters of 7-day old algal stock culture,

containing approximately 1.5 X 106

 cells/mL, are transferred to each 100 mL of fresh culture

medium. The inoculum should provide an initial cell density of approximately 10,000-30,000

cells/mL in the new stock cultures. Aseptic techniques should be used in maintaining the stock

algal cultures, and care should be exercised to avoid contamination by other microorganisms. 

6. Stock cultures should be examined microscopically weekly, at transfer, for microbial

contamination. Reserve quantities of culture organisms can be maintained for 6-12 months if

stored in the dark at 4°C. It is advisable to prepare new stock cultures from "starter" cultures

obtained from established outside sources of organisms every four to six months. 

3.10.3.2.3 Establishing and Maintaining "Food" Cultures of Algae 

1. "Food" cultures are started seven days prior to use for Ceriodaphnia cultures and tests. 

Approximately 20 mL of 7-day-old algal stock culture (described in the previous paragraph),

containing 1.5 X 106

 cells/mL, are added to each liter of fresh algal culture medium (i.e., 3 L of

medium in a 4-L bottle, or 18 L in a 20-L bottle). The inoculum should provide an initial cell

density of approximately 30,000 cells/mL. Aseptic techniques should be used in preparing and

maintaining the cultures, and care should be exercised to avoid contamination by other

microorganisms. However, sterility of food cultures is not as critical as in stock cultures because

the food cultures are terminated in 7-10 days. A one-month supply of algal food can be grown at

one time, and the excess stored in the refrigerator. 

2. Food cultures may be maintained at 25°C in environmental chambers with the algal stock cultures

or cultures of other organisms if the illumination is adequate (continuous "cool-white" fluorescent
136

lighting of approximately 86 ± 8.6 μE/m2/s, or 400 ft-c). 

3. Cultures are mixed continuously on a magnetic stir plate (with a medium size stir bar) or in a

moderately aerated separatory funnel, or are mixed twice daily by hand. If the cultures are placed

on a magnetic stir plate, heat generated by the stirrer might elevate the culture temperature several

degrees. Caution should be exercised to prevent the culture temperature from rising more than

2-3°C.

3.10.3.3 Preparing Algal Concentrate for Use as Ceriodaphnia Food 

1. An algal concentrate containing 3.0 to 3.5 X 107

 cells/mL is prepared from food cultures by

centrifuging the algae with a plankton or bucket-type centrifuge, or by allowing the cultures to

settle in a refrigerator for approximately two-to-three weeks and siphoning off the supernatant. 

2. The cell density (cells/mL) in the concentrate is measured with an electronic particle counter,

microscope and hemocytometer, fluorometer, or spectrophotometer, and used to determine the

concentration required to achieve a final cell count of 3.0 to 3.5 X 107 cells/mL.

3. Assuming a cell density of approximately 1.5 X 106

 cells/mL in the algal food cultures at 7 days,

and 100% recovery in the concentration process, a 3-L, 7-10 day culture will provide 4.5 X 109

algal cells. This number of cells would provide approximately 150 mL of algal cell concentrate

(1500 feedings at 0.1 mL/feeding) for use as food. This would be enough algal food for four

Ceriodaphnia tests.

4. Algal concentrate may be stored in the refrigerator for one month. 

3.11 FEEDING 

3.11.1 Cultures should be fed daily to maintain the organisms in optimum condition so as to provide maximum

reproduction. Stock cultures which are stressed because they are not adequately fed may produce low numbers of

young, large number of males, and ephippial females. Also, their offspring may produce few young when used in

toxicity tests. 

1. If YCT is frozen, remove a bottle of food from the freezer 1 h before feeding time, and allow to

thaw. 

2. Mass cultures are fed daily at the rate of 7 mL YCT and 7 mL algae concentrate/L culture. 

3. Individual cultures are fed at the rate of 0.1 mL YCT and 0.1 mL algae concentrate per 15 mL

culture. 

4. YCT and algal concentrate should be thoroughly mixed by shaking before dispensing. 

5. Return unused YCT food mixture and algae concentrate to the refrigerator. Do not re-freeze

YCT. Discard unused portion after one week.

3.12 FOOD QUALITY 

3.12.1 The quality of food prepared with newly acquired supplies of yeast, trout chow, dried cereal leaves, or

algae, should be determined in side-by-side comparisons of Ceriodaphnia survival and reproduction, using the new

food and food of known, acceptable quality, over a seven-day period in control medium. 

4. TEST ORGANISMS

4.1 Neonates, or first instar Ceriodaphnia less than 24 hours old, taken from the 3rd or 4th brood, are used in

toxicity tests. To obtain the necessary number of young for an acute toxicity test, it is recommended that the

animals be cultured in individual 30 mL beakers or plastic cups for seven days prior to the beginning of the test. 

Neonates are used from broods of at least eight young. Fifty adults in individual cultures will usually supply

enough neonates for one toxicity test. 
137

4.2 Use a disposable, widemouth pipette to transfer Ceriodaphnia. The diameter of the opening should be

approximately 4 mm. The tip of the pipette should be kept under the surface of the water when the Ceriodaphnia

are released to prevent air from being trapped under the carapace. Liquid containing adult Ceriodaphnia can be

poured from one container to another without risk of injuring the animals. 
138

SELECTED REFERENCES

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Microsc. Soc. 101(1):96-99.

Brandl, Z., and C.H. Fernando. 1971. Microaggregation of the cladoceran Ceriodaphnia affinis Lilleborg with a

possible reason for microaggregation of zooplankton. Can. J. Zool. 49:775. 

Cowgill, U.M., K.I. Keating, and I.T. Takahashi. 1985. Fecundity and longevity of Ceriodaphnia dubia/affinis in

relation to diet at two different temperatures. J. Crust. Biol. 5(3):420-429. 

Devaux, J. 1980. Contribution to limnological study of Lake Pavin, France. 2: Relationship between abiotic

parameters, phytoplankton and zooplankton in the 0-20 meter zone. Hydrobiologia 68(1):17-34.

Fairchild, G.W. 1981. Movement and micro distribution of Sidia crystalline and other littoral micro Crustacea.

Ecology 62(5):1341-1352. 

Geller, W., and H. Mueller. 1981. The filtration apparatus of Cladocera filter mesh sizes and their implications on

food selectivity. Oecologia (Berl.) 49(3):316-321. 

Gophen, M. 1976. Temperature dependence of food intake, ammonia excretion, and respiration in Ceriodaphnia

reticulata, Lake Kinneret, Israel. Freshwat. Biol. 6(5):451-455. 

Kititsyna, L.A., and O.A. Sergeeva. 1976. Effect of temperature increase on the size and weight of some

invertebrate populations in the cooling reservoir of the Kinakhovsk State Regional Electric Power Plant. 

Ekologyia 5:99-102. 

Lynch, M. 1978. Complex interactions between natural coexploiters - Daphnia and Ceriodaphnia. Ecology

59(3):552-564. 

Lynch, M. 1979. Predation, competition, and zooplankton community structure: An experimental study. Limnol.

Oceanogr. 24(2):253-272. 

McNaught, D.C., and D.I. Mount. 1985. Appropriate durations and measures for Ceriodaphnia toxicity tests. In:

R.C. Bahner and D.J. Hansen (eds.), Aquatic Toxicology and Hazard Assessment: Eighth Symposium. ASTM

STP 891, American Society for Testing and Materials, Philadelphia, PA. pp. 375-381. 

Norberg, T.J., and D.I. Mount. 1985. Diets for Ceriodaphnia reticulata life-cycle tests. In: R.D. Cardwell, R.

Purdy and R.C. Bahner (eds.), Aquatic Toxicology and Hazard Assessment: Seventh Symposium. ASTM STP

854. American Society for Testing and Materials, Philadelphia, PA. pp. 42-52. 

Pal, G. 1980. Characterization of water quality regions of the Lake of Velence, Hungary with planktonic

crustaceans. Allattani Kozl. 67(1-4):49-58. 

Pennak, R.W. 1989. Fresh-water invertebrates of the United States. 3rd ed. Protozoa to Mollusca. John Wiley &

Sons, New York, NY. 

Shuba, T., and R.R. Costa. 1972. Development and growth of Ceriodaphnia reticulata embryos. Trans. Am.

Microsc. Soc. 91(3):429-435. 

Smagowicz, K. 1976. On the zooplankton of Lake Zeribar, Western Iran. Acta Hydrobiol. 18(1):89-100. 
139

USEPA. 1986. Taxonomy of Ceriodaphnia (Crustacea: Cladocera) in U.S. Environmental Protection Agency

cultures. D.B. Berner. U. S. Environmental Protection Agency, Environmental Monitoring and Support 

Laboratory, Cincinnati, OH. EPA/600/4-86/032

USEPA. 1989. Culturing of Ceriodaphnia dubia. Supplemental report for video training tape. U. S.

Environmental Protection Agency, Washington, D.C. EPA/505/8-89/002a.

Vigerstad, T.J., and L.J. Tilly. 1977. Hyper-thermal effluent effects on heleo planktonic Cladocera and the

influence of submerged macrophytes. Hydrobiologia 55(1):81-86. 

Wong, C.K. 1981. Predatory feeding behavior of Epischura lacustris (Copepoda: Calanoida) and prey defense.

Can. J. Fish. Aquat. Sci. 38:275-279. 
140

APPENDIX A

DISTRIBUTION, LIFE CYCLE, TAXONOMY, AND CULTURE METHODS

A.2. DAPHNIA (D. MAGNA AND D. PULEX)

1. SYSTEMATICS

1.1 MORPHOLOGY AND TAXONOMY 

1.1.1 The generalized anatomy of a parthenogenetic female is shown in Figure 1. Daphnia pulex is an extremely

variable species consisting of several reproductively isolated clonal groups and is often not distinguishable from

other species (such as D. obtusa) that have large teeth on the middle pecten of the postabdomenal claw (Figure 2C)

(Lynch, 1985; Dodson, 1981). Probably the most distinctive feature of the parthenogenetic female D. pulex is the

long second abdominal process of the abreptor (postabdomen) that extends beyond the base of the anal setae (Figure

2A). 

1.1.2 D. pulex is a wide ranging species that shows little variation throughout its range. Two of its most distinctive

characteristics are the deeply sinuate posterior margin of the abreptor (Figures 3A and 3D) and the ridges on the

head which run parallel to the mid-dorsal line (Figure 3B). 

1.1.3 D. pulex is much smaller than D. magna, attaining a length of up to 3.5 mm compared to 5.0 or 6.0 mm for

D. magna. Although the two species can often be separated by size, they can be differentiated with certainty only

by examining the postabdominal claws for size and number of spines using a compound microscope. D. pulex has

5-7 stout teeth on the middle pecten (Figure 2C) while D. magna has a uniform row of 20 or more small teeth

(Figure 3E). Another characteristic for separating the neonates of the two species is the location of the nuchal organ

which is higher up on the posterior margin of the head in D. magna than in D. pulex (Schwartz and Hebert, 1984). 

For a more complete taxonomic discussion of the two species see Brooks (1957). 

2. DISTRIBUTION

2.1 D. magna has a worldwide distribution in the northern hemisphere. In North America it appears to be absent

from the eastern United States (except for Northern New England) and Alaska (Figure 4). D. pulex occurs over most

of North America except the tropics and high arctic (Figure 5), and probably occurs in Europe and South America

as well. Both species often occur in the same pools but D. pulex usually out-competes D. magna in mixed

populations and takes over as the sole inhabitant by summer's end (Modlin, 1982; Lynch, 1983).
141

Figure 2. Female Daphnia pulex. A, lateral aspect (note smoothly rounded posterior margin of

postabdomen); B, ephippial female; C, postabdomen showing large spines on the claw. (From

Brooks, 1957)

Figure 1. Generalized anatomy of a female Daphnia, X70; A, antenna; AS, anal

setae; BC, brood chamber; H, heart; INT, intestine; L, legs; OV, ovary;

P, postabdomen; PC, posbdominal claw. (From Pennak, 1989).
142

Figure 3. Female D. Magna. A. lateral aspect; B. dorsal aspect; C. ephippial female; D. postabdomen

showing sinuate posterior margin; E. postabdominal claw. (From Brooks, 1957)
143

Figure 5. Map showing the North American distribution of D. pulex.

Figure 4. Map showing the North American distribution of D. magna.
144

3. ECOLOGY AND LIFE HISTORY

3.1 GENERAL ECOLOGY

3.1.1 D. magna is principally a lake dweller and is restricted to waters in northern and western North America

exceeding a hardness of 150 mg/L (as CaCO3) (Pennak, 1989). In the Netherlands, D. magna are found in shallow

ponds with muddy bottoms rich in organic matter and with low oxygen demand (3 to 4 mg/L). D. pulex is

principally a pond dweller where the oxygen content is higher, but is also found in lakes. It is generally considered

a clean water species being dominant in nature during periods of low turbidity. However, Scholtz, et al. (1988)

found that high turbidity had little effect on survival and reproduction in laboratory studies. 

3.1.2 Daphnia populations are generally sparse in winter and early spring, but as water temperatures reach 6°C to

12°C, they increase in abundance and subsequently may reach population densities as high as 200 to 500

individuals/L (Pennak, 1989). Populations in ponds decline to very low numbers during the summer months. In

autumn there may be a second population pulse, followed by a decline to winter lows.

3.1.3 During most of the year, populations of Daphnia consist almost entirely of females, the males being

abundant only in spring or autumn when up to 56% of the offspring of D. magna may be males (Barker and Hebert,

1986). Males are distinguished from females by their smaller size, larger antennules, modified postabdomen, and

first legs, which are armed with a stout hook used in clasping. Production of males appears to be induced

principally by low temperatures or high densities and subsequent accumulation of excretory products, and/or a

decrease in available food. These conditions may induce the appearance of sexual (resting) eggs (embryos) in cases

called ephippia (Figures 2B and 3C), which are cast off during the next molt. It appears that the shift toward male

and sexual egg production is related to the metabolic rate of the parent. Any factor which tends to lower

metabolism may be responsible. Ruvinsky et al. (1978) suggested that the genome of the animal has two

developmental programs based on identical sets of chromosomes. The female program consistently functions under

a wide range of conditions, whereas the male program is turned on by specific ecological stimuli. The eggs from

which the males and females develop have identical chromosome sets. Sex determination is based on changes in

chromatin structure when the mother receives a specific signal that sexual reproduction is needed for adaptation to

extreme conditions. 

3.1.4 D. magna reproduce only by cyclic parthenogenesis in which males contribute to the genetic makeup of the

young during the sexual stage of reproduction, whereas D. pulex may reproduce either by cyclic or obligate

parthenogenesis in which the zygotes develop within the ephippium by ameoitic parthenogenesis with no genetic

contribution from the males. Thus, the ephippial and live-born offspring are genetically identical to their mothers. 

Both forms may be present in the same population resulting in cyclic populations exhibiting considerable genetic

variation early in the year and an obligate population with a low range of genotypic values. After 25 generations of

asexual reproduction the variation in the cyclic parthenogenesis group becomes about the same as that in the

obligate group (Lynch, 1984). These populations exhibiting a low range of genotypic values are much more

vulnerable to perturbations such as nutrient introduction or toxic discharges. The clonal makeup of a Daphnia

population is effected by food, oxygen, temperature and predation (Weider, 1985; Brookfield, 1984). 

3.1.5 Ephippia are small and lightweight and can be dried and stored for long periods making them easy to

transport. They may be shipped in envelopes like seeds. Upon arrival at the new location the ephippia can be

hatched in a few days when placed in water at the proper temperature (Schwartz and Hebert, 1987). 

3.1.6 Daphnia are preyed upon by many predators and have developed behavioral and morphological antipredator

defenses to make themselves more difficult to catch and consume. Dodson (1988) showed that D. pulex responded

to a possible chemical stimuli released by the predator which resulted in the daphnids retreating from the vicinity of

the predators. Certain clones of D. pulex may develop morphological changes when predators are present but not

when they are absent from the pond. Some of these changes are of such magnitude that they have been described as

separate species. D. minnehaha is a morphological variation of D. pulex which develops spines in response to the
145

stimuli of predators (Krueger and Dodson, 1981). Different genotypes of D. pulex react in different ways to the

predator (Chaoborus) factor and to temperature (Havel, 1985). 

3.2 FOOD AND FEEDING

3.2.1. Both D. pulex and D. magna are well adapted to live in algal blooms, which are high in proteins and

carbohydrates, where they feed on algae and bacteria. D. magna prefers bacteria to algae as food (Ganf, 1983;

Hadas et al., 1983) while D. pulex uses bacteria as food only when algal biomass declines (Borsheim and Olsen,

1984). Food type and abundance affect the sensitivity of Daphnia to pollutants and their reproduction rate. Keating

and Dagbusan (1986) showed that both D. pulex and D. magna fed diatoms were more tolerant of pollutants than

those fed only green algae. Lipid reserves are a good indication of the nutritional condition of the animals (Holm

and Shapiro, 1984; Tessier and Goulden, 1982). 

3.3 LIFE HISTORY 

3.3.1 Four distinct periods may be recognized in the life history of Daphnia: (1) egg, (2) juvenile, (3) adolescence,

and (4) adult (Pennak, 1989). The life span of Daphnia, from the release of the egg into the brood chamber until the

death of the adult, is highly variable depending on the species and environmental conditions (Pennak, 1989). 

Generally the life span increases as temperature decreases, due to lowered metabolic activity. The average life span

of D. magna is about 40 days at 25°C, and about 56 days at 20°C. The average life span of D. pulex at 20°C is

approximately 50 days. Typically, a clutch of 6 to 10 eggs is released into the brood chamber, but as many as 57

have been reported. The eggs hatch in the brood chamber and the juveniles, which are already similar in form to the

adults, are released in approximately two days when the female molts (casts off her exoskeleton or carapace). The

time required to reach maturity (produce their first offspring) in D. pulex varies from six to 10 days (mean = 7.78

days) and also appears to be dependent on body size. The growth rate of the organism is greatest during its juvenile

stages (early instars), and the body size may double during each of these stages. D. pulex has three to four juvenile

instars, whereas D. magna has three to five instars. Each instar stage is terminated by a molt. Growth occurs

immediately after each molt while the new carapace is still elastic. 

3.3.2 Following the juvenile stages, the adolescent period is very short, and consists of a single instar. It is during

the adolescent instar that the first clutch of eggs reaches full development in the ovary. Generally, eggs are

deposited in the brood chamber within minutes after molting, and the young which develop are released just before

the next molt.

3.3.3 D. magna usually has 6-22 adult instars, and D. pulex has 18-25. In general, the duration of instars increases

with age, but also depends on environmental conditions. A given instar generally lasts approximately two days

under favorable conditions, but when conditions are unfavorable, may last as long as a week. 

3.3.4 Four events take place in a matter of a few minutes at the end of each adult instar: (1) release of young from

the brood chamber to the outside, (2) molting, (3) increase in size, and (4) release of a new clutch of eggs into the

brood chamber. The number of young per brood is highly variable for Daphnia, depending primarily on food

availability and environmental conditions. D. magna and D. pulex may both produce as many as 30 young during

each adult instar, but more commonly the number is six to 10. The number of young released during the adult

instars of D. pulex reaches a maximum at the tenth instar, after which there is a gradual decrease (Anderson and

Zupancic, 1937). Scholtz et al. (1988) reported that nearly all of the eggs that are oviposited by D. pulex became

neonates, indicating a highly successful hatching rate. The maximum number of young produced by D. magna

occurs at the fifth adult instar, after which it decreases (Anderson and Jenkins, 1942). 
146

4. CULTURING METHODS

4.1 SOURCES OF ORGANISMS

4.1.1 Daphnia are available from commercial biological supply houses. Only a small number of organisms (20-30)

are needed to start a culture. D. pulex is preferred over D. magna by some biologists because it is more widely

distributed, is tolerant of a wider range of environmental conditions, and is easier to culture. However, the neonates

are smaller, swim faster and are more difficult to count, and produce more "floaters" than D. magna and, therefore,

are somewhat more difficult to use in toxicity tests. Guidance on the source and species of Daphnia to be used by a

permittee for effluent toxicity tests should be obtained from the permitting authority. 

4.1.2 Cultures of test organisms should be started at least three weeks before the brood animals are needed, to

ensure an adequate supply of neonates for the test.

4.1.3 Starter animals may be obtained from an outside source by shipping in polyethylene bottles. Approximately

20-30 animals and 3 mL of food (see below) are placed in a 1-L bottle filled full with culture water. Animals

received from an outside source should be transferred to new culture media gradually over a period of 1-2 days to

avoid mass mortality. 

4.1.4 It is best to start the cultures with one animal, which is sacrificed after producing young, embedded, and

retained as a permanent microscope slide mount to facilitate identification and permit future reference. The species

identification of the stock culture should be verified by a taxonomic authority. The following procedure is

recommended for making slide mounts of Daphnia (Beckett and Lewis, 1982): 

 1. Pipet the animal onto a watch glass.

 2. Reduce the water volume by withdrawing excess water with the pipet.

 3. Add a few drops of carbonated water (club soda or seltzer water) or 70% ethanol to relax the specimen

so that the post-abdomen is extended. (Optional: with practice, extension of the postabdomen may be

accomplished by putting pressure on the cover slip). 

 4. Place a small amount (one to three drops) of mounting medium on a glass microscope slide. The

recommended mounting medium is CMCP-9/9AF Medium, prepared by mixing two parts of CMCP-9

with one part of CMCP-9AF. For more viscosity and faster drying, CMC-l0 stained with acid fuchsin

may be used. 

 5. Using a forceps or a pipet, transfer the animal to the drop of mounting medium on the microscope slide. 

 6. Cover with a cover slip and exert minimum pressure to remove any air bubbles trapped under the cover

slip. Slightly more pressure will extend the postabdomen.

 7. Allow mounting medium to dry.

 8. Make slide permanent by placing CMC-10 around the edges of the coverslip. 

 9. Identify to species (see Pennak, 1989). 

10. Label with waterproof ink or diamond pencil. 

11. Store for permanent record. 

4.2 CULTURE MEDIA

4.2.1 Although Daphnia stock cultures can be successfully maintained in some tap waters, well waters, and surface

waters, use of synthetic water as the culture medium is recommended because (1) it is easily prepared, (2) it is of

known quality, (3) it yields reproducible results, and (4) allows adequate growth and reproduction. Reconstituted

hard water (total hardness of 160 -180 mg/L as CaCO3) is recommended for D. magna culturing, and reconstituted

moderately hard water (total hardness of 80-90 mg/L CaCO3) is recommended for D. pulex culturing. The quality

of the dilution water is important in Daphnia culture. The use of MILLIPORE MILLI-Q® or SUPER-Q®, or

equivalent, to prepare reconstituted water is highly recommended. The use of diluted mineral water (DMW) for

culturing and testing is widespread due to the ease of preparation.
147

4.2.2 The chemicals used and instructions for preparation of reconstituted water are given in Section 7, Dilution

Water. The compounds are dissolved in distilled or deionized water and the media are vigorously aerated for

several hours before using. The initial pH of the media is between 7.0 and 8.0, but it will rise as much as 0.5 unit

after the test is underway.

4.3 CULTURE CONDITIONS 

4.3.1 Daphnia can be cultured successfully over a wide range of temperatures, but should be protected from

sudden changes in temperature, which may cause death. The optimum temperature is approximately 20°C, and if

ambient laboratory temperatures remain in the range of 18-26°C, normal growth and reproduction of Daphnia can

be maintained without special temperature control equipment. D. magna can survive when the DO concentration is

as low as 3 mg/L but D. pulex does best when the DO concentration is above 5 mg/L. Therefore it is recommended

that the DO concentration in the culture be maintained at 5 mg/L or above. Unless the cultures are too crowded or

overfed, aeration is usually not necessary.

4.3.2 Illumination 

4.3.2.1 The variations in ambient light intensities (10-20 μE/m2

/s, or 50-100 ft-c) and prevailing day/night cycles in

most laboratories do not seem to affect Daphnia growth and reproduction significantly. However, a minimum of 16

h of illumination should be provided each day. 

4.3.3 Culture Vessels

4.3.3.1 Culture vessels of clear glass are recommended since they allow easy observation of the Daphnia. A

practical culture vessel is an ordinary 4-L glass beaker, which can be filled with approximately 3 L medium

(reconstituted water). Maintain several (at least five) culture vessels, rather than only one. This will ensure back-up

cultures so that in the event of a population "crash" in one or several chambers, the entire Daphnia population will

not be lost. If a vessel is stocked with 30 adult Daphnia, it will provide approximately 300 young each week. 

4.3.3.2 Initially, all culture vessels should be washed well (see Section 5, Facilities and Equipment). After the

culture is established, clean each chamber weekly with distilled or deionized water and wipe with a clean sponge to

rid the vessel of accumulated food and dead Daphnia (see section on culture maintenance below). Once per month,

wash each vessel with detergent during medium replacement. Rinse three times with tap water and then with culture

medium to remove all traces of detergent.

4.3.4 Weekly Culture Media Replacement

4.3.4.1 Careful culture maintenance is essential. The medium in each stock culture vessel should be replaced three

times each week with fresh medium.

This is best accomplished by changing solutions Monday, Wednesday, and Friday, as follows: 

1. Place about 300 mL of the old media in a temporary holding vessel. 

2. Transfer about 25 or 30 adults from the old culture vessel to the holding vessel using a wide bore

pipette. 

3. Discard the remaining Daphnia along with the media. 

4. Clean the culture vessel as described above. 

5. Fill the newly-cleaned vessel with fresh medium. 

6. Gently transfer (by pouring) the contents of the temporary holding vessel (old medium with the

Daphnia) into the vessel containing the new medium making sure that none of the animals stick to

the sides of the vessel. 
148

7. Feed the animals 

4.3.4.2 If the medium is not replaced three times weekly, waste products will accumulate, which could cause a

population crash or the production of males and/or sexual eggs.

4.3.4.3 Daphnia cultures should be thinned whenever the population exceeds 200 individuals per stock vessel to

prevent over-crowding, which may cause a population crash, or the production of males and/or ephippia. A good

time to thin the populations is on Monday, Wednesday, and Friday, before feeding. To transfer Daphnia, use a

15-cm disposable, jumbo bulb pipette, or 10-mL "serum" pipette which has had the delivery tip cut off and fire

polished. The diameter of the opening should be approximately 5 mm. A serum pipette, a pipette bulb, such as a

PROPIPETTE®, or (MOPET®) portable, motorized pipettor, will provide the controlled suction needed when

selectively collecting Daphnia. 

4.3.4.4 Liquid containing adult D. pulex and D. magna can be poured from one container to another without risk of

air becoming trapped under their carapaces. However, the very young Daphnia are much more susceptible to air

entrapment and for this reason should be transferred from one container to another using a pipette. The tip of the

pipette should be kept under the surface of the liquid when the Daphnia are released. 

4.3.4.5 Each culture vessel should be covered with a clear plastic sheet or glass plate to exclude dust and dirt, and

minimize evaporation. 

4.4 FOOD PREPARATION AND FEEDING 

4.4.1 Feeding the proper amount of the right food is extremely important in Daphnia culturing. The key is to

provide sufficient nutrition to support normal reproduction without adding excess food which may reduce the

toxicity of the test solutions, clog the animal's filtering apparatus, or greatly decrease the DO concentration and

increase mortality. YCT, a combination of Yeast, CEROPHYLL®, and Trout chow (or flake food), along with the

unicellular green alga, Selenastrum capricornutum, will provide suitable nutrition if fed daily.

4.4.2 The YCT and algae are prepared as follows: 

4.4.2.1 Digested trout chow (or flake food): 

1. The preparation requires one week. Use starter or No. 1 pellets prepared according to current U.S.

Fish and Wildlife Service specifications, or flake food. 

2. Add 5.0 g of trout chow pellets or flake food to 1 L of MILLI-Q® water. Mix well in a blender and

pour into a 2-L separatory funnel. Digest prior to use by aerating continuously from the bottom of

the vessel for one week at ambient laboratory temperature. Water lost due to evaporation is replaced

during digestion. Because of the offensive odor usually produced during digestion, the vessel

should be placed in a fume hood or other isolated, ventilated area. 

3. At the end of digestion period, place in a refrigerator and allow to settle for a minimum of 1 h. 

Filter the supernatant through a fine mesh screen (i.e., NITEX® 110 mesh). Combine with equal

volumes of supernatant from CEROPHYLL® and yeast preparations (below). The supernatant can

be used fresh, or frozen until use. Discard the sediment. 

4.4.2.2 Yeast: 

1. Add 5.0 g of dry yeast, such as FLEISCHMANN'S® to 1 L of MILLI-Q® water. 

2. Stir with a magnetic stirrer, shake vigorously by hand, or mix with a blender at low speed, until the

yeast is well dispersed. 

3. Combine the yeast suspension immediately (do not allow to settle) with equal volumes of

supernatant from the trout chow (above) and CEROPHYLL® preparations (below). Discard excess
149

material. 

4.4.2.3 CEROPHYLL® (Dried, Powdered, Cereal Leaves): 

1. Place 5.0 g of dried, powdered, cereal leaves in a blender. Dried, powdered, alfalfa leaves obtained

from health food stores have been found to be a satisfactory substitute for cereal leaves. 

2. Add 1 L of MILLI-Q® water. 

3. Mix in a blender at high speed for 5 min, or stir overnight at medium speed on a magnetic stir plate. 

4. If a blender is used to suspend the material, place in a refrigerator overnight to settle. If a magnetic

stirrer is used, allow to settle for 1 h. Decant the supernatant and combine with equal volumes of

supernatant from trout chow and yeast preparations (above). Discard excess material.

4.4.2.4 Combined YCT Food: 

1. Mix equal (approximately 300 mL) volumes of the three foods as described above.

2. Place aliquots of the mixture in small (50-mL to 100-mL) screw-cap plastic bottles and freeze until

needed.

3. Freshly prepared food can be used immediately, or it can be frozen until needed. Thawed food is

stored in the refrigerator between feedings, and is used for a maximum of one week.

4. It is advisable to measure the dry weight of solids in each batch of YCT before use. The food

should contain 1.7 - 1.9 g solids/L. Cultures or test solutions should contain 12-13 mg solids/L. 

4.4.3 Algal (Selenastrum) Food 

4.4.3.1 Algal Culture Medium 

1. Prepare (five) stock nutrient solutions using reagent grade chemicals as described in Table 1.

2. Add 1 mL of each stock solution, in the order listed in Table 1, to approximately 900 mL of

MILLI-Q® water. Mix well after the addition of each solution. Dilute to 1 L and mix well. The

final concentration of macronutrients and micronutrients in the culture medium is given in Table 2.

3. Immediately filter the medium through a 0.45μm pore diameter membrane at a vacuum of not more

than 380 mm (15 in.) mercury, or at a pressure of not more than one-half atmosphere (8 psi). Wash

the filter with 500 mL deionized water prior to use.

4. If the filtration is carried out with sterile apparatus, filtered medium can be used immediately, and no

further sterilization steps are required before the inoculation of the medium. The medium can also

be sterilized by autoclaving after it is placed in the culture vessels. 

5. Unused sterile medium should not be stored more than one week prior to use, because there may be

substantial loss of water by evaporation.

4.4.3.2 Algal Cultures

4.4.3.2.1 Two types of algal cultures are maintained: (1) stock cultures, and, (2) "food" cultures.

4.4.3.2.2 Establishing and Maintaining Stock Cultures of Algae 

1. Upon receipt of the "starter" culture (usually about 10 mL), a stock culture is initiated by aseptically

transferring one milliliter to each of several 250-mL culture flasks containing 100 mL algal culture

medium (prepared as described above). The remainder of the starter culture can be held in reserve

for up to six months in a refrigerator (in the dark) at 4°C.

2. The stock cultures are used as a source of algae to initiate "food" cultures for Daphnia toxicity tests. 

The volume of stock culture maintained at any one time will depend on the amount of algal food

required for the Daphnia cultures and tests. Stock culture volume may be rapidly "scaled up" to
150

several liters, if necessary, using 4-L serum bottles or similar vessels, each containing 3 L of growth

medium. 

3. Culture temperature is not critical. Stock cultures may be maintained in environmental chambers

with cultures of other organisms if the illumination is adequate (continuous "cool-white" fluorescent

lighting of approximately 86 ± 8.6 μE/m2

/s, or 400 ft-c). 

4. Cultures are mixed twice daily by hand or stirred continuously.

5. Stock cultures can be held in the refrigerator until used to start "food" cultures, or can be

transferred to new medium weekly. One-to-three milliliters of 7-day old algal stock culture,

containing approximately 1.5 X 106

 cells/mL, are transferred to each 100 mL of fresh culture

medium. The inoculum should provide an initial cell density of approximately 1,000-30,000

cells/mL in the new stock cultures. Aseptic techniques should be used in maintaining the stock algal

cultures, and care should be exercised to avoid contamination by other microorganisms. 

6. Stock cultures should be examined microscopically weekly, at transfer, for microbial contamination. 

Reserve quantities of culture organisms can be maintained for 6-12 months if stored in the dark at

4°C. It is advisable to prepare new stock cultures from "starter" cultures obtained from established

outside sources of organisms every four to six months. 
151

TABLE 1. NUTRIENT STOCK SOLUTIONS FOR MAINTAINING ALGAL STOCK CULTURES AND

TEST CONTROL CULTURES

STOCK COMPOUND AMOUNT DISSOLVED IN 

SOLUTION 500 ML MILLI-Q® WATER 

1. MACRONUTRIENTS

 A. MgCl2•6H2O 6.08 g 

 CaCl2•2H2O 2.20 g 

 NaNO3 12.75 g 

 B. MgSO4•7H2O 7.35 g 

 C. K2HPO4 0.522 g 

 D. NaHCO3 7.50 g 

2. MICRONUTRIENTS:

H3BO3 92.8 mg 

MnCl2•4H2O 208.0 mg 

ZnCl2 1.64 mga

 FeCl3•6H2O 79.9 mg 

 CoCl2•6H2O 0.714 mgb

 Na2MoO4•2H2O 3.63 mgc

 CuCl2•2H2O 0.006 mgd

 Na2EDTA•2H2O 150.0 mg 

 Na2SeO4 1.196 mge

a

ZnCl2 - Weigh out 164 mg and dilute to 100 mL. Add 1 mL of this solution to Stock #2. 

b

CoCl2•6H2O - Weigh out 71.4 mg and dilute to 100 mL. Add 1 mL of this solution to Stock #2. 

c

Na2MoO4•2H2O - Weigh out 36.6 mg and dilute to 10 mL. Add 1 mL of this solution to Stock #2. 

d

CuCl2•2H2O - Weigh out 60.0 mg and dilute to 1000 mL. Take 1 mL of this solution and dilute to 10 mL. Take 1 mL

of the second dilution and add to Stock #2. 

e

Na2SeO4 - Weigh out 119.6 mg and dilute to 100 mL. Add 1 mL of this solution to Stock #2. 
152

TABLE 2. FINAL CONCENTRATION OF MACRONUTRIENTS AND MICRONUTRIENTS IN THE

CULTURE MEDIUM

MACRO CONCENTRATION ELEMENT CONCENTRATION 

NUTRIENT (MG/L) (MG/L) 

NaNO3 25.5 N 4.20 

MgCl2•6H2O 12.2 Mg 2.90 

CaCl2•2H2O 4.41 Ca 1.20 

MgSO4•7H2O 14.7 S 1.91 

K2HPO4 1.04 P 0.186 

NaHCO3 15.0 Na 11.0 

K 0.469 

C 2.14 

MICRO CONCENTRATION ELEMENT CONCENTRATION 

NUTRIENT (μG/L) (μG/L) 

H3BO3 185 B 32.5 

MnCl2•4H2O 416 Mn 115 

ZnCl2 3.27 Zn 1.57 

CoCl2•6H2O 1.43 Co 0.354 

CuCl2•2H2O 0.012 Cu 0.004 

Na2MoO4•2H2O 7.26 Mo 2.88 

FeCl3•6H2O 160 Fe 33.1 

Na2EDTA•2H2O 300 -- ---- 

Na2SeO4 2.39 Se 1.00 
153

4.4.3.2.3 Establishing and Maintaining "Food" Cultures of Algae 

1. "Food" cultures are started seven days prior to use for Daphnia cultures and tests. Approximately

20 mL of 7-day-old algal stock culture (described in the previous paragraph), containing 1.5 X 106

cells/mL, are added to each liter of fresh algal culture medium (i.e., 3 L of medium in a 4-L bottle, or

18 L in a 20-L bottle). The inoculum should provide an initial cell density of approximately 30,000

cells/mL. Aseptic techniques should be used in preparing and maintaining the cultures, and care

should be exercised to avoid contamination by other microorganisms. However, sterility of food

cultures is not as critical as in stock cultures because the food cultures are terminated in 7-10 days. 

A one-month supply of algal food can be grown at one time, and the excess stored in the

refrigerator. 

2. Food cultures may be maintained at 25°C in environmental chambers with the algal stock cultures or

cultures of other organisms if the illumination is adequate (continuous "cool-white" fluorescent

lighting of approximately 86 ± 8.6 μE/m2

/s, or 400 ft-c).

3. Cultures are mixed continuously on a magnetic stir plate (with a medium size stir bar) or in a

moderately aerated separatory funnel, or are mixed twice daily by hand. If the cultures are placed on

a magnetic stir plate, heat generated by the stirrer might elevate the culture temperature several

degrees. Caution should be exercised to prevent the culture temperature from rising more than

2-3°C.

4.4.3.3 Preparing Algal Concentrate for Use as Daphnia Food 

1. An algal concentrate containing 3.0 to 3.5 X 107

 cells/mL is prepared from food cultures by

centrifuging the algae with a plankton or bucket-type centrifuge, or by allowing the cultures to settle

in a refrigerator for approximately two-to-three weeks and siphoning off the supernatant. 

2. The cell density (cells/mL) in the concentrate is measured with an electronic particle counter,

microscope and hemocytometer, fluorometer, or spectrophotometer, and used to determine the

concentration required to achieve a final cell count of 3.0 to 3.5 X 107

/mL.

3. Assuming a cell density of approximately 1.5 X 106

 cells/mL in the algal food cultures at 7 days, and

100% recovery in the concentration process, a 3-L, 7-10 day culture will provide 4.5 X 109

 algal

cells. This number of cells would provide approximately 150 mL of algal cell concentrate.

4. Algal concentrate may be stored in the refrigerator for one month.

4.5 FEEDING

4.5.1 Feeding rate and frequency are important in maintaining the organisms in optimal condition so that they

achieve maximum reproduction. Stock cultures which are stressed because they are not adequately fed may produce

low numbers of young, large numbers of males, and ephippial females. When the young taken from these

inadequately fed Daphnia cultures are used in toxicity tests, they may show higher than acceptable mortality in

controls and greater than normal sensitivity to toxicants. Steps to follow when feeding the YCT and algal diet are as

follows:

1. If YCT is frozen, remove a bottle of the food from the freezer at least 1 h before feeding time, and

allow to thaw. 

2. Mass cultures are fed Monday, Wednesday, and Friday at the rate of 4.5 mL YCT and 2 mL of

algae concentrate per 3-L culture. 

3. On Tuesday and Thursday the culture water is stirred to re-suspend the settled algae and another 2

mL of algal concentrate is added.

4. The YCT and algal concentrate is thoroughly mixed by shaking before dispensing. 

5. Return unused YCT food mixture and algal concentrate to the refrigerator. Do not re-freeze the

YCT. Discard unused portion of YCT after one week.

.
154

4.5.2 The quality of food prepared with newly acquired supplies of yeast, trout chow, and dried cereal leaves, or

algae, should be determined in side-by-side comparisons of Daphnia survival and reproduction tests, using the new

food and food of known, acceptable quality, over a seven-day period in control medium.
155

SELECTED REFERENCES

Adema, D.M.M. 1978. Daphnia magna as a test animal in acute and chronic toxicity tests. Hydrobiologia

59(2):125-134.

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159

APPENDIX A

DISTRIBUTION, LIFE CYCLE, TAXONOMY, AND CULTURE METHODS

A.3. MYSIDS (MYSIDOPSIS BAHIA AND HOLMESIMYSIS COSTATA)

1. DISTRIBUTION

1.1 Mysids (Figure 1) are small shrimp-like crustaceans found in both the marine and freshwater environments. 

The mysid(s) that currently are of primary interest in the NPDES program are the estuarine species, Mysidopsis

bahia (now identified as Americamysis bahia; Price et al., 1994) and the marine species, Holmesimysis costata. 

It occurs primarily at salinities above 15‰; Stuck et al. (1979a) and Price (1982) found greatest abundances at

salinities near 30‰. Three sympatric species of Mysidopsis, M. almyra, M. bahia, and M. bigelowi, have been

cultured and used in toxicity testing. The distribution of Mysidopsis species has been reported by Stuck et al.

(1979b), Price (1982), and Heard et al. (1987).

1.2 M. bahia occurs primarily at salinities above 15‰; Stuck et al. (1979a) and Price (1982) found greatest

abundances at salinities near 30‰. Three sympatric species of Mysidopsis, M. almyra, M. bahia, and M. bigelowi,

have been cultured and used in toxicity testing. The distribution of Mysidopsis species has been reported by Stuck

et al. (1979b), Price (1982), and Heard et al. (1987). 

1.3 H. costata (Holmes 1900; previously referred to as Acanthomysis sculpta) is a west coast species that lives in

the surface canopy of the giant kelp Macrocystis pyrifera where it feeds on zooplankters, kelp, epiphytes, and

detritus. There are few references to the ecology of this mysid species (Holmquist, 1979; Clutter, 1967, 1969;

Green, 1970; Turpen et al., 1994). H. costata is numerically abundant in kelp forest habitats and is considered to

be an important food source for kelp forest fish (Clark 1971, Mauchline 1980). H. costata eggs develop for about

20 days in their marsupium (abdominal pouch) before the young are released as juveniles; broods are released at

night during molting. Females release their first brood at 55 to 70 days post-release (at 12°C), and may have

multiple broods throughout their approximately 120-day life. 

1.4 Other marine mysids that have been used in toxicity testing and held or cultured in the lab include Metamysidopsis elongata, Neomysis americana, Neomysis awatschensis, Neomysis intermedia, and recently for the Pacific

coast, Holmesimysis sculpta and Neomysis mercedis. A freshwater species, Mysis relicta, presently not used in

toxicity testing, but found in the same habitat as Daphnia pulex, might be considered in the future for toxicity

testing.

2. MYSIDOPSIS BAHIA

2.1 LIFE CYCLE

2.1.1 In laboratory culture, Mysidopsis bahia reach sexual maturity in 12 to 20 days, depending on water

temperature and diet (Nimmo et al., 1977). Normally, the female will have eggs in the ovary at approximately 12

days of age. The lamellae of the marsupium pouch have formed or are in the process of forming when the female

is approximately 4 mm in length (Ward, 1993). Unlike Daphnia, the eggs will not develop unless fertilized. 

Mating takes place at night and lasts only a few minutes (Mauchline, 1980). 

2.1.2 Brood pouches are normally fully formed at approximately 15 days (approximately 5 mm in body length),

and young are released in 17 to 20 days (Ward, 1993). The number of eggs deposited in the brood and the number

of young produced per brood are a direct function of body length as well as environmental conditions. Mature

females have produced as many as 25 Stage I larvae (egg-shaped embryo) per brood (8-9 mm in body length) in

natural and artificial seawater (FORTY FATHOMS®) but average 11 ± 6 Stage III larvae (final stage before larvae
160

Figure 1. Lateral and dorsal view of a mysid with morphological features identified (From Stuck et al.,

1979a).

are released), with increasing numbers correlated with increasing body length (Ward, 1993). A new brood is

produced every 4 to 7 days.

2.1.3 At time of emergence, juveniles are immobile, making them susceptible to predation by adult mysids. The

juveniles are planktonic for the first 24-48 hours and then settle to the bottom, orient to the current, and actively

pursue food organisms such as Artemia. Carr et al. (1980) reported that the stage in the life cycle of M. almyra

most sensitive to drilling mud was the juvenile molt, which occurs between 24 and 48 hours after release from the

brood pouch. Ward (1989) found a relationship between CaCO3 level and growth and reproduction and that

M. bahia were more sensitive to cadmium during molting (24-72 h post release) in high or low levels of CaCO3. 

Work done by Lee and Buikema (1979) for Daphnia pulex also showed increased sensitivity during molting.
161

Figure 2. Morphological features most useful in identifying Mysidopsis bahia. a. male; b. female; c. thoracic

leg 2; d. telson; e. right uropod, dorsal; f. male, dorsal (redrawn from Molenock, 1969; Heard et al.,

1987). Note gonad in area where marsupium is located on female and length of male pleopods as

compared to female. Also note the 3 spines on the endopod of the uropod (e).
162

TABLE 1. GENUS MYSIDOPSIS: COMMON AND SPECIFIC CHARACTERS OF SPECIES KNOWN FROM U.S. ALTANTIC AND

GULF OF MEXICO WATERS (HEARD, ET AL., 1987 AND MODIFIED IN PART FROM BRATTEGARD, 1969)

M.

Eclipes

M.

Brattstroemi

M.

Mortenseni

M.

Furca

M.

Almyra

M.

Bahia

M.

Bigelowi

M. sp.

(Inshore)

M. sp.

(Offshore)

Anterior dorsal marginof carapace

Triangular Triangular Triangular Rounded Rounded Triangular Triangular Triangular Triangular

Presence of distalsegment on antennal

yes yes yes yes no no no no no

Length/breadth ratioof antennal scale

2-2.5 3-3.5 3.5-4 4 6 6 5.4 5.4 5.2

# segments incarpoporpodus ofthoracic endopods 3-8

333

(2 in juv.)

32 2 2 2 2

# segments in exopodof male pleopod 4

? 6 6-7 7 7 7 7-8 7 7

# spines on uropodalendopod

8-9 10-20 18-31 20-40 1 1-4 5

(occ. 3-4)

3-4

(occ.2 or 5)

5

(occ. 4)

Length of terminalpair(s) of telson spinesrelative to lateralmargin spines

Almost

twice as

long

slightly

longer

Slightly

longer

> twice

as long

Gradually

increasing

Gradually

increasing

Abruptly

increasing

Abruptly

increasing

Abruptly

increasing

# of pairs of apicaltelson spines

1 1 1 2 4-8 3-6 3 3-4 3

# setae on innermargin of segment 6of second thoracicendopod

ca 3 ca 4 ca 3 ca 3 2-3 2-3 6-12 6-12 6-12

# setae on innermargin of segment 5of second thoracicendopod

ca 5 ca 4 ca 2 ca 3 7-18 7-18 2 2 5-7
163

2.2 MORPHOLOGY AND TAXONOMY

2.2.1 Since Mysidopsis bahia occur with two other species of Mysidopsis, an understanding of the taxonomy of

M. almyra, M. bahia, and M. bigelowi is important for culturing and testing practices. The taxonomic key of

Heard et al. (1987) is suggested (see Table 1 for morphological guide to Mysidopsis).

2.2.2 Adults of M. bahia range in length from 4.4 mm to 9.4 mm (Molenock, 1969), measured from the anterior

margin of the carapace to the end of uropods. The mature females are normally larger than the males and the

pleopods of the female are smaller than those of the male (Ward, 1993) (Figure 2). Mysidopsis bahia can be

positively identified as male or female when they are 4 mm in body length (Ward, 1993). Living organisms are

usually transparent, but may be tinted yellow, brown or black. Mysidopsis bigelowi can be readily distinguished

from M. almyra and M. bahia by the morphology of the second thoracic leg. Mysidopsis bigelowi has a greatly

enlarged endopod of the thoracic limb 2 ("first leg") and the limb has a distinctive row of 6 to 12 spiniform setae

on the inner margin of the sixth segment (Heard et al., 1987). Mysidopsis bahia can also be distinguished from

other species of Mysidopsis by the number of apical spines on the telson (4-5 pairs) and the number of spines on

the inner uropods distal to the statocyst (normally 2-3) (Figure 2).

2.2.3 Heard et al. (1987) state that the most reliable character for separating adult M. almyra and M. bahia is the

number of spines on the inner uropods (M. almyra will always have a single spine). Further, Price (1982) found

that for all stages of development for both species, the shape of the anterior margin of the carapace (rostral plate)

could be used to distinguish M. almyra (broadly rounded) from M. bahia (more produced). Figure 2 illustrates the

morphological features most useful in identifying M. bahia (redrawn Molenock, 1969; Heard et al., 1987).

2.3 CULTURE METHODS

2.3.1 SOURCE OF ORGANISMS

2.3.1.1 Starter cultures of mysids can be obtained from commercial sources, particularly in the Gulf of Mexico

region for M. almyra and M. bahia.

2.3.1.2 Mysids of different species can also be collected by plankton tows or dip nets (approximately 1.0 mm

mesh size) in estuarine systems. Heard et al. (1987) have identified specimens of M. bahia along the eastern coast,

however, it has been principally identified as a subtropical species found in the Gulf of Mexico and along the east

coast of Florida. Since many species of mysids may be present at a given collection site, the identification of the

organisms selected for culture should be verified by an experienced taxonomist. The permittee should consult the

permitting authority for guidance on the source of test organisms (indigenous or laboratory reared) before use.

2.4 CULTURING SYSTEM

2.4.1 Stock cultures can be maintained in continuous-flow or closed recirculating systems. In laboratory culture

of M. bahia, recirculating systems are probably the most common practice. During the past ten years, a number of

closed recirculating systems have been described. Since no single recirculating technique is the best in all respects,

the system adopted will depend on the facilities and equipment available and the objectives of the culturing

activities. Two other species of mysid, M. almyra and M. bigelowi, have also been successfully reared in the

system described in this section (Ward, 1991). Further, there now exist a number of review papers (Venables,

1987 and Lussier et al., 1988) that describe in detail techniques developed by others that will be very helpful in

culturing Mysidopsis.

2.4.2 Closed recirculating systems are unique because the re-used seawater they contain develops an unusual set

of characteristics caused primarily by metabolic waste produced by the mysids. The accumulation of waste

products and suspended particles in the water column is prevented by passing the seawater through a biological

filtration system, in which ammonia and nitrite are oxidized by nitrifying bacteria. 
164

2.5 CULTURE TANKS

2.5.1 Stock cultures of mysids are maintained in a closed recirculating system. The system should consist of four

200-L glass aquaria. However, smaller tanks, such as 80-L glass aquaria, can be used. When setting up a system,

it is important to consider surface to volume ratio since this will determine how many mysids can be held in each

aquarium. If smaller tanks must be used, the 20-gallon "high" form is recommended. Figure 3 (Ward, 1984;

1991) illustrates the main components of the biological filtration system. The flow rate through the filter is

controlled by the water valve and is maintained between 4-5 L/min. This flow will be sufficient to establish a

moderate current (from the filter return line) in the aquarium to allow the mysids (which are positively rheotactic)

to align themselves with the current formed.

2.5.2 The filtration system consists of commercially-available under-gravel filter plates and external power filter. 

Each aquarium has two filter plates, forming a false bottom on each side of the tank, on which 2 cm of crushed

coral are placed. The external power filter (Eheim, model 2017) canister is layered as shown in Figure 3 with a

thin layer of filter fiber between each layer of carbon and crushed oyster shells. There has been some modification

of the original filtration system (Ward, 1984), with crushed coral instead of oyster shells used on the filter bed,

because crushed coral does not dissolve in seawater as readily as crushed oyster shells. If the system described

above cannot be used, an acceptable alternative is an airlift pumping arrangement (Spotte, 1979). Crushed coral

and oyster shells are commercially available and should be washed with deionized water and autoclaved before

use.

2.6 CULTURE MEDIA

2.6.1 A clean source of filtered natural seawater (0.45 μm pore diameter) should be used to culture Mysidopsis

bahia, however, artificial seasalts (FORTY FATHOMS®) have also been successfully used (Ward, 1993). A

salinity range between 20 and 30‰ can be used (25‰ is suggested) to culture M. bahia. Leger and Sorgeloos

(1982) reported success in culturing M. bahia in a formula following Dietrich and Kalle (Kalle, 1971), and still

report continued use of this formula (Leger et al., 1987b). Other commercial brands have also been used

(Reitsema and Neff, 1980; Nimmo and Iley, 1982; Nimmo et al., 1988) with varying degrees of success. The

culture methods presented in Ward (1984; 1991) have been tried with a number of commercial brands of artificial

seawater listed in Bidwell and Spotte (1985). Commercial brands of seasalts can be extremely variable in the

amount of NaHCO3 they provide, which, if not controlled, can affect growth and reproduction (Ward; 1989, 1991). 

In a comparative study, Ward (1993) found normal larval development within the marsupium using both natural 

seawater and FORTY FATHOMS® (i.e., Stage I - embryo; Stage II - eyeless larva; Stage III - eyed larva which is

the final stage before release) and stressed the importance of proper preparation of the seasalts and monitoring of

conditions in the tank. 

2.6.2 The culture media should be aged to allow the build-up of nitrifying bacteria in the filter substrate. To

expedite the aging process, 15 mL of a concentrated suspension of Artemia should be added daily. If using natural

or artificial seawater, the carbonate alkalinity level should be maintained between 90 and 120 mg/L. It is also

important to establish an algal community, Spirulina subsalsa, in the filter bed (Ward, 1984) and a healthy surface

dwelling diatom community, Nitzchia sp., on the walls (Ward, 1991) in conjunction with the transfer of part of the

biological filter from a healthy tank, when possible. After seven days, the suitability of the medium is checked by

adding 20 adult mysids. If the organisms survive for 96 hours, the culture should be suitable for stocking. 

2.6.3 If brine solutions are used, 100‰ salinity must not be exceeded. This corresponds to a carbonate alkalinity

value of approximately 50 mg/L, which will allow relatively normal physiological mechanisms associated with

CaCO3 to occur during certain phases of the life cycle for M. bahia (Ward, 1989).
165

Figure 3. Closed recirculating system showing the two phases of the biological filtration system which consists

of the filter bed and external power filter (from Ward, 1984; Ward, 1991).
166

2.7 ENVIRONMENTAL FACTORS

2.7.1 Temperature must be maintained within a range of 24°C to 26°C. Twelve to sixteen hours illumination

should be provided daily at 50 to 100 ft-c. The daily light cycle can be provided by combining overhead room

lights, cool-white fluorescent bulbs (approx. 50 ft-c, 12L:12D), with individual Grow-lux fluorescent bulbs placed

horizontally over each tank (approx. 65 ft-c, 10L:14D). This procedure will avoid acute illumination changes by

allowing the room lights to turn on one hour before and one hour after the aquaria lights. A timing device, such as

an electronic microprocessor-based timer (ChronTrol®, model CD, or equivalent) can be used to control the light

cycle. These procedures are fully outlined in Ward (1984; 1991).

2.7.2 Good aeration ($ 60% saturation by vigorous aeration with an air stone), a 10-20 percent exchange of

seawater per week, and carbonate in the filtration system are essential in helping to control pH drops caused by

oxidation of NH4-N and NO2-N by bacteria.

2.7.3 The single most important environmental factor when culturing Mysidopsis bahia or other organisms in

recirculators is the conversion of ammonia to nitrite, and nitrite to nitrate by nitrifying bacteria. Spotte (1979) has

suggested upper limits of 0.1 mg total NH4-N/L, 0.1 mg NO2-N/L and 20 mg NO3-N/L for good laboratory

operation of recirculating systems. For the recirculating system and techniques described here for mysids, the

levels of ammonia, nitrite and nitrate never exceeded 0.05 mg of total ammonia-N/L (NH3(aq)and NH4

+

), 0.08 mg

NO2-N/L and 18 mg NO3-N/L (Ward, 1991). The toxicity of ammonia is based primarily on unionized ammonia

(NH3) and the proportion of NH3 species to NH4

+

 species is dependent on pH, ionic strength and temperature. It is

strongly recommended that the concentrations of total ammonia, nitrite and nitrate do not exceed those reported

here. The ammonia, nitrite, and nitrate levels can be checked by using color comparison test kits such as those

made by LaMotte Chemical or equivalent methods.

2.7.4 Bacterial oxidation of excreted ammonia by two groups of autotrophic nitrifying bacteria (Nitrosomonas

and Nitrobacter), results in an increase of hydrogen ions, which causes a drop in pH and subsequent loss of

buffering capacity. Typically, the culturist responds to the change in pH by adding Na2CO3 or NaHCO3. 

However, such efforts to buffer against a drop in pH will result in an increase in alkalinity and the uncontrolled use

of carbonates can affect reproduction, especially at higher alkalinity values (Ward; 1989, 1991). Therefore, when

using carbonates to buffer against pH changes, alkalinity values should not exceed 120 mg/L, which is easily

measured by using a titrator kit such as that available from LaMotte Chemical or equivalent methods.

2.7.5 Figure 4 (Ward, 1991) depicts juvenile production per aquarium, no buffer added, over a period of 24

weeks. A regression line was calculated for these data and the slope and correlation coefficient were analyzed by

Student's t test. The data showed that even when the pH dropped as low of 7.5, there was a significant increase (P

< 0.001) in juvenile production. However, the pH should be maintained above 7.8 by the controlled use of

NaHCO3 and frequent water exchanges.

2.8 FEEDING

2.8.1 Frequent feeding with live food is necessary to prevent cannibalism of the young by the adults. McKenny

(1987) suggests feeding densities of 2-3 Artemia per mL of seawater and Lussier et al. (1988) suggest a feeding

rate of 150 Artemia nauplii per mysid daily. 

2.8.2 In the M. bahia-Artemia predator-prey relationship, it is also important to provide sufficient quantities of

nutritionally viable free-swimming stage-I nauplii (Ward, 1987); final hatching from the membranous-sac (prenauplii) into stage-I nauplii does not always occur. Artemia cysts that have been incubated for 24 h should be

periodically examined with a stereozoom microscope to enumerate free-swimming stage-I nauplii and prenauplii

(membranous-sac stage). 
167

Figure 4. Juvenile production per aquarium over time (from Ward, 1991).
168

2.8.3 It has also been found that heavy metals can affect the hatchability of Artemia (Rafiee et al., 1986; Liu and

Chen, 1987), therefore, when using natural seawater the level of metals should always be checked.

2.8.4 Ward (1987; 1991) has tried different brands of Artemia from different geographic origins and lot numbers;

many achieved stage I nauplii and still caused variability in production of mysids which suggests that they were

nutritionally lacking. Leger et al. (1985; 1987a) have drawn attention to poor larval survival of M. bahia and low

levels of certain polyunsaturated fatty acids found in the Artemia fed. The enhancement of Artemia has also been

studied and there are numerous techniques that have been successful (Leger et al., 1986).

2.8.5 Ward (1987; 1991) has found that it is important to control the flow of seawater in recirculating systems

(keep below 5 L/min) so that Artemia does not become limiting to the mysid. Newly hatched Artemia should be fed

to mysids at least twice a day. To supply Artemia to the mysid population on the weekend and prevent cannibalism

of newly released mysids, an automatic feeder such as described by Schimmel and Hansen (1975) or Ward (1984;

1991) could be used. Ward (1991) designed a system to hatch Artemia when personnel were not available to set

up Artemia for the following morning and afternoon feeding, such as Monday. Cysts were placed in two 4-L

Erlenmeyer flasks (dry), an airstone was placed in each flask, and two vessels overhead were filled with 3500 mL

of 30‰ seawater each. The previously described timer (ChronTrol®, Model CD) was used to open the normally

closed solenoids, allowing the seawater to gravity feed and hydrate the cysts.

2.8.6 It is possible that a surface dwelling diatom community acts as a secondary food that supplements deficient

brands of Artemia, especially for newly released juveniles. Ward (1991) has observed that a strong fertilizing

action is caused by the excretory products of the mysid population. As the concentration of nitrate increases

(nitrification) to about 5 mg/L (in approximately 7-10 weeks in an aquarium), a bloom of surface dwelling diatoms,

principally Nitzschia, but including Amphora and Cocconeis, occurs in natural or artificial seawater (Ward, 1993). 

It is interesting to note that, at the same time, there is a dramatic increase in the number of juveniles observed in the

aquaria (Figure 4). The diatoms form layers on the walls of the aquarium and swarms of newly released juveniles

have been found among them, possibly feeding upon them.

2.8.7 Nitzschia has been identified as a food source for the marine mud snail, Ilyanassa obsoleta (Collier, 1981),

and the sea urchin, Lytechinus pictus (Hinegardner and Tuzzi, 1981). The diatom, Skeletonema, has also been

used as a supplemental food for M. bahia (Venables, 1987). De Lisle and Roberts (1986) reported on the use of

rotifers, Branchionus plicatilis, as a superior food for juvenile mysids. Rotifers are active swimmers, ranging in

size from 100-175 μm as compared to 420-520 μm for Artemia, and would provide a good alternative food source

if their fatty acid profile is adequate. 

2.9 CULTURE MAINTENANCE

2.9.1 To avoid an excessive accumulation of algal growth on the internal surfaces of the aquaria, the walls and

internal components should be scraped periodically and the shell substrate (coral or oyster) turned over weekly. 

Also, the filter plates must be completely covered so that the biological filter functions properly. After a culture

tank has been in operation for approximately 2-3 months, detritus builds up on the bottom, which is removed with

a fish net after first removing the mysids. The rate of water flow through the tanks should be maintained between

4-5 L/min, and 10-20% of the seawater in each aquarium should be exchanged weekly. 

2.9.2 Some culturists have noted problems with hydrozoan pests in their cultures and there are procedures for

their eradication, if necessary (Lawler and Shepard, 1978; Hutton et al., 1986).

2.10 PRODUCTION LEVEL

2.10.1 At least four aquaria should be maintained to insure a sufficient number of organisms on a continuing

basis. If each 200-L aquarium is initially stocked with between 200 and 500 adults (do not exceed 500 adults),

they will provide sufficient numbers of test organisms (Figure 4) each month. If the cultures are correctly
169

maintained, at least 20 percent of the adult population should consist of gravid females (have a visible oostegite

brood pouch with young). It is also advantageous to cull older mysids in the population every 4-6 weeks and to

move mysids among the four aquaria to diversify the gene pool.

2.11 TEST ORGANISMS

2.11.1 Juvenile Mysidopsis bahia, one to five days old, are used in the acute toxicity test and the survival, growth

and fecundity test (USEPA, 1994). To obtain the necessary number for a test, there are a number of techniques

available. A mysid generator such as the one described by Reistsema and Neff (1980) has been successfully used. 

Another method to obtain juveniles is to take approximately 200 adult females (bearing embryos in their brood

pouches) from the stock culture and place them in a large (10 cm X 15 cm) standard fish transfer net (2.0 to 3.0

mm openings) that is partially submerged in an 8-L aquarium containing 4 L of clean culture medium. As the

juveniles are released from the brood pouches, they drop through the fish net into the aquarium. The adults and

juveniles in the aquarium are fed twice daily 24-hour post hydrated Artemia. The adults are allowed to remain in

the net for 48 h, and are then returned to the stock tanks. The juveniles that are produced in the small tank may be

used in the toxicity tests over a five-day period. Another method for obtaining juveniles (Ward 1987; 1989) is

simply to remove juveniles from the stock culture with a fine mesh net, place them in 2-L PYREX® crystalline

dishes with media, positioned on a light table that has an attached viewing plate (2 mm squares), and remove

juveniles less than 2 mm in length (approximately 24 h old).

3. HOLMESIMYSIS COSTATA

3.1 MORPHOLOGY AND TAXONOMY

3.1.1 Laboratories unfamiliar with the test organism should collect preliminary samples to verify species

identification. Refer to Holmquist (1979) or send samples of mysids and any similar co-occurring organisms to a

qualified taxonomist. Request certification of species identification from any organism supplier. Records of

verification should be maintained along with a few preserved specimens. A review by Holmquist (1979)

considered previous references to Acanthomysis sculpta in California to be synonymous with Holmesimysis

costata and this is considered definitive at this time.

3.2 SOURCE OF BROODSTOCK AND TRANSPORT 

3.2.1 Broodstock of H. costata are collected by sweeping a small-mesh (0.5-1 mm) hand net through the water

just under the surface canopy blades of giant kelp Macrocystis pyrifera. Although this method collects mysids of

all sizes, attention should be paid to the number of gravid females collected because these are used to produce the

juvenile mysids used in toxicity testing. Gravid females are identified by their large, extended marsupia filled with

young. Mysids should be collected from waters remote from sources of pollution to minimize the possibility of

physiological or genetic adaptation to toxicants. 

3.2.2 Mysids can be transported for a short time (< 3 h) in tightly covered 20 L plastic buckets. The buckets

should be filled to the top with seawater from the collection site, and should be gently aerated or oxygenated to

maintain dissolved oxygen above 60% saturation. Transport temperatures should remain within 3°C of the

temperature at the collection site. 

3.2.3 For longer transport times of up to 36 h, mysids can be shipped in sealed plastic bags filled with seawater. 

The following transport procedure has been used successfully: 

1) fill the plastic bag with one L of dilution water seawater, 

2) saturate the seawater with oxygen by bubbling pure oxygen for at least 10 minutes, 

3) place 25-30 adult mysids, or up to 100 juvenile mysids in each bag, 

4) for adults add about 20 Artemia nauplii per mysid, for 100 juveniles add a pinch (10 to 20 mg) of
170

ground Tetramin® flake food and 200 newly-hatched Artemia nauplii, 

5) seal the bag securely, eliminating any airspace, and 

6) place it within a second sealed bag in an ice chest. 

Do not overfeed mysids in transport, as this may deplete dissolved oxygen, causing stress or mortality in transported

mysids. A well-insulated ice chest should be cooled to approximately 15°C by adding one 1-L blue ice block for

every five 1-L bags of mysids (organisms will tolerate the temperature range of 12 to 16°C). Wrap the ice in

newspaper and a plastic bag to insulate it from the mysid bags. Pack the bags tightly to avoid shifting within the

cooler. 

3.3 HOLDING AND CULTURING

3.3.1 After collection, the mysids should be transported directly to the laboratory and placed in seawater tanks or

aquaria equipped with flowing seawater or adequate aeration and filtration. Initial flow rates should be adjusted so

that any temperature change occurs gradually (0.5°C per h). Broodstock will be collected and maintained at two

temperatures as follows: 1) maintain the water temperature of 15 ± 1°C for mysids collected south of Pt.

Conception, CA and 2) maintain the water temperatures of 13 ± 1°C for mysids collected north of Pt. Conception,

CA. Mysids can be cultured in tanks ranging from 4 to 1000 L. Tanks should be equipped with gentle aeration and

blades of Macrocystis to provide habitat. Static culture tanks can be used if there is constant aeration, temperature

control, and frequent water changes (one half the water volume changed at least twice a week). Maintain culture

density below 20 animals per L by culling out adult males or juveniles. 

3.4 FEEDING

3.4.1 Adult mysids should be fed 100 Artemia nauplii per mysid per day. Juveniles should be fed 5 to 10 newly

released Artemia nauplii per juvenile per day and a pinch (10 to 20 mg) of ground Tetramin® flake food per 100

juveniles per day. Static chambers should be carefully monitored and rations adjusted to prevent overfeeding and

fouling of culture water.

3.5 TEST ORGANISMS

3.5.1 Juvenile Holmesimysis costata three to four days old, are used in the acute toxicity test and the survival and

growth test (Hunt et al., 1997; USEPA, 1995). To obtain the necessary number for a test, there are a number of

techniques available for the acute toxicity test and the survival and growth test (USEPA, 1995). Approximately 150

gravid female mysids will typically produce approximately 400 juveniles. Gravid females can be identified by their

large, extended marsupia filled with (visible) eyed juveniles. Marsupia appear distended and gray when females are

ready to release young, due to presence of the juveniles. Gravid females are easily isolated from other mysids using

the following technique: 1) use a small dip net to capture about 100 mysids from the culture tank, 2) transfer the

mysids to a screen-bottomed plastic tube (150 μm-mesh, 25-cm diameter) partly immersed in a water bath or bucket,

3) lift the screen-tube out of the water to immobilize mysids on the damp screen, 4) gently draw the gravid females

off the screen with a suction bulb and fire-polished glass tube (5-mm I.D.), and 5) collect gravid females in a

separate screen tube. Re-immerse the screen continuously during the isolation process; mysids should not be

exposed to air for more than a few seconds at a time. 

3.5.2 Four to five days before a toxicity test begins, transfer gravid females into a removable, 2-mm-mesh screened

cradle suspended within an aerated 80-L aquarium. Before transfer, make sure there are no juveniles in with the

adult females. Extraneous juveniles are excluded to avoid inadvertently mixing them with the soon-to-be released

juveniles used in testing. Provide the gravid females with newly hatched Artemia nauplii (approximately 200 per

mysid) to help stimulate juvenile release. Artemia can be provided continuously throughout the night from an

aerated reservoir holding approximately 75,000 Artemia. Direct the flow from the feeder into the screened

compartment with the females, and add a few blades of Macrocystis for habitat. The females are placed within the

screened compartment so that as the juveniles are released, they can swim through the mesh into the bottom of the
171

aquarium. Outflows on flow-through aquaria should be screened (150-μm-mesh) to retain juveniles and allow some

Artemia to escape. 

3.5.3 Juveniles are generally released at night, so it is important to turn off all lights at night to promote release. 

In the morning, the screened compartment containing the females should be removed and placed in a separate

aquarium. Juveniles should be slowly siphoned through a wide-diameter hose into a 150-μm-mesh screen-bottom

tube (25 cm diam.) immersed in a bucket filled with clean seawater. Once the release aquarium is emptied, it should

be washed with hot fresh water to eliminate stray juveniles that might mix with the next cohort. 

3.5.4 After collection, the number of juveniles should be estimated visually or by counting subsamples with a small

beaker. If there are not enough juveniles, the juveniles from previous or subsequent releases can be combined so

that the test is initiated with three and/or four-day old juveniles. Mysids 2-days old and younger have higher

mortality rates, while mysids older than four days may vary in their toxicant sensitivity or survival rate (Hunt et al.,

1989; Martin et al., 1989). 

3.5.5 Test juveniles should be transferred to additional screen-tubes (or to 4-L static beakers if flowing seawater is

unavailable). The screen-tubes are suspended in a 15-L bucket so that dilution water seawater (0.5 L/min) can flow

into the tube, through the screen, and overflow from the bucket. Check water flow rates (< 1 L/min) to make sure

that juveniles or Artemia nauplii are not forced down onto the screen. The height of the bucket determines the level

of water in the screen tube. About 200 to 300 juveniles can be held in each screen-tube (200 juveniles per static 4-L

beaker). Juveniles should be fed 40 newly hatched Artemia nauplii per mysid per day and a pinch (10 to 20 mg) of

ground Tetramin® flake food per 100 juveniles per day. A blade of Macrocystis (well rinsed in seawater) should be

added to each chamber. Chambers should be gently aerated and temperature controlled at 15 ± 1°C (or 13 ± 1°C if

collected north of Pt. Conception). Half of the seawater in static chambers should be changed at least once between

isolation and test initiation. 

3.5.6 The day juveniles are isolated is designated day 0 (the morning after their nighttime release). The toxicity test

should begin on day three or four. For example, if juveniles are isolated on Friday, the toxicity test would begin on

the following Monday or Tuesday. Pool all of the test juveniles into a 1-L beaker. Using a 10-mL wide-bore pipet

or fire-polished glass tube (approximately 2-3 mm I.D), place one or two juveniles into as many plastic cups (one

for each test chamber). These cups should contain enough clean dilution seawater to maintain water quality and

temperature during the transfer process (approximately 50 mL per cup). When each of the cups contains one or two

juveniles, repeat the process, adding mysids until each cup contains 10 organisms. Carefully pour or pipet off

excess water in the cups, leaving less than 5 mL with the test mysids. This 5 mL volume can be estimated visually

after initial measurements. Carefully pour or pipet the juveniles into the test chambers immediately after reducing

the water volume. Gently rocking the water back and forth before pouring may help prevent juveniles from clinging

to the walls of the randomization cups. Juveniles can become trapped in drops; have a squirt bottle ready to gently

rinse down any trapped mysids. If more than 5 mL of water is added to the test solution with the juveniles, report

the amount on the data sheet. Be sure that all water used in culture, transfer, and test solutions is within 1°C of the

test temperature. Because of the small volumes involved in the transfer process, temperature control is best

accomplished in a constant-temperature room. 

3.5.7 Immobile mysids that do not respond to a stimulus are considered dead. The stimulus should be two or three

gentle prods with a disposable pipet. Mysids that exhibit any response clearly visible to the naked eye are

considered living. The most commonly observed movement in moribund mysids is a quick contraction of the

abdomen. This or any other obvious movement qualifies a mysid as alive.
172

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Nimmo, D.R., T.L. Hamaker, J.C. Moore, and R.A. Wood. 1980. Acute and chronic effects of Dimilin on survival and

reproduction of Mysidopsis bahia. In: J.G. Eaton, P.R. Parrish, and A.C. Hendricks, eds., ASTM STP 707,

American Society for Testing and Materials, Philadelphia, Pennsylvania. pp. 366-376.

Nimmo, D.R., R.J. Mirenda, and C.A. Carlson. 1991. Culturing the estuarine mysid, Mysidopsis bahia: a synopsis of

three case studies. In: T.P. Nesler and E. P. Bergersen, eds., Mysids in fisheries: hard lessons from headlong

introductions. Proceedings of a symposium held at the 118th Annual Meeting of the American Fisheries

Society, September 9-15, 1988, Toronto, Ontario. Amer. Fish. Soc. Symp. 9, pp. 160-168.

Nimmo, D.R., R.A. Rigby, L.H. Bahner, and J.M. Sheppard. 1978. The acute and chronic effects of cadmium on the

estuarine mysid, Mysidopsis bahia. Bull. Environm. Contam. Toxicol. 19(1):80-84.

Price, W.W. 1982. Key to the shallow water Mysidacea of the Texas coast with notes on their ecology. Hydrobiol.

93(1/2):9-21.

Price, W.W., A.P. McAllister, R.M. Towsley, and M. DelRe. 1986. Mysidacea from continental shelfwaters of the

northwestern Gulf of Mexico. Contrib. Marine Sci. 29:45-58.

Price, W.W., R.W. Heard, and L. Stuck. 1994. Observations on the genus Mysidopsis Sars, 1864 with the designation

of a new genus, Americamysis, and the descriptions of Americamysis alleni and Americamysis stucki

(Peracarida: Mysidacea: Mysidae), from the Gulf of Mexico. Procedure. Biol. Soc. Wash. 107: 680-698.

Rafiee, P., C.O. Matthews, J.C. Bagshaw, and T.H. MacRae. 1986. Reversible arrest of Artemia development by

cadmium. Can. J. Zool. 64:1633-1641.

Reitsema, L.A. 1981. The growth, respiration, and energetics of Mysidopsis almyra (Crustacea; Mysidacea) in relation

to temperature, salinity, and hydrocarbon exposure. Ph.D. thesis, Texas A&M University, College Station,

Texas.

Reitsema, L.A., and J.M. Neff. 1980. A recirculating artificial seawater system for the laboratory culture of

Mysidopsis bahia (Crustacea; Pericaridea). Estuaries 3:321-323.

Roberts, M.H., J.E. Warinner, C.F. Tsai, D. Wright, and L.E. Cronin. 1982. Comparison of estuarine species

sensitivities to three toxicants. Arch. Environm. Contam. Toxicol. 11:681-692.

Salazar, M.H., S.C. U'ren, and S.A. Steinert. 1980. Sediment bioassays for San Diego dredging project. Naval

Oceans Systems Center, San Diego, Calif. Techn. Rept. 570. 46 pp.

Schimmel, S.C., and D.J. Hansen. 1975. An automatic brine shrimp feeder for aquatic bioassays. J. Fish. Res. Board

Can. 32: 314-316.

Shuba, P.J., H.E. Tatem, and J.H. Carroll. 1978. Biological assessment methods to predict the impact of open-water

disposal of dredged material. Techn. Rept. D-78-50. U.S. Army Engineer Waterways Experiment Station,

Vicksburg, Mississippi. 77 pp.
176

Spotte, S. 1979. Fish and invertebrate culture. John Wiley and Sons, New York, NY, 179 pp.

Stuck, K.C., H.M. Perry, and R.W. Heard. 1979a. An annotated key to the Mysidacea of the North Central Gulf of

Mexico. Gulf Res. Rept. 6(3):225-238.

Stuck, K.C., H.M. Perry, and R.W. Heard. 1979b. Records and range extensions of Mysidacea from coastal and shelf

water of the Eastern Gulf of Mexico. Gulf Res. Rept. 6(3):39-248.

Tattersall, W.M., and Tattersall. 1951. The British Mysidacea. Royal Soc. London. 460 pp.

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forest mysid, Holmesmysis costata in Monterey Bay, California. J. Crust. Biol. 14(4): 657-664.

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Bioassay Procedures for the Ocean Disposal Permit Program. U. S. Environmental Protection Agency,

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Hamaker, and C.A. Sommers. In: Bioassay Procedures for the Ocean Disposal Permit Program, U. S.

Environmental Protection Agency, Environmental Research Laboratory, Gulf Breeze, Florida. EPA-600/9-78-

010. pp. 64-68.

USEPA. 1978c. Entire life cycle toxicity test using mysids (Mysidopsis bahia) in flowing water. D.R. Nimmo, T.L.

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USEPA. 1981b. Acute toxicity test standard using mysid shrimp in static and flow-through systems. Toxic

Substances Control Act, Section 4. Office of Toxic Substances, Health and Environmental Review Division,

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902.

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held at the 118th Annual Meeting of the American Fisheries Society, September 9-15, 1988, Toronto, Ontario. 

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13(4):254-262.
178

APPENDIX A

DISTRIBUTION, LIFE CYCLE, TAXONOMY, AND CULTURE METHODS

A.4. BRINE SHRIMP (ARTEMIA SALINA)

1. SYSTEMATICS

1.1 MORPHOLOGY AND TAXONOMY

1.1.1 The taxonomic status of Artemia has long been controversial because there is considerable morphological

variability over parts of its range. The present consensus is that there is a single cosmopolitan species, Artemia

salina, which has numerous intergrading physiological and morphological varieties (Pennak, 1989). Brine shrimp

belong to the subclass Branchiopoda which is characterized by many pairs of flattened appendages on the thorax

(Figure 1), in contrast to other members of the Crustacea that have no more than six pairs. Probably the most

distinctive feature of Artemia salina is the compressed, triangular, and blade-shaped distal segment of the second

antenna of the male (Figure 2). The mature adult is 8-10 mm long with a stalked lateral eye, sensorial antennulae,a

linear digestive tract and 11 pairs of thoracopods. In the male the antennae are transformed into muscular claspers

used to secure the female during copulation. 

2. DISTRIBUTION

2.1 Artemia are found nearly worldwide in saline lakes and pools. In North America, they have been reported

throughout the western United States, in Nebraska and Connecticut and in Saskatchewan, Canada. They are

probably more widely distributed than indicated because of limited effort in collecting from many areas of the

country. They are absent from many suitable habitats, probably because of their limited dispersal methods. 

3. ECOLOGY AND LIFE HISTORY

3.1 GENERAL ECOLOGY

3.1.1 The ecological conditions under which brine shrimp live are highly variable. The salinity can exceed 300‰,

where most other life cannot survive. Favored by the absence of predators and food competitors in such places,

Artemia develop very dense populations. Although not a marine species, they sometimes occur in bays and lagoons

where brines are formed by evaporation of seawater (salt pans). They are more commonly found in highly saline

lakes, such as the Great Salt Lake, where the shoreline may become ringed with brown layers of accumulated brine

shrimp cysts. Brine shrimp are also common in evaporation basins used for the commercial production of salt. 

3.1.2 The reproductive habits of different populations vary considerably. In parts of Europe parthenogenesis is the

rule, males being rare or absent, but in North America most Artemia populations seem to be diploid with males

common. 

3.1.3 The principal mechanism of Artemia dispersion is transportation of the cysts by wind or waterfowl and by

deliberate or accidental human inoculation. 

3.1.4 Growth of brine shrimp is influenced by many factors and the tolerance of these factors is strain dependent. 

Optimum temperature for most strains ranges between 25 and 35EC but strains have been reported thriving at 40EC. 

Most geographical strains do not survive temperatures below 6EC except as cysts. These cysts are tolerant of

temperatures from far below 0EC to near the boiling point of water. Although Artemia can survive and reproduce

under a wide range of salinity, they are seldom found in nature in salinities below 45‰ or above 200‰. The pH

tolerance of Artemia varies from neutral to highly alkaline but the cysts will hatch best at a pH of 8 or higher.
179

3.1.5 Many predators including many zooplankton that populate natural salt waters, many salt water fish, several

insect groups (odonates, hemipterans and beetles), and birds feed on brine shrimp in situations where they can

tolerate the conditions.

3.2 FOOD AND FEEDING

3.2.1 Brine shrimp are typically filter-feeders that consume organic detritus, microscopic algae and bacteria. 

Blooms of microscopic algae are favorite habitats of Artemia, and large populations develop in such areas where

they feed on the algae and heterotrophic bacteria that are produced by these blooms. Brine shrimp populations have

done well in cultures when fed algae, rice bran (Sorgeloos et al., 1979), soybean meal or whey powder (Bossuyt and

Sorgeloos, 1979). The nauplii do not need food for four days after hatching. 

3.3 LIFE HISTORY

3.3.1 Most strains of Artemia produce cysts that float (cysts from the Mono Lake, California strain sink). These

cysts remain in diapause as long as they are kept dry or under anaerobic conditions. Upon hydration, the embryo in

the cyst becomes activated. After several hours the outer membrane bursts and the embryo emerges still encased in

the hatching membrane. Soon the hatching membrane is ruptured and the free-swimming nauplius is born. The

first instar is brownish-orange colored and has three pairs of appendages (Figure 3). The larva grows through about

15 molts and becomes differentiated into male or female after the tenth molt. Copulation is initiated when the male

grasps the female with its modified antennae (Figure 4). The fertilized eggs develop either into free-swimming

nauplii, or they are surrounded by a thick shell and deposited as cysts which are in diapause.

4. METHODS FOR HATCHING ARTEMIA CYSTS

4.1 SOURCES OF CYSTS 

4.1.1 Brine shrimp cysts are available from many commercial sources, representing several geographical strains. 

The cysts from any source can vary from batch to batch in terms of nutritional quality for the test organisms. 

Therefore, it is recommended that each new batch purchased should be analyzed chemically, and that a side-by-side

feeding test be performed on their nutritional suitability by comparing the response of the test organisms with the

new cysts and cysts of known quality (ASTM, 1993). A list of sources of cysts is provided at the end of this

chapter.

4.2 STORAGE OF CYSTS

4.2.1 Sealed cans of Artemia cysts can be stored for years at room temperature, but once opened, should be used

up within two months. After each use, the can should be tightly covered with a plastic lid and stored in the

refrigerator. If the entire contents of a can will not be used up in two months, it is recommended that the portion

that is expected to be unused be placed in a tightly closed container and frozen until needed. 

4.3 HATCHING OF CYSTS

4.3.1 A 2-L separatory funnel makes a convenient brine shrimp hatching vessel, but nearly any transparent or

translucent (preferably colorless) conical shaped container that will hold water may be used. A satisfactory

apparatus can be prepared by removing the bottom of a 2 L plastic soft drink bottle and inserting a rubber stopper

with a flexible tube and pinch cock. The hatching chambers must be clean and free from toxic material. All

detergents should be completely removed by rinsing well with deionized water.
180
181

4.3.2 Salinity of the water used for hatching brine shrimp cysts should be between 25 and 35‰. Natural sea water

or water made up from artificial sea salts may be used. The hatching medium can be prepared by placing 1800 mL

of deionized water in the hatching chamber and adding 50-70 g non-iodized salt. After the salt is added, lower a 1

mL pipette or glass tube fitted to an air supply into the vessel, so that the tip rests on the bottom, and bubble air

vigorously through it to dissolve the salt.

4.3.3 Add the desired quantity of cysts to the vessel. Approximately 15 mL of cysts in a 2-L hatching vessel will

provide enough brine shrimp nauplii to feed three large stock cultures of mysids in 76-L aquaria, or 1000-1500

newly hatched fish in four to six 8-L tanks.

4.3.4 Continue the aeration to keep the cysts and newly hatched nauplii from settling to the bottom where the DO

would quickly be depleted and the newly hatched animals would die. 

4.3.5 The area in which the cysts are hatched should be provided with approximately 20 FE/m2

/s (100 ft-c) of

illumination. 

4.3.6 The cysts will hatch in about 24 h at a temperature of 25EC. Hatching time varies with incubation

temperature and the geographic strain of Artemia used. 

4.4 HARVESTING THE NAUPLII

4.4.1 When the brine shrimp nauplii first emerge from the cyst, they are enclosed in a membranous sac (Figure 3). 

To be taken as food by the test organisms, the pre-nauplii must emerge from the sac and swim about (Stage I or first

instar nauplius). 

4.4.2 The first instar (Stage I) nauplii do not feed. Their value as food for the test organisms decreases from birth

until they begin feeding. Because they do not feed in the hatching vessels, it is important to harvest and use the

nauplii soon after hatching. The nauplii can be easily harvested in the following manner: 

1. After approximately 24 h at 25EC, remove the pipet supplying air and allow the nauplii to settle

to the bottom of the hatching chamber. The empty egg shells will float to the top and the newly

hatched nauplii and unhatched eggs will settle to the bottom. A light trained on the bottom of the

separatory funnel will hasten the settling process. 

2. After approximately 5 min, using the stopcock, drain off the nauplii into a 250 mL beaker. 

3. After another 5 min, again drain the nauplii into the beaker. 

4. The nauplii are further concentrated by pouring the suspension into a small cylinder which has

one end closed with #20 plankton netting or they may be washed through a 150 μm net or screen.

5. The concentrate is resuspended in 50 mL of appropriate culture water, mixed well, and dispensed

with a pipette. (Mysids require approximately 100-150 nauplii/mysid/day).

6. Discard the remaining contents of the hatching vessel and wash the vessel with hot soap and

water.

7. Prepare fresh salt water for each new hatch. 

4.4.3 To have a fresh supply of Artemia nauplii daily, at least two hatching vessels should be used, so that the

newly-hatched can be harvested daily. 
182

4.5 FEEDING ASSAY

4.5.1 Before using brine shrimp nauplii from a new batch of cysts for routine feeding of cultures and test

organisms, they should be tested for their ability to support life, growth, and reproduction of the test animals. Two

treatments with four replicates each are required for this test. In Treatment (A), the test organisms are fed the

nauplii from the new batch of Artemia cysts, and in Treatment (B), the test organisms are fed nauplii of known,

good quality, such as from the reference Artemia cysts or from a batch of Artemia cysts that have been successfully

used in culturing and testing. 

4.5.2 If there is no significant difference in the survival, growth, and/or reproduction of the organisms in the two

treatments at the end of a 7-day period, it is assumed that the new batch of Artemia cysts is satisfactory. If the

survival, growth, and/or reproduction in treatment A is significantly less than the response in treatment B over a 7-

day test period it is assumed that the new batch of brine shrimp cysts are unsuitable for use as a food source for the

organisms tested. 

4.5.3 Test chambers and all test conditions during the feeding assay should be similar to those planned for use in

the subsequent toxicity tests.
183

SELECTED REFERENCES

ASTM. 1993. Standard practice for using brine shrimp nauplii as food for test animals in aquatic toxicology. 

Standard E1203-87, Annual Book of ASTM Standards, Vol. 11.04, American Society for Testing and

Materials, Philadelphia, PA. 

Beck, A.D. and Bengtson, D.A. 1982. International study on Artemia XXII: Nutrition in aquatic toxicology - Diet

quality of geographical strains of the brine shrimp, Artemia. In: J.G. Pearson, R.B. Foster, and W.E. Bishop

(eds.), Aquatic Toxicology and Hazard Assessment: Fifth Conference. ASTM STP 766, American Society for

Testing and Materials, Philadelphia, PA. pp. 161-169. 

Beck, A.D., Bengtson, D.A., and Howell, W.H. 1980. International study on Artemia. V. Nutritional value of five

geographical strains of Artemia: Effects of survival and growth of larval Atlantic silversides, Menidia menidia. 

In: G. Persoone, P. Sorgeloos, D.A. Roels, and E. Jaspers, eds. The brine shrimp, Artemia. Vol. 3. Ecology,

culturing, use in aquaculture. Universa Press, Wetteren, Belgium. pp. 249-259. 

Bengtson, D.A.S., Beck, A.D., Lussier, S.M., Migneault, D., and Olney, C.B. 1984. International study on

Artemia. XXXI. Nutritional effects in toxicity tests: Use of different Artemia geographical strains. In: 

G. Persoone, E. Jaspers, and C. Claus, (eds.). Ecotoxicological testing for the marine environment, Vol. 2. 

State Univ. Ghent and Inst. Mar. Sci. Res., Bredene, Belgium. pp. 399-416. 

Bossuyt, E. and Sorgeloos, P. 1979. Technological aspects of the batch hatching of Artemia in high densities. In: 

G. Persoone, P. Sorgeloos, O. Roels and E. Jaspers (eds.), The brine shrimp Artemia. Vol. 3. Ecology,

culturing, use in aquaculture. Universa Press, Wetteren, Belgium. pp. 133-152. 

Browne, R.A. 1982. The cost of reproduction in brine shrimp. Ecology 63(1):43-47. 

Johns, D.M., Berry, W.J., and Walton, W. 1981. International study on Artemia. XVI. Survival, growth and

reproductive potential of the mysid, Mysidopsis bahia Molenock fed various geographical strains of the brine

shrimp, Artemia. J. Exp. Mar. Biol. Ecol. 53:209-219. 

Kuenen, D.J. and Baas-Becking, L.G.M. 1938. Historical notes on Artemia salina (L.). Zool. Med. 20:222-230. 

Leger, P., Bengtson, D.A., Simson, K.L., and Sorgeloos, P. 1986. The use and nutritional value of Artemia as a

food source. Oceanogr. Mar. Biol. Ann. Rev. 24:521-623. 

Lenz, P.H. 1980. Ecology of an alkali-adapted variety of Artemia from Mono Lake, California, U.S.A. In:

G. Persoone, P. Sorgeloos, O. Roels, and E. Jaspers (eds.), The brine shrimp Artemia. Vol. 3. Ecology,

culturing, use in aquaculture. Universa Press, Wetteren, Belgium. pp. 79-96. 

Nikonenko, Y.M. 1986. Adaptation of Artemia salina to toxicants. Hydrobiol. J. 22(5):94-98. 

Pennak, R.W. 1989. Fresh-water invertebrates of the United States. Protozoa to mollusca. John Wiley and Sons,

New York, New York. pp. 358-359.

Persoone, G., Sorgeloos, P., Roels, O., and Jaspers, E., (eds.). 1980a. The brine shrimp Artemia. Vol. 1. 

Morphology, genetics, radiobiology, toxicology. Universa Press, Wetteren, Belgium. 318 pp. 

Persoone, G., Sorgeloos, P., Roels, O., and Jaspers, E., (eds.). 1980b. The brine shrimp Artemia. Vol. 2. 

Physiology, biochemistry, molecular biology. Universa Press, Wetteren, Belgium. 636 pp. 

Persoone, G., Sorgeloos, P., Roels, O., and Jaspers, E., (eds.). 1980c. The brine shrimp Artemia. Vol. 3. Ecology,

culturing, use in aquaculture. Universa Press, Wetteren, Belgium. 428 pp. 
184

Sorgeloos, P. 1980. Life history of the brine shrimp Artemia. In: G. Persoone, P. Sorgeloos, D.A. Roels, and E.

Jaspers (eds.), The brine shrimp, Artemia. Vol. 1. Morphology, genetics, radiobiology, toxicology. Universa

Press, Wetteren, Belgium. pp. ixx-xxii. 

Sorgeloos, P., Baesa-Mesa, M., Bossuyt, E., Bruggeman, E., Dobbeler, J., Versichele, D., Lavina, E., and 

Bernardine, A. 1979. Culture of Artemia on rice bran: The conversion of waste-products into highly nutritive

animal protein. Aquaculture 21:393-396. 

Usher, R.R. and Bengtson, D.A. 1981. Survival and growth of sheepshead minnow larvae and juveniles on diet of

Artemia nauplii. Prog. Fish-Cult. 43:102-105. 
185

APPENDIX A

DISTRIBUTION, LIFE CYCLE, TAXONOMY, AND CULTURE METHODS

A.5 FATHEAD MINNOW (PIMEPHALES PROMELAS)

1. MORPHOLOGICAL AND ANATOMICAL CHARACTERISTICS

1.1 Fathead minnows vary greatly in many characteristics throughout their wide geographic range. The

morphology and characters for identification are taken from Clay (1962), Hubbs and Lagler (1964), Eddy and

Hodson (1961), Scott and Crossman (1973), and Trautman (1981). Adults (Figure 1) are small fish, typically 43

mm to 102 mm, and averaging about 50 mm, in total length. The standard lengths are usually less than four and

one-half times the body depth. The first rudimentary ray of the dorsal fin is more or less thickened and distinctly

separated from the first well-developed ray by a membrane. The lateral line is usually incomplete, but may be

complete in specimens from some geographic areas. The scales are cycloid and moderate in size. Andrews (1970),

reporting on fish collected in Colorado, noted that no scales were found on fish smaller than 14 mm, and the

average length for first scale formation was 16.3 mm. The scales in the lateral series number 41 to 54. 

1.2 The mouth is terminal. The snout does not extend beyond the upper lip and is decidedly oblique. Nuptial

tubercles occur on mature males only, are large and well-developed on the snout, and rarely extend beyond the

nostrils. They occur in three main rows, with a few on the lower jaw. In addition to nuptial tubercles, the males

have an elongate, fleshy, or spongy pad extending in a narrow band from the nape to the dorsal fin. The pad is wide

anteriorly, and narrows to engulf the first dorsal ray. In addition, the sides of the body become almost black except

for two wide vertical bars which are light in color. In contrast to the males, the mature females remain quite drab.

1.3 The peritoneum is brownish-black, and the intestine is long and coiled one or more times.

1.4 Some external markings occur infrequently. Young occasionally have a dusky band on the snout and

opercules. Other young and adults, from clear and weedy waters, have a distinct, lateral band across the body. The

band may be absent in breeding males or, if present, becomes very diffuse anteriorly. This band is usually most

apparent on preserved specimens. Dymond (1926), Trautman (1981), and others described the saddle-like pattern

often associated with breeding males in which a light area develops just behind the head and another beneath the

dorsal fin, the areas between producing a saddle affect. A dark spot is usually present in front of the dorsal fin in

mature males, and a narrow, dark, vertical bar or spot is present at the base of the caudal fin, but often is not very

distinct.
186

2. TAXONOMY 

2.1 The specific name (Pimephales promelas) appears to be incorrectly applied to this fish because the fathead

minnow does not fit the description originally given by Rafinesque (1820) (Lee et al., 1980). Common names

include "northern fathead minnow", and "blackhead minnow," in addition to fathead minnow. The holotype was

collected near Lexington, Kentucky. 

2.2 Some geographic variations have been noted in the morphology of the fathead minnow. Vandermeer (1966)

indicated that the introduction of this species outside its native range may have resulted in some local deviations

from the broad patterns of geographic variation in taxonomic characters. Some populations have been designated as

subspecifically distinct: Pimephales promelas promelas, the northern form; P. p. harveyensis, the Harvey Lake

form, from Isle Royal in Lake Superior and P. p. confertus, the southern form (Hubbs and Lagler, 1949, 1964). 

However, Taylor (1954), Vandermeer (1966), and others expressed doubt concerning the validity of assigning

subspecific status to the variants and recommended against their recognition. Vandermeer (1966), in a statistical

analysis of the geographic variations in taxonomic characters, stated that two of the three described subspecies

intergrade clinally. 

2.3 Of the eight characters measured, two showed a north-south trend; (1) eye diameter, with the northern fish

having smaller eyes, and (2) completeness of the lateral line, with the northern fish having the least complete lateral

line. However, Scott and Crossman (1973), indicated that some Canadian populations exhibit a nearly complete

lateral line. The American Fisheries Society (1980) does not recognize any of the fathead minnow subspecies.

3. DISTRIBUTION

3.1 The fathead minnow is widely distributed in North America (Figure 2). It is a popular bait fish, and the ease

with which it is propagated has led to its widespread introduction both within and outside the native range of the

species. It has been so widely distributed in the eastern and southwestern United States by bait transportation that it

is difficult to determine its original range. The presumed native distribution (Vandermeer, 1966; Scott and

Crossman, 1973; Lee, et al., 1980) extended from the Great Slave Lake in the northwest to New Brunswick, in

eastern Canada, southward throughout the Mississippi valley in the United States, to southern Chihuahua in Mexico. 

Distribution records for this species also now include Oregon (Andreasen, 1975), and the Central Valley (Kimsey

and Fisk, 1964) and other locations in California (Andreasen, 1975), but there are no records for British Columbia. 

3.2 This species is found in a wide range of habitats. It is most abundant in muddy brooks, streams, creeks, ponds,

and small lakes, is uncommon or absent in streams of moderate and high gradients and in most of the larger and

deeper impoundments, and is tolerant of high temperature and turbidity, and low oxygen concentrations.

3.3 Species associated with the fathead minnow seem to vary greatly throughout its range (Scott and Crossman,

1973; Trautman 1981). Trautman (1981) reported that fathead minnows and bluntnose minnows, Pimephales

notatus (Rafinesque), were competitors, and that fathead minnows occurred in greatest numbers only where

bluntnose minnows were absent or comparatively few in number. He also stated that the fathead minnow may

hybridize with the bluntnose minnow.

3.4 The fathead minnow is primarily omnivorous, although Coyle (1930) reported algae to be one of its main foods

in Ohio. Elsewhere in the United States, young fish have been reported to feed on organic detritus from bottom

deposits, and unicellular and filamentous algae and planktonic organisms. Adults feed on aquatic insects, worms,

small crustaceans, and other animals. Scott and Crossman (1973) and others regard the fathead minnow as a highly

desirable forage fish, providing food for other fishes and birds. 
187

4. GENERAL LIFE HISTORY 

4.1 The natural history and spawning behavior (Markus, 1934; Flickinger, 1973; Andrews and Flickinger, 1974;

and others) of the fathead minnow are well known because of the early interest in raising the fish for bait and for

feeding other pond fish, such as bass. Sexual dimorphism occurs at maturity. Breeding males develop a

conspicuous, narrow, elongated, gray, fleshy pad of spongy tubercles on the back, anterior to the dorsal fin, and two

or three rows of strong nuptial tubercles across the snout. The sides of the body become almost black except for

two wide vertical bars which are light in color. In contrast, the females remain quite drab.

4.2 The initiation of spawning varies with temperature throughout its geographic range. Isaak (196l), Carlander

(1969), and others reported that, in the wild, fathead minnows begin spawning in the spring, when the water

temperature reaches 16-18EC, and continue to spawn throughout most of the summer. The minimum spawning

temperature, however, may vary with population and latitude. 

4.3 Markus (1934) reported that spawning always occurred at night, whereas Isaak (1961) observed spawning

during the day, as well as at night. Gale and Buynak (1982) and others reported that spawning often began before

dawn and usually was completed before noon. Observations of the fathead minnow cultures at EPA's Newtown

Facility also indicate the majority of fathead minnows spawn in early morning.
188

4.4 Breeding males are very territorial and select sites for spawning, such as the underside of a log or branch, rock,

board, tin can, or almost any other solid inanimate object, usually in water from 7 cm to 1 m in depth. A receptive

female is sought out and brought into position below the nest site. After circling below the nesting site, the female

is nudged and lifted on the male's back until she lies on her side immediately below the undersurface of the

spawning substrate, where she releases a small number of eggs (usually 100 to 150) at a time. The eggs are

adhesive and attach to the underside of the spawning substrate. The females have a urogenital structure (ovipositor)

to help deposit the eggs on the underside of objects. Flickinger (1966) indicated that the ovipositor is noticeable at

least a month prior to spawning. The reported size of the eggs varies from 1.15 mm (Markus, 1934) to 1.3 mm in

diameter (Wynne-Edwards, 1932).

4.5 Immediately after the eggs are laid, they are fertilized by the male, and the female is driven off. Once eggs are

deposited in the nest, the male becomes very aggressive and will use the large tubercles on his snout to help drive

off all intruding small fishes. In addition to fertilizing and guarding the eggs, the male agitates the water around the

eggs, which ventilates them and keeps them free of detritus. Some males will spawn with several females on the

same substrate, so that the nest may contain eggs in various stages of development. The number of eggs per nest

may vary from as few as nine or 10 to as many as 12,000. 

4.6 The ovaries of the females contain eggs in all stages of development, and they spawn repeatedly as the eggs

mature. A female may deposit eggs in more than one nest. Although the average number of eggs per spawn is

generally 100 to 150, large females may lay 400 to 500 eggs per spawn.

4.7 Gale and Buynak (1982), in a study using five captive pairs of fathead minnows in separate outdoor pools,

observed that each pair produced 16 to 26 clutches of eggs between May and August. The time between spawns,

which ranged from 2-l6 days, was affected by water temperature. As the temperature increased, the intervals

between spawning sessions become shorter and more uniform. In their study, from nine to 1,136 (mean of 414)

eggs were deposited per spawn. The average number of eggs deposited per spawn ranged from 371 to 480, and the

total number of eggs spawned per female ranged from 6,803 to 10,164 (mean of 8,604). The length of the spawning

period during a given season also varied greatly between females. The authors suggested that the fecundity of

fathead minnows is much higher than has generally been recognized, but they noted that fecundity of fish in the

natural environment, where conditions might be more or less favorable, might differ from that of captive fish.

4.8 The incubation time depends on temperature, and is 4.5 to 6 days at 25EC. The newly-hatched young (larvae)

are about 5 mm long, white in color, and have large black eyes. The general appearance and typical pigmentation of

the various larval stages are illustrated in Figures 3A-3M. In a warm, food-rich environment, growth is rapid. 

Markus (1934) stated that fish hatched in May in Iowa reached adult size and were spawning by late July. Hubbs

and Cooper (1935) and others noted that such rapid growth is unlikely in more northerly waters, and that the young

do not spawn the first year. In cooler water the adult size is probably not reached until the second year. The males

generally grow faster than the females, a characteristic of minnow species. 

4.9 The fathead minnow is short lived, and rarely survives to the third year. However, Scott and Crossman (1973)

stated that longevity varies throughout the geographic range of the species. Post-spawning mortality was reported

to be great by several authors, but was not observed by Gale and Buynak (1982). However, in defending their

territory, male fish, may become weakened by a lack of food over a prolonged period and their resistance to disease

may be lowered. Also, at spawning time, many waters are warm and somewhat stagnate, favoring the spread of fish

parasites and disease. 

5. CULTURE METHODS 

5.1 OUTSIDE SOURCES OF FATHEAD MINNOWS 

5.1.1 Fathead minnows are available from commercial biological supply houses. Fish obtained from outside

sources for use as brood stock or in toxicity tests may not always be of suitable age and quality. Fish provided by

supply houses should be guaranteed to be of (1) the correct species, (2) disease free, (3) in the requested age range,
189

(4) and in good condition. The latter can be done by providing the record of the date on which the eggs were laid

and hatched, and information on LC50 of contemporary fish using reference toxicants.
190
191
192

5.2 INHOUSE SOURCES OF FATHEAD MINNOWS 

5.2.1 Problems in obtaining suitable fish from outside laboratories can be avoided by developing an inhouse

laboratory culture facility. Fathead minnows can be easily cultured in static, recirculating, or flow-through systems.

5.2.2 Flow-through systems require large volumes of water and may not be feasible in some laboratories. The

culture tanks should be shielded from extraneous disturbances using opaque curtains, and should be isolated from

toxicity testing activities to prevent contamination. 

5.2.3 To avoid the possibility of inbreeding of the inhouse brood stock, fish from an outside source should be

introduced yearly into the culture unit.

5.2.4 The inhouse culture facility consists of the following components:

5.2.4.1 Water Supply 

5.2.4.1.1 Water Quality 

5.2.4.1.1.1 Reconstituted (synthetic) water or dechlorinated tap water can be used, but natural water may be

preferred. To determine water quality, it is desirable to analyze the water for toxic metals and organics quarterly

(see Section 4, Quality Assurance). Temperature, dissolved oxygen, pH, hardness, and alkalinity should also be

measured periodically. 

5.2.4.1.1.2 If a static or recirculating system is used, it is necessary to equip each tank with an outside activated

carbon filter system, similar to those sold for tropical fish hobbyists (or one large activated carbon filter system for a

series of tanks) to prevent the accumulation of toxic metabolic wastes (principally nitrite and ammonia) in the water. 

5.2.4.1.2 Dissolved oxygen

5.2.4.1.2.1 The DO concentration in the culture tanks should be maintained near saturation, using gentle aeration

with 15 cm air stones if necessary. Brungs (1971), in a carefully controlled long-term study, found that the growth

of fathead minnows was reduced significantly at all DO concentrations below 7.9 mg/L. Soderberg (1982)

presented an analytical approach to the re-aeration of flowing water for culture systems.

5.2.4.2 Maintenance 

5.2.4.2.1 Adequate procedures for culture maintenance must be followed to avoid poor water quality in the culture

system. The spawning and brood stock culture tanks should be kept free of debris (excess food, detritus, waste,

etc.) by siphoning the accumulated materials (such as dead brine shrimp nauplii or cysts) from the bottom of the

tanks daily with a glass siphon tube attached to a plastic hose leading to the floor drain. The tanks are more

thoroughly cleaned as required. Algae, mostly diatoms and green algae, growing on the glass of the spawning tanks

are left in place, except for the front of the tank, which is kept clean for observation. To avoid excessive build-up of

algal growth, the walls of the tanks are periodically scraped. The larval culture tanks are cleaned once or twice a

week to reduce the mass of fungus growing on the bottom of the tank. 

5.2.4.2.2 Activated charcoal and floss in the tank filtration systems should be changed weekly, or more often if

needed. Culture water may be maintained by preparation of reconstituted water or use of dechlorinated tap water. 

Distilled or deionized water is added as needed to compensate for evaporation.

5.2.4.2.3 Before new fish are placed in tanks, salt deposits are removed by scraping or with 5% acid solution, the

tanks are washed with detergent, sterilized with a hypochlorite solution, and rinsed well with hot tap water and then

with laboratory water.
193

5.2.5 SPAWNING TANKS AND CULTURE CONDITIONS 

5.2.5.1 For breeding tanks, it is convenient to use 60 L (l5 gal) or 76 L (20 gal) aquaria. The spawning unit is

designed to simulate conditions in nature conductive to spawning, such as water temperature and photoperiod. 

Spawning tanks must be held at a temperature of 25 ±2EC. Each aquarium is equipped with a heater, if necessary, a

continuous filtering unit, and spawning substrates. The photoperiod for the culture system should be maintained at

16 h light and 8 h darkness. For the spawning tanks, this photoperiod must be rigidly controlled. A convenient

photoperiod is 5:00 AM to 9:00 PM. Fluorescent lights should be suspended about 60 cm above the surface of the

water in the brood and larval tanks. Both DURATEST® and cool-white fluorescent lamps have been used, and

product similar results. An illumination level of 10-20 μE/m2

/s (50-100 ft-c) is adequate.

5.2.6 SPAWNING BEHAVIOR AND CONDITIONS 

5.2.6.1 To simulate the natural spawning environment, it is necessary to provide substrates (nesting territories)

upon which the eggs can be deposited and fertilized, and which are defended and cared for by the males. The

recommended spawning substrates consist of inverted half-cylinders, such as 7.6 cm x 7.6 cm (3 in. X 3 in.)

sections of schedule 40, PVC pipe. The substrates should be placed equi-distant from each other on the bottom of

the tanks.

5.2.6.2 To establish a breeding unit, 15-20 pre-spawning adults six to eight months old are taken from a "holding"

or culture tank and placed in a 76 L spawning tank. At this point, it is not possible to distinguish the sexes. 

However, after less than a week in the spawning tank, the breeding males will develop their distinct coloration and

territorial behavior, and spawning will begin. As the breeding males are identified, all but two are removed,

providing a final ratio of 5-6 females per male. The excess spawning substrates are used as shelter by the females. 

5.2.6.3 Sexing of the fish to ensure a correct female/male ratio in each tank can be a problem. However, the task

usually becomes easier as experience is gained (Flickinger, 1966). Sexually mature females usually have large

bellies and a tapered snout. The sexually mature males are usually distinguished by their larger overall size, dark

vertical color bands, and the spongy nuptial tubercles on the snout. Unless the males exhibit these secondary

breeding characteristics, no reliable method has been found to distinguish them from females. However, using the

coloration of the males and the presence of an enlarged urogenital structures and other characteristics of the females,

the correct selection of the sexes can usually be achieved by trial and error.

5.2.6.4 Sexually immature males are usually recognized by their aggressive behavior and partial banding. These

undeveloped males must be removed from the spawning tanks because they will eat the eggs and constantly harass

the mature males, tiring them and reducing the fecundity of the breeding unit. Therefore, the fish in the spawning

tanks must be carefully checked periodically for extra males. 

5.2.6.5 A breeding unit will remain in their spawning tank about four months. Thus, each brood tank or unit is

stocked with new spawners about three times a year. However, the restocking process is rotated so that at any one

time the spawning tanks contain different age groups of brood fish. 

5.2.7 EMBRYO COLLECTION 

5.2.7.1 Fathead minnows spawn mostly in the early morning hours. They should not be disturbed except for a

morning feeding (approximately 8:00 AM) and daily examination of substrates for eggs in late morning or early

afternoon. In nature, the male protects, cleans, and aerates the eggs until they hatch. In the laboratory, however, it

is necessary to remove the eggs from the tanks to prevent them from being eaten by the adults, and for ease of

handling for purposes of recording embryo count and hatchability, and for the use of the newly hatched for young

fish for toxicity tests. 

5.2.7.2 Daily, beginning six to eight hours after the lights are turned on (i.e., 11:00 AM - 1:00 PM), the substrates

in the spawning tanks are each lifted carefully and inspected for embryos. Substrates without embryos are
194

immediately returned to the spawning tank. Those with embryos are immersed in clean water in a collecting tray,

and replaced with a clean substrate. A daily record is maintained of each spawning site and estimated number of

embryos on the substrate. 

5.2.8 EMBRYO INCUBATION 

5.2.8.1 Three different methods are described for embryo incubation. 

5.2.8.1.1 Incubation of Embryos on the Substrates: Several (2-4) substrates are placed on end in a circular pattern

(with the embryos on the inner side) in 10 cm of water in a tray. The tray is then placed in a constant temperature

water bath, and the embryos are aerated with a 2.5 cm airstone placed in the center of the circle. The embryos are

examined daily, and the dead and fungused embryos are counted, recorded, and removed with forceps. At an

incubation temperature of 25EC, 75-100% hatch occurs in five days. At 22EC, embryos incubated on aerated tiles

require seven days for 50% hatch.

5.2.8.1.2 Incubation of Embryos in a Separatory Funnel: The embryos are removed from the substrates with a

rolling action of the index finger ("rolled off")(Gast and Brungs, 1973), their total volume is measured, and the

number of embryos is calculated using a conversion factor of approximately 430 embryos/mL. The embryos are

incubated in about l.5 L of water in a 2 L separatory funnel maintained in a water bath. The embryos are stirred in

the separatory funnel by bubbling air from the tip of a plastic micro-pipette placed at the bottom, inside the

separatory funnel. During the first two days, the embryos are taken from the funnel daily, those that are dead and

fungused are removed, and those that are alive are returned to the separatory funnel in clean water. The embryos

hatch in four days at a temperature of 25EC. However, usually on day three the eyed embryos are removed from the

separatory funnel and placed in water in a plastic tray and gently aerated with an air stone. Using this method, the

embryos hatch in five days. 

5.2.8.1.2.1 Hatching time is greatly influenced by the amount of agitation of the embryos and the incubation

temperature. If on day three the embryos are transferred from the separatory funnel to a static, unaerated container,

a 50% hatch will occur in six days (instead of five) and a l00% hatch will occur in 7 days.

5.2.8.1.3 Incubation in Embryo Incubation Cups: The embryos are "rolled off" the substrates, and the total number

is estimated by determining the volume. The embryos are then placed in incubation cups attached to a rocker arm

assembly (Mount, 1968). Both flow-through and static renewal incubation have been used. On day one, the

embryos are removed from the cups and those that are dead and fungused are removed. After day one, only dead

embryos are removed from the cups. Most of the embryos will hatch in five days if incubated at 25EC. 

5.2.8.1.4 During the incubation period, the eggs are examined daily for viability and fungal growth, until they

hatch. Unfertilized eggs, and eggs that have become infected by fungus, should be removed with forceps using a

table top magnifier-illuminator. Non-viable eggs become milky and opaque, and are easily recognized. The

non-viable eggs are very susceptible to fungal infection, which may then spread throughout the egg mass. Removal

of fungused eggs should be done quickly, and the spawning substrates should be returned to the incubation tanks as

quickly as possible so that the good eggs are not damaged by desiccation. 

5.2.9 LARVAE REARING TANKS 

5.2.9.1 Newly-hatched larvae are transferred daily from the egg incubation apparatus to small rearing tanks, using

a large bore pipette, until the hatch is complete. New rearing tanks are set up on a daily basis to separate fish by age

group. Approximately 1500 newly hatched larvae are placed in a 60 L (15 gal) or 76 L (20 gal) all-glass aquarium

for 30 days. A density of 150 fry per liter is suitable for the first four weeks. The water temperature in the rearing

tanks is allowed to follow ambient laboratory temperatures of 20-25EC, but sudden, extreme, variations in

temperature must be avoided.
195

5.2.10 HOLDING OR CULTURE TANKS FOR REPLACEMENT SPAWNERS 

5.2.10.1 Replacement spawners (brood stock) are cultured from larvae produced in the spawning tanks. After 30

days in a larval rearing tank, a number of juveniles, equivalent to 2-4 days hatch are transferred to brood stock tanks

for a 30-60 day growth period. The sub-adults then are transferred to 500-L brood stock tanks to provide about 500

sub-adult fish per month for the brood tank rotation. The surplus fish are transferred to 2000-L fiber glass, or

equivalent, holding tanks. 

5.2.10.2 Surplus young males removed from spawning tanks, and other surplus mature males, are placed in

all-male holding tanks for future use as spawners. Similarly, young and surplus mature females are held in

all-female holding tanks until needed as spawners. Tanks holding replacement spawners need not be

temperature-controlled, but for ease of transfer to the spawning tanks, it is preferable to hold the water temperature

close to that of the spawning tanks (25 ± 2EC). 

5.2.11 FOOD AND FEEDING 

5.2.11.1 Newly hatched brine shrimp nauplii or frozen adult brine shrimp and commercial fish starter are fed to the

fish cultures in volumes based on age, size, and number of fish in the tanks. The amount of food and feeding

schedule affects both growth and egg production.

5.2.11.2 Fish from hatch to 30 days old are fed starter food at the beginning and end of the work day, and newly

hatched brine shrimp nauplii (from the brine shrimp culture unit) twice a day, usually mid-morning and

mid-afternoon. Utilization of older (larger) brine shrimp nauplii may result in starvation of the young fish because

they are unable to ingest the larger food organisms (see Appendix A.4 for instructions on the preparation of brine

shrimp nauplii). Avoid introducing Artemia cysts and empty shells when the brine shrimp nauplii are fed to the fish

larvae. Some of the mortality of the larval fish observed in cultures could be caused from the ingestion of these

materials. 

5.2.11.3 Fish older than four weeks are fed frozen brine shrimp and commercial fish starter (#l and #2), which is

ground fish meal enriched with vitamins. As the fish grow, larger pellet sizes are used, as appropriate. 

5.2.11.4 The spawning fish and pre-spawners in holding tanks usually are fed all the adult frozen brine shrimp and

tropical fish flake food or dry commercial fish food (No. l or No. 2 granules) that they can eat (ad libitum) at the

beginning of the work day and in the late afternoon (i.e., 8:00 AM and 4:00 PM). The fish are feed twice a day,

twice with dry food and once with adult shrimp, during the week, and once a day on weekends.

5.2.12 DISEASE CONTROL 

5.2.12.1 Fish are observed daily for abnormal appearance or behavior. Bacterial or fungal infections are the most

common diseases encountered. However, if normal precautions are taken, disease outbreaks will rarely, if ever,

occur. Hoffman and Mitchell (1980) have put together a list of some chemicals that have been used commonly for

fish diseases and pests. 

5.2.12.2 Treatment of individual lots of infected fish should be carried out separate from the main culture. Use of

treated fish should be avoided, if possible, and diseased cultures should be replaced.

5.2.12.3 In aquatic culture systems where filtration is utilized, the application of certain antibacterial agents should

be used with caution. A treatment with a single dose of antibacterial drugs can interrupt nitrate reduction and stop

nitrification for various periods of time, resulting in changes in pH, and in ammonia, nitrite and nitrate

concentrations (Collins et al., 1976). These changes could cause the death of the culture 

organisms. 
196

5.2.12.4 To prevent possible rapid spread of disease, do not transfer equipment from one tank to another without

first disinfecting tanks and nets. If an outbreak of disease occurs, any equipment, such as nets, airlines, tanks, etc.,

which has been exposed to diseased fish should be disinfected with sodium hypochlorite. Also to avoid the

contamination of cultures or spread of disease, each time nets used to remove live or dead fish from tanks, they are

first sterilized with sodium hypochlorite or formalin, and rinsed in hot tap water. Before a new lot of fish is

transferred to culture tanks, the tanks are cleaned and sterilized as described above. 

5.2.13 RECORD KEEPING 

5.2.13.1 Records are kept in a bound notebook, include: (1) type of food and time of feeding for all fish tanks; (2)

time of examination of the tiles for embryos, the estimated number of embryos on the tile, and the tile position

number; (3) estimated number of dead embryos and embryos with fungus observed during the embryonic

development stages; (4) source of all fish; and (5) daily observation of the condition and behavior of the fish.

5.2.14 REFERENCE TOXICANTS 

5.2.14.1 It is recommended that static acute toxicity tests be performed monthly with a reference toxicant. Fathead

minnow larvae one to 14 days old are used to monitor the acute toxicity of the reference toxicant to the test fish

produced by the culture unit.

6. TEST ORGANISMS 

6.1 Fish 1-14 days old are used in acute toxicity tests.

6.2 If the fish are kept in a holding tank or container, most of the water should be siphoned off to concentrate the

fish. The fish are then transferred one at a time randomly to the test chambers until each chamber contain 10 fish. 

Alternately, fish may be placed one to two at a time into small beakers or plastic containers until they each contain

five fish. Two of these beakers/plastic containers (total of l0 fish) are then assigned to each randomly-arranged

control and exposure chamber.

6.3 The fish are transferred directly to the test vessels or intermediate chambers using a large-bore, fire-polished

glass tube (6 mm to 9 mm I.D. X 30 cm long) equipped with a rubber bulb, or a large volumetric pipet with tip

removed and fitted with a safety type bulb filler. The glass or plastic containers should only contain a small volume

of dilution water.

6.4 It is important to note that larvae should not be handled with a dip net. Dipping small fish with a net may

result in damage to the fish and cause mortality.
197

SELECTED REFERENCES

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Canada. 4th ed. American Fisheries Society, Committee on Names of Fishes. 174 pp.

ASTM. 1993. Standard practice for using brine shrimp nauplii as food for test animals in aquatic toxicology. 

Designation: E 1203-87, Annual Book of Standards, Vol. 11.04, ASTM, Philadelphia, PA.

Andreasen, J.K. 1975. Occurrence of the fathead minnow, Pimephales promelas, in Oregon. Calif. Fish Game

6(3):155-156. 

Andrews, A.K. 1970. Squamation chronology of the fathead minnow, Pimephales promelas. Trans. Amer. Fish.

Soc. 99(2):429-432. 

Andrews, A.K. 1971. Altitudinal range extension for the fathead minnow (Pimephales promelas). Copeia 1:169.

Andrews, A. and Flickinger, S. 1974. Spawning requirements and characteristics of the fathead minnow. 

Proc. Ann. Conf. Southeastern Assoc. Game Fish Comm. 27:759-766.

Benoit, D.A. and Carlson, R.W. 1977. Spawning success of fathead minnows on selected artificial substrates. 

Prog. Fish. Cult. 39(2):67-69. 

Brown, B.E. 1970. Exponential decrease in a population of fathead minnows. Trans. Am. Fish. Soc.

99(4):807-809.

Brungs, W.A. 1971a. Chronic effects of elevated temperature on the fathead minnow (Pimephales promelas

Rafinesque). Environmental Research Laboratory. U.S. Environmental Protection Agency, Duluth, MN. EPA

600/8-81/011.

Brungs, W.A. 1971b. Chronic effects of low dissolved oxygen concentrations on fathead minnows (Pimephales

promelas). J. Fish. Res. Bd. Can. 28:1119-1123.

Buttner, J.K. and Duda, S.W. 1988. Maintenance and reproduction of fathead minnows in the laboratory. Aquatic

Ecology Section, Department of Biological Sciences, SUNY College at Brockport, Brockport, NY 14420.

Carlander, K. 1969. Handbook of freshwater fishery biology, Vol. 1. Iowa State Univ. Press, Ames, IA.

Chiasson, A.G. and Gee, J.H. 1983. Swim bladder gas composition and control of buoyancy by fathead minnows

(Pimephales promelas) during exposure to hypoxia. Can. J. Zool. 61(10):2213-2218.

Clay, W. 1962. The Fishes of Kentucky. Kentucky Dept. Fish and Wildlife Res., Frankfort, KY.

Coble, D.W. 1970. Vulnerability of fathead minnows infected with yellow grub to largemouth bass predation. J.

Parasitol. 56(2):395-396.

Collins, M.T., Gratzer, J.B., Dawe, D.L., and Nemetz, T.G. 1976. Effects of antibacterial agents on nitrification in

aquatic recirculating systems. J. Fish. Res. Bd. Can. 33:215-218. 

Coyle, E.E. 1930. The algal food of Pimephales promelas (fathead minnow). Ohio J. Sci. 30(1):23-35. 

Cross, F.B. 1967. Handbook of fishes of Kansas. Univ. Kansas Mus. Natur. Hist. Misc. Publ. 45:1-357. 
198

Denny, J.S. 1987. Guidelines for the culture of fathead minnows Pimephales promelas for use in toxicity tests. 

Environmental Research Laboratory, U.S. Environmental Protection Agency, Duluth, MN. EPA 600/3-87-001. 

Dixon, R.D. 1971. Predation of mosquito larvae by the fathead minnow, Pimephales promelas Rafinesque. Manit.

Entomol. 5:68-70.

Drummond, R.A. and Dawson, W.F. 1970. An inexpensive method for simulating diel patterns of lighting in the

laboratory. Trans. Am. Fish Soc. 99:434-435. 

Dymond, 1926. The Fishes of Lake Nipigon. Univ. Toronto Stud. Biol. Ser. 27 Publ. Ont. Fish. Res. Lab 27:1-108. 

Eddy, S. and Hodson, A.C. 196l. Taxonomic keys to the common animals of the north central states. 

Burgess Publ. Co., Minneapolis, Minnesota.

Flickinger, S.A. 1966. Determination of sexes in the fathead minnow. Trans. Amer. Fish. Soc. 98(3):526-527. 

Flickinger, S.A. 1973. Investigation of pond spawning methods for fathead minnows. Proc. Ann. Conf. Southeast.

Assoc. Game and Fish Commiss. 26:376-391.

Gale, W.F. and Buynak, G.L. 1982. Fecundity and spawning frequency of the fathead minnow--A fractional

spawner. Trans. Amer. Fish. Soc. 111:35-40.

Gast, M.H. and Brungs, W.A. 1973. A procedure for separating eggs of the fathead minnow. Prog. Fish. Cult.

35:54.

Guest, W.C. 1977. Technique for collecting and incubating eggs of the fathead minnow. Prog. Fish. Cult.

39(4):188. 

Hedges, S. and Ball, R. 1953. Production and harvest of bait fishes in ponds. In: Michigan Dept. Conservation. 

Misc. Publ. 6, Lansing, Michigan. pp. 1-30.

Held, J.W. and Peterka, J.J. 1974. Age, Growth, and food habits of the fathead minnow, Pimephales promelas, in

North Dakota saline lakes. Trans. Am. Fish. Soc. 103(4):743-756.

Hendrickson, G.L. 1979. Ornithodiplostomum ptychocheilus: migration to the brain of the fish intermediate host,

Pimephales promelas. Exp. Parasit. 48:245-258. 

Herwig, N. 1979. Handbook of drugs and chemicals used in the treatment of fish diseases. Charles C. Thomas,

Publ., Springfield, IL. 272 pp.

Hoffman, G.L. 1958. Studies on the life cycle of Ornithodiplostomum ptychocheilus (Faust) (Trematoda:

Strigeoidea) and the "self cure" in infected fish. J. Parasitol. 44(4):416-421.

Hoffman, G.L. and Mitchell, A.J. 1980. Some chemicals that have been used for fish diseases and pests. Fish

Farming Exp. Sta., Stuttgart, AR. 72160. 8 pp.

Hubbs, C.L. and Cooper, G.P. 1935. Age and growth of the long eared and the green sunfishes in Michigan. Pap.

Mich. Acad. Sci. Arts. Letts. 20:669-696.

Hubbs, C.L. and Lagler, K.F. 1949. Fishes of Isle Royale, Lake Superior, Michigan. Pap. Mich. Acad. Sci. Arts.

Letts. 33:73-133. 

Hubbs, C.L. and Lagler, K.F. 1964. Fishes of the Great Lakes Region. Univ. Mich. Press, Ann Arbor, MI.
199

Ingram, R. and Wares, II, W.D. 1979. Oxygen consumption in the fathead minnow (Pimephales promelas

Rafinesque) II: Effects of pH, osmotic pressure, and light level. Comp. Biochem. Physiol. 62A:895-897. 

Isaak, D. 1961. The ecological life history of the fathead minnow, (Pimephales promelas Rafinesque). Doctoral

dissertation, Univ. Minnesota. Microfilm 6104598, Univ. Microfilms International. Ann Arbor, MI. 150 pp.

Kimsey, J.B. and Fisk, L.O. 1964. Freshwater nongame fishes of California. Calif. Dept. Fish and Game.,

Sacramento, CA.

Klak, G.E. 1940. Neascus infestation of blackhead, blunt nosed, and other forage minnows. Trans. Amer. Fish.

Soc. 69:273-278. 

Klinger, S.A., Magnuson, J.J., and Gallepp, G.W. 1982. Survival mechanisms of the central mudminnow (Umbra

limi), fathead minnow (Pimephales promelas), and brook stickleback (Culea inconstans) for low oxygen in

winter. Envirn. Biol. Fish. 7(20):113-120. 

Konefes, J.L. and Bachmann, R.W. 1972. Growth of the fathead minnow (Pimephales promelas) in tertiary

treatment ponds. Proc. Iowa Acad. Sci. 77:104-111.

Lee, D.S., Gilbert, C.R., Hocutt, C.H., Jenkins, R.E., McAllister, D.E., and Stauffer, R., Jr. 1980. Atlas of North

American freshwater fishes. Publ. 1980-12, N. Carolina State Museum Nat. Hist., Raleigh, NC. 27611.

Lord, R.R., Jr. 1927. Notes on the use of the blackhead minnow, Pimephales promelas, as a forage fish. 

Trans. Am. Fish. Soc. 57:92-99.

Manner, H.W. and Casimira, C.M. 1974. Early embryology of the fathead minnow Pimephales promelas

Rafinesque. Anat. Rec. 180(1):99-109.

Manner, H.W., VanCura, M., and Muehlman, C. 1977. The ultrastructure of the chorion of the fathead minnow,

Pimephales promelas. Trans. Amer. Fish. Soc. 106(1):110-114.

Markus, H. 1934. Life history of the blackhead minnow (Pimephales promelas). Copeia 1934:116-122. 

McMillan, V. 1972. Mating of the fathead. Nat. Hist. 81(5):73-78.

Ming, F.W. and Noakes, D.L.G. 1984. Spawning site selection and competition in minnows (Pimephales notatus

and P. promelas) (Pisces, Cyprinidae). Biol. Behav. 9(3):227-234. 

McCarraher, D.B. and Thomas, R. 1968. Some ecological observations on the fathead minnow, Pimephales

promelas, in the alkaline waters of Nebraska. Trans. Am. Fish. Soc. 97(1):52-55.

Mount, D.I. 1968. Chronic toxicity of copper to fathead minnows (Pimephales promelas Rafinesque). Wat. Res. 

2:214-223. 

Nagel, T. 1976. Technique for collecting newly hatched fathead minnow fry. Prog. Fish. Cult. 38(3):137. 

Pickering, Q.H., Horning, W.B., and Hall, C. 1985. Techniques used to transfer live fish and invertebrates from

the Environmental Monitoring and Support Laboratory, U.S. Environmental Protection Agency, Cincinnati, 

OH. 18 pp.

Radcliff, L. 1931. Propagation of minnows. Trans. Amer. Fish. Soc. 61:131-137.
200

Rafinesque, C.S. 1820. Ichthyologia Ohiensis, or natural history of the fishes inhabiting the river Ohio and its

tributary streams, preceded by a physical description of the Ohio and its branches. Lexington, KY. 90 pp.

Richardson, L.R. 1937. Observations on the mating and spawning of Pimephales promelas (Rafinesque). 

Can. Field-Natur. 51(1):1-4.

Scott, W. and Crossman, E. 1973. Freshwater fishes of Canada. Fish. Res. Bd. Can. Bull. 184. 966 pp. 

Smith, H.T., Schreck, C.B., and Maughan, O.E. 1978. Effect of population density and feeding rate on the fathead

minnow (Pimephales promelas). J. Fish. Biol. 12:449-455.

Smith, R.J.F. 1978. Seasonal changes in the histology of the gonads and dorsal skin of the fathead minnow,

Pimephales promelas. Can. J. Zool. 56:2103-2109. 

Smith, R.J.F. and Murphy, B.D.. 1974. Functional morphology of the dorsal pad in fathead minnows (Pimephales

promelas). Trans. Am. Fish. Soc. 103(1):65-72.

Snyder, D.E., Snyder, M.B.M., and Douglas, S.C. 1977. Identification of golden shiner, Notemigonus crysoleucas,

spotfin shiner, Notropis spilopterus, and fathead minnow, Pimephales promelas, larvae. J. Fish. Res. Board

Can. 34:1397-1409.

Soderberg, R.W. 1982. Aeration of water supplies for fish culture in flowing water. Prog. Fish-Cult. 44(2):89-93.

Syrett, R.F. and Dawson, W.F. 1972. An inexpensive electronic relay for precise water temperature control. Prog.

Fish. Cult. 34(4):241-242. 

Syrett, R.F. and Dawson, W.F. 1975. An inexpensive solid state temperature controller. Prog. Fish. Cult.

37(3):171-172.

Taylor, W.R. 1954. Records of fishes in the John N. Lowe collection from the Upper Peninsula of Michigan. 

Misc. Publ. Mus. Zool. Univ. Michigan. 87. 50 pp.

Trautman, M.B. 1981. The fishes of Ohio. Rev. ed., Ohio State Univ. Press., Columbus, Ohio. 782 pp.

Vandermeer, J.H. 1966. Statistical analysis of geographic variation of the fathead minnow, Pimephales promelas. 

Copeia 1966(3):457-466.

Westman, J. 1938. Studies on the reproduction and growth of the bluntnose minnow Hydorhynchus notatus

(Rafinesque). Copeia 1938:57-61.

Wynne-Edwards, V.C. 1932. The breeding habits of the black-headed minnow (Pimephales promelas Raf.). 

Trans. Amer. Fish. Soc. 62:382-383.
201

APPENDIX A

DISTRIBUTION, LIFE CYCLE, TAXONOMY, AND CULTURE METHODS

A.6 RAINBOW TROUT, ONCORHYNCHUS MYKISS AND

BROOK TROUT, SALVELINIUS FONTINALIS

1. RAINBOW TROUT

1.1 SYSTEMATICS AND TAXONOMY

1.1.1 Rainbow trout are native to the streams of the Pacific coast where several varieties or strains have developed. 

The seagoing form is known as the steelhead trout and is thought to be identical to the strictly freshwater rainbow

form. Many other strains, for example, the inland lake form (Kamloops trout) are found in other watersheds. 

Because of the ease with which the eggs can be transported, different strains have been distributed all over the

world.

1.1.2 Rainbow trout are a variable species that differ considerably over the whole of their range. Populations in

different regions and watersheds of North America have been referred to over the years by different scientific names

(e.g. species, distinct subspecies, or variants of a single species and different regional common names). In recent

years the validity of the generic name, Salmo, for some western North American trout species has been questioned. 

Fish taxonomists agree that native "Salmo" trouts of the northern Pacific Ocean drainage are closely related with

Pacific salmon Oncorhynchus spp. The American Society of Ichthyologists and Herpetologists and the American

Fisheries Society have accepted Oncorhynchus as the appropriate generic name for all native Pacific drainage trouts

that are presently called Salmo, based on new data and evidence by Smith and Stearly (1989). Furthermore, the

Names of Fishes Committee of the American Fisheries Society has adopted the specific name, Oncorhynchus

mykiss, for the rainbow trout and its anadromous form, steelhead trout. The new names for the other North

American species affected are the following: Apache trout (O. apache), cutthroat trout (O. clarki), Gila trout (O.

gilae), golden trout (O. aguabonita), and Mexican golden trout (O. chrysogaster).

1.2 DISTRIBUTION

1.2.1 The native range of the rainbow trout group (all varieties) in North America is west of the Rocky Mountains

and along the eastern Pacific Ocean, but the species (Oncorhynchus mykiss) has now been introduced into many

parts of the continent (Figure 1). Except for the northern and southern extremes of the rainbow trout range,

anadromous populations occur in all coastal rivers. This species, under all its common names (rainbow trout,

Kamloops trout, steelhead trout, steelhead, coast rainbow trout, and silver trout), has been so widely introduced in

North America outside its natural range as to suggest it may occur throughout the United States in all suitable

habitats. Rainbow trout are widely introduced and established in appropriate cold water habitats all over the world. 

1.3 GENERAL LIFE HISTORY

1.3.1 In its natural environment of flowing streams of the western mountains, the rainbow trout (Figure 2) thrives

best at temperatures ranging from 3EC in the winter to 21EC in the summer, but the optimum temperature is

between 10-16EC. The rainbow trout can withstand higher and lower temperature if it is acclimated gradually. 

However, the rainbow trout's growth is impeded by extremes of temperature, for example, above 27EC which it can

tolerate only for short periods of time. 
202

 
203

1.3.2 Rainbow trout are basically spring spawners, but they can spawn at the beginning of summer or early winter,

depending on climate, elevation, and genetic strain. If the spawning occurs in late fall or in winter, the eggs do not

hatch until spring. Prior to the spawning season adult males develop a kype (elongated hooked snout) on the lower

jaw and their colors intensify. Males and females usually migrate upstream and select spawning sites in beds of

fine, clean gravel in riffles or runs above pools in streams. Long journeys may be made by lake-dwelling rainbow

(or Kamloops) and steelhead trouts or anadromous, ocean-run rainbow steelheads. If the rainbow trout are confined

to land-locked lakes, they move into shallow shoals or reefs of gravel and sand for spawning. Females dig out pits

or sweep out depressions (redds) in the gravel or sand and later spawn with males. Males are capable of displaying

aggressive behavior on the spawning grounds and can drive other males away from a redd occupied by a female. In

general, one or more males court the digging female by sliding along side and crossing over her body and rubbing

their snout against her caudal peduncle with body pressing and body vibrations. The female deposits her eggs,

which are 3-5 mm in diameter, demersal, and pink to orange in color. The eggs are immediately fertilized by one or

more males, fall into spaces between the gravel, and are covered with loose gravel or sand to depths of 20 cm or

more by the female. Females are capable of digging and spawning in several redds with the same male or different

males. The number of eggs released can range from 400-3000, depending on the size of the female.

1.3.3 Eggs usually hatch in approximately four to seven weeks. The time of hatching, however, varies greatly with

region and habitat. If the stream temperature averages 7EC, eggs will hatch in about 48 days. The newly hatched

fish, called alevins, have a yolk sac, which is absorbed in three to seven days. After the yolk sac is absorbed, the

young are called fry, and begin feeding in 10-15 days. In general, rainbow trout feed on a variety of invertebrates. 

Also, depending on their size and the habitat in which they live, other fishes and fish eggs, especially salmon, can

be important food. The fry of lake-resident spawners move up or down the spawning river to the lake, or they may

spend as much as one to three years in the streams. The stream-resident spawners remain in the streams, whereas

the steelhead trout, which are stream-spawners, migrate to the sea, usually after 1-4 years in freshwater.

1.3.4 The growth of rainbow trout is highly variable with the area, habitat, type of life history, and quantity and

type of food. Some males may be good breeders at two years of age, but few females produce eggs until their third

year of life. Rainbow trout young attain fingerling size of about 76 mm by the end of their first summer. The

length may range between 178-204 mm at the end of the second year, 279-382 mm after the third year, 356-406 mm

after the fourth year, and 406 mm or more after the fifth year. Lake- and ocean-run rainbows may grow over twice

as fast as this. However, the average length of rainbow trout (or Kamloops trout) is 305-458 mm and that of

steelhead trout is 508-762 mm. Under favorable conditions of artificial propagation, yearlings average about 28 g,

2-year-olds about 255 g, 3-year-olds between 0.45-9 kg, and 4-year-olds between 1.4-1.8 kg. Returning sea-run

individuals weigh up to 18 kg, or even more, but usually between 1.4-9 kg with the majority weighing less than 5.4

kg. Some western varieties weight up to 23 kg, but the midwest rainbows are much smaller. Those in streams are

rarely over 1.4 kg, but in some large lakes (e.g., Lake Superior) and in some western lakes they may reach 7 kg or

much larger. The life expectancy of rainbow trout can be as low as three or four years in many streams and Lake

populations, but that of seagoing steelhead rainbow trout and Great lakes populations would appear to be 6 to 8

years (Scott and Crossman, 1973).

1.4 GENERAL DESCRIPTION

1.4.1 Adult rainbow trout are bluish or olive green above and silvery on the sides, with a broad pink lateral stripe

that is enhanced during the spawning season. The back, the sides, and the dorsal and caudal fins are profusely

dotted with small dark spots. Their color is variable with habitat, size, and sexual condition. Stream forms and

spawners are generally darker with color more intense, lake forms lighter, brighter, and more silvery. Different

color types are often called by different names, e.g., darker stream fish often called rainbows; larger, brighter,

silvery fish in western lakes often called Kamloops trout, and large silvery specimens returning from the sea and in

the Great Lakes or tributaries called steelhead trout. The scales are large, numbering 120 to 150 in the lateral line. 

The caudal fin is very slightly forked. The dorsal fin has 11 rays, and the anal fin has from 10 to 12 rays. 

1.4.2 Young rainbow trout are typically blue to green on the dorsal surface, silver to white on the sides and white

ventrally. There are 5-10 dark marks on the back between the head and dorsal fin. Also, there are 5-10 short, dark,
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oval parr marks widely spaced on the sides, straddling the lateral line with some small dark spots above but not

below the lateral line. The dorsal fin has a white to orange tip and a dark leading edge, or a series of bars or spots. 

The adipose fin is edged with black, and the anal fin has an orange to white tip.

2. BROOK TROUT

2.1 SYSTEMATICS AND TAXONOMY

2.1.1 Brook trout can be found exhibiting some variation in growth rate and color throughout its range, but is

considered a stable and well-defined species (American Fishery Society, 1980). Male brook trout may be crossed

with female lake trout (Salvelinus namaycush) to produce fertile hybrids that are known as splake. Troutman

(1981) and other papers cited in this section indicate that brook trout can naturally and artificially hybridize with

brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss). For additional information and discussion on

freshwater and anadromous brook trout stocks and systematic notes of brook trout, see Scott and Crossman (1973)

and other papers cited in this section.

2.2 DISTRIBUTION

2.2.1 The native range of the brook trout (Figure 3) is eastern North America, extending throughout much of

eastern Canada from Hudson Bay and Ungava Bay drainages and Labrador; southward through the New England

States and in the Appalachian Mountains to the headwaters of the Savannah, Chattahoochee, and Tennessee Rivers

in the Carolinas and Georgia. In the Great Lakes, brook trout are native to Lake Superior and tributaries to the

northern tip of the Lower Peninsula, the interior of the Great Lakes basin. They are also native to a few far-northern

headwaters of the upper Mississippi river system, and western Minnesota and northeastern Iowa.

 

2.2.2 The brook trout has been widely introduced to higher elevations in western North America. This species is

also found in temperate regions of other continents. Inland forms are found in colder lakes and streams, and sea-run

(anadromous) forms are found in the northeastern North American coastal water areas.
205

2.3 GENERAL LIFE HISTORY

2.3.1 Brook trout (Figure 4) are generally found in clear brooks, streams, and rivers in which the mean temperature

rarely exceeds 10EC. The optimum temperature is reported as ranging from 7 to 13EC, but they may be found living

in waters with temperatures ranging from 1 to 22EC (Piper et al. 1982). The brook trout usually inhabits waters

which flow less swiftly than those inhabited by the rainbow. Brook trout also thrive in the small cold-water lakes of

the Great Lakes region, provided that suitable spawning conditions exist. 

2.3.2 Brook trout spawn in late summer or autumn, the date varying with latitude and temperature, usually from

late October to December when the water temperature is suitable although some may start spawning in September in

certain streams flowing into large lakes. Some females are capable of spawning when they are a year old, while

others do not mature until the second year. When the spawning season occurs, brook trout move upstream into

small head waters or brooks where they select gravel and sand substrates usually in shallow riffle areas or the tailends of pools for the spawning beds. Spawning usually occurs during the day.

2.3.3 The female prepares a nest (redd), similar to those of the rainbow trout, by sweeping out a depression in the

gravel and sand substrate. During preparation of the redd, the male starts courtship by quivering around the female

and driving off all intruders. When the female is ready to spawn, she takes a position above and close to the redd. 

The male gets close to her side and arches his body over hers, discharging milt as the female deposits her eggs. 

Occasionally second male may join them in the spawning. After spawning, the male leaves.

2.3.4 The eggs are 3.5 to 5.0 mm in diameter, are adhesive, and adhere to the gravel at the bottom of the redd. The

female pushes loose gravel and sand to the center, covering the entire redd, and then desert the nest. A female may

spawn several times, and the number of eggs can vary from l00 to 5000, depending on the size of the female.

2.3.5 The eggs remain in the redd until the water temperature rises during the following spring. If the level of DO

is adequate, the eggs will hatch in approximately 75 days at an average water temperature of 6.1EC, and in

approximately 50 days at an average temperature of 10EC. The upper lethal temperature limit for developing eggs is

about 11.7EC (Scott and Crossman, 1973).

2.3.6 After the eggs hatch, the larvae (sac fry) remain in the gravel of the redd until the yolk is absorbed. 

Depending on the water temperature, it may take from one to three months for the yolk sac to be absorbed (Lagler,
206

1956). While the yolk sac is absorbed, the fry work themselves free from the gravel and start feeding. They

become free swimming at about 38 mm long. Under natural conditions, newly hatched brook trout establish small

feeding territories in the stream and feed on small aquatic insects, insect larvae, and other organisms.

2.3.7 Growth of brook trout is extremely variable, depending on the suitability of the environment. The average

length attained at various ages may approximate 8.9 cm the first year; 15.2 cm the second year, 22.9 cm the third

year, 30.5 cm the fourth year, and 33 cm the fifth year. Brook trout generally do not exceed a length of 54 cm and a

weight of 1.5 kg (Trautman, 1981). However, Scott and Crossman (1973) reported a brook trout as large as 6.6 kg. 

Rumors of larger brook trout have been circulated, but none have been verified. Brook trout may overpopulate

small streams, resulting in large numbers of small trout less than 25.4 cm long. Wild brook trout seldom live longer

than five years, and rarely live more than eight years.

2.4 GENERAL DESCRIPTION

2.4.1 The sides of large young and adult brook trout are dark olive, sprinkled with light spots and red spots

outlined with purplish or blue hue. Some forms have red spots with light brown margins. The scales are cycloid,

small, in about 215 to 250 rows at the lateral line. The top of the head and back is dark olive and heavily

vermiculated. There are no black or brown spots on the head, back, adipose, or caudal fin. The anterior rays of the

pectoral, pelvic, and anal fins are milk-white, bordered posteriorly with a dusky hue and the remainder of the fins

yellowish or reddish.

2.4.2 The back of young or immature brook trout is olive, the sides are lighter and more silvery, and the belly is

whitish. There are between 8-12 rectangular parr marks on the sides, also a few yellow and blue spots, but no black

spots.

2.4.3 The dorsal fin has 10 rays, and the anal fin has 9 rays. The belly of breeding males is red, and some males

may develop a hook (or kype) at the front of the lower jaw. The tail or caudal fin is slightly notched in the young

but is generally square in older brook trout.

3. HOLDING AND ACCLIMATION PROCEDURES FOR TROUT STOCKS

3.1 SOURCES OF ORGANISMS

3.1.1 Trout fry are obtained from commercial hatcheries during March through July. However, if trout are needed

for toxicity testing, it is advisable to contact the hatchery for its trout hatching and rearing schedule. If trout must be

ordered from out-of-state, the State Fish and Game Agency should be contacted concerning regulations on fish

importation. The recommended age for test organisms is approximately 15-30 days (after yolk sac absorption to 30

days) for rainbow trout and 30-60 days for brook trout. Trout are purchased 36 to 48 h prior to their use as testing

organisms, but they must have time to stabilize over the acclimation period. Trout should appear disease-free and

unstressed, with fewer than 5% of the animals dying during the 24-48 hours preceding use in a toxicity test.

3.1.2 Trout fry are usually transported in plastic bags of at least 4-mil plastic or thicker in shipping containers. The

bags are partially filled with water saturated with oxygen. During warm weather the shipping containers are cooled

with ice or cold packs to prevent temperature increases which will result in the loss of fish. Trout should be

acclimated gradually from the temperature of the transportation unit to that of holding environment. Upon arrival at

the destination the plastic bags should be allowed to float unopened in the holding tank for about 30 minutes to

acclimate the fish.

3.2 HOLDING CONDITIONS

3.2.1 Trout are held in 200 L (50 gal) or larger tanks supplied with a flow-through water system, or with

recirculated water and a biological filtration system. The holding water should be moderately hard and free of

chlorine, have low concentrations of metals, and should have a pH between 6 and 9. Provide a daily photoperiod of
207

16 hours light, 8 hours darkness with an illumination at 10-20 μE/m2/s (50-100 ft-c, or ambient laboratory levels). 

A 15 min dimmer timer should be used to gradually increase or decrease the illumination when lights are turned on

or off. The gradual increase and decrease of illumination at the beginning and ending of the photoperiod is

important because trout tend to jump when startled by a sudden change in light intensity. Holding water

temperature is maintained at 12EC ±2EC and is aerated as close as possible to saturation. Measurements of

temperature, DO, pH, conductivity, and ammonia are made on holding water daily.

3.3 FEEDING

3.3.1 Trout are fed fine texture trout chow. The fry in the holding tank are fed (ad libitum) up to 24 hours before

the start of the acute toxicity test. Dead or moribund fish should be removed from the holding tanks every day. 

Excess food and feces are vacuum-siphoned off the bottom of the tank daily.

3.3.2 Daily records should be maintained for organism survival, health, and acclimation conditions.

4. TEST ORGANISMS

4.1 Rainbow trout fry 15-30 days old, and Brook trout 30-60 days old, are used in acute tests (see summary tables

of test conditions in Section 9, Acute Toxicity Test Procedures). The fry in the holding tank are not fed for 24 hours

prior to the start of the test. The fry are caught carefully with a fine mesh net and placed gently in the 5 L (4 L test

solution volume) test chambers, until 10 fish are reached per test chamber. Larger test chambers or 5 fish/chambers

may be necessary if DO or pH problems are encountered. Placement of the test chambers is random.

4.2 After the fish are introduced, the behavior should be noted and recorded throughout the test period. At the

beginning and ending of the photoperiod, during the test, the light intensity should be raised and lowered gradually

over a 15 min period using a dimmer switch or suitable device. Between observations the test vessels are covered to

act as a dust barrier and to prevent fish from jumping out.
208

SELECTED REFERENCES

American Fisheries Society. 1980. A list of common and scientific names of fishes from the United States and

Canada. Special Publication No. 12. Amer. Fish. Soc., Bethesda, MD.

Bailey, R.M and Robins, C.R. 1989. Changes in North American fish names, especially as related to the

International Code of Zoological Nomenclature, 1985. Bull. Zool. Nomencl. 45(2):92-103.

Eddy, S. and Hodson, A.C. 1970. Taxonomic keys to the common animals of the north central states. Burgess

Publ. Co., Minneapolis, MN. 

Eddy, S. and Underhill, J.C. 1974. Northern fishes. Univ. Minnesota Press, Minneapolis, MN. 

Hubbs, C.L. and Lagler, K.F. 1967. Fishes of the Great Lakes Region. Univ. Michigan Press, Ann Arbor, MI.

Lagler, K.F. 1956. Freshwater Fishery Biology. Wm. C. Brown Co., Publ., Dubuque, IA. 

Lee, D.S., Gilbert, C.R., Hocutt, C.H., Jenkins, R.E., McAllistger, D.E., and Stauffer, R., Jr. 1980. Atlas of North

American freshwater fishes. Publ. 1980-12, North Carolina State Museum Nat. Hist., Raleigh, NC.

Leitritz, E. and Lewis, R.C. 1976. Trout and salmon culture (Hatchery methods). California Dept. Fish and Game,

Fish Bulletin 164. Sacramento, CA.

National Academy of Sciences. 1974. Fishes - Guidelines for the breeding, care, and management of laboratory

animals. Printing and Publishing Office, National Academy of Sciences, Washington, D.C.

Piper, R.G., McElwain, I.B., Orme, L.E., McCraren, J.P., Fowler, L.G., and Leonard, J.R. 1982. Fish hatchery

management. U.S. Dept. Interior, Fish and Wildlife Service, Washington, D.C.

Scott, W.B. and Crossman, E.J. 1973. Freshwater fishes of Canada. Fisheries Research Board of Canada, Ottawa,

Canada.

Smith, G.R. and Stearly, R.F. 1989. The classification and scientific names of rainbow and cutthroat trouts. 

Fisheries 14(1):4-10.

Trautman, M.B. 1981. The fishes of Ohio. Ohio State Univ. Press and Ohio Sea Grant Program, Center Lakes Erie

Area Research, Columbus, OH. 

Willers, B. 1991. Trout Biology: A natural history of trout and salmon. Lyons and Burfoud, 31 West 21 Street,

New York, NY. 10010.
209

APPENDIX A 

DISTRIBUTION, LIFE CYCLE, TAXONOMY, AND CULTURE METHODS

A.7 SHEEPSHEAD MINNOW (CYPRINODON VARIEGATUS)

1. MORPHOLOGY AND TAXONOMY

1.1 The sheepshead minnow (Cyprinodon variegatus) belongs to the family Cyprinodonitidae (killifishes), which

includes 45 genera and 300 species worldwide, occurring on all continents except Australia. Most species are

freshwater, but some occur in brackish and coastal marine waters. There are thirteen species in the Genus

Cyprinodon in the United States (American Fisheries Society, 1980). The sheepshead minnow is the only marine

species, and is widely distributed in the coastal waters of the Atlantic and Gulf of Mexico.

1.2 Adult sheepshead minnows (see Hardy, 1978, for a complete description) can attain a total length of 93 mm,

but the average standard length report for adults is 35-50 mm. The males are usually somewhat longer than

females. The fish have the following morphological characteristics: lack a lateral line; have 24-29 lateral scale

rows; have a large elongate humeral scale just above the pectoral base; the dorsal fin has nine to 13 rays; the anal fin

has nine to 12 rays; the caudal fin has 14-16 principal rays and a total of 28-29 rays; the pectoral fin has 14-17 rays,

and the ventral fin has five to seven rays. 

1.3 The body of males is short, compressed, and deep. The depth increases with age. The upper profile is evenly

elevated. The males are olivaceous above with a lustrous steel blue or bluish green area on the back from nape to

dorsal or beyond, and have a series of poorly defined dark bars on the sides and a belly that is yellowish white to

deep orange. The dorsal fin ocellus on posterior rays is lacking or developed as faint dusky spot.

1.4 The females are light olive, brown, brassy, or light orange above with 14 dark crossbars on the lower sides

alternating with seven to eight crossbars on the back. The lower sides and belly are yellowish or white. The dorsal

fin is olive or dusky and has one or two prominent ocelli on the posterior rays.

2. LIFE HISTORY

2.1 DISTRIBUTION AND GENERAL ECOLOGY 

2.1.1 Sheepshead minnows occur in estuaries along the Atlantic and Gulf coasts (Figure 1). They are a schooling,

euryhaline species that inhabit a variety of shallow water habitats, such as coves, bays, ponds, inlets, harbors,

bayous, salt marshes, and along open beaches. In some cases, they may be very abundant where the bottom is

partially sandy, emergent vegetation lacking, and little current or wave action are present. This species may

establish populations in inland lakes containing relatively high concentrations of dissolved salts. They are tolerant

of extreme changes in water temperatures, ranging from 0-40EC, and in salinities, ranging from 0.1-149‰ (Simpson

and Grunter, 1956; Nordlie, 1987).

2.1.2 This omnivorous fish is an important component of the estuarine ecosystem serving as a link in transferring

energy from lower trophic levels, detritus and benthic plants and animals, to carnivores in higher trophic levels

(Hansen and Parrish, 1977). Sheepshead minnows serve as forage fish for commercially and recreationally valued

fish species, such as the black drum (Pogonias cromis), red drum (Sciaenops ocellata), bluefish (Pomatomus

saltatrix), spotted seatrout (Cynoscion nebulosus), striped bass (Morone saxatilis), and snook (Centropomus

undecimalis) (Gunter, 1945; Darnell, 1958; Grant, 1962; Sekavec, 1974, and Carter et al., 1973).
210

2.2 GENERAL SPAWNING BEHAVIOR 

2.2.1 Sheepshead minnows (Figures 2, 3, 4) spawn at depths of 2.5-60 cm in shallow bays, tide pools, mangrove

lagoons, and pools in shallow, gently flowing streams, and other similar habitats over bottoms of sand, black silt, or

mud. Males occupy territories up to 0.3-0.6 m in diameter and may or may not construct nest pits. Spawning may

take place out of both pit and territory. Besides temperature, Martin (1972) reported that sudden changes in salinity

can initiates spawning activities. Eggs (Figure 2) are demersal, adhesive or semi-adhesive with very minute

attachment filaments (threads) more or less evenly distributed over the chorion. They stick to a variety of

substrates, such as plants, sand, rocks, logs, and to each other. Sometimes they stick to plants near the surface, and

at other times become partially buried in the bottom. The yolk contains one very large and many minute oil

globules. Adults spawn possibly throughout the year on the Gulf coast of the United States. Hansen and Parrish

(1977) reported that in an estuary near Pensacola, Florida, spawning may occur during any month of the year. Ripe

females are found April to October in North Carolina, throughout the summer in the Chesapeake Bay, May to

August in Delaware Bay, May to September in New Jersey and New York, and June to mid-July in Massachusetts. 
211
212
213
214

3. CULTURE METHODS AND FACILITIES

3.1 SOURCES OF ORGANISMS 

3.1.1 Juvenile and adult sheepshead minnows (Figure 4) for use as brood stock spawners may be obtained from

commercial biological supply houses or taken by seine in coastal estuaries of the Atlantic coast and Gulf of Mexico. 

They may also be obtained from young fish raised to maturity in the laboratory. Feral brood stock and first

generation laboratory fish may be preferred, to minimize inbreeding. A continuous supply of wild stock, however,

may be more cost effective. Neither fish nor eggs of feral stock should contain excessive contaminants nor exhibit

excessive mortality, and the fish should demonstrate normal behavior. Before being used as a source of gametes,

field-caught adults should be maintained and observed in the laboratory for at least one week to permit detection of

disease and to allow time for acute mortality resulting from stress of capture. Injured or diseased fish should be

discarded.

3.2 LABORATORY CULTURE FACILITIES 

3.2.1 Sheepshead minnows can be cultured in a static, recirculated, or flow-through systems. Flow-through

systems require large volumes of water and may not be feasible in some laboratories. 

3.3 LABORATORY YEAR-ROUND SPAWNING 

3.3.1 In the laboratory, adults may be kept in breeding condition year round. Females may spawn a number of

times at intervals of one to seven days, and will generally produce an average of 10 to 30 eggs per spawning

(USEPA, 1978a). To obtain large number of eggs at one particular time, adult fish of 27 mm standard length or

greater should be used. If fish are taken in the field, they should be acclimated for at least one to two weeks in

20-30‰ salinity, a water temperature of 25-28EC, and a photoperiod of 16 h light and 8 h dark.

3.3.2 Sheepshead minnows can be continuously cultured in the laboratory from eggs to adults. The eggs

(embryos), larvae, juveniles, and adults (Figures 2, 3, 4) should be kept in rearing and holding tanks of appropriate

size and maintained at ambient laboratory temperature. The larvae should be fed sufficient newly-hatched Artemia

nauplii daily to assure that live nauplii are always present. At the juvenile stage, they are fed frozen adult brine

shrimp and a commercial flake food. Adult fish are fed flake food two or three times daily, supplemented with

frozen adult brine shrimp. 

3.3.3 Sheepshead minnows normally reach sexual maturity three to five months after hatching, and have an

average standard length of approximately 27 mm for females and 34 mm for males, if held at a temperature of

25-30EC in rearing tanks of adequate size, and fed adequately. At this time, the males begin to exhibit sexual

dimorphism and initiate territorial behavior. When the fish reach sexual maturity, and are to be used to obtain large

number of embryos by natural spawning, the brood stock should be kept in a temperature controlled system at

18-20EC. To initiate spawning, the spawners are moved to spawning tanks with a temperature of 25EC. Adults can

be maintained in natural or artificial seawater in a flow-through, static, or recirculating, aerated system consisting of

an all-glass aquarium, or equivalent (see USEPA, 1985 and USEPA, 1987).

3.3.4 Static systems are equipped with an undergravel filter. Recirculating systems are equipped with an outside

biological filter constructed in the laboratory using a reservoir system of crushed coral, crushed oyster shells, or

dolomite and gravel, charcoal, floss, (see Spotte, 1973; 1979, Bower, 1983 for information on filters and

conditioning the biological filter), or a commercially available cartridge filter or an equivalent system. The culture

conditions should include seawater at 20-30‰, and a photoperiod of 16 h light and 8 h dark. Water temperature

may be controlled or maintained at ambient laboratory levels. 
215

3.4 OBTAINING EGGS (EMBRYOS) FOR TOXICITY TESTS 

3.4.1 Embryos can be shipped to the laboratory from an outside source or obtained from adults held in the

laboratory. Ripe eggs can be obtained either by natural spawning or by intraperitoneal injection of the females with

human chorionic gonadotrophin (HCG) hormone. If the culturing system for adults is temperature controlled,

natural spawning can be induced to obtain large number of embryos by raising the temperature to 25EC. Natural

spawning is preferred because repeated spawning can be obtained from the same brood stock, whereas with

hormone injection, the brood stock is sacrificed in obtaining gametes. It should be emphasized that the injection and

hatching schedules given below are to be used only as guidelines. Response to the hormone varies with brood stock

and temperature. Time-to-hatch and percent hatch also vary among stocks and among batches of embryos obtained

from the same stock, and are dependent on temperature, DO, and salinity.

3.5 NATURAL SPAWNING 

3.5.1 Adult fish should be maintained at 18-20EC in a temperature controlled system. The number of spawning

chambers and fish to be spawned should be based on the requirements for providing sufficient numbers of viable

embryos. As indicated above, an adult female in spawning condition will generally produce an average 10 to 30

eggs per spawn. To obtain embryos for a test, adult fish (generally, at least eight-to-ten females and three males)

are transferred to a spawning chamber in a 57 L (15 gal) aquarium with the correct photoperiod and temperature (16

h light/8 h dark, and a temperature of 25EC), seven to eight days before the larval fish are needed. The spawning

tank is fitted with a spawning chamber and an embryo collection tray. The spawning chamber consists of a basket

of 3-5 mm NITEX® mesh, approximately 20 x 35 x 22 cm high (USEPA, 1978a), designed to fit into the aquarium. 

Spawning generally will begin within 24 h or less. The embryos will fall through the bottom of the spawning

chamber and lightly adhere onto a collecting screen or tray placed on the bottom of the tank. The collecting tray

should be checked for embryos the next morning. The number of eggs produced is highly variable. The number of

spawning units required to provide the fish needed to perform a toxicity test (generally two to four) as determined

by experience. If the collecting trays do not contain sufficient embryos after the first 24 h, discard the embryos,

replace the tray, and collect the embryos for another 24 h. To help keep the embryos clean, the adults are fed while

the screens are removed. Spawning fish should be shielded from excessive outside disturbance, e.g. an opaque

curtain should surround the entire culture system. Care should also be taken so that outside light sources do not

interfere with the photoperiod.

3.5.2 The embryos are collected in a tray placed on the bottom of the tank. The collecting trays are fabricated from

plastic fluorescent light fixture diffusors (grids), with cells approximately 14 mm deep x 14 mm square. A screen

consisting of 250-500 μm mesh is attached to one side (bottom) of the grid with silicone adhesive. The depth and

small size of the grid protects the embryos from predation by the adult fish. The collecting trays with

newly-spawned embryos are removed from the spawning tank, and the embryos are collected from the screens by

washing them with a wash bottle or removing them gently with a fine brush. The embryos from several spawning

units are generally pooled in a single container to provide a sufficient number to conduct the test(s). The embryos

are transferred to a petri dish, or equivalent, filled with fresh culture water, and are examined using a dissecting

microscope or other suitable magnifying device. Damaged and infertile eggs are discarded (see Figure 2). The

embryos are then placed in incubation dishes (e.g. KIMAX® or PYREX® crystallizing dishes, Carolina culture

dishes, or equivalent; see Subsection 3.8, Embryo Incubation and Hatching Facility). It is recommended that the

embryos be obtained from fish cultured inhouse, rather than from outside sources, to eliminate the uncertainty of

damage caused by shipping and handling that may not be observable, but which might affect the results of the test. 

After sufficient number embryos are collected for the test, the adult fish are returned to the (18-20EC) culture

holding tanks.

3.6 SUSTAINED NATURAL EMBRYO PRODUCTION 

3.6.1 Sustained (long-term), daily, embryo production can be achieved by maintaining mature fish (ratio of

approximately 12-15 males to 50-60 females) in tanks, such as a 285-L LIVING STREAM® tank, or equivalent, at a

temperature of 23-25EC. Embryos are collected seven or eight days prior to starting the acute or chronic toxicity
216

tests for less than 24 hr or older larvae. Embryos are produced daily, and when needed, collecting trays are placed

on the bottom of the tank. The next morning, the embryo collectors are removed, and the embryos are washed into

a shallow glass culture dish using artificial seawater. Four collecting trays, each approximately 20 cm x 45 cm, will

cover the bottom of a 285 L tank.

3.7 FORCED SPAWNING 

3.7.1 Human chorionic gonadotrophin (HCG) is reconstituted with sterile saline or Ringer's solution immediately

before use. The standard HCG vial contains 1,000 IU, which is reconstituted in 10 mL of saline. Freeze-dried

HCG, which comes with premeasured and sterilized saline, is the easiest to use. The reconstituted HCG may be

used for several weeks if kept in the refrigerator.

3.7.2 Each female is injected with HCG on two consecutive days. The HCG is injected into the peritoneal cavity,

just below the skin, using the smallest needle possible. A 50 IU dose (0.5 mL of reconstituted hormone solution) is

recommended for females approximately 27 mm in standard length. A larger or smaller dose may be used for fish

which are significantly larger or smaller than 27 mm. It may be helpful if fish that are to be injected are maintained

at 20EC before injection, and the temperature raised to 25EC on the day of the first injection. Injected females

should be isolated from males.

3.7.3 With injections made on days one and two, females which are held at 25EC should be ready for stripping on

Days 4, 5, or 6. Ripe females should show pronounced abdominal swelling, and release at least a few eggs in

response to a gentle squeeze. Eggs are stripped from the ripe females and mixed with sperm derived from excised,

macerated testes. At least ten females and five males are used per test to ensure that there is a sufficient number of

viable embryos. 

3.7.4 Prepare the testes immediately before stripping the eggs from the females. Remove the testes from

three-to-five males. The testes are paired, dark-grey organs along the dorsal midline of the abdominal cavity. If the

head of the male is cut off and pulled away from the rest of the fish, most of the internal organs can be pulled out of

the body cavity, leaving the testes behind. The testes are placed in a few mL of seawater until the eggs are ready. 

3.7.5 Strip the eggs from the females into a dish containing 50-100 mL of seawater, by firmly squeezing the

abdomen. Sacrifice the females and remove the ovaries if all the ripe eggs do not flow out freely. Break up any

clumps of ripe eggs and remove clumps of ovarian tissue and under-ripe eggs. Ripe eggs are spherical,

approximately 1.0-1.7 mm in diameter, and almost clear. Place the testes in a fold of NITEX® screen (250-500 μm

mesh), dampen with seawater, and macerate while holding over the dish containing the eggs. Rinse the testes with

seawater to remove the sperm from the tissue, and wash the remaining sperm and testes into the dish with the eggs. 

Let the eggs and sperm stand together for 10-15 minutes, swirling occasionally.

3.7.6 Pour the contents of the dish into a crystallizing dish or equivalent and insert an airstone. Aerate gently, so

that the water moves slowly over the eggs, and incubate at 25EC for 60-90 min. After this period of time, wash the

fertilized eggs on a NITEX® screen, place them in clean seawater in an incubation chamber.

3.8 EMBRYO INCUBATION AND HATCHING FACILITY 

3.8.1 Embryos are incubated in KIMAX® or PYREX® crystallizing dishes, Carolina culture dishes, or equivalent,

at a temperature of 25EC and 14-h light/10-h dark photoperiod. An air stone is placed in each dish, and the contents

are gently aerated for the duration of the incubation. The water in the incubation chambers is replaced daily. 

Approximately 24 h prior to hatching, the salinity of the seawater in the incubation chambers is changed to that of

the test salinity, if different. The salinity must remain within the 20-30‰ range. The embryos should hatch in 6 to

7 days at 25EC, and in 4 to 5 days at 30EC. 
217

3.9 FEEDING AND STOCKING DENSITY 

3.9.1 The sheepshead minnow cultures should be provided a sufficient amount of high quality nutrition without

over-feeding. The adult and juvenile sheepshead minnows are fed, frozen adult brine shrimp and flake food,

ad libitum, daily. The larvae are fed newly hatched Artemia nauplii and crushed flake food, ad libitum, daily. 

Methods for culturing brine shrimp are discussed in Appendix A.4. The stocking of adult fish in the holding tanks

depends on the biological filter system (see Subsection 3.11, Biological Filters and Substrate Conditioning). A

circular, 1.3 m (48 in.) diameter, 880 L (235 gal), fiberglass tank will hold approximately 30-50 adult fish with a

varied sex ratio. A stocking density of about 300 larvae is suitable in a 76 L aquarium. Brood stock should be

replaced with feral fish annually, or whenever the fecundity of the females diminishes, and they appear spent with

age and from frequent breeding.

3.10 CULTURE TANKS 

3.10.1 Larvae, juvenile, and adult fish should be kept in holding and rearing tanks of appropriate size. The tanks

can be all-glass aquaria, fiberglass tanks, or equivalent. All tanks should have appropriate biological filtration

systems, and the culture filtration system should be conditioned properly before adding the fish (see Spotte, 1973,

1979; Bower, 1983).

3.11 BIOLOGICAL FILTERS AND SUBSTRATE CONDITIONING 

3.11.1 Holding and rearing aquaria and tanks can accommodate as many fish as its biological filter will permit. 

The substrate conditioning for the undergravel or outside filters is also important to the life and health of the fish. 

Substrate conditioning is the process to develop nitrifying bacteria (Nitrosomonas and Nitrobacter) that can convert

ammonia and nitrite to nitrate. A conditioned filter bed is defined as one in which the capacity for ammonia and

nitrite oxidation is sufficient to keep pace with the production of ammonia by the fish. Consult Spotte (1973; 1979)

or Bower (1983) for a thorough understanding of the biological filter and conditioning process.

3.12 CULTURE WATER 

3.12.1 Artificial seawater is prepared by dissolving FORTY-FATHOMS® or equivalent artificial sea salts in

deionized water to a salinity of 20-30‰. Synthetic sea salts are packaged in plastic bags and mixed with deionized

(MILLI-Q® or equivalent) water. The instructions on the package of sea salts should be followed carefully, and the

salts should be mixed in a separate container, and not in the culture tank. The deionized water used in hydration

should be in the temperature range of 21-26EC. Seawater made from artificial sea salts is conditioned (see Spotte,

1973, 1979; Bower, 1983) before it is used for culturing by aerating mildly for at least 24 h.

3.12.2 Adequate aeration will bring the pH and concentration of dissolved oxygen and other gases into

equilibrium. The concentration of dissolved oxygen in the water supply should be 90-100% saturation before it is

used. If a residue or precipitate is present, the solution should be filtered before use. The seawater should be

monitored periodically to insure a constant salinity.

3.13 CULTURE CONDITIONS

3.13.1 Holding and rearing tanks and any area used for manipulating live sheepshead minnows should be located

in a room or space separated from that in which toxicity test(s) are to be conducted. The salinity of the culture

systems should be between 20 and 30‰. Water temperature for the brood stock should be maintained at 18-20EC. 

A photoperiod of 14 h illumination (10-20 μE/m2

/s, or 50-100 ft-c) and 10 h dark, should be provided. The holding

and rearing tanks should be aerated so that the DO is not less than 1.0 ppm below saturation at any given

temperature, with 5.0 ppm (60% saturation) being the absolute lowest limit. 
218

3.14 CULTURE MAINTENANCE 

3.14.1 Replace approximately l0% of the culture water every two weeks, or 25% monthly. The culture water

should be clear. If the water appears cloudy or discolored, replace at least 50% of it. Replacement water should be

well oxygenated and at the same temperature and salinity as the culture water. Salinity is maintained at the proper

level by adding deionized water to compensate for evaporation. A replenisher, made of the trace elements, iodine

(KI) and bromine (KBr), is added (1 mL/400 L) to the culture water each week, or commercial trace elements

replenisher should be used as directed by the artificial sea salt manufacturer. 

3.14.2 To avoid excessive build up of algal growth, periodically scrape the walls of culture system. Some of the

algae will serve as a supplement to the diet of the fish. A partial activated carbon "charcoal" change in the filtration

systems should be done monthly or as needed. The detritus (dead brine shrimp nauplii and cysts, adult brine

shrimp, other organic material accumulation) should be siphoned from the bottom of rearing and holding aquaria or

tanks each week or as needed. 

3.15 WATER QUALITY MONITORING 

3.15.1 Checking the chemistry of the sea water is critical to the success of the marine culture system. The water

quality will determine whether the life support processes in the filter bed work at reasonable and steady rates. The

culture water is checked routinely for temperature, alkalinity, pH, DO, total ammonia, nitrite, and nitrate. More

frequent monitoring of these parameters is recommended during periods of organism procurement and starting new

culture systems with inside underground filters and outside-of-tank biological filtration. The DO should be

maintained at greater than 60% saturation. The pH should not go below 7.5 with an acceptable range between 7.5

and 8.3. Low pH levels can result from overcrowding, overfeeding, or waste accumulation, especially in static or

recirculating culture systems. 

3.15.2 Acceptable pH levels can be re-established by siphoning off 50-75% of the water and replacing it with

conditioned artificial seawater of the same temperature. Also, sodium bicarbonate or commercially available liquid

buffers can be added to the tanks whenever the pH falls below 7.5. Un-ionized ammonia, total (NH3 + NH4), and

nitrite ion (NO2) levels should not exceed 0.1 ppm in the holding tanks. It is recommended that the ammonia and

nitrite concentrations be determined prior to starting new culture systems. It is recommended that nitrate (NO3)

concentrations be determined prior to starting new culture systems, and the nitrate ion concentrations should not

exceed 20 mg/L.

3.15.3 A specific schedule for water quality monitoring should be established for each culture system. All water

quality measurements and data are recorded in the culture and environmental conditions log books.

3.16 DISEASE CONTROL AND TREATMENT 

3.16.1 Discussions of identification and treatment of common parasites of marine fish culturing can be found in

Spotte (1973), Sindermann (1970), and Bower (1983). Several commercial companies sell various kinds of

medication to treat common parasites of marine fish.

3.16.2 A colorless medication, FORMALITE II®, has been used successfully for the treatment of the protozoan

parasites, Chilodonella, Costia, Trichoina, Scyphidia, Trichophrya, and Ichyophirius. 
219

4. TEST ORGANISMS

4.1 Sheepshead minnows 1-14 days old are used in the acute toxicity test. If the larvae are used one or two days

after hatching, they can be held in the crystallizing or culture dishes. If they are to be used later, they should be

placed in larger holding aquarium or tanks. Prior to beginning the test, the larvae can be transferred to small

beakers or plastic cups, using a large-bore, fire-polished glass tube (6 mm to 9 mm I.D. x 30 cm long) equipped

with a rubber bulb.

4.2 If the larvae are to be moved to holding aquaria, a large-bore, fire-polished glass tube should also be used to

move them. It is important to note that larvae and fry should not be handled with a dip net. Dipping larvae and fry

with a net can result in very high mortality. Some of the water in the holding aquarium or tank containing the larvae

should be siphoned off before they are transferred using the large-bore tube. This should make them easier to catch. 

The same large-bore, fire-polished glass tube discussed above should be used to gently transfer the fish from the

holding vessels to the test vessels. As the fish are counted, they can be transferred to small plastic cups before they

are added to the test vessels. It is more convenient to first transfer five fish to each of several small beakers or

plastic containers with a few mL of 20-30‰ saline dilution water. The appropriate number of fish (multiples of

five) can then be added to the test vessels.
220

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Bur. Fish. 34(831):409-429.

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American freshwater fishes. Publ. 1980-12, North Carolina State Museum Natural History, Raleigh, NC.

Martin, F.D. 1972. Factors influencing local distribution of Cyprinodonvariegatus (Pisces: Cyprinodontidae). 

Trans. Am. Fish. Soc. 101(1):89-93. 

Martin, B.J. 1980. Effects of petroleum compounds on estuarine fishes. Govt. Reports Announcements & Index

(GRA&I), Issue 11.

Nordlie, F.G. 1987. Plasma osmotic Na+

 and Cl- regulation under euryhaline conditions in Cyprinodon variegatus

Lacepede. Comp. Biochem. Physiol. A, 86A(l):57-61. 

Perschbacker, P.W. and Strawn, K. 1986. Feeding selectivity and standing stocks of Fundulus grandis in an

artificial brackishwater pond, with comments on Cyprinodon variegatus. Contrib. Mar. Sci. 29: 103-111. 

Sekavec. G. B. 1974. Summer Foods, length-weight relationship, and condition factor of juvenile ladyfish, Elops

saurus Linnaeus, from Louisiana Coastal Streams. Trans. Amer. Fish. Soc. 3: 472-476. 

Schimmel, S.C. and Hansen, D.J. 1974. Effects of Aroclor® 1254 on the embryo and fry of sheepshead minnows. 

Trans. Amer. Fish. Soc. 103(3):522-586.

Schimmel, S.C., Parrish, P.R., Hansen, D.J., Patrick, J.M., Jr., and Forester, J. 1975. Endrin: effects on several

estuarine organisms. Proc. 28th Ann. Conf. Southeast. Assoc. Game Fish. Comm. pp. 187-194. 

Schimmel, S.C. and Hansen, D.J. 1975. Sheepshead minnow (Cyprinodon variegatus): An estuarine fish suitable

for chronic (entire life-cycle) bioassays. Proc. 28 Ann. Conf. Southeast. Assoc. Game Fish Comm.

pp. 392-398. 
222

Schimmel, S.C., Hansen, D.J., and Forester, J. 1974. Effects of Aroclor® 1254 on the embryo and fry of

sheepshead minnow. Trans. Amer. Fish. Soc. 103(3):522-586. 

Seligmann, E.B., Jr. 1951. Cyprinodon variegatus reverindi (Poey) and other aquatic notes. Aquarium

20(9):234-236. 

Sindermann, C.J. 1970. Principal diseases of marine fish and shellfish. Academic Press, New York, NY. 

Simpson, D.G. and Gunter, G. 1956. Notes on habitats, systematics characters, and life histories of Texas salt

water cyprinodontes. Tulane Stud. Zool. 4:113-134. 

Spotte, S. 1973. Marine aquarium keeping. John Wiley and Sons, New York, NY. 

Spotte, S.H. 1979. Fish and invertebrate culture: water management in closed systems. Wiley-Interscience

Publication, John Wiley and Sons, New York, NY. 

USEPA. 1973. Ecosystem analysis of the Big Cypress Swamp and estuaries. M.A. Carter, L.A. Burns,

T.R. Cavinder, K.R. Dugger, P.L. Fore, D.B.Hicks, H.L. Revells, and T.W. Schmidt. Surveillance and

Analysis Division, U.S. Environmental Protection Agency, Athens, GA. EPA 904/9-74-002. 

USEPA. 1978a. Laboratory culture of sheepshead minnow (Cyprinodon variegatus). D.J. Hansen. In: Bioassay

procedures for the ocean disposal permit program. U.S. Environmental Protection Agency, Environmental

Research Laboratory, Gulf Breeze, Florida. EPA-600/9-78-010, pp. 107-108.

USEPA. 1978b. Bioassay procedures for the ocean disposal permit program. Environmental Research Laboratory,

Gulf Breeze, Florida. EPA-600/9-78-010. 

USEPA. 1978c. Chronic toxicity of chlordane, Trifluralin, and pentachlorophenol to sheepshead minnows

(Cyprinodon variegatus). P.R. Parrish, E.E. Dyar, J.M. Enos, and W.G. Wilson. Environmental Research

Laboratory, U.S. Environmental Protection Agency, Gulf Breeze, FL 32561. EPA-600/3-78-010. 

USEPA. 1978d. Life-cycle toxicity test using sheepshead minnows (Cyprinodon variegatus). D.J. Hansen,

P.R. Parish, S.C. Schimmel, and L.R. Goodman. In: Bioassay procedures for the ocean disposal permit

program, U.S. Environmental Protection Agency, Environmental Research Laboratory, Gulf Breeze, FL. 

EPA 600/9-78-010, pp. 109-117. 

USEPA. 1985. Distribution, life cycle, taxonomy, and culture methods. Silversides (Menidia). D.J. Middaugh. In: 

W.H. Peltier and C.I. Weber, eds. Methods for measuring the acute toxicity of effluents to freshwater and

marine organisms. Environmental Monitoring and Support Laboratory, U.S. Environmental Protection

Agency, Cincinnati, OH. EPA 600/4-85/013. pp. 126-137.

USEPA. 1987a. Guidance manual for conducting complex effluent and receiving water larval fish growth-survival

studies with the sheepshead minnow (Cyprinodon variegatus). M.M. Hughes, M.A. Heber, S.C. Schimmel,

and W.J. Berry. Contribution No. 104. In: Schimmel, S.C., ed. Users guide to the conduct and interpretation

of complex effluent toxicity tests at estuarine/marine sites. Contribution No. 796. Environmental Research

Laboratory, U.S. Environmental Protection Agency, Narragansett, RI.

USEPA. 1987b. Methods for spawning, culturing and conducting toxicity-tests with early life stages of four

atherinid fishes: the inland silverside, Menidia beryllina, Atlantic silverside, M. menidia, tidewater silverside,

M. peninsulae, and California grunion, Leuresthes tenuis. D.P. Middaugh, M.J. Hemmer, and L.R. Goodman. 

Office of Research and Development, U.S. Environmental Protection Agency, Washington, D.C. 20460. EPA600/8-87-004. 
223

USEPA. 1988. Short-term methods for estimating the chronic toxicity of effluents and receiving water to marine

and estuarine organisms. C.I. Weber, W.B. Horning, II, D.J. Klemm, T.W. Neiheisel, P.A. Lewis, E.L.

Robinson, J. Menkedick, and F. Kessler. eds. Environmental Monitoring and Support Laboratory, U.S.

Environmental Protection Agency, Cincinnati, OH 45268. EPA-600/4-87-028. 

USEPA. 1990. Sheepshead minnow and inland silverside larval survival and growth toxicity tests. Supplemental

report for training videotape. Office of Research and Development, U. S. Environmental Protection Agency,

Washington, D.C. EPA-600/3-90/075. 

Usher, R.R. and Bengtson, D.A. 1981. Survival and growth of sheepshead minnow larvae and juveniles on diet of

Artemia nauplii. Prog. Fish-Cult. 43(2):102-105. 

Ward, G.S. and Parrish, P.R. 1980. Evaluation of early life-stage toxicity tests with embryos and juveniles of

sheepshead minnows (Cyprinodon variegatus). In: Aquatic toxicology, ASTM STP 707. J.G. Eaton,

P.R. Parrish, and A.C. Hendricks, Eds. American Society of Testing and Materials, Philadelphia, PA. pp.

243-247.
224

APPENDIX A

DISTRIBUTION, LIFE CYCLE, TAXONOMY, AND CULTURE METHODS

 A.8 SILVERSIDES: INLAND SILVERSIDE (MENIDIA BERYLLINA)

ATLANTIC SILVERSIDE (M. MENIDIA), AND 

TIDEWATER SILVERSIDE (M. PENINSULAE)

1. MORPHOLOGY AND TAXONOMY 

1.1 Adult Atlantic silversides attain a total length of up to 117 mm (Figure 1A and 1B). Females in general are

slightly larger than males. The first dorsal fin has three to seven, usually four or five spines. The second dorsal fin

has one spine and eight or nine rays; the anal fin has one spine and 19 to 29, usually 21 to 26, rays; and the pectoral

fin has 12 to 16, usually 14 or 15, rays (Robbins, 1969). Atlantic silverside embryos are easily distinguished from

those of the closely related inland silverside, Menidia beryllina. The former have a bundle of elastic filaments

attached to the chorion at one small area of insertion (Figure 1C and 1D). These filaments, typically longer than the

diameter of the egg, are all the same diameter. In contrast, inland silverside eggs posses one or two thick, elongated

filaments, up to 50 mm long and four to nine shorter, thinner filaments (Figures 1E and 1F). 

2. GENERAL LIFE HISTORY

2.1 DISTRIBUTION 

2.1.1 Silversides occur in estuaries along the Atlantic, Gulf, and Pacific coasts (Figures 2-4). The Atlantic

silverside, Menidia menidia, is a resident of estuaries from Maine to northern Florida. It occurs at intermediate to

high salinities, typically of 12 to 30 parts per thousand (ppt), and remains in Atlantic estuaries throughout most of

the year (De Sylva et al., 1962; Dahlberg, 1972). Recent evidence indicates an offshore migration at northern

latitudes in the fall and reappearance of adults in estuaries in late spring (Conover and Kynard, 1984). This species

is an important component in estuarine ecosystems, serving as forage fish for commercially and recreationally

valued species such as striped bass, bluefish and spotted seatrout (Merriman, 1941; Bayliff, 1950; Middaugh, 1981). 

2.1.2 Although the culturing methods described in this section were written primarily for Menidia menidia, they

are also suitable for the inland silverside, M. beryllina, and the tidewater silverside, M. peninsulae (USEPA, 1987). 

The staff of the Environmental Research Laboratory, Gulf Breeze, Florida, have developed procedures for

spawning, culturing, and testing of other fishes, including the California grunion, Leuresthes tenuis, and the

topsmelt, Atherinops affinis. The availability of these fishes as test organisms will permit the use of indigenous fish

in toxicity tests of wastes discharged along the entire coast line of the contiguous United States and Alaska.

2.2 SPAWNING BEHAVIOR 

2.2.1 The Atlantic silverside spawns during spring and summer. Spawning runs generally occur during April -

June or July at northern latitudes, and March through July or August at southern latitudes (Bayliff, 1950;

Hildebrand and Schroeder, 1928; Middaugh and Lempesis, 1976). Spawning occurs in the upper intertidal zone

during daytime high tides (Middaugh, 1981). Eggs are deposited on a variety of substrates which provide

protection from thermal stress and desiccation (Middaugh et al., 1981; Conover and Kynard, 1981). Females

typically release 200 to 800 eggs, 1.0-1.2 mm diameter, as they spawn. Individuals may spawn up to five or six

times, at two week intervals, during the reproductive season. The life span is generally 12-15 months, although year

class-2 fish are occasionally found (Beck, 1979). 
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226
227
228

3. CULTURING METHODS

3.1 SOURCES OF ORGANISMS 

3.1.1 Menidia may be obtained from commercial biological supply houses or collected in the field. 

3.1.1.1 The optimal time for collecting ripe M. menidia in the field is just prior to daytime high tides between 8:00

AM and Noon (usually one to four days after the occurrence of a new or full moon), when prespawning schools

move into the upper intertidal zone (Middaugh, 1981; Middaugh et al., 1981). Since the Atlantic silverside prefers

relatively high salinities, it is recommended that collections be made in areas with salinities of 20‰ or greater. 

Sandy beaches, bordering open but protected estuarine bays, are suitable for collecting adults. A 1 x 10 m bag seine

with knotless 5 mm mesh is ideal for collecting. Since Atlantic silversides typically reside in shallow water, 1.5 m

deep, they are easily captured by seining close to shore. It is important to avoid total beaching of the bag seine

when collecting M. menidia. These fragile fish will quickly die if removed from water and, more importantly, ripe

females often abort their eggs if stranded. Ideally, the bag portion of the seine, containing captured adults, should

remain in water 5-15 cm deep (Middaugh and Lempesis, 1976). 

3.1.1.2 It is possible to transport the spawn (fertilized eggs) or adults to the laboratory. The following procedure is

recommended for stripping, fertilizing and transporting eggs from the field to the laboratory: 

1. Immediately after seining (while still on the beach) three to five ripe females should be dipped

into a bucket of seawater to remove sand and detritus. 

2. Eggs are stripped into a glass culture dish containing seawater or onto a nylon screen

(0.45-1.0 mm mesh) (Figure 5), which is then gently lowered into a culture dish of seawater with

the eggs on the upper surface of the screen (Barkman and Beck, 1976). If excessive pressure is
229

required to strip the eggs, the female should be discarded. Mature eggs, 1.0-1.2 mm in diameter,

are clear, and have an amber hue. 

3. Milt from several males can then be stripped into the culture dish and mixed with the eggs by

gently tilting the dish from side to side. Upon contact with seawater, adhesive threads on mature

eggs uncoil, making enumeration and separation difficult. If eggs are stripped directly into the

culture dish, one end of a nylon string may be dipped into the dish and gently rolled so the

embryos adhere (Middaugh and Lempesis, 1976). The Barkman and Beck (1976) technique for

attaching the eggs to nylon screening minimizes the natural clumping tendency due to

entanglement of the filaments on M. menidia eggs. 

4. Strings of embryos or embryos on screens may be transported to the laboratory by placing them in

an insulated glass container filled with seawater at the approximate temperature and salinity of

fertilization. If gravid fish are transported to the laboratory for subsequent spawning, care must

be taken to avoid overcrowding of fish in transport containers. Continuous, vigorous aeration is

required and any increase in container water temperature should be minimized (Beck, 1979). A

mass culture system for incubating the screen-adhered eggs and collecting the hatched larvae in a

flowing seawater system (Figure 5) was described in detail by Beck (1979). A similar procedure

utilizing a recirculating system was described by Middaugh and Lempesis (1976). 

3.2 Laboratory Year-round Spawning 

3.2.1 Atlantic, inland, and tidewater silversides may be spawned in the laboratory on a year-round basis. 

Procedures described by Middaugh and Takita (1983), and Middaugh and Hemmer (1984), provide for maintenance

of a brood stock of 30 to 50 fish, sex ratio 1:1, in 1.3 m diameter, circular holding tanks which are part of a

recirculating seawater system (Figure 6). The photoperiod should be adjusted to 14 L:10 D (lights on at 5:00 AM

and off at 7:00 PM, intensity 10-20 μE/m2

/s, or 50-100 ft c), with the water temperature maintained at 18-20EC for

fish from northern latitudes, and 20-25EC for southern latitudes. Suitable salinities for the culture units would be

25-30 ppt for the Atlantic and tidewater silversides, and 7‰ for the inland silverside. Fish are fed 8 g Tetramin®

each morning and afternoon, and concentrated Artemia nauplii (hatch obtained from approximately 15 mL of eggs

after 48 h of incubation at 25EC) in mid-afternoon (see section on Artemia culture). Excess food should be

siphoned from the holding tanks weekly. Filter media (activated charcoal) located in a reservoir tray should be

changed weekly, immediately after cleaning the holding tanks. To induce spawning by the Atlantic silverside, the

circulation current velocity in the holding tanks should be reduced to zero (from 8 to 0 cm/sec) twice daily by

turning off the seawater circulation pump from midnight to 1:00 AM, and from Noon to 1:00 PM. Atlantic

silversides will spawn in response to interrupted current velocities during daytime (Noon to 1:00 PM). Spawning of

the tidewater silverside also is enhanced by reducing the current velocity twice daily, but spawns primarily during

nighttime. No interruption in current is necessary to enhance spawning by the inland silverside. 

3.2.2 A suitable spawning substrate can be made by cutting enough 25 cm lengths of No. 18 nylon string to form a

small bundle, and tying a string around the middle of the bundle to form a "mop." The mop is suspended just below

the surface of the water, in contact with the side of the holding tanks. Spawning fish will deposit eggs on this

substrate. The mops are removed from the holding tanks daily and suspended in incubation vessels. Typical egg

production ranges from 300 to 1200 per spawn. Fish generally can be expected to spawn three to four days each

week.

3.2.3 It is essential that light-tight curtains surround the holding tanks. These curtains should remain closed except

during periodic feedings, tanks cleaning, and during removal and replacement of spawning substrates.
230
231

3.2.4 Embryos attached to nylon screening or nylon string may be suspended in a culture system such as shown in

Figure 6. The culture chambers for embryos should be constructed of glass. Upon hatching, larvae may be

transferred from the collection container to a 90 cm diameter glass or fiberglass tank with a volume of 350 L. Tanks

receive a continuous flow of seawater at 2 L/min. Water is introduced at the tank periphery causing a gentle current

sufficient to induce orientation to water movement and normal schooling behavior. Water is discharged from the

tank by two automatic siphons. Siphon openings are protected by a 400 μm nylon screen to prevent escape of

larvae. An inverted funnel is used at the siphon to decrease the velocity of discharge water, thus preventing

impingement of larvae.
232

3.2.5 Embryos can also be incubated in small (4-10 L) glass aquaria, by placing the nylon screening or strings just

below the surface of the water. Gentle aeration should be provided by an airstone positioned near the bottom of the

holding aquaria. 

3.3 CULTURE MEDIA 

3.3.1 Use natural seawater if it is available and unpolluted. Otherwise use synthetic seawater prepared by adding

artificial marine salts, such as FORTY FATHOMS®, to deionized water. If synthetic seawater is used, it should be

aged for a least one week before being utilized in culture aquaria.

3.4 CULTURE CONDITIONS 

3.4.1 The salinity maintained during incubation should be similar to that of the water from which the adults were

taken, if collected in the field, or at which the adults are being maintained in the laboratory, if the embryos 

originate from laboratory brood stock. Water temperature should be maintained at 20 to 25EC depending upon the

latitude where fish are collected. Provide a photoperiod of 12-14 h of illumination daily at 10-20 μE/m2

/s, or

50-100 ft-c (12 h minimum light/24 h). Embryos will hatch in seven to 14 days, depending upon the incubation

temperature and salinity (Middaugh and Lempesis, 1976). 

3.5 FEEDING AND STOCKING DENSITY

3.5.1 Upon hatching, Menidia larvae should be fed immediately. Newly hatched brine shrimp (Artemia) nauplii

(less than eight hours old) are fed to the larvae twice daily. It is essential to feed M. menidia and M. peninsulae

larvae newly-hatched brine shrimp nauplii (USEPA, 1987). Utilization of older, larger, brine shrimp nauplii will

result in starvation of the larvae since they are unable to ingest the larger food organisms. Three to four days after

hatching, the fish are able to consume older (larger) brine shrimp nauplii. Because of their small size M. beryllina

larvae must be fed a mixohaline rotifer, Branchionus plicatilus from day of hatch through day five. Thereafter, they

are able to consume newly-hatched and older Artemia nauplii (USEPA, 1987; USEPA 1988). Methods for

culturing brine shrimp are discussed in the Appendix. A stocking density of about 300 larvae is suitable in an 76 L

aquarium. 

3.6 CULTURE MAINTENANCE 

3.6.1 To avoid excessive build up of algal growths, periodically scrape the walls of aquaria. Activated charcoal in

the aquarium filtration systems should be changed weekly and detritus (dead brine shrimp nauplii or cysts) siphoned

from the bottom of holding aquaria each week. Salinity may be maintained at the proper level by addition of

distilled or deionized water to compensate for evaporation.

4. TEST ORGANISMS

4.1 Fish one to 14 days old are used in acute toxicity tests. Most of the water in the holding aquarium should be

siphoned off before removal of larvae. Larvae can then be siphoned from the holding tanks into a holding vessel. It

is essential that larvae not be handled with a dip net, because it will result in very high mortality. A large-bore,

fire-polished glass tube, 6 mm I.D. x 500 mm long (1/4 in. ID x 18 in. long), equipped with a rubber squeeze bulb

should be used to transfer the larvae from the holding vessel to the test vessels. It is more convenient to first

transfer five fish to each of several small beakers containing 20 mL of saline dilution water. The appropriate

number of fish (multiples of five) can then be added to test vessels. 
233

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Middaugh, D.P., H.W. Kohn III, and L.E. Burnett. 1983. Concurrent measurement of intertidal environmental

variables and embryo survival for the California grunion, Leuresthes tenuis, and Atlantic silverside, Menidia

menidia (Pisces:Atherinidae). Calif. Fish and Game. 69(2):89-96.

Middaugh, D.P. and P.W. Lempesis. 1976. Laboratory spawning and rearing of a marine fish, the silverside,

Menidia menidia. Mar. Biol. 35:295-300.

Middaugh, D.P., G.I. Scott, and J.M Dean. 1981. Reproductive behavior of the Atlantic silverside, Menidia

menidia (Pisces, Atherinidae). Environ. Biol. Fish. 6(3/4):269-276. 

Middaugh, D.P. and J.M. Shenker. 1988. Salinity tolerance of young topsmelt, Atherinops affinis, cultured in the

laboratory. Calif. Fish Game. 74:231-235.

Middaugh, D.P., J.M. Shenker, M.J. Hemmer, and T. Takita. 1989. Laboratory culture of embryonic and larval

jacksmelt, Atherinopsis californiensis, and topsmelt, Atherinops affinis, with notes on identification of each

species. Calif. Fish Game. 76:4-12.
236

Middaugh, D.P. and T. Takita. 1983. Tidal and diurnal spawning cues in the Atlantic silverside, Menidia menidia. 

Environ. Biol. Fish. 8(2):97-104.

Moore, C.J. 1980. Spawning of Menidia menidia (Pisces:Atherinidae). Copeia. 1980:886-887. 

Mulkana, M.S. 1966. The growth and feeding habits of juvenile fishes in two Rhode Island estuaries. Gulf Res.

Rep. 2:97-168.

Penttila, D. 1977. Studies of the surf smelt (Hypomesus pretiosus) in Puget Sound. State of Washington, Dept.

Fish., Techn. Rept. No. 42. pp. 47.

Richards, C.E. and M. Castagna. 1970. Marine fishes of Virginia's eastern shore (inlet and marsh, seaside waters). 

Chesapeake Sci. 11:235-248.

Robbins, T.W. 1969. A systematic study of the silverside Membras Ronaparte and Menidia (Linnaeus)

(Atherinidae, Teleostei). Ph.D. Dissertation, Cornell University. 282 pp.

Rubinoff, I. 1958. Raising the atherinid fish, Menidia menidia, in the laboratory. Copeia, 1958(2):146-147. 

Rubinoff, I. and E. Shaw. 1960. Hybridization in two sympatric species of atherinid fishes, Menidia menidia

(Linnaeus) and Menidia beryllina (Cope). Amer. Mus. Nov. 1999:1-13.

Ryder, J.A. 1883. On the thread-bearing eggs of the silverside, Menidia. Bull. U.S. Fish Comm. 3:193-196. 

Stoeckel, J.N. and R.C. Heidinger. 1988. Overwintering of the inland silverside in southern Illinois. North Amer.

J. Fish. Manage. 8:127-131.

Thomson, D.A. and K.A. Muench. 1976. Influence of tides and waves on the spawning behavior of the Gulf of

California grunion, Leuresthes sardina (Jenkins and Evermann). Southern Calif. Acad. Sci. Bull. 75:198-203. 

Thompson, W.F. and J.B. Thompson. 1919. The spawning of the grunion. Calif. Fish and Game Comm. Bull.

3:1-29. 

USEPA. 1981. Nutritional requirements of marine larval and juvenile fish. Environmental Research Laboratory,

K.L. Simpson, P.S. Schauer, C.R. Seidel, and L.M. Richardson. U.S. Environmental Protection Agency,

Narragansett, Rhode Island. EPA-600/S3-81/049.

USEPA. 1987. Methods for spawning, culturing and conducting toxicity-tests with early life stages of four

atherinid fishes: the inland silverside, Menidia beryllina, Atlantic silverside, M. menidia, tidewater silverside,

M. peninsulae, and California grunion, Leuresthes tenuis. D.P. Middaugh, M.J. Hemmer, and L.R. Goodman. 

Office of Research and Development, U.S. Environmental Protection Agency, Washington, D.C. 20460. EPA600/8-87-004.

USEPA. 1988. Short-term methods for estimating the chronic toxicity of effluents and receiving waters to marine

and estuarine organisms. C.I. Weber, W.B. Horning, II, D.J. Klemm, T.W. Neiheisel, P.A. Lewis, E.L.

Robinson, J. Menkedick, and F. Kessler. Environmental Monitoring and Support Laboratory, U.S.

Environmental Protection Agency, Cincinnati, Ohio 45268. EPA-600/4-87/028.

USEPA. 1990. Sheepshead minnow and inland silverside larval survival and growth toxicity tests. Supplemental

report for training videotape. Office of Research and Development, U. S. Environmental Protection Agency,

Washington, DC. EPA-600/3-90/075.
237

Walker, B.W. 1949. Periodicity of spawning by the grunion, Leuresthes tenuis, an atherine fish. Ph.D.

Dissertation, Univ. California, Los Angeles. 166 pp.

Walker, B.W. 1952. A guide to the grunion. Calif. Fish and Game 38:409-420.

Wang, J.C. 1974. Antherinidae - silversides. In: Lippson, A.J., and R.L. Moran, Manual for identification of early

developmental stages of fishes of the Potomac River estuary. pp. 143-151. Power Plant Siting Program,

Maryland Dept. Nat. Resour., Baltimore, Maryland. PPSP-MP-13. 282 pp.

Wexler, M. 1983. The fish that spawns on land. Nat. Wildl. 21(3):33-36.

Wurtzbaugh, W. and H. Li. 1985. Diel migration of a zooplanktivorous fish (Menidia beryllina) in relation to the

distribution of its prey in a large eutrophic lake. Limnol. Oceanogr. 30(3):565-576.

Yan, H-Y. 1984. Occurrence of spermatozoa and eggs in the gonad of a tidewater silverside, Menidia beryllina.

Copeia. 2:544-545.
238

APPENDIX B

SUPPLEMENTAL LIST OF ACUTE TOXICITY TEST SPECIES

TEST ORGANISM

TEST TEMP

(EC) LIFE STAGE

FRESHWATER SPECIES: VERTEBRATES - WARMWATER

Cyprinella leedsi1 Bannerfin shiner 25 1-14 days

Lepomis macrochirus Bluegill sunfish 20,25 " "

Ictalurus punctatus Channel catfish " " "

FRESHWATER SPECIES: INVERTEBRATES - COLDWATER 

Pteronarcys spp. Stoneflies* 12 larvae

Pacifastacus 

 leniusculus Crayfish* " juveniles

Baetis spp. Mayflies* " nymphs

Ephemerella spp. " " "

FRESHWATER SPECIES: INVERTEBRATES - WARMWATER

Hyalella spp. Amphipods 20,25 juveniles

Gammarus lacustris " " "

G. fasciatus " " "

G. pseudolimnaeus " " "

Hexagenia limbata Mayflies " nymphs

H. bilineata " " "

Chironomus spp. Midges " larvae

*Stoneflies, crayfish, and mayflies may have to be field collected and acclimated for a period of time to ensure

the health of the organisms and that stress from collection is past. Species identification must be verified.

1

 Test conditions for Cyprinella leedsi and Holmesimysis costata are found in Table 14 and Table 19, 

 respectively, in Section 9.
239

SUPPLEMENTAL LIST OF ACUTE TOXICITY TEST SPECIES (CONTINUED)

TEST ORGANISM

TEST TEMP

(EC)

SALINITY

(‰) LIFE STAGE

MARINE AND ESTUARINE SPECIES: VERTEBRATES - COLDWATER

Parophrys vetulus English sole 12 32-34 1-90 days

Citharichys sitigmaeus Sanddab " " " "

Pseudopleuronectes

 americanus Winter flounder " " post metamorphosis

MARINE AND ESTUARINE SPECIES: VERTEBRATES - WARMWATER

Paralichthys dentatus Flounder 20,25 32-34 1-90 days

P. lethostigma " " " " "

Fundulus simillis Killifish " 20-32 1-30 days

Fundulus heteroclitus Mummichog " 25-32 " "

Lagodon rhomboides Pinfish " 20-32 1-90 days

Orthipristis chrysoptera Pigfish " 15-30 " "

Leostomus xanthurus Spot " 10-30 " "

Gasterosteus aculeatus Threespine

stickleback

" 20-32 1-30 days

Atherinops affinis Topsmelt 21 10-30 7-15 days

MARINE AND ESTUARINE SPECIES: INVERTEBRATES - COLDWATER 

Pandalus jordani Oceanic shrimp 12 25-32 juvenile

Strongylocentrotus

droebachiensis Green sea urchin " 32-34 gametes/embryo

Strongylocentrotus

purpuratus Purple sea urchin " " " "

Dendraster excentricus Sand dollar " " " "

Cancer magister Dungeness crab " " juvenile

Holmesimysis costata2 Mysid " " 1-5 days

MARINE AND ESTUARINE SPECIES: INVERTEBRATES - WARMWATER

Callinectes sapidus Blue crab 20,25 10-30 juvenile

Palaemonetes pugio Grass shrimp " 10-32 1-10 days

P. vulgaris " " " " " "

P. intermedius " " " " " "

Penaeus setiferus White shrimp " 20-32 post-larval 

Penaeus duorarum Pink shrimp " " " "

Penaeus aztecus Brown shrimp " " " "

Crangon septemspinosa Sand shrimp " 25-32 " "

Mysidopsis almyra Mysid " 10-32 1-5 days

Neomysis americana " " " " "

Metamysidopsis elongata " " " " "

Crassostrea virginica American oyster " 20-32 embryo

Crassostrea gigas Pacific oyster " 25-32 "

Arbacia punctulata Purple sea urchin " 32-34 gametes/embryo

2

 Test conditions for Holmesimysis costata are found in Table 19.
240

APPENDIX C

DILUTOR SYSTEMS

Two proportional dilutor systems are illustrated: the solenoid valve system, and the vacuum siphon system. 

1. Solenoid and Vacuum Siphon Dilutor Systems

The designs of the solenoid and vacuum siphon dilutor systems incorporate features from devices

developed by many other Federal and state programs, and have been shown to be very versatile for on-site bioassays

in mobile laboratories, as well as in fixed (central) laboratories. The Solenoid Valve system is fully controlled by

solenoids (Figures 1, 2, and 3), and is preferred over the vacuum siphon system. The Vacuum Siphon system

(Figures 1, 4, and 5), however, is acceptable. The dilution water, effluent, and pre-mixing chambers for both

systems are illustrated in Figures 6, 7, and 8. Both systems employ the same control panel (Figure 9). 

If in the range-finding test, the LC50 of the effluent falls in the concentration range, 6.25-100%,

pre-mixing is not required. The pre-mixing chamber is bypassed by running a TYGON® tube directly from the

effluent in-flow pipe to chamber E-2 (see Figures 3 and 5), and Chambers E-l and D-1 and the pre-mixing chamber

are deactivated. 

The dilutor systems described here can also be used to conduct tests of the toxicity of pure compounds by

equipping the control panel with an auxiliary power receptacle to operate a metering pump to deliver an aliquot of

the stock solution of the pure compound directly to the mixing chamber during each cycle. In this case, chamber E-l

is de-activated and chamber D-1 is calibrated to deliver a volume of 2000 mL, which is used to dilute the aliquot to

the highest concentration used in the toxicity test.
241
242
243
244

SOLENOID SYSTEM EQUIPMENT LIST

1. Dilator Glass.

2. Stainless Steel Solenoid Valves

a. 3, normally open, two-way, 55 psi, water, 1/4" pipe size, 9/32" orifice size, ASCO 8262152, for

incoming effluent and dilution water pipes and mixing chamber pipe.

b. 1, normally closed, two-way, 15 psi, water, 3/8" pipe size, 3/8" orifice size, ASCO 8030865, for

D-l chamber evacuation pipe.

c. 12, normally closed, two-way, 36 psi, water, 1/4" pipe size, 9/32" orifice size. ASCO 8262C38,

for remaining dilution chambers (D2-D6) and effluent chamber (E1-E6) evacuation pipes.

3. Stainless steel tubing, seamless, austenitic, 304 grade for freshwater and 316 grade for saline water.

a. 10 ft of 3/8" OD, 0.035" wall thickness, for dilution water and effluent pipes.

b. 60 ft of 1/4" OD, 0.035" wall thickness, for dilution water and effluent pipes.

c. 1 ft of 3/4" OD, 0.035" wall thickness, for standpipe in D1 chamber.

4. Swagelok tube connectors, stainless steel.

a. 4, male tube connectors, male pipe size 1/4", tube OD 3/8".

b. 2, male tube connectors, male pipe size 1/2", tube OD 3/8".

c. 26, male tube connectors, male pipe size 1/4", tube OD 1/4".

d. 2, male tube connectors, male pipe size 3/8", tube OD 3/8".

e. 2, male adaptor, tube to pipe, male size 1/2", tube OD 3/8".

5. 7, 1200 mL stainless steel beakers.

6. Several Ibs each of Neoprene stoppers, sizes 00, 0, and 1; 1 lb of size 5.

7. 14 - aquarium (1-20 liters).

8. Magnetic stirrer.

9. 2 - PVC ball valves, 1/2" pipe size.

10. Dilutor control panel - see Fig. 9 and equipment list.

11. Plywood sheeting, exterior grade: one - 4' x 8' x 3/4", one - 4' x 8' x 1/2".

12. Pineor redwood board, 1" x 8", 20 ft.

I3. Epoxy paint, 1 gal.

14. Assorted wood screws, nails, etc.

15. 25 ft - 14" ID, TEFLON® tubing, to connect the mixing chambers to the test chambers.
245
246

VACUUM SIPHON SYSTEM EQUIPMENT LIST

1. Dilutor Glass.

2. Stainless steel solenoid valves.

a. 2, normally open, two-way, 55 psi, water, 1/4" pipe size, 9/32" orifice size, ASCO 8262152, for

incoming effluent and dilution water pipes.

b. 2, normally closed, two-way, 15 psi, water, 3/8" pipe size, 3/8" orifice size, ASCO 8030865, for

dilution water chamber D-6 and effluent chamber E-2.

3. Stainless steel tubing, seamless, austenitic, 304 grade for freshwater and 316 grade for saline water.

a. 60 ft of 3/8" OD, 0.035" wall thickness, for dilution water and effluent pipes.

b. 20 ft of 5/16" OD, 0.035" wall thickness, for standpipes in mixing chambers.

c. 1 ft of 3/4" OD, 0.035" wall thickness, for standpipe in D1 chamber.

4. Swagelok tube connectors, stainless steel.

a. 4, male tube connectors, male pipe size l/4", tube OD 3/8".

b. 2, male tube connectors, male pipe size 3/8", tube OD 3/8".

c. 2, male adaptor, tube to pipe, male pipe size 1/2", tube OD 3/8".

d. 2, male tube connectors, male pipe size 1/2", tube OD 3/8".

5. 7, 1,200 mL stainless steel beakers.

6. Several Ibs each of Neoprene stoppers, sizes 00, 0, and 1; 1 lb of size 5.

7. 14 - aquarium (1-20 liters).

8. Magnetic stirrer.

9. 2, PVC Ball valves, 1/2" pipe size.

10. Dilutor control panel equipment - see Fig. 9 and equipment list.

11. 7, 120 mL NALGENE® bottles.

12. 3 ft, 1-in-2 aluminum bar, for siphon support brackets.

13. Stainless steel set screws, box of 50, for securing SS tubing in siphon support brackets.

14. Stainless steel hose clamps, box of 10, size #4 or 5, (need 3 boxes).

15. 6, NALGENE® T's, 5/16" OD.

16. 12, TYGON® Y connectors, 3/8" I.D.

17. TYGON® tubing, 3/8" OD, 10 ft.

18. Plywood sheeting, exterior grade: one - 4' x 8' x 3/4", one - 4' x 8' x 1/2".

19. Pine or redwood board, 1" x 8", 20 ft.

20. Epoxy paint, 1 gal.

21. Assorted wood screws, nails, etc.

22. 25 ft of 5/16" ID, TEFLON® tubing, to connect the mix5ng chambers to the test chambers.
247
248
249
250
251
252

DILUTOR CONTROL PANEL EPUIPMENT LIST*

Designation CKT Description Manufacturer

A1 Encapsulated amplifier Cutler Hammer 13535H98C

CTR-1 Cycle counter Redington #P2-1006

ET Elapsed time indicator Conrac #636W-AA H&T

F1 Input power fuse Little fuse 342038

J1 Receptacle Amphenol 91PC4F

J2 Aux A.C. output jack Stand. 3-prong AC Rcpt.

J3 Main input power cord Stand. 3-prong AC male plug

L1 Fill indicator light Dialco 95-0408-09-141

L2 Emptying indicator light Dialco 95-0408-09-141

L.S. Liquid level sensor (Dual Sensing Probe) Cutler Hammer 13653H2

P1 Plug Amphenol 91MC4M

S1 On-off main power switch (spst) Cutler Hammer 7580 K7

S2 On-off aux power switch (spst) Cutler Hammer 7580 K7

SJ1 Solenoid (See Solenoid and Vacuum System

equipment lists)

SJ2 " " " "

SJ3 " " " "

SJ4-SJ6 Additional Solenoids " " "

for Solenoid Valve System

TDR-1 Time delay relay Dayton 5x829

TDR-2 Aux time delay relay Dayton 5x829

*Consult local electric supply house.
253

APPENDIX D

PLANS FOR MOBILE TOXICITY TEST LABORATORY

D.1. TANDEM-AXLE TRAILER
254
255
256

APPENDIX D

PLANS FOR MOBILE TOXICITY TEST LABORATORY

D.2. FIFTH WHEEL TRAILER
257

APPENDIX E

CHECK LISTS AND INFORMATION SHEETS

E.1. TOXICITY TEST FIELD EQUIPMENT LIST
258

E.1. TOXICITY TEST FIELD EQUIPMENT LIST (CONT.)
259

APPENDIX E

CHECK LISTS AND INFORMATION SHEETS

E.2. INFORMATION CHECK LIST FOR ON-SITE INDUSTRIAL

OR MUNICIPAL WASTE TOXICITY TEST
260
261
262
263
264

APPENDIX E

CHECK LISTS AND INFORMATION SHEETS

E.3. DAILY EVENTS LOG
265

APPENDIX E

CHECK LISTS AND INFORMATION SHEETS

E.4. DILUTOR CALIBRATION FORM