Brunswick . Steam Electric Plant

1984 BIOLOGICAL

MONITORING REPORT

- 1

- 1

- 1

BIOLOGY UNIT

ENVIRONMENTAL SERVICES SECTION

Carolina Power & Light Company

CP&L

BRUNSWICK STEAM ELECTRIC PLANT

1984

BIOLOGICAL MONITORING REPORT

Prepared by:

C. Bened i ct

G. F. Booth

K. N. Cates

D. S. Cooke

W. E. Herring

K. A. MacPherson

L. W. Po 11 ard

M. E. Shepherd

R. G. Sherfinski

T. E. Thompson

M. T. Tyndall

W. Warren-Hicks

Juveni 1 e and Adu 1 t Imp i ngement

Project Scientist

Entrainment , Larval Impingement

Larval Fish

Water Quality

Editor

High Marsh

Statistics

Discrete Depth

Nekton

Survival Studies

Statistics

Biology Unit

Environmental Services Section

CAROLINA POWER & LIGHT COMPANY

NEW HILL, NORTH CAROLINA

August 1985

Rev i ewed and Approved by:

J . 

Principal Scientist

Biology Unit

This report was prepared under my supervision and direction , and 

accept full responsibility for its content.

Environmental Services Section
COVER:

This copy of this report is not a controlled

in Environmental Services Section Procedures.

the original of this report subsequent to the

be obtained from:

document as deta i led

Any changes made to

date of issuance can

Manager

Envfronmental Services Section

Carol ina Power & Light Company

Shearon Harris Energy & Environmental

Route 1 , Box 327

New Hi II , North Carol ina 27562

Center

Larval weakfish iCynoscio/l regalis);

by. L. W. Pollard
Acknowl edgments

Many thanks are extended to the individuals who without their assistance and long hours of collection, identification, and processing of

samples, this report would not have been possible. Debbie Calhoun, Scott

Cates, Donna Coleman, Dana Eakins, Della Lanier, Preston McLendon , Tina

Reece, and Scott Taylor dedicated many hours to the laboratory and field

support for all studies. Steve Parrish assisted in field collections as

boat captain of the Pisces and constructed and ma i nta i ned fie 1 d and aboratory equipment.

Thanks also go to Sandra Pri ce and members of the Data Management &

Control Unit, Biology Unit, and Word Processing Subunit at the Shearon

Harri s Energy & Envi ronmenta 1 Center.

Special thanks are given to Drs. B. J. Copeland, Ronald Hodson

Michael Weinstein , and Alan Wells for their review of this report.

A very special thank you is extended to Anne L. Lineback who spent

long hours typing the many drafts associated with the preparation of this

report.

Tab 1 e of Contents

Ac know 1 ed gme n t s . . 

. . . . . . . . . . . . . . . .

Li st of Tabl es. 

Li st of F i gu re s . . . . . . . . 

. . . . . . . . . .

Metr i c-Eng 1 ish Convers; on Tab 1 e. . . . . . . . . . . . . . . . . 

Execut; ve Summary..................................................

1.0 INTRODUCTION. . . . . 

. . . . . . . .

WATER QUALITY.............................................. Introduction.............................................. 

Method s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . . . .

Results and Discussion.....................................

RIVER LARVAL FISH..........................................

Introduction....................... ........... 

.......... ...

Method s . . . . . . . . . . . . . . 

Sample Collection and Processing...........................

Data Analyses..............................................

Results and Discussion.....................................

Domi nant Spec i es. 

. . . . . . . .

Station Groupings..........................................

Species-- Station Group Association.........................

Ti me-Ser i es Ana ys is. . . . . . . 

Length- Frequency Ana ys is. . . . . 

Summary....................................................

DISCRETE DEPTH............................................. Introduction.............................................. Methods................................................... 

Samp 1 e Co 11 ect ion. . . . . 

. . .

Data Anal ys is. . . . 

. . . . . . . .

Results and Discussion.....................................

Water Temperature and Salinity.............................

Analysis of Variance and Duncan s Multiple

Range Test Results.........................................

Croak er . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . . . . .

Spot. . . . . . . . . . . . . . . . . . 

Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . 

HIGH MARSH................................................. Introduction.............................................. 

Method s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . . . .

Station Description........................................

Samp 1 i ng Me t hod s . 

. . . . . . . .

i i

Page

xv; i

xv; i i
Table of Contents (cont i nued)

Data Ana lys is.. .. .... .. 

. . . .. .... ..... ..... .. 

Results and Discussion.....................................

Sediment Parameters........................................

Catch by Gear Type.........................................

Relationships with Abiotic Variables.......................

Seine.. .......... ........ .......... ..... ..... 

..............

Trawl......................................................

Spati al Analysi s..... .. 

.... . ... .. . . . ... .. .. . ....... .. . . .. .

Wi thi n Creek...............................................

Within the Estuary.........................................

Seasonal Distribution......................................

Time- Series Analysis.......................................

Alligator Creek............ 

........ .......... ..............

Mottl s Bay. ...... 

................. ...................... ...

Walden Creek...............................................

Baldhead Creek.............................................

Return Basin Evaluation....................................

Summa ry and Conc 1 u s ions. . . . . 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

NEKTON.................................................... 

I nt roduct i on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . .

Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . . .

Resu 1 ts and 0 i scu s s i on. . 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Total Organi sms. . ... .... ... ... 

...... .. .. .. .. . ... .. .... . . . ..

Seasonality, Recruitment, and Time-Series Analysis.........

Bay anchovy................................................

Spot....... .... 

.............. ................ ... ........ ...

Croaker....................................................

Menhaden..... ... 

....................................... 

Brown shrimp......................... ......................

Blue crab.......................

Weakfish....... ......................................... 

...

Pink

White shrimp...............................................

Total organi sms............................................

Spatial Analysis...........................................

You ng -of - Year F i nf ish. . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . . . . . .

Juvenile/Adult Finfish and Invertebrate Catch..............

Diversion Structure Evaluation.............................

Summary and Concl us ions. .... .. 

.. ..... ... ..... ....................... ........ .....

shrimp................................................

ENTRA I NME NT. 

. . . . . . . . . . . . . . . . . . . . . . .

Introduct i on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Methods............. .. .. 

. . .. .. .. ... . . ... ..... ..... .... ... 

Results and Discussion.....................................

Dominant Species...........................................

Seasonal ity and Abundance..................................

Numbe rEnt r a i ned . . . . . . . . . . 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Di e 1

Entrainment Special Study..................................

Flow Minimization..........................................

Patterns. .. . . 

.... .. . . . . .... .. . .. ... ... ....... . . .. . ....

i i i

Page

7 -
Tab 1 e of Contents (cont i nued)

10.

10.

10.

10.

10.

10.

10.

10.

10.

10.

11.0

Summary and Conclusions....................................

SURVIVAL STUDIES........................................... Introduction.............................................. 

Methods. ........... ...... 

.... ...... ...... ..................

Collection................................................ 

Ho 1 ding Fac i 1 it i es . . . . . . . . . . . . . . . 

. . . .

Stocking and Monitoring..............................

Definitions, Calculations, and Analyses..........

Results and Discussion...........................

Total Organ isms. . . 

 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Speci es Accounts................................. Croaker....................................................

Spot...... .............. ...... ........... ............

Penaeid Postlarvae...................................

Pink and White Shrimp................................

Brown Shrimp...............................................

Blue Crab.................................................. Weakfish.................................................. 

Bay Anchovy................................................

St r i ped Mu 11 et . 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Flounder. . . . . . . . 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Menhaden. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . .

Mi sce 11 aneous Spec i es. . . . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . . . .

Summary and Conc 1 u s ions. . . . . 

IMPINGEMENT (Larval)....................................... Introduction.............................................. 

Methods... ..... ..... 

..... ........ ....... ....... ..... .......

Sample Collection..........................................

Sample Analysis............................................

Results and Discussion.....................................

Dominant Species...........................................

Seasonal i ty and Abundance..................................

Di el

Tidal

Surv i val Est i mates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . . . .

Summary and Conc 1 us ions. . . . . 

Patterns. ...... ......... 

.................. ............

Patterns............................................ 

IMPINGEMENT (Juvenile and Adult)...........................

I nt roduct i on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . .

Methods.............................. .. 

....................

Results and Discussion.....................................

Spec i e s Compos i t i on. . . . . . . . . . . . . . . . . . . 

Di e 1 Patterns............................................. 

Flow Rates.................................................

Length-Frequency Di stri but ions.....

Estimated Survival Adjustments.....

Summary and Conclusions............

...... ..... ....... ...... ........................

REFERENCES. . . . . 

. . . . . . . . . .

Page

10-

10-

10-

10-

10-

10-

10-

10-

10-

10-

11-
Table of Contents (continued)

APPEND IX A

Brunswick Steam Electric Plant Intake Modifications

and Flow Minimization..........................................

APPEND IX 8

Statistical Explanation of Time- Series and Milivariate

Analyses.... .... 

........ .......... .......................... ...

APPEND IX C

River Larval Fish and Tucker Trawl Gear Comparison Study..........................................................

Page
Table

1.1

1.2

1.3

List of Tables

BSEP 1984 biological monitoring program summary............

Species of fish and shellfish analyzed by program

during 1984................................................

Species of fish and shellfish collected by program

during 1984................................................

Annual mean density and the percentage of the total

mean density for the eight most abundant species

collected in the river larval fish program, 1979- 1984......

Principle component scores by station and ranked

correlations of larvaljpostlarval organisms, water

temperature, and salinity for the 1977- 1984 river

larval fish data...........................................

Results of time- series analysis for river larval

fish data by station group indicating significant

changes in density along with amount of variance

explained by the model.....................................

Results of analysis of variance for spot and croaker

for the 1984 Cape Fear River discrete depth program........

Analysis of variance cell means for croaker densities

collected in the 1984 Cape Fear River discrete depth

, .

samp, 1 ng program...........................................

Results of analysis of variance cell means for spot

densities collected in the 1984 Cape Fear River

discrete depth sampling program............................

Sediment parameters for the high marsh seine and trawl

stations during 1984.......................................

Tota 1 catch and percent total of the ten most abundant

species collected in the high marsh study during 1984......

Results of the principle component analysis by station

for organisms collected by seines in the high marsh

study duri ng 1984..........................................

Results of the principle component analysis by station

for organisms collected in Baldhead Creek by trawl in

the high marsh study during 1984...........................

Results of the principle component analysis by station

for organisms collected in Walden Creek by trawl in the

high marsh study during 1984...............................

Page
List of Tables (continued)

Tota 1 catch- per-uni t- effort by creek system for 12

selected species in the high marsh study during 1984.......

Results of time-series analysis of high marsh data by

creek showing trends in abundance from 1981

through 1984...............................................

Tota 1 number, percent total number , and annual catchper- unit-effort of the ten most abundant species collected in the nekton study during 1984.....................

Resu 1 ts of t ime-seri es ana lys i s of nekton ri ver data

indicating significant increase or decrease in CPUE

for 1979 through 1984......................................

Results of the principle component analysis by

station for young-of-year finfish collected in

the nekton study, years 1983 and 1984 combined.............

Results of the principle component analysis by

station for juveniles/adults collected in the

nekton study, years 1983 and 1984 combined.................

Results of analysis of variance and Duncan

multiple range test for selected species utilized

in the evaluation of the BSEP diversion structure

during 1984................. .......... 

...... ...............

Mean density and percent total of fish , penaeid

shrimp, and portuni d crabs entrained , September

1978-August 1984...........................................

Entrainment densities at the BSEP from September

1983 through Apri 1 1985....................................

Entra i nment rates at the BSEP from September 1983

through Apri 1 1985.........................................

Reduct ion in entra i nment by number and mean dens i ty

for selected species for the three special

study periods..............................................

Comparative reductions in entrainment of total

organisms due to flow minimization.........................

Mean lengths of organisms examined during 96- hour

survival studies conducted at the BSEP during 1984

and 1985...................................................

vi i
List of Tables (continued)

10.

10.

10.

10.

Survival percentages for organisms collected during

fast and slow screen operation at the BSEP during 1984

and 1985........ ..... ............... 

....... .... ............

Survi va 1 percentages for contro 1 organ isms co 11 ected

for survival studies at the BSEP during 1984 and 1985......

Mean percent 96- hour unadjusted survival values for

croaker held during survival studies at the BSEP during

1984 and 1985..............................................

Mean percent 96- hour unadjusted survival values for spot

held during survival studies at the BSEP during 1984 and

1985....... ...... ..... 

............. ........ ................

Mean percent 96- hour unadjusted survival va lues for

penaeid shrimp held during survival studies at the

BSEP duri ng 1984 and 1985..................................

Mean percent 96- hour unadjusted survival for blue crab

held during survival studies at the BSEP during 1984 and . 1985..................................................

Mean percent 96- hour unadjusted survival for weakfish

held during survival studies at the BSEP during 1984 and . 1985..................................................

Mean percent 96- hour unadjusted survival for mi scellaneous species held during survival studies at the

BSEP during 1984 and 1985..................................

Ranking by percent of total impingement of species

collected in the BSEP larval impingement program during

1984....... .......... ..... ...... 

.............. .............

Total number of selected species collected by trip in

larval impingement during 1984.............................

Overall percent survival and number of larval impinged

organisms returned alive to the Cape Fear Estuary..........

A summary of expanded juvenile/adult impingement at

the BSEP during 1984.......................................

A summary of expanded juveni e/adul t impi ngement by

year at the BSEP...........................................

A summary of juvenile/adult impingement by species at

the BSEP during 1984.......................................

Estimated survival of juvenile and adult organisms

impinged during 1984.......................................

viii

10-

10-

10-

10-

F i aure

1.1

1.2

1.3

List of Fi gures

River larval fish and water quality sampling locations

in the Cape Fear Estuary during 1984.......................

High marsh sampling areas and nekton sampling locations

in the Cape Fear Estuary during 1984.......................

Locat i on of divers i on structure, s 1 u i ceways, and return

basin at the Brunswick Steam Electric Plant................

Bottom sal inity values for selected stations in the Cape

Fear Estuary from September 1983 through December 1984.....

Bottom temperature values for selected stations in the

Cape Fear Estuary from September 1983 through December

1984.. .. . . . 

........... .... .. .. . ... .. ..... ....... .. ..... . . .

Results of principle component ordination on 1977- 1984

river larval fish data.....................................

Results of time-series analysis of larvaljpostlarval

croaker co 11 ected at Stat ions 34 and 41 in the Cape

F ea rEs t u a r y, 1977 - 1984. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. .

Results of time-series analysis of larvaljpostlarval

anchovy collected at Station 24 in the Cape Fear

Estuary, 1977- 1984.........................................

Results of time-series analysis of larvaljpostlarval

flounder collected at Station 24 the Cape Fear Estuary,

1977- 1984... ........... .............. ..... 

..... ............

Results of time-series analysis of larvaljpostlarval

Gobiosoma spp. collected at Station 24 in the Cape Fear

E s tu ary, 1977- 1984.........................................

Results of time-series analysis of larvaljpostlarval

menhaden collected at Station 24 in the Cape Fear

Estuary, 1977- 1984.........................................

Results of time-series analysis of larvaljpostlarval

mullet collected at Station 24 in the Cape Fear Estuary,

1977-1984................................................. 

Results of time-series analysis of larvaljpostlarval

seatrout collected at Station 24 in the Cape Fear

Estuary, 1977 - 1984. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

. . . . . . .

Results of time-series analysis of larvaljpostlarval

spot collected at Station 24 in the Cape Fear Estuary,

1977- 1984..... ...... 

.......................................

i x

Page
List of Figures (continued)

Results of time-series analysis of postlarval shrimp

collected at Station 24 in the Cape Fear Estuary,

1977-1984................................................. 

Results of time-series analysis of total larval/

postlarval organisms collected at Station 24 in the

Cape Fear Estuary, 1977- 1984...............................

A typical plot of cumulative length distributions

showi ng a greater percentage of small er croaker

in downriver areas than upriver areas in 1983..............

Discrete depth sampling tide tabulation graph..............

Discrete depth sampling temperature profiles at

Stations 25 and 34 in the Cape Fear River, February 6-

and 14- 17, 1984............................................

Discrete depth sampling salinity profiles at Stations 25

and 34 in the Cape Fear River , F ebru ary 6-9 and 14- 17,

1984........... .............. ...... 

........ ...... ..........

Densities of croaker collected by period and depth at

Stations 25 and 34 in the Cape Fear River , February 6-

and 14- 17, 1984............................................

Densities of croaker collected by tide and depth at

Station 25 in the Cape Fear River, February 6-9 and

14- , 1984................................................

Densities of croaker collected by tide, depth, and period

at Station 25 in the Cape Fear River , February 6- 9 and

14- , 1984..... ......... ...... .... 

..... ...................

Dens i ties of croaker co 11 ected by tide and depth at

Station 34 in the Cape Fear River, February 6-9 and

14- , 1984................................................

Densities of spot collected by period and depth at

Stations 25 and 34 in the Cape Fear River, February 6-

and 14- , 1984............................................

Densities of spot collected by tide and depth at

Stations 25 and 34 in the Cape Fear River, February 6-

and 14- 17, 1984............................................

Length-frequency distributions of spot collected in

Walden Creek by trawl in the high marsh study during 1984.......................................................
List of Figures (continued)

Length-frequency distributions of croaker collected in

Matti s Bay by trawl in the high marsh study during 1984....

Length- frequency distributions of striped mullet collected in Walden Creek by seine in the high marsh study

during 1984...................... ......... 

...... ...........

Length- frequency distributions of white mullet collected in Baldhead Creek by seine in the high marsh

study during 1984..........................................

Length- frequency distributions of flounder collected in

Alligator Creek by trawl in the high marsh study during

1984.............. ........... 

..............................

Length- frequency distributions of menhaden collected in

Walden Creek by trawl in the high marsh study during

1984........... ........ ........ ........... 

.... ....... ......

Length-frequency d i stri but ions of bay anchovy co 

lected in Walden Creek by trawl in the high marsh

study during 1984..........................................

Length- frequency distributions of mummichog collected in Walden Creek by seine in the high marsh

study during 1984.....................i....................

Length- frequency distributions of Atlantic silverside

collected in Baldhead Creek by seine in the high marsh

study during 1984..........................................

Length- frequency distributions of brown shrimp collected in Walden Creek by trawl in the high marsh

study dur i ng 1984..........................................

Length- frequency distributions of pink shrimp collected in Walden Creek by trawl in the high marsh

study during 1984..........................................

Length- frequency distributions of blue crab collected

in Walden Creek by trawl in the high marsh study during 1984.......................................................

Results of time-series analysis for flounder collected

in Alligator Creek in the high marsh study from 1981

through 1984...............................................

Results of time-series analysis for spot collected in

All igator Creek in the high marsh study from 1981

through 1984...............................................
List of Figures (continued)

Results of time-series analysis for menhaden collected

in Alligator Creek in the high marsh study from 1981

through 1984...............................................

Results of time-series analysis for bay anchovy collected in Alligator Creek in the high marsh study from

1981 through 1984..........................................

Results of time- series analysis for flounder collected

in Mott I s Bay in the high marsh study from 1981

through- 1984...............................................

Results of time-series analysis for spot collected in

Mott I s Bay in the high marsh study from 1981 through

1984.... ... ....... 

.......... .......... ............ .........

Results of time- series analysis for brown shrimp

collected in Mottl s Bay in the high marsh study from

1981 through 1984..........................................

Results of time- series analysis for pink shrimp collected in Mott I s Bay in the high marsh study from 1981

through 1984...............................................

Results of time- series analysis for white mullet collected in Mott I s Bay in the high marsh study from 1981

through 1984..................... .............. 

............

Results of time-series analysis for croaker collected

in Walden Creek in the high marsh study from 1981

through 1984...............................................

Results of time-series analysis for striped mullet

co 11 ected in Walden Creek in the high marsh study

from 1981 through 1984.....................................

Results of time-series analysis for flounder

collected in Walden Creek in the high marsh study

from 1981 through 1984.....................................

Results of time-series analysis for menhaden collected in Walden Creek in the high marsh study from

1981 through 1984..........................................

Results of time-series analysis for menhaden colected in Ba dhead Creek in the high marsh study from

1981 through 1984..........................................

Results of time-series analysis for croaker collected in Baldhead Creek in the high marsh study

from 1981 through 1984.....................................

xii
List of Fiqures (continued)

Results of time-series analysis for spot collected

in Baldhead Creek in the high marsh study from 1981

through 1984...............................................

Results of time-series analysis for blue crabs collected in Baldhead Creek in the high marsh study

from 1981 through 1984.....................................

Results of time-series analysis for brown shrimp

collected in Baldhead Creek in the high marsh study

from 1981 through 1984.....................................

Results of time-series analysis for pink shrimp

collected in Baldhead Creek in the high marsh study

from 1981 through 1984.....................................

Cumulative length- frequency analysis of spot colected by trawl in upper Walden Creek and the

return basin in the high marsh study during 1984...........

Cumulative length-frequency analysis of croaker

co 11 ected by trawl in upper Walden Creek and the

return basin in the high marsh study during 1984...........

Length- frequency distributions of bay anchovy collected in nekton trawls during 1984........................

Results of time-series analysis for juvenile/adult

bay anchovy co 11 ected in nekton small trawl s at

Stations 1, 4. 7 and 8 combined for 1979 through 1984......

Results of time-series analysis for young-of-year bay

anchovy co 11 ected in nekton small trawl s at Stat ions 1,

7. and 8 combined for 1979 through 1984.................

Length-frequency di stri but ions of spot co 11 ected in

nekton trawl s duri ng 1984..................................

Results of time-series analysis for juvenile/adult

spot collected in nekton small trawls at Stations 

, and 8 combined for 1979 through 1984.................

Results of time-series analysis for young-of-year spot

collected in nekton small trawls at Stations 1, 4, 7,

and 8 combined for 1979 through 1984.......................

Length- frequency distributions of croaker collected

in nekton trawls during 1984...............................

xiii
List of Figures (continued)

Results of time- series analysis for juvenile/adult

croaker collected in nekton small trawls at Stations

, and 8 combined for 1979 through 1984..............

Results of time- series analysis for young-of-year

croaker collected in nekton small trawls at Stations

, and 8 combined for 1979 through 1984..............

Length- frequency distributions of menhaden collected

in nekton trawls during 1984...............................

Results of time-series analysis for juvenile/adult

menhaden collected in nekton small trawls at Stations

8, and 10 combined for 1981 through 1984.......

Results of time- series analysis for young- of-year

menhaden collected in nekton small trawls at Stations

1, 2, 4 , 7, 8, and 10 combined for 1981 through 1984.......

Length- frequency distributions of brown shrimp collected

in nekton trawls during 1984...............................

Results of time-series analysis for brown shrimp

collected in nekton small trawls at Stations 1, 4

, and 8 combined for 1979 through 1984....................

Length-frequency distributions of blue crab collected

in nekton trawls during 1984...............................

Results of time-series analysis for blue crab collected

in nekton small trawls at Stations 1, 4, 7, and 8

combined for 1979 through 1984.............................

Length- frequency distributions of weakfish collected

in nekton trawls during 1984...............................

Results of time-series analysis for young-of-year

weakfish collected in nekton small trawls at Stations

, and 8 combined for 1979 through 1984..............

Length- frequency distributions of pink shrimp collected

in nekton trawls during 1984...............................

Results of time-series analysis for pink shrimp collected in nekton small trawls at Stations 1,

and 8 combined for 1979 through 1984.......................

Length-frequency distributions of white shrimp collected in nekton trawls during 1984........................

xiv
List of Figures (continued)

Results of time-series analysis for white shrimp collected in nekton small trawls at Stations 1 , 4 , 7

and 8 combined for 1979 through 1984.......................

Results of time- series analysis for total organisms

collected in nekton small trawls at Stations 1, 4 , 7

and 8 combi ned for 1979 through 1984....................... 6-

Principle component ordination of the nekton youngof-year finfish data for 1983 and 1984 combined............

Principle component ordination of the nekton juvenile/

adult data for 1983 and 1984 combined......................

Results of time- series analysis for juvenile/adult

spot co 11 ected in the intake canal by the nekton trawl

for 1981 through 1984......................................

Results of time-series analysis for juvenile/adult

croaker co 11 ected in the intake cana' by the nekton

trawl for 1981 through 1984................................

Results of time-series analysis for juvenile/adult

menhaden co 11 ected in the intake canal by the nekton

trawl for 1981 through 1984................................

Cumulative length- frequency analysis of spot collected

by the nekton trawl inside and outside the diversion

structure during 1984......................................

Cumu 1 at i ve 1 ength-frequency anal ys i s of croaker co 

lected by the nekton trawl inside and outside the

diversion structure during 1984............................

Cumu 1 at i ve ength- frequency ana 1 ys is of menhaden co 

lected by the nekton trawl inside and outside the

diversion structure during 1984............................

Length- frequency distributions of menhaden collected

by the nekton trawl inside and outside the diversion

structure duri ng 1984......................................

Density of total fish entrained at the BSEP from May

1974 through August 1984...................................

Density of croaker entrained at the BSEP from May 1974

through August 1984........................................

Density of flounder entrained at the BSEP from May 1974

through August 1984........................................
List of Figures (continued)

10.

10.

10.

10.

Density of menhaden entrained at the BSEP from May 1974

through August 1984........................................

Density of mullet entrained at the BSEP from May 1974

through August 1984........................................

Density of shrimp entrained at the BSEP from May 1974

through August 1984........................................

Density of spot entrained at the BSEP from May 1974

through August 1984........................................

Density of anchovy entrained at the BSEP from May 1974

through August 1984........................................

Density of Gobionellus spp. entrained at the SSEP from

May 1974 through August 1984...............................

Density of Gobiosoma spp. entrained at the BSEP from

May 1974 through August 1984...............................

Density of seatrout entrained at the BSEP from May

1974 through August 1984...................................

Entrainment day/night mean densities for total fish.

September 1974 through August 1984.........................

Time line depicting initiation dates of the Brunswick

Steam Electric Plant modifications and maximum flow/unit

from June 1981 through April 1985..........................

Mean percent survival of croaker during survival

studies conducted at the BSEP during 1984 and 1985.........

Survival/mortality comparisons of spot by size class

collected during fast screen operation at the BSEP

during 1984- 1985 survival studies..........................

7~27

Day/night comparison of juveni lejadult impingement at

the BSEP during 1984....................................... 10-

Mean monthly rates of water entrained at the BSEP,

January-December, 1977- 1982 and 1984....................... 10-

Length- frequency distributions of bay anchovy and

menhaden imp i nged at the SSE P, January-December 1984....... 10-

Length-frequency di stribut ions of spot and croaker

impinged at the BSEP, January-December 1984................ 10-

xvi
Metric- English Conversion Table

Length

1 micron (~m) = 4. 0 x 10- 5 inch

1 millimeter (mm) = 1000 um = 0. 04 inch

1 centimeter (em) = 10 mm = 0. 4 inch

1 meter (m) = 100 em = 3. 28 feet

1 kilometer (km) = 1000 m = 0. 62 mile

Area

1 square meter (m ) = 10. 76 square feet

1 hectare = 10, 000m2 = 2. 47 acres

Weight

1 milligram (~g) = 3. 5 x 10- 5 ounce

1 gram (g) = 1000 mg = 0. 035 ounce

1 kilogram (kg) = 1000 9 = 2. 2 pounds

Volume

1 milliliter (ml) = 0. 034 fluid ounce

1 liter = 1000 ml = 0. 26 gallon

1 cubic meter per second (cms) = 35. 7 cubic feet per second (cfs)

Temperature

Degrees centigrade (O C) = 5/9 (O F - 32)

xvii

Execut i ve Summary

This report contains the results of biological monitoring efforts

conducted in the Cape Fear Estuary and around the Brunswick Steam Electric

Plant in 1984. In addition to the results contained in earlier reports,

two new studies were conducted in 1984. The installation of fine-mesh

screens on the BSEP intake structure reduced the entrainment of organi sms

through the cooling system. This resulted in large numbers of small fish

and invertebrates being impinged on the screens and subsequently returned

to the estuary via the fish return flume. To estimate these numbers, a

larval impingement program was initiated in conjunction with the juvenile

and adult impingement program. Further , survival studies which estimated

the number of sel ected organi sms returned to the estuary a 1 i ve were also

begu n in 1984.

During 1984 , the overall hydrographic conditions in the estuary did

not change substantially from previous years, except an increased freshwater flow occurred in the late winter and early spring. These flows were

similar to those in 1983 but were hig.her than in previous years. These

high-flow conditions depressed the salinity levels in the estuary during

recruitment of many selected species which in turn affected the abundance

and distributions of these organisms.

Samples of populations of fish and invertebrates in the estuary

during their various life stages indicated that no unexplained trends

occurred in 1984. For example, the river larval fish study indicated that

the abundance and distributions of larval and postlarval organisms were

unchanged from previous years. Samples of the successive ife stages in

the tidal creeks indicated that the abundance during residency of some

species decreased in the upper estuary. This decrease was a result of

high- flow conditions during recruitment which effectively prevented organisms from establishing residence in the upper estuary in the numbers observed during previous years. The juvenile and adult fish and shellfish

reflected the trends of the organisms in the tidal creeks. Any decreases

in abundance was attributed to high-flow conditions and the cycl ic nature

of many organisms residing in the nursery areas.

xviii
Additional studies indicate that the modifications made to the BSEP

intake are effective in improving survival of all ife stages of impinged

organisms. The diversion structure prevents larger individuals of the

populations from entering the intake canal and from the possibility of

being impinged. This is important in that these larger individuals are or

will soon be members of the reproducing populations. These individuals

have survived the high natural mortality of the younger life stages and

have increased their chances of propagation. While the number of organisms impinged has increased greatly due to the installation of fine-mesh

screens, there has been a correspond i ng decrease in organi sms entra i ned

through the plant. Therefore, fewer organisms have been permanently lost

from the estuary. Survival studies indicate that substantial numbers of

the organi sms impinged are returned to the estuary al ive whi ch further

reduced the impact of the BSEP. Finally, the flow-minimization scheme,

which was fully implemented in July 1983, was also effective in further

reduci ng entra i nment and imp i ngement.

Evidence accumulated in 1984 , as well as previous years, indicates

that the ope rat i on of the BSEP has not affected the abundance, seasonality, or distributions of organisms in the estuary. Environmental conditions have been and continue to be the dominant force influencing the

population of the commercial and/or recreational organisms in the CFE.

xix
1.0 INTRODUCTION

In January 1981 Carolina Power & Light Company (CP&L) was issued a

permi t to discharge coo 1 i ng water from the Brunswi ck Steam E ectri c Pl ant

(BSEP) to the Atlantic Ocean under the National Pollutant Discharge

Elimination System (NPDES). Water used for cooling is drawn from the Cape

Fear River (CFR). One stipulation of the permit was that biological

monitoring be continued that would provide sufficient information to allow

for a continuing assessment of the impact of the BSEP on the Cape Fear

Estuary (CFE) with particular emphasis on the marine fisheries. With some

modification, this biological monitoring requirement was a continuation of

research that had been conducted on the CFE by various investigators since

1976, and as a result, some programs in this report will discuss trends

from 1976 to 1984. Earlier BSEP annual biological monitoring reports

(CP&L 1982, 1983) contain more detailed sampling methodology and station

descriptions than are included in this report.

Another stipulation of the permit was the requirement for the construction of two intake mod ifications to reduce entrainment and impingement. A permanent fish diversion structure was built across the mouth of

the intake canal to prevent arger fi sh and shell fi sh from enteri ng the

cana 1 and from be i ng imp i nged at the plant. The effect i venes s of the

structure is discussed in the nekton and impingement sections of this

report. In addition, fine-mesh (l-mm) screens were installed on two of

the four trave 1 i ng screen as semb 1 i es on each un i t to reduce entra i nment.

The effectiveness of this modification is addressed in the entrainment and

larval impingement sections of this report. In addition to these modifications, the NPDES permit also required a reduction in the volume of cooling water used by the plant. This flow minimization scheme and the two.

intake modifications are discussed in more detail in Appendix A.

As a result of the plant modifications, two new studies were added to

the program in 1984 (Table 1.1). Larval impingement was added to

determine how many larvae were impinged on the fine-mesh traveling

screens. Percent survival was studied to determine how many impinged

organisms were returned to the estuary alive.
The study periods evaluated in this report differ by program. The

entra i nment program reports on data co 11 ected from September 1983 through

April 1985. The river larval fish program reports on data collected from

September 1983 through August 1984 to correspond to periods of larval

recruitment, while the nekton, high marsh, and impingement programs report

on data collected from January through December 1984. The survival

program reports on data collected from April 1984 through April 1985.

The stations sampled by each program are shown in Figures 1.1 and

1.2. Figure 1.1 contains the sampling locations for the river larval

fish, discrete depth, and entrainment programs, while Figure 1. 2 shows the

high marsh and nekton sampling locations. Because several stations were

sampled in each creek by the high marsh program, the entire creek is

designated as a sampling area. A more detailed illustration of specific

sampling locations within these areas can be found in the 1981 annual

report (CP&L 1982).

A list of fish and shellfish on which statistical analyses were

performed is presented by program in Table 1.2. The majority of these are

recreationally and/or commercially important species and, with few except ions, are ocean spawned. The others were ana yzed becau se they occur in

arge numbers with i the estuary and are cons i dered i nd i cators of

estuarine conditions. A list of all the fish and shellfish collected by

each program is presented in Table 1.3. A full description of the

ana 1 yses used is presented in Append i x B.
Tab 1 e 1.1 BSEP 1984 biological monitoring program summary.

Program Samp 1 i ng Frequency Sampling Locations

Entrai nment

Impingement (larval)

Imp i ngement

(juvenile and adult)

Water quality

River larval fish

Oi screte depth

Nekton

Weekly

Weekly

Weekly

Once every week

Once every two weeks

September-May;

once every month

June-August

February-March

(four 24- hour tri ps)

Once every three

weeks

Discharge weir

Return flume

Return flume

Dutchman Creek (Station 11)

Walden Creek (Station 24)

Buoy 15 (Stat i on 15)

Buoy 19 (Stat i on 19)

Buoy 25 (Station 25)

Buoy 29 (Station 29)

Buoy 35 (Station 35)

Buoy 38 (Station 38)

Buoy 42 (Stat ion 42)

Dutchman Creek

(Station 11)

Walden Creek (Station 24)

Buoy 15 (Stat i on 18)

Buoy 19 (Station 25)

Buoy 29 (Station 37)

Buoy 38 (Stat i on 34)

Buoy 42 (Station 41)

Buoy 19 (Station 25)

Buoy 38 (Stat ion 34)

Freshwater drainage canal

(Station 1)

Slough east of Buoy 18

(Station 2)

Intake canal west of

Buoy 19 (Stat i on 4)

Walden Creek (Station 7)

Sha 11 ows west of Buoy 23

(Station 8)

ICW Marker 174 (Station 10)

ICW Marker 10 (Station 14)

Shallows east of Buoy 42

(Station 11)

Shallows southwest of

Buoy 49 (Station 15)

Sha 11 ows southwest of

Buoy 51 (Station 16)
Tab 1 e (continued)

Program Samp 1 i ng Frequency Samp 1 i ng Locat ions

Nekton Alligator Creek

(Station 12)

Intake canal

Inside di version

structure (Stat i on 6)

Between canal bends

(Station 13)

Adjacent to plant

(Station 5)

High marsh

trawl and seine Once every three

weeks

Ba 1 dhead Creek

Trawl: 7 stations

Seine: 2 stations

Wa 1 den Creek

Trawl: 9 stations

Seine: 2 stations

Mott I s Creek Bay

Trawl: 2 stations

Siene: 2 stations

Alligator Creek

Trawl: 4 stations

Return bas in

Trawl: 1 station

Survival Dependent on organism Return flume (experimental) availability Intake canal (controls)
Table 1.2 Speci es of fi sh and she 11 fi sh analyzed by program.

Sc i ent if i c Name Common Name Program

C 1 upe i d ae

Bevoortia tyrannus At 1 ant i c menhaden

Engraul idae

Anchoa hepsetus Striped anchovy

A. mitchilli Bay anchovy ~J ~J

Cypr i nodont i d ae

Fundulus heteroclitus Mummi chog

F. majalis Striped killifish

Atherinidae

Membras martinica Rough s i vers i de

enidia beryllina Inland silverside

M. menidia Atlantic silvers ide 

Sci aeni dae

Cynoscion nebulosus Spotted seatrout

C. regalis Weakfi sh ~J ~J

Leiostomus xanthurus Spot

Micropogonias undulatus Atlantic croaker

Mugil idae

Mugil cephalus Striped mullet

M. curema Wh ite mu 11 et J Xl

Gobiidae

Gobionellus boleosoma Darter goby

G. hastatus Sharpta i 1 goby

G. shufeldti Freshwater goby

Gobiosoma bosci Naked goby

G. ginsburgi Seaboard goby

Trigl idae

Prionotus spp. Searob i n sp.

Both i dae

Paralichthys albigutta Gu If flounder

P. dentatus Summer flounder

P. lethostigma Southern flounder

Cynogloss idae

Symphurus plagiusa B 1 ackcheek tonguef ish

L = Larval fish D = Discrete depth

E = Entra i nment M = Hi gh marsh

S = Survival

J = Spec; es grouped for ana lys is purposes

N = Nekton

I = Impingement
Tab 1 e 1. 2 (cant i nued)

Scientific Name Common Name Program

Penaei dae

Penaeus aztecus Brown shrimp

P. duorarum Pink shrimp

P. setiferus White shrimp

Trachypeneus constrictus Hardback shrimp

Portun i dae

Callinectes sapidus Blue crab

C. similus Lesser blue crab X..

L : Larval fi sh D : Discrete depth E : Entrainment M = High marsh

S : Survi va 

J = Speci es grouped for ana lys is purposes

N = Nekton

I = Imp i ngement
Table 1.3 Species of fish and shellfish collected by program during 1984.

Scientific Name Common Name Program

Carcharhi ni dae Requi em sharks Rhizoppionodon teppaenovae At 1 ant i c sha rpnose sha rk Dasyatidae Sti ngrays

Dasyatis sabina At 1 ant i c st i ngray

Lepi sostei dae Gars

Lepisosteus osseus Longnose gar

Ami i dae Bowfi ns

Amia calva Bowfi n

Elopidae Tarpons Elops sau2'US Ladyfi sh

Elops saupus( eptocepha 1 us) Ladyfi sh( eptocepha 1 us)Megalops atlantious( eptocepha us) Tarpon ( eptocepha 1 us)

Albul idae Bonefi shes

.....

A LbuLa vulpes (1 eptocepha us) Bonefi sh (1 eptocephal us)

--.J Angu ill i dae Freshwater eels

AnguilLa postpata Ameri can eel

Congridae Conger eels Congep ooeanious Conger eel

Ophi chthi dae Snake eels

Mypophis punotatus Speckled worm eel

MYpophis punetatus( eptocepha 1 us) Speckled won" eel(lepto.

Ophiohthus gomesi Shrimp eel

Cl upei dae Herri ngs

ALosa spp. Unidentified shadALosa aestivaLis Blueback herringA Losa medioepis Hi ckory shadA Losa pseudohapengus Alewife

L = Larval fi sh D = Di screte depth N = Nekton

E = Entrai nillent 0= Hi gh marsh I = Juvenil e and ClrtUlt impi ngernent LI= Larval impl ngernent
Table 1.3 (cont i nued)

Sc i ent Hi c Name Common Name Program

A Losa sapidissima Ameri can shad

Brevoortia tyrannus At 1 ant i c menhaden

Dorosoma ~epedianum Gi zzard shad

Dorosoma petenense Th readf i n shad

Opisthonema ogLinum Atlantic thread herring Engraul i dae Anchovi esAn~hoa spp. Uni denti fi ed anchovy Anehoa hepsetus Stri red anchovy An~hoa mit~hiL~i Bay anchovy

Umbri dae Mudmi nnows

Umbra pygmaea Eastern mudmi nnow

Synodontidae L i zardfi shes

.....

Synodus foetens Inshore 1 i zardfi sh

Cypri ni dae Carps and mi nnows ill

cyprinus oorpw Common carp

Notemigonu8 ~ryso~eu~a8 Golden shiner

Catostomi dae Suckers

Erimyzon suoetta Lake chubsucker

Ictal uri dae Bullhead catfishes

I~ta~urus spp. Uni dent i fi ed bull head

I ~ta~urus ~atus White catfish

I~ta~urus furoatus Blue catfish

I etaLurus punotatus Channel catfish

Batrachoi d i dae Toadfi shes

Opsanus tau Oyster toadfi sh Gobiesocidae Cl i ngfi shesGobiesox spp. Un i dent ifi ed cl i ngfi sh Gobiesox strumosus Sk ill etfi sh

L = Larval fi sh 0 = Oi screte depth N = Nekton

E = Entrainment M = Hi gh marsh I = J uvenil and adult lmpi ngernent LI= Larval impl ngement
Table 1.3 (cont i nued)

Scientific Name Common Name Program

Gad i dae Codfi shes

Urophyois s pp. Uni dent i fi ed hake

Urophyois fLoridana Southern hake

Urophyois regia Spot ted hake

Ophidi idae Cusk-eel s

BrotuLa barbata Bearded brotul a

Ophidion weLshi Crested cusk-eel

Exocoet i dae Flyi ngfi shes

HyporhamphuB unifasoiatus Ha 1 fbeak

Belonidae Needl efi shes

StrongyLuY'a marina Atlantic needlefish

Cypri nodont i dae Kill ifishes

Cyprinodon variegatus Sheepshead mi nnow f-'

FunduLus spp. Unidentified killifish I.D

FunduLus heterooLitus Mummi chog

FunduLus majaLis Striped killifish

Poeci 1 i idae L i vebearers

Gambusia affinis Mosquitofi sh

Atheri ni dae Si 1 versi des

Membras martiniea Rough si vers ideMenidia beryLLina Inland silverside

Menidia menidia Atlantic silverside

Syngnath i dae Pi pefi shes

Hippocampus erectus Lined seahorseSyngnathus S pp. Unidentified pipefishSyngnathus fuscus Northern pi pefi Syngnathus Louisianae Chai n pi pefi sh

L = Larval fi sh 0 = Di screte depth N = Nekton

E = Ent ra i nment M = Hi gh marsh I = Juvenile and adul t impi ngement LI= Larval , mp i n gement
Table 1.3 (cont i nued)

Scientific Name Common Name Program

Centropomi dae Snooks

entropomus undeeimaLis Snook

Perci chthyi dae Temperate basses

Morone spp. Uni dent ifi ed whi te bass

Morone saxatilis St ri ped bass

Serrani dae Sea basses

entropristis phi ladelphiea Rock sea bass

MYeteroperea spp. Uni dent i fi ed grouper

MYeteroperea mierolep~s Gag

Cent ra rch i dae Sunfi shes

entrarehus maeropterus F 1 i 

I--' Enneaeanthus ehaetodon Bl ackbanded sunfi sh

Lepomis spp. Unidentified sunfish I--'

Lepomis auri tUg Redbreast sunfi sh

Lepomis gibbosus Pumpki nseed

Lepomis gulosus WarmouthLepomis maeroehirus Bluegill

Lepomis mierolophus Redear sunfi sh

Mieropterus salmoides Largemouth bass

Pomoxis spp. Uni dent i fi ed crappi 

Pomoxis nigromaou latus Black crappi e

Perci dae Perches

Perea flaveseens Yellow perch

Pomatomi dae Bl uefi shes

Pomatomus gal tatrix B 1 uefi sh

Rachycent ri dae Cobi as

Raehyeentron eanadum Cobi a

Carangi dae Jacks

aranx hippos Crevalle jack

L = Larval fi sh D = Di screte depth N = Nekton

E = Entrainment t~ = Hi gh marsh I = J uvenil and adult lmpi ngement LI= Larval lmpi ngement
Table 1.3 (cant i nued)

Scientific Name Common Name Program

LlChLoPosBombpus Bhpysupus Atlantic bumper

SeLene vomep LoakdownTpaBhinotus faLBatus Permit

Lutj an i dae Snappers Lutjanus anaHs Mutton snapper Lutjanus gpiseus Gray snapper

Gerrei dae Mojarras

Diaptepus QUpatus I ri sh pompanoEuBinostomus S pp. Unidentified mojarra EuBinostomus apgenteus Spatfin majarra

EuBinostomus guLa Sil ver jenny

Haemu 1 i d ae Grunts

I-' Orthopristis Bhrysoptera Pi gfi sh

I-' Sparidae Porgi es I-' ArBhosargus probatocephaLus Sheepshead

Lagodon phomboides Pinfish

Sciaenidae Drums

BairdieLLa chrysoura Silver perch

Cynoscion nebuLosus Spotted seat rout Cynoscion regaLia Weakfi sh

Larimus fasBiatus Banded drum

Leiostomus xanthurus SpotMenticirrhus spp. Unidentified kingfish

Menticirrhus ameriBanus Southern kingfish MiBropogonias undu Latus Atlantic croaker

pogonias cromis Black drumSBiaenops aGeL Latus Red drum

SteLLifer LanceoLatus Star drum , X

L = Larval fi sh D = Di screte depth N = Nekton

E = Entrai nment M = Hi gh marsh I = Juvenil e and adul t impi ngement LI= Larval lmpi ngement
Table 1.3 (cont i nued)

Sci ent i fi c Name Common Name Program

Kyphos i dae Sea chubs

haet odorz oaeUatus Spotfi n butterflyfi sh

Ephi ppi dae Spadefi shes

Chaetodipterus Jaber At 1 ant i c spadefi sh

Labri dae Wrasses

Tautoga orzitis Tautog Mugil idae Mull ets

MugU spp. Uni dent i fi ed mull et

MugU cephaL us St ri red mu 11 et

Mugi 1. curema White mull et

Sphyraeni dae Ba r racudas

Sphyraerza boreaLis Northern sennet

,.....

ranoscop i dae Stargazers Astrosoopus Unidentified stargazer

......

spp.

Astrosoopus guttatus Northern stargazer Astrosoopus graecum Southern stargazer

B 1 enni i dae Combtooth blennies

Chasmodes bosquiarzus Stri red blenny

Hypsob1.erzrzius hentzi Feather b 1 enny

Hypsob1.ennius ionthas Freckled blenny

E 1 eat ri dae Sleepers Dormitator m::wu Latus Fat sl eeper

Gobi i dae Gobi es

Evorthodus 1.yrious Lyre goby

GobiorzeUus s pp. Unidentified gobi one 11 us goby

Gobiorze1.1.us bo1.eosoma Darter gobyGobiorze1.1.us hastatus Sharptai 1 goby

Gobiorze1.1.us shufeldti Freshwater goby

L = Larval fi sh D = Di screte depth N = Nekton E = Ent rai nment M = High ma rs h I = Juveni le and adult impl ngement LI= Larval impl ngement
Tabl e 1.3 (continued)

Sci ent ifi c Name Common Name

I--'I--'

Gobiosoma spp.

Gobiosoma bosciGobiosoma ginsbupgi

Microgobius spp. Microgobius thaLassinus

Mi crodesmi dae

Microdesmus Longipinn~s Trichiuridae

Trichiupus Leptupus

Scombri dae

Seomberomopus spp.S eombepomopus macu Latus

St romatei dae

PeprHusPeprHus PeprHus

Tri gl i dae

ppionotus Ppionotus Pnonotus

prionotus Prionotus

Bothidae

AneyLopsetta quadpoceL Lata

Cithapichthys spp.

Citharichthys spiLopterus

Unidentified gobiosoma goby

Naked goby

Seaboard goby

Uni dent i fi ed mi crogobi us goby

Green goby

Wormfi shes

Pink wormfi sh

Cutlassfishes

Atlantic cutlassfish

Mackerel s

Inidentified mackerel

Spani sh mackerel

Butterfi shes

Unidentified butterfish

Harvestfi sh

Butterfi sh

Searobi ns

Unidentified searobinNorthern searobi Striped searobin

Leopard searobi n

Bi ghead searobi n

Lefteye flounders

Ocellated flounder

Uni dent i fi ed whi ff

Bay whi 

spp.

aLepidotus

tpiacarzthus

spp.

capoHnus

evoLans

sci tutus

tpibu LUB

L = larval fi 

E = Entrai nment

LI= Larval lmpingement

D = Di screte depth

M = Hi gh marsh

N = NektonI = Juveni 1 e and adult 

Program

D M

lmpi ngement
Table 1.3 (continued)

Sc i ent ifi c Name Common Name Program

Etpopus apossotus Fringed flounder

PapaLiehthys spp. Unidentified flounder

PapaLiehthys aLbigutta Gulf flounder

PapaLiehthys dentatus Summer fl Gunder

PapaLiehthys Lethostigma Southern flounder

SeophthaLmus aquosus 14i ndowpane Soleidae Sol es

Tpineetes rmeu1.atus Hogchoker

Cynogl ass i dae Tonguefi shes

Symphupus spp. Unidentified tonguefish

Symphupus aivitatus Offshore tonguefi 

Symphupus pLagiusa Bl ackcheek tonguefi sh f-' Ba 1 i st i dae Leatherjackets f-' Monacanthus hispidus Pl anehead fi efi sh Tetraodontidae Puffers

Sphoeroides rmcu1.atus Northern puffer

Di octant i dae Porcupi nefi shes ChiLomyctepus sehoepfi Striped burrfish Squill idae SquiUa empusa Mantis shrimp

Penaei dae Penaeid shrimp

Penaeus sp. (adul t) Penaeus (adult)

Penaeus sp. (postlarvae) Penaeus (post 1 arvae) Penaeus aztecus Brovin shrimp

Penaeus duorapum Pink shrimpPenaeus setiferus White shrimp

Tpachypeneus constpietus T -can or hardback sh ri mp

Sicyonia spp. Rock shrimp

L = Larval fi sh D = Di screte depth N = Nekton

E = Entrainment M = Hi gh marsh I = Juvenile and adult impingement LI= Larval impl ngement
Tabl e 1.3 (cont i nued)

Scientific Name Common Name P rag ram

Pa 1 aemoni dae Pal aemonid shrimp

Macpobpachium spp. Freshwater prawns

PaLaemonetes spp. Grass sh ri 

A 1 pIlei dae Snapp i ng sh ri mp

ALpheus spp. Snappi ng shrimp Crangonidae Sand shrimp

Cpangon Beptemspinosa Sand shrimp

Upogebia spp. and CaLLianassa spp. Mud shri mps

Portuni dae Swimmi ng crabs

Portuni dae(meya lops) Swimmi ng crabs (mega lops)

OvaUpes spp. Calico crabsPoptunus spp. Unidentified swimming crabs

t--' CaLLinectes spp. Call i nectes crab

CaLLinectes sapidus Blue crab t--' CJ1 CaLLinectes simiLus Lesser blue crab

LoLLiguncuLa bpevis Brief squid

MaLacLemys teppapin Di amondback terrapi n

L = Larval fi 

E = Ent ra i nment

LI= Larval impi nyement

0 = Di screte depth

M = High marsh

N = Nekton

I = Juveni 1 e and adul t impi ngement
o. WATER QUALITY STATIONS'

* = RIVER LARVAL FISH STATIONS

0 = DISCRETE DEPTH STATIONS

ENTRAINMENT STATIONS

,///,,/ ... ,,/ ...

KILOMETERS

Figure 1.1 River larval f'JSh and water quality sampling locations in the Cape Fear

Estuary during 1984.
0 = WATER QUALITY STATIONS

RIVER LARVAL FISH STATIONS

0 = DISCRETE DEPTH STATIONS

t::. 

= ENTRAINMENT STATIONS

Figure 1.1 (continued)
HIGH MARSH SAMPLING

AREAS

NEKTON SAMPLING

LOCATIONS

,;,;,;,;,;,;

,;1'

... ..,;

'1'_....

,,;

,~I'

KILOMETERS

Figure 1.2 High marsh sampling areas and nekton sampling locations in the

Cape Fear Estuary during 1984.
HIGH MARSH SAMPLING

AREAS

NEKTON SAMPLING

LOCATIONS

Figure 1.2 (continued)
ACCESS ROAD

INTAKE CANAL

I-'

Figure 1.3 Location of div.ersion structure, sluiceways, and return basin at the Brunswick Steam Electric Plant.
WATER QUALITY

I ntroduct i on

Salinity is a major factor influencing the spatial distribution of

estuarine species (Weinstein et ale 1980). Fluctuations in salinity

caused by freshwater inflow and variations in tidal stages produce changes

in the abundance of speci es in an area. In 1982 the water qual i ty program

was initiated to supplement water temperature and salinity data for the

river larval fish. high marsh~ and nekton programs in an attempt to better

determine periods of freshwater inflow.

The estuary is subject to highly variable and relatively large

inflows of freshwater from the Cape Fear drainage basin. The two- layered

flow regime typical of coastal plain estuaries is usually present in the

portion of the estuary above Sunny Point. Net nontidal drift results in a

net upstream flow of more saline water in the lower layer and a net

seaward flow of less saline water in the upper layer. These flows result

in a salinity gradient whose position and shape is constantly being modified. The portion of the estuary seaward of Sunny Point, in which the

Brunswick Plant is located. is typical of a marine. well-mixed system.

Complex water circulation patterns, vigorous tidal action and high

exchange ratios wi th the ocean resu 1 t in th is reach of the estuary act i ng

as an extension of the nearby coastal zone.

Methods

Nine water quality stations (HG) were sampled weekly. Seven of these

stations were located in the CFR channel at Buoys 15 , 19, 25, 29, 35. 38.

and 42. Station HGll was a shallow-water station west of Southport in

Dutchman Creek, and Station HG24 was northwest of the plant site in lower

Walden Creek. Water quality data were also collected every three weeks

from the high marsh (BH) and nekton (BN) programs (Figure 1. 1).

Surface samples were dipped from the surface with a bucket, and bottom samples were collected with a two- liter Kemmerer water sampler.
Temperature was measured in degrees Celsius (o C) using a Yellow Springs

Instruments Model 4310 te ethermometer. Sa 1 i nity was measured in parts

per thou sand (ppt) wi th an Ameri can Opt i ca 1 Mode 1 10419 refractometer.

Bottom salinity and temperature values were plotted for three

stations in the CFR channel representative of the various sal inity regimes

along with stations which are characteristic of three creek systems:

Baldhead, Walden, and Alligator Creeks (Figures 2. 1 and 2. 2).

Results and- Discussion

A period of high freshwater flow was observed in December 1983 and

continued well into May 1984. These increased flows caused salinity

va 1 ues to drop in the creeks and upstream nursery areas (Fi gure 2. 1).

However , this effect was not observed at Station 15 because this area 

strongly influenced by the surrounding coastal waters. Historically,

freshwater inflows begin to decline around May with this decline lasting

into the early winter. This pattern was found to hold true for the most

part, with salinity values increasing in the upriver nursery areas and

creek systems as the summer progressed. Exceptions occurred during early

June and late July when sharp decreases in sal inity were observed as a

resul t of unseasonably heavy freshwater i nfl ows from the upper CFR

basin. The June decreases were not evident on the creek data because the

stations were not sampled during that period. Another deviation from the

historical trend occurred in September when Hurricane Diana passed over

the CFE. depositing over 40 cm of precipitation on the area. This caused

salinity values in the creeks and nursery areas to plummet, but only for a

short time, as values were observed to increase the following week.

maximum bottom temperature of 31. was observed in early

September at Station HGll, and a minimum bottom temperature of 3. C was

observed in Alligator Creek at Station BH42 in early January. The main

factor influencing water temperature in the CFE was seasonal variation

(Figure 2.2). The river channel and creek stations both experienced

similar fluctuations in temperature throughout the year.
RIVER

~ 25

)- 20

...I

,... ..

1983~1 'I( 1984

S1 A TION .........-. H GIS &-&-8- HG29

HG42

(DOWNR!VER) (MIDRIVER) (UPRIVER)

CREEK

g 

t;I 

\ \ . ,... , \ . ,

JI. "I C1 G----EJ

.. /

~ 19.._.a...,

, .

.s.. )A. 

\ / 

'B" - 

,.. 

..f f'\ tt 

...... :?.. / \

"'*-~4 

.....

I'" ' " I'" '

I'" '.,.., '

I'" '

J 25

~ 20

:i 15

(I) 19

1983~1 1984

STATION Be I dhead Creek &-&-8- \.10 I den Creek

+-...-+ A I I I ge tor Cr eek

Figure 2. Bottom salinity values for selected st;ttions in the Cape Fear

Estuary from September 1983 through December 1984,
RIVER

~1983

..J

" I"

, 

..J ..J

1984

LEGEND, 5T A TIOH ........ H G 1 5

(DOWNRIVER!

&-er-& HG29

(MIDRIVER)

+-"-$ HG42

(UPRIVER)

CREEK

;:) 

~ 20

1~1983

..J

-o(

..J ..J

1984

D-EJ-e Wa! d~n Cr~ek ST A rION Bal dhead Cre.k

..... 

Alligator C,.eek

Figure 2. Bottom temperature values for selected stations in the Cape

Fear Estuary from September 1983 through December 1984.
RIVER LARVAL FISH

I ntroduct i on

Sampling for larvaljpostlarval organisms continued in 1984 to monitor

the abundance, species composition spatial distribution, temporal

distribution, and size distribution of fish and shellfish in the CFR.

This was done to detect and quantify any significant changes in the

numbers of larvaljpostlarval organisms which utilize the CFE and are

susceptible to being " cropped I' by the operation of the BSEP.

Results from 1984 were compared with results from previous years to

determine if the time periods in which particular species occurred have

remained the same, if species were still moving through the estuary and

establishing in the same areas, if the same species were occurring most

frequently, and if there were any declining trends in the number of

organisms in the estuary.

Behavioral responses which aid the transport of larvaljpostlarval

fish from the ocean into the CFE have been addressed by Copeland et ale

(1979), Weinstein (1979a), and Weinstein et al. (1979) and are discussed

in Section 4. 0 of this report.

Methods

Samp 1 e Co 11 ect i on and Process i 

The seven sampl ing stat ions used in thi s study have remai ned

unchanged since 1981. There were two shallow-water stations: one in

Dutchman Creek (Station 11), south of and away from the influence of the

plant, and one in Walden Creek (Station 24), north of and bisected by the

intake canal. The other five stations were located in the CFR channel

between Buoys 15 and 42 (Stations 18, 25, 37 , 34, and 41) (Figure 1.1,

CP&L 1982).
Simultaneous replicate samples were collected from the surface and

bottom at each station with l-m diameter , 505-um mesh nets mounted 

rectangular frames. An electric winch was used to raise and lower the

sled used for collecting samples near the bottom during 1984. Previously

the sled had been allowed to free-fall to the bottom before towing;

otherwise, no changes were made to the river larval fish sampling

procedures, gear, or frequency in 1984. Further description and

performance data of this gear were reported by Hodson et ale (1981) and

are discussed in Appendix C of this report.

Samples were preserved in approximately a 10% formalin solution. 

the lab, species were sorted, identified, counted , and standard length

recorded. The volume of water filtered by a net was obtained by the use

of a flowmeter. Typically 200m3 of water was filtered during a fiveminute tow. Larval densities were computed by expanding the volume and

correspondi ng number of organi sms to obta i n number of organ i sms/1000m 3 .

This then was the constant unit used for analysis.

Sampling trips were scheduled biweekly except during June, July, and

August when sampling was conducted once a month. Stations were sampled

from the lower estuary to the upper estuary in an attempt to sample all

stations during the same tidal stage. Previous studies (Copeland et ale

1979; CP&L 1980) have shown that greater numbers of larval/postlarval fish

are collected after sunset and that night samples alone adequately

reflected the population.

Data Ana lyses

For the purpose of analysis, a larval fish year began in September

and continued through the following August. The 1984 larval reporting

year included data from September 1983 through August 1984.

For the time-series plots, surface and bottom larval densities were

combined to give an average density in the water column. This average

water column density predicted from two depths is not significantly

different from a mean density predicted from six discrete depths (Appendix
C). Because sampling trips were not equally spaced, monthly averages of

loge (density + 1) were used (Appendix B).

Results and Discussion

Domi nant Speci es

The larval taxa collected in the greatest densities during each of

the past six years are, in order of abundance: anchovy, croaker , portunid

megalops, Gobiosoma. spp. , spot, Penaeus spp., menhaden , and silverside.

These eight taxa have accounted for approximately 90% of the total density

during this time (Table 3. 1). Other recreationallyfcommercially important

species collected included seatrout, flounder, and mullet. Mean density

fluctuations between years are due primarily to spawning success,

transport mechanisms (wind and currents), water temperature and salinity,

and other natural factors which affect the survival of larvalfpostlarval

organisms. (Norcross and Shaw 1984)

Station Groupi ngs

From 1976 to 1978 the larval fish monitoring program consisted of 28

stations located throughout the estuary. These studies addressed spatial

differences in the estuary by averaging data from stations which were

within four regions, designated by their distance from the mouth of the

river. Data collected by CP&L since 1979 also used this method for

grouping stations to describe four areas, although the number of stations

was reduced to seven. Using this method caused data from shallow creek

stations to be combined and averaged with data from deep river channel

stations. A more accurate picture of what was occurring at each station

was obtained by using principle component analysis to identify and

statistically group stations which showed similarities in species

association , temperature, and salinity. A matrix of the seven stations by

seven organisms (anchovy, croaker, Gobiosoma spp., portunid megalops

spot, shrimp, and menhaden) was constructed using data from 1976 to 1984

so that each observation represented the mean for all years. These

species were selected because of their abundance and they provide a good
mi x of estuari ne and ocean spawners occurri ng duri ng ei ther the summer or

winter.

A positive relation with downriver shallow-water stations and high

(polyhaline) salinity (Principle Component 1) accounted for 73% of the

variation in the total data set (Table 3.2). The second principle

component accounted for an additional 17% of the variation and appeared to

represent the comparative changes in salinities of stations due 

freshwater runoff. This is indicated by the similarity of the downriver

shallow-water stations (11 and 24) to the upriver channel stations (34 and

41) regarding salinity. During periods of freshwater runoff , salinity at

these stations showed the greatest fluctuation (downward) as opposed to

the midestuary channel stations which had more stable salinity.

A cluster analysis was performed to indicate which stations were not

statistically different. The three-cluster solution, representing 86% of

the variation, was overlain on the results of the principle component

analysis (Figure 3. 1). The three groups were I--Stations 11 and 24, the

shallow water creek stations which showed large fluctuations in salinity

due to freshwater runoff; II--Stations 18, 25, and 37 , the midestuary

river channel stations which show the least amount of fluctuation in

salinity; and III--Stations 34 and 41 , the upper estuary river channel

stations which , being at the upper boundary of the salt wedge, normally

had lower salinity readings and were as sensitive to freshwater runoff as

the creek stations.

These three station groupings were used in other analyses in this

sect i on of the report except that Stat ions 11 and 24 were analyzed

individually. This was done to better identify any significant trends in

Walden Creek (Station 24). Walden Creek was bisected by the intake canal

and it was believed that this area would first show any effect of the

operation of the BSEP. Dutchman Creek (Station 11) was chosen as a

control area to be compared with Walden Creek. The fact that the cluster

analysis grouped these two stations together indicates that the species

distributions in these creeks are statistically similar.
Species--Station Group Association

Correlation coefficients of water temperature, salinity, and species

to Principle Components I and II are listed in Table 3. 2. These analyses

show no change in spatial distribution from what Copeland et al. (1979)

descri bed: flounder, shrimp, and spot moved out of the channe 1 and into

the shallows; croaker utilized the upriver channel areas much more

extensively than did other species; menhaden moved upstream (shallow or

deep) to the oligohaline (0. ppt salinity) areas; and anchovy

preferred areas of stable, higher salinity which are more likely to occur

in the summer when they spawn. These results are also consistent with

behaviors reported by Weinstein et ale (1980) for juveniles and adults.

Time-Seri es Ana lys i s

Data was subjected to t ime- seri es anayl s is to determi ne if there has

been any change in the periods of occurrence of particular species and if

the abundance of any species has been declining over the past eight

years. The data cons i sted of 12 observa t ions each year where each

observation was the mean of all surface and bottom samples collected

during a month.

The model , described in Appendix B , fit the data at a high level

(~ 0. 85) (Table 3. 4) indicating a consistent period of occurrence for each

species over the years. Periods of recruitment for species of interest

were as fo 11 ows:
Spot

Croaker

* Flounder

* Mullet

Menhaden

Shrimp

- brown

Late December- Early May

Early October- Late Apri 

Late December- Late March

Late December- Late March

Late February-Mid-May

- pink and white

* Anchovy

* Seatrout

Gobionellus spp.

Mi d-February-Mi d-May

Late May- Early October

Late Apri l- Late October

Early May-Mid-October

Mi d-March-Mi d-December

Gobiosoma spp. Early May- Late October

*See Table 1. 2 for species analyzed.

These periods are similar to previous reports (Copeland et al. 1979; CP&L

1982, 1983).

Plots of mean loge (density + 1) versus time over the past eight

years are presented for selected species of interest (Figures 3. 11).

Because the analysis was done on species by station group, plots were

selected for the station group which was highly associated with a

particular species. For instance, croaker was most highly associated with

the upriver channel stations; therefore, time-series plots of croaker are

shown for station Group III (Stations 34 and 41) only. All other species

plots are shown for Walden Creek (Station 24) which was typical of the

other station groups. Table 3. 3 summarizes these results for the selected

species at each station group. Although there have been year-to-year

fluctuations in densities, no declining trends have been observed for any

larval species. Time-series analysis indicates an overall increasing

trend in the density of total organisms in the past eight years. This

increase is primarily due to increases in anchovy in the upper river

stations and Gobionellus spp. croaker, and shrimp, throughout the

estuary. There has been an increasing trend in densities of larval fish

in Wa 1 den Creek.
Length- Frequency Ana 1 ys i s

One way of assessing whether larval organisms were able to move past

the influence of the plant, accumulate upriver , and grow is to compare the

engths of the organi sms upri ver versus those downri ver. Larger organ isms

upriver should affirm this was occurring. Copeland et ale (1979) stated

that "in all cases and for all species considered, the larvae and

postlarvae upstream were significantly larger than those downstream.

To confirm that this was still the case, lengths of postlarval

croaker collected from October 1982 to May 1983 were analyzed. Croaker

was chosen because of its preference for upriver areas. The analysis

period was chosen because it was the latest recruitment period of croaker

before the operation of the return system in July 1983 (Section 9. 0).

This was done to ensure that any effect which might occur in the lengthfrequency distributions after the return system was in operation would not

influence the data.

The majori ty of croaker co 11 ected ranged from 8 to 21 mm. 

Kolmogorov-Smirnov two-sample test was run on the cumulative length

distributions for Stations 18 and 25 (downriver) versus Stations 34 and 41

(upriver). Analysis results indicate that the two curves are

significantly different (P ~ 0. 05). Examination of the distribution plots

shows that greater percentages of smaller fish are located downriver

(Figure 3. 12). This is consistent with earlier findings and supports the

idea of fish accumulating and growing above the influence of the plant.

Summary

The relative abundance , spatial distribution, and seasonal occurrence

of larvae and postlarvae in the CFE have not significantly changed during

the past eight years.

The decimation of populations in Walden Creek due to the

construction and operation of the BSEP has not occurred. This is

demonstrated best by the fact that the density of organisms in Walden

Creek has been increasing over the past eight years.
Length-frequency data indicate that larvae are able to move past the

influence of the intake, accumulate in an area , and grow without risk of

exposure to entrainment/impingement

Seasonality, station depth , and salinity appear to be the principle

variables controlling larval/postlarval abundance and species distribution

in the CFE.
Table 3. Annual mean density (organisms/1O00m ) and the percentage of the total mean density for the eight

most abundant species collected in the river larval fish program, 1979- 1984.

Taxa 1979 1980 1981 1982 1983 1984

Anchoa s pp. 691 43. 1937 63. 581 34. 733 35. 614 41.6 578 47.

Croaker 170 10. 232 200 11.9 501 24. 367 24. 210 17.

Portunid megalops 1.9 176 153 253 12. 114 104

Gobiosoma spp. 366 22. 359 11.8 421 25. 197

'-D Spot 129

Penaeus spp. 122

Menhaden 1.0 1.3 1.6

Silversi des 1.5

Tota 1 organi sms 1602 92. 3046 96. 1679 92. 2052 92. 1475 90. 1218 91.9
Table 3. Principle component scores by station and ranked correlations of larvaljpostlarval organisms, water temperature, and

salinity for the 1977- 1984 river larval fish data.

Principle Component

PCI PC2

Score

1.14

1.67

1.43

1.17

73% 17%

Corre 1 at i 

Station

% Total variation explained

Vari ab 1 e

Temperature

Shrimp

Spot

Gobiosoma spp.

Anchovy

Portunid megalops

Salinity

Menhaden

Croaker

See Appendix B for a detailed explanation of principle component analysis.
Tab 1 e 3. Results of time- series analysis for river larval fish data

by station group (1977- 1984)! indicating significant changes

(+ or - ) in de~sity along with amount of variance explained

by the model- (R ).

Station Group

18 + 25 + 37 34 + 41

////

Taxon

Anchovy

Croaker

Flounder

Gobiosoma spp.

Gobionellus spp.

Menhaden

Mullet

Seatrout

Spot

Penaeus spp.

Total organi sms

995

NS P )0 0.

* 0. 01 ~ P ~ 0.

** 0. 001 ~ P ~ 0.

*** P -:: 0. 001

2 is an adjusted value; see Appendix B.
Figure 3.

PC1

Shrjrnp

Gobiosoma spp.

Spot

Anchovy

Portunid mega lops

Lower river

Shallow water

High salinity

Croaker

Upper river

Deep water

Low salinity

Fluctuating

salinity

PC2

Menhaden

Results of principle component ordination on 1977-1984 river larval fish

data. Each axis represents a continuum along an environmental gradient.

Solid lines encircle station groups with similiar species distnbutions as

determined from cluster analysis. Species listed have strong associations

with the gradient. See' Appendix B for more explanation.
c.:J

, , ,...,, 

t ! 

I.l

, , ,.. ,.. . .

T"O"

.

TTTLEGEND:

Figure 3.

4.-

c.:J

..J

LEGEND:

Figure 3.

0."--

,.. ,.. ,.. ,..

TRIP DATE-

---n_- PREDICTED

....... 

OBSERVED YEAR LEVEL

Results of time-series analysis of larval/postla.rval croaker collected 

Stations 34 and 41 in the Cape Fear Estuary, 1977- 1984.

:.. . , , , . ,

0 ,

0 ,

... .... . ,. , .......

TT".

OBSERVED

TRIP DATE

-uu_- fREDICtED

.,.... 

YEAR LEVEL

Results of time-series analysis of larval/postlarval anchovy collected at

Station 24 in the Cape Fear Estuary, 1977- 1984.
c:J

...J

LEGEND:

Figure 3.4

8--

)- 6-

5--

c:J

9 3

w 2 :E 

LEGEND:

Figure 3.

. ... . ;\ .. .. ..

TRIP DAfE

----- OBSERVED PREOICfEO .-.-. YERR LEVEL

Results of time-series analysis of larvaljpostlarval flounder collected at

Station 24 in the Cape Fear Estuary, 1971- 1984.

, \....... .....

TRIP DATE

OBSERVED PREDICTED .-..-+ YEAR LEVEL

Results of time-series analysis of larval/postlarval Gobiosoma spp. collected

at Station 24 in the Cape Fear Estuary, 1977-1984.
)

.

ii5

ell

:l:

L fGENO:

Figure 3.

ii5

0 -

:l:

TRIP OAfE

DBSERVEO PREDICTED .-. -. YER~ LEvEL

Results of time-series analysis of larval/postlarval menhaden collected at

Station 24 in the Cape Fear Estuary, 1977-1984. 

, .

LEGEND: OBSERVED

TRIP DAfE

---m- PREDICIED ..-.-. YEAR LEVEL

Figure 3. Results of time-series analysis of larval/postlarval mullet collected at

Station 24 in the Cape Fear Estuary, 1977- 1984.
...

(!;I

..J

c:(

LEGEND:

Figure 3.

"1-

...

CI)

(!;I

..J

c:(

LEGEND:

Figure 3.

.......

+ i

TRIP DATE

OBSERVED PREDICTED +-~-~ YEAR LEVEL

Results of time-series analysis of larval/postlarval seatrout collected at

Station 24 in the Cape Fear Estuary, 1977. 1984.

...     . ,  .     

TRIP DATE

OBSERVED PREDICTED .-~-... YEAR LEVEL

Results of time-series analysis of larval/postlarval spot collected at

Station 24 in the Cape Fear Estuary, 1977- 1984.
...

LEGEND:

Figure 3.

...

..J

LEGEND:

Figure 3.

ffi

... . . ...

LlJ.

,

TRIP DATE

OBSERVED PREDICTED .-.... YEA LEVEL

Results of time-series analysis of postIarval shrimp collected at Station 24

in the Cape Fear Estuary. 1977- 1984.

No Data

..... Available

IOT I "'..

,.,., .,, ..,

. 7

T RIP OR r E

08SERVED PREDICTED .-.-. YEAR LEVEL

Results of time-series analysis of totallarval/postlarval organisms collected

at Station 24 in the Cape Fear Estuary, 1977- 1984.
.......

100

75~1

;::.D.....J

, 

) 

:

:

..

. 

.

1 4 1 5 1 6 1 7 1 8 1 9

LENGTH

DOWNRIVER LARVAL

FISH STATIONS

UPR IVEH LA'RV Al

FISH STATIONS.

LEGEtW:

Figure 3. 12 A typical plot of cumulative length distributions showing a greater percentage of smaller

croaker in downriver areas than upriver areas in 1983.
DISCRETE DEPTH SAMPLING

Introduct ion

The discrete depth sampling program was established to characterize

vertical distributions and movements of larvae in the water column during

both tide and photoperi od changes. The discrete depth samp 1 i ng program

was first conducted in 1979 and again from 1981 through 1984. The objective of this study was to assess the effectiveness of the river larval

fish sampling program which collects only nightly surface and bottom samples. The methods and results of the 1984 discrete depth sampling program

are presented be 1 ow.

Discrete depth sampling was not conducted at the identical time that

river larval fish samples are taken. To account for potential errors when

comparing river larval fish and discrete depth densities resulting from

different temporal samp es, a speci a 1 study was conducted that matched

river larval fish and discrete depth samples on a temporal, tide, and

photoperiod basis. The results of this special study are presented in

Append i xC.

Methods

Sample Collection

Larval depth-density distributions were determined by collecting

samples from six specific depths during two 24- hour rounds (trips) 

Stations 25 and 34 (Figure 1. 1). Sampling was conducted during periods of

peak abundance of winter-spawned larvae (primarily spot and croaker) in

the estuary.

In 1984 the two 24- hour sampling rounds were conducted on February

7 and 14- 15 at Station 34 and February' 8- 9 and 16- 17 at Station 25.

Each round was divided into five sets corresponding to period and tide

direction. Figure 4. 1 graphically illustrates the sequence of these sets

and series as they relate to period, tide, and the order of depths sampled.
A 11 gear and samp 1 i ng procedures were the same as used in 1982 and

1983 (CP&L 1983). Sample preservation and processing and data analyses

were unchanged from 1983.

Data Analysis

The primary emphas i s of the 1984 di screte depth sampling program was

to further define the depth distributions of larval fish. A split-plot

design was used with period and tide combinations blocked on rounds as the

whole-plot units. Each unit was then subdivided into subplots corresponding to the depths sampled. This design was . developed in 1982 (CP&L

1983). This same split-plot design was used in 1983 and 1984. Two wholeplot units occurred at each mean tide direction which were averaged prior

to analysis. Each station was analyzed separately.

The split-plot design was constructed to effectively isolate (from

the other vari ab 1 es in the AN OVA mode 1) and emphas i ze the role of depth in

predicting densities of fish. The analysis can be considered as two

parts--a whole-plot and a subplot analysis. The whole-plot analysis looks

at peri od and tide effects across all 1 eve 1 s of depth , wh il e the subp 1 ot

ana lys is focuses on the effect of depth. In keep i ng with the intent and

design of the discrete depth sampling program, only the subplot results

wi 11 be reported.

Results and Discussion

Water Temperature and Salinity

Water temperature during Round 1 ranged from 4. 80 to 8. C at Station

25 and 4. 60 to 8. C at Station 34. Temperatures were generally lowest at

night on the surface and highest during the day near the bottom during

Round 1. During Round 2, temperatures ranged from 8. 80 to 11. C at Station 25 and 8. 00 to 10. C at Station 34. Temperatures were generally

lowest at night on the bottom during Round 2 and highest during the day on

the surface (Figure 4. 2).
Salinities ranged from 9 to 33 ppt at Station 25 and 1 to 12 ppt at

Station 34 during Round 1. Round 2 salinities ranged from 11 to 32 ppt at

Station 25 and 2. 5 to 20 ppt at Station 34 (Figure 4.3). The lowest

salinities were recorded near the surface around low tide with the highest

salinities found near the bottom around high tide.

Analysis of Variance and Duncan s Multiple Range Test Results

Croaker

Due to the presence of interactions, i nterpretat i on of the sp 1 i t- p 1 

results is accompl i shed by examination of interaction plots. Data for

these plots are presented in Tables 4. 2 and 4.

Plots of croaker densities and a list of cell means show a definite

increase with depth at both stations, especially during the day (Figure

4 and Table 4.2). At night at Station 34, densities increased at all

depths but not as much as during the day. The densities increased from

the surface (1 m) to the bottom (11 m) with the highest densities at the

bottom. At Station 25, however, there was a crossover in the plot (Figure

4) of day/night densities. The daytime densities at the bottom (7 and

9 m) exceeded the nighttime densities at the bottom.

A significant tide- by-depth interaction for croaker occurred at Station 25. An examination of plots of tide- by-depth means (Figure 4.

shows that the depth distribution pattern (5 through 11 m) of croaker

became mixed during the low and mean in tidal stages. At the high and

mean out tidal stages, a generally linear pattern is shown.

A significant period- by-tide- by-depth interaction for croaker also

occurred at Station 25. Plots of period- by-tide- by-depth means (Figure

6) show that during the day the depth distribution pattern looked very

much like the overall pattern with mixing at the lower levels (5 m through

bottom) during the mean and low tidal stages and all depths mixing at the

high tidal stages. At night however, the pattern was different with the

l-m depth showing the lowest densities throughout the entire period with

the other depths showing a well-mixed pattern throughout all tidal stages.
A significant tide-by-depth interaction for croaker also occurred at

Station 34. An examination of plots of tide- by-depth means (Figure 4.

show that the depth di stri bution pattern of croaker at 7 and 9 m became

mixed during the low tidal stages. At the high and mean tidal stages , a

generally linear pattern was shown. There were no significant period-bytide-by-depth- interactions for croaker at Station 34 , with both day and

night data displaying similar patterns.

The plots of depth-by- tide (Figures 4. 5 and 4. 7) effects show that at

the surface (1 m) and bottom (11 m), the densities were more closely

grouped than the other depths. There was more vari at i on in dens it i es

between tides at 3 through 9 m than at the surface and bottom.

Figures 4. 4 through 4. 7 also show that the densities at the bottom

are always greater than the surface during all tides and period. There

was no significant difference between means of densities for all depths

and an average of just surface and bottom means (Appendix C); therefore,

the river larval fish method is doing an effective job of estimating river

larval populations.

Spot

An examination of Table 4. 1 shows that although the depth effect 

always significant, it is not independent of the period. The density of

spot at any depth does not vary depending upon the tides. Due to the

presence of interactions, interpretation of the split-plot results is

accomplished by examination of interaction plots. Data for these plots

are presented in Table 4.

Plots of depth- by-period densities of spot (Figure 4.8) show that

densities increase with depth during the day. At night, although the

densities at the bottom (11 m) were greater than the surface (1 m), the

densi ties at 3 and 5 meters exceeded the 7- and 9-meter dens it i es. 

with croaker at Station 25, there was a crossover in the plots at both

stations, with the densities at the bottom (7 , 9, and 11 m) during the day

exceeding the densities at the bottom during the night. This is explained
by the fact that some of the fish are moving upward in the water column at

night, thereby they are more equally spread out in the column. During

both periods however , if depths were averaged, the number would not be

significantly different than when averaging only the surface and bottom as

the river larval fish program does (Appendix C).

Figure 4. 9 also show that densities at the bottom were always greater

than at the surface during all tides. When means of densities were averaged over all depths there was no significant difference between that

average and the average of just surface and bottom densities

(Appendix C). This again shows that the river larval fish program is

doing an effective job of estimating river larval populations.

Summary

Discrete depth sampl ing was conducted in both downriver and upriver

areas (Stations 25 and 34). Croaker and spot arvae were concentrated

near but not on the bottom. Spot deviated from this at night and showed

higher densities near but not at the surface. Croaker had maximum densities on or near the bottom and minimum densities near the surface.

Si nce both spot and croaker were more abundant in the bottom half of

the water column under almost all conditions, they were carried upstream

with the net nontidal drift. In analyzing both period- by-depth and depthby-tide effects, the bottom densities were always greater than the surface

densities. There was no significant difference between the averages of

the means over all depths and the average of the means of just surface and

bottom. These results show that the river larval fish program by sampling

just surface and bottom at night provides a valid assessment of larval

density in the water column.
Table 4. Results of analysis of variance (split-plot model) for spot

and croaker for the 1984 Cape Fear River discrete depth

program.

Source

Spot 1

Station 25 Station 34

Croaker

Station 25 Station 34

Whole plot

Round

Period

Tidal

Peri od*Ti da 

Subp 1 ot

Depth

Period*Depth

Ti da 1 *Depth

Peri od*Ti da *Depth

See Table 4. 2 for cell-means

See Table 4. 3 for cell-means

Not significant - P ;;. 0.

01 ~ P ~ 0.

O. 05 ~ P ~ 0. 001

*** P ~ 0. 001
Table 4. Analysis of variance cell means for croaker densities collected in the 1984 Cape Fear River discrete depth sampling

program.

Source Station 25 Stat i on 34

Subplot

Depth

Ce ll-means Loge ~p~h Loge Dep~h

1. 76

Depth*Period

Cell-means Day Night Day Night

Loge Depth Loge Depth Loge Depth Loge Depth

1.69 1.56

Depth*Tide

Cell-means High Slack High Out High Slack Hi gh Out

Loge Depth Loge Depth Loge Depth Loge Depth

1.61

33.
Table 4. (continued)

Source Station 25 Stat i on 34

Mean Out Low Ou t Mean Out Low Out

Loge Depth Loge Depth Loge Depth Loge Depth

1.42

Low Slack Low In Low Slack Low In

Loge Depth Loge Depth Loge Depth Loge Depth

1.60

Mean In High In Mean In Hiqh In

Loge Depth Loge Depth Loge Depth Loge Depth

1.47 1.85
Table 4. Results of analysis of variance cell means for spot densities collected in the 1984 Cape Fear River discrete depth

samp 1 i ng program.

Source Station 25 Station 34

Subp 1 at

Depth

Ce ll-means Loge Depth Loge Depth

Depth*Peri ad

Cell-means Day Night Day Night

Depth Loge Depth Loge Depth Loge Depth

1 1

.1..1.

1.34

1.07

Depth*Tide

Cell-means High Slack High Out High Slack High Out

Loge Depth Loge Depth Loge Depth Loge Depth

1.97
Table 4. (cont i nued)

Source Stat i on 25 Station 34

Mean Out Low Out Mean Out Low Ou t

Loge Loge DeDth Loge Depth Loge Depth

1.92

1 1 .LJ.

Low 51 Low In Low Slack Low In

Loge Depth Loge Depth Loge Depth Loge Depth

Mean In High In Mean In High In

Loge Depth Loge Depth Loge Depth Loge Depth
DAY NIGHT

MEAN 44%

c:-

"1.'Ii' '

LOW 28%

LS.

L.5o L.S.

Figure 4. Discrete depth sampling tide tabulation graph.
DEPTH (m)

13'

Ii!J3

136

, t

LEGEND .

DEPTH 1m)

1 1

.. .

LEGEND,

Figure 4.

5T A T:ION-25

 

JI: ..

"jc .

-/. 4

. . . . . 

. I

9. :3 10.

TEMPERATURE :IN C

+-+-+ DAY. ROUND 1

8-S-e NIGHT. ROUND I

*-*-~ DAY. ROUND 2

..--.. NIGHT. ROUND 

STAT:ION-34

I !

I I

'J(. I I I I

I I I I

)I: . . I . . . . . I . 

. . . . 

I . . . . . I . . . . . I . . . . . I S 8. 1 8.7 9.3 9.9 la.

TEMPERATURE iN C

+-+-+ DAY. ROUND I e-a-a N:IGHT. ROUND 

*-*-~ DAY. ROUND 2

..--.. NIGHT. ROUND 

Discrete depth sampling temperature prof1les at Stations 25 and 34

in the Cape Fear River, February 6-9 and 14-17, 1984.
DEPTH 1m) ST A TJ:ON-2S

.......: , ,,, \ \ \ \ \ ,\ ).;,,\\ \

'0 rn"'-"' rn...nH ......n nn.

DEPTIi 1m)

Figure 4.

...

LEGEND .

....... ...n....

Hi! ,.0+

SALJ:NJ:TY J:N PPT

+-+-+ DAY . ROUND I e-s-& NJ:GHT. ROUND I

ST A T:ION-34

\ \\

...n .... .nn'p""'" n.n 

LEGEND.

1121

2121 '26

SALJ:NJ:TV J:N PPT

+-+-+ DAY. ROUND I

e-e-e NZGHT. ROUND I

*-M-M DAY. ROUND 2

. 

NIGHT. RCUNO 2

,..,...... ,......... ,.... ....,......... .,........

2121

*-M-M DAY. ROUND 2

.. 

N:IGHT. ROUND 2

Discrete depth sampling salinity prof1.les at Stations 25 and 34 in the

Cape Fear River, February 6-9 and 14-17, 1984.
...

)- 6

u; 

GO 4

-' 3 o

~ 2

1 :ru; 

5 D'

GO 4

-' 3

Figure 4.4

STATION 25

fi.J

... .... .... ... .... ...............  ..

D....... .................. '.",0' c...........

.... ...

DEPTH (m)

LEGEND: PER rOD ~DAY o.. o..Q NIGHf

STATION 34

.,.,. ,........ :..

~~9 -c..

............. 

.c.

0 3

DEPTH (ml

LEGEND: PER IOD ~DAY 0...0... rnGHT

Densities of croaker collected by period and depth at Stations 25 and 34 in the

Cape Fear River, February 6-9 and 14-17, 1984.
/ 

/

/ 

._ ,

::::

:

:

/ 

. 

/ /

/ 

.

z 3 

// / 

/ / , .... 

_

::.:..

q: "J ' /

/ 

, 

/

- c'--

/. .

/,

:;; 2 - 

- c.--- --

/ _

- - - - 2--"

::::,

,

:::.

, 

,..

,r1 1./

~ 7

6-j1

U) w 5-

Q) 4 c..9 "

-.J

.....

CJ'I

1 1

DEPTH (m)

LEGEND:

Figure 4.

TIDE

----- La ---._---- L S

 

--------- H S --------- L I

 

 

 

 

Densities of croaker collected by tide and depth at Station 25 in the Cape Fear River, February 6-9 and 14-17, 1984.
PERIOD-DA Y

; 

- r 1: 10--- 

\

'" g "?t"-

~or 

\ ;

Z ...

.. ; , ,:

---e--.

.....::::

c -

(

'"Y

:III:

. ./ \ / ,...

..J 3 /

.

z / W 2 ,

, \

"\.. .l'

\ /

.I'

1'10 M.I

LEGEND I DEPTH (m)

TIDE

-+-+-+ 9 

...~. 97

~-e 

.......... 1 1

otC-M-M 0:3

..-- 99

PERIOD-NIGHT

8 ~~-

)/ ..:

I- ,

&

in ~,.-..;z::--

, 

Z S 

,,

:;7 -.........,.

....

/F~/

, ... ... /...

-.,;c -

..;. q 

~o- 

..... /:. 

..J 

Figure 4.

LO LS LX HI 

TIDE

LEGEND I DEPTH (m) ~91

...~. a'

otC-M-N 93

..... 

- as

tr-S-e a6

....

1 1

Densities of croaker collected by tide, depth, and period at Station 25 in

the Cape Fear River, February 6-9 and 14-17, 1984.

. 4':'16
(!)

~ 7

!:: 6

CI)

QJ 4

...J

Z 3

~ 2

j:::o

'-I

Figure 4.

. / . / 

: 

. 

: 

: ::::. ::::::.:::::::::. 

/ / . 

/ / ./

.... 

;;:;

/

/

/ , 

, 

. /

/ 

/ . .

/

/ ::

/ . ........

/ 

. / .

-r 

/ .

~~~u

:

. . / /. .

LEGEND:

1 1

DEPTH (m)

TIDE

----- Lo

----_u_-- H S

----- M 

-------- L I

110

Densities of croaker collected by tide and depth at Station 34 in the Cape Fear River, February 6-9 and 14- , 1984.
STATION 25

)...

en 

;~ 4 jo.

c:C

0..

... .... .

01 03 05 07 89 

DEPTH (m)

LEGEND: PER roo ~DAY 8... 1J... (;) N I G H T

STATION 34

... ..,

(J)

GO 4...:10.

(!1

:IE

....

~li-

.

DEPTH (m)

LEGEND: PER roo ~DAY

(;)...(;)..

IJ ~j IGH T

Figure 4. Densities of spot collected by period and depth at Stations 25 and 34 in the

Cape Fear River, February 6-9 and 14-17, 1984.
STATION 25

III

(:J

...J

0::(

:!E

~~~~S;~::) '7 

DEPTH 1m)

LEGEND: TIDE

L 0

............... HO .-.-.-.- H S

r'r I

nmu L I

110

STATION 34

+' 7

. ;: 

2 .

/ /

:!E /

fJ 1

DEPTH 1m)

LEGUm: HOE -HI

......

.-.---.- H S

M I

------_. L I

MiJ

Figure 4. Densities of spot collected by tide and depth at Stations 25 and 34

in the Cape Fear River, February 6-9 and 14-17, 1984.

HIGH MARSH

Introduct i 

The marshes of the CFE provide nursery areas for many fish and shellfish. It has been estimated that as much as 93% of the East Coast' s commercial fish , shellfish, and sportfish spend at least a portion of their

lives in estuaries (McHugh 1967). Biological monitoring of the fish and

shellfish in the CFE marshes is important to determine if the BSEP'

removal of estuarine water for cool ing purposes has any adverse effect on

their populations and distributions. The high marsh study began in

January 1981 wi th the main object i ves to determi ne the seasona 1 and

spatial distributions of , the influence of physical variables on, and any

abnormal trends in populations of selected fish and shellfish. Results

from 1981 through 1984 are discussed in this section.

Methods

Station Description

The study area consisted of four tidal creek systems (Figure 1.2).

Baldhead, a polyhaline creek (16- 30 ppt) adjacent to the mouth of the CFR

had seven trawl stations and two seine stations. Walden Creek is located

adjacent to the BSEP intake canal and is considered to be mesohaline (8-

ppt). Nine trawl stations and two seine stations were sampled in this

creek. Mott I s Bay, an 01 i goha 1 i ne-mesoha 1 i ne (1-8 ppt) area, is located

upriver from the BSEP. From 1981 to 1983 , Mott' s Bay had one trawl and

one seine station. In 1984 a second trawl and a second seine station were

added to better sample that area. Alligator Creek is a fresh-oligohaline

creek (.:: 1- ppt) located in the upper estuary west of Wilmi ngton and

included four trawl stations.

A 3. 24- hectare return bas i n was constructed in 1983 as part of the

modifications made to the BSEP intake system. These modifications were

designed to reduce entrainment and to increase survival of organisms

imp i nged on the intake screens. The return bas in rece i ves wash water and
organisms from the screen-wash system via a 1. 37-km sluiceway. A weir on

the north side of the bas i n allows water to flow out of the bas i n on ebb

tide and back into the basin on flood tide. Water from the basin flows

into Gum Log Branch which joins Nancys Creek and then Walden Creek. 

this route, surviving organisms were returned to the open estuary (Figure

1.3). One trawl station was sampled in the return basin in 1984. More

detailed descriptions of the high marsh stations are presented in CP&L

(1982) .

Samp 1 i ng Methods

The 1984 trawl and sei ne samp 1 i ng gear , samp 1 i ng methods, and aboratory procedures were identical to those used in previous years (CP&L 1982,

1983, 1984). Discussions of variables affecting the organisms in this

study are based on data gathered by the gear types considered the most

effective for each species as follows:

Trawl

Spot

Bay anchovy

Brown shrimp

Menhaden

Seine

Striped mullet

Mummi chog

White mullet

Atlantic silverside

Croaker

Blue crab

Flounder

Pink shrimp

White shrimp

Three sediment samples were collected at each trawl station and two

samples were collected at each seine station in September with a 3. 8-cm

coring tube. The top 5 cm of sediment was removed for grain-size and percent organics determination. The grain-size analysis was a modified version of that used by Ingram (1965). Percent organics was determined by

loss of weight after ashing at 550o
Data Ana ys is

Recruitment sizes and periods were examined for each species by

examining length- frequency distributions fitted to a natural log (loge

catch-per-unit-effort (CPUE) scale for each creek. Occasionally the

number of individuals collected in a given creek system was low, thus

making reliable recruitment size and period estimates impractical.

The blue crabs Callinectes similus and C. sapidus were grouped for timeseries analysis because prior to 1983 these species were only identified

to genus. However , 99. 4% of the Callinectes spp. co 11 ected in 1983 and

1984 were C. sapidus.

Lower identification cutoff limits were enforced at 20 mm for each of

the penae i d shrimp spec i es and 10 mm for blue crabs. Shrimp and blue

crabs below the cutoff limits were identified to genus only due to difficulties in identifying these organisms to species. As a result of the

identification cutoff limits, 1. 2% and 19. 0% of the respective shrimp and

blue crab catches were not included in the analysis.

Principle component analysis was used to examine the preferences of

selected organisms for various abiotic variables and their spatial distributions. A more detailed discription of this analysis is presented in

Append i x B.

Data collected in the high mars h study from 1981 through 1984 were

subjected to a time-series analysis. Catch- per-unit-effort data (by

creek) were transformed to natural logs before analysis. Significance of

the upward or downward trends was determined at the P ~ 0. 05 level. More

detailed explanations of the statistical analysis are presented in

Appendix B.
Results and Discussion

Sed iment Parameters

Baldhead Creek is characterized by sediments ranging from fine sand

in the downstream stations to very fine sand and clay in the upstream

areas. The percent organics in Baldhead Creek was greatest in the uppermost station followed by the midcreek stations and then the downstream

stations (Table 5. 1).

The upstream Walden Creek sediments were primarily very fi ne sand,

while the middle to downstream sediments were coarse silt and clay. The

percent organics was greatest in the middle to downstream stations (Table

1).

The Mott' s Bay sediments were fine sand, coarse silt, and clay. The

percent organics ranged from very low on the mainland side of the bay to

relatively high on the island side (Table 5. 1).

All Alligator Creek stations contained sediments classified as clay

except the downstream station which contained primarily fine sand. The

percent organics was higher in Alligator Creek than in any other system.

Percent organics was highest in the uppermost station followed by the midstream stations and then the downstream station (Table 5. 1).

Catch by Gear Type

A total of 138, 359 fish representing 93 species and 85, 569 invertebrates representing 10 species was collected in 1984. A total of 414

trawl samples yielded 101 180 fish (CPUE of 244) and 53, 984 invertebrates

(CPUE of 130), while 108 seine samples yielded 37, 179 fish (CPUE of 344)

and 31, 585 invertebrates (CPUE of 292). Spot was the most abundant

organi sm in 1984 wi th a CPUE of 150 and compri sed 40. 1% of the tota 1 catch

(Table 5.2). Spot was followed in abundance by grass shrimp (CPUE of 96),

bay anchovy (CPUE of 35), brown shrimp (CPUE of 20), and menhaden (CPUE of

18). Previous studies by Hodson (1979), Hui sh and Geaghan (1979), and
Weinstein (1979b) also indicated that catches were generally dominated by

the same species. Grass shrimp was the most abundant species collected by

seines with a CPUE of 281 and comprising 44. 2% of the total catch. Grass

shrimp was followed in abundance by spot (CPUE of 128), menhaden (CPUE of

101), striped mullet (CPUE of 27), bay anchovy (CPUE of 24), and mummichog

(CPUE of 23). The dominant species collected with seines were similar to

those obtained by Weinstein (1979b) using seines in selected tidal creeks.

Relationships with Abiotic Variables

Seine

Principle component analysis was performed on the 1984 seine data for

all i dent if i ed groups of stations based on geograph i ca 1 d is tri but ions of

selected species. The first two components were used to examine the relationships between abiotic variables and species. Component 1 accounted

for 62. 4% of the total variation in the data set, while Component 2 accounted for an additional 32. 9% (Table 5. 3).

Weak relationships were indicated between striped mullet, mummichog,

white mullet, and the salinity and temperature parameters (Table 5. 3).

These three species appeared to be more closely related to mesohal ine

areas. Atlantic silverside were strongly correlated to Component 2 which

reflects their strong association with polyhaline areas.

Striped mullet, mummichog, and white mullet had weak negative associations with the sediment organics, while Atlantic silverside were not

associated with the percent organics parameter (Table 5. 3).

Principle component analysis appeared to indicate that there was no

relationship between striped mullet, mummichog, white mullet, Atlantic

silverside, and the size of the particles in the substrate (Table 5. 3).

Weinstein et al. (1980) also concluded that sediment size had ittle

effect on the distributions of most of these species.
Trawl

Due to within creek salinity and sediment variability combined with

the sal inity and sediment variabil ity within the estuary. PCA was performed on Baldhead and Walden Creeks individually.

The location-by-species matrix of Baldhead Creek trawl data was

analyzed by PCA. A total of 64. 5% of the variation was explained by PC1,

while PC2 explained another 20. 0% (Table 5.4). These components were used

to determine associations between species and the abiotic variables.

Relationships between species and stations will be discussed in the

following sect ion.

Moderate relationships were noted between penaeid shrimp, spot , blue

crab, and menhaden and low salinity (Table 5. 4). These species were also

weakly associated with smaller sediment grain size. No relationship with

sediment percent organics and these species was observed. Bay anchovy

were weakly associated with low organic sediments and higher salinity. 

association with sediment grain size was discernible.

Principle Component Analysis on the location by species matrix of

Walden Creek data indicated that 41. 5% of the total variation was

explained by PC1. Principle Component 2 explained 31. 0%. while PC3

explained another 14. 7% of the variation in the data set (Table 5. 5).

These three components were used to examine the effects of abiotic variables on the distribution of selected . species in Walden Creek.

The analysis indicated that spot. blue crab, menhaden, brown shrimp,

and croaker were most closely related with areas in Walden Creek that were

low in salinity and sediment organics. These species were also associated

with the more coarse sediment particles. Flounder , white shrimp, pink

shrimp. and bay anchovy were not associated with salinity or sediment

organics in Walden Creek. A weak relationship was observed between these

species and finer sediment particles.
Spatial Analysis

Withi n Creek

The spatial distribution of selected organisms in Baldhead and Walden

creeks were determi ned using PCA on 1984 trawl data. Seven speci es from

Baldhead Creek and nine species from Walden Creek were used for analysis.

In Baldhead Creek , penaeid shrimp, spot, blue crab, and menhaden had

moderate to strong associations with the headwaters (Stations 15 , 16 , and

17) (Table 5.4). Bay anchovy had a weak preference for two of the headwater stations (Stations 15 and 16) and one of the downstream stations

(Station 12).

In Walden Creek , spot , blue crab, menhaden , brown shrimp, and croaker

were associated with the uppermost stations (Stations 26 and 27) (Table 5). Flounder, white shrimp, pink shrimp, and bay anchovy were moderately associated with the middle Walden Creek stations (Stations 24 and

29) and the Gum Log Branch station (Station 28).

These spatial distributions were similiar to those observed by

Weinstein (1979b) and CP&L (1982 , 1983, 1984). These distributions seemed

to be most associated with the upstream/downstream salinity gradients in

the two creek systems.

Wi th in the Estuary

The distribution of most aquatic organisms in the estuary is determined by sal inity (Copeland and Hodson 1977; Weinstein et ale 1980).

Therefore, the selection of a particular area (creek system) by the

migrating organisms within the estuary is primarily influenced by the

sal inity regime of that area.

The CPUE by creek was used to determine the creek systems that

supported the greatest abundance of each selected species (Table 5. 6).

Baldhead Creek which is generally a polyhaline system, yielded the
highest catches of white mullet and Atlantic silverside. This lower

estuary preference is comparable to previous studies in the CFE (Weinstein

et a 1. 1980; CP&L 1982, 1983, 1984).

Walden Creek , which is generally a mesohal ine system, had substantially higher CPUEs for spot , brown shrimp, striped mullet, and mummichog. The CPUEs for blue crab and pink shrimp in Walden Creek were only

slightly greater than the CPUEs in Mott' s Bay and Baldhead Creek, respectively. These results, except for pink shrimp, are consistent with the

findings of CP&L (1982 , 1983, 1984) and Weinstein et al. (1980).

Mott I Bay is an 01 i gha 1 i ne-mesoha 1 i ne area located in the upper

estuary well past the influence of the BSEP. This sampling area contained

relatively large populations of bay anchovy, menhaden, and croaker. These

results were similar to previous years (CP&L 1982, 1983, 1984) except for

menhaden which were generally more abundant in Walden Creek in 1981- 1983.

Alligator Creek is a fresh-oligohaline area which supported the

largest concentrations of flounder. As indicated by Weinstein et al.

(1980), this preference for the upper estuary was normal.

Seasonal Distribution

The seasonal d i stri but ions of the commerc i a lly and recreat i ona lly

important species were associated with the immigration of postlarvae and

early juveniles into the marshes. The subsequent decrease in abundances

was due to natural mortality and to emigration from the marshes.

The recruitment of spot in the estuary began during January and

coni i nued through March and Apri 1 wi th the majori ty co 11 ected from Walden

Creek (Figure 5. 1) The abundance of spot remained relatively high until

early summer. Recruitment of croaker began in September and October 1983

and continued through January and February 1984. The peak abundance of

the 1983 through 1984 year class occurred in March and May 1984. The

major part of the croaker catches duri ng peak abundance was from Mott I

Bay (Figure 5.2) The recruitment of 1984 through 1985 year class of

croaker began in October 1984 and cont inued through the end of the year.
The two species of mullet exhibited different seasonal and spatial

occurrences. Striped mullet y~y were most abundant in April and May with

the dominant catch occurring in Walden Creek (Figure 5. 3). This species

was fairly common in all months at a variety of sizes. White mullet,

however , displayed more distinct seasonal presence in the estuary (Figure

4). Practically all of the white mullet were YOY collected from May to

October in Ba dhead Creek. The peak catches of th i s spec i es occurred in

July and continued through September and October.

Flounder were collected in relatively low numbers. except during

recruitment, which occurred from January through May with a peak in March

(Figure 5.5). The majority of the flounder were collected from Alligator

Creek with a modal length of 20 mm.

Young-of-year dominated the menhaden catch in the CFE (Figure 5.

The abundance of this species peaked in May and was dominated by catches

from Walden Creek and Mott' s Bay during recruitment. Bay anchovy were

collected practically year round in all study areas with the peak

abundance of YOY occurring during July in the lower estuary (Figure

7). The greates t total CPUE of bay anchovy occurred in Mott I s Bay and

consisted of individuals from the previous year class.

Mummichog and Atlantic silverside displayed similar seasonal distribut ions in that the catches were dominated by adu 1 ts from January through

May. During the late spring and summer months, spawning occurred after

which the catches were dominated by the YOY (Figures 5. 8 and 5.9). The

peak abundance for YOY Atlantic silverside occurred during July in Baldhead Creek , while the peak for YOY mummichog occurred during September in

Walden Creek.

All three species of penaeid shrimp exhibit distinct seasonal distribut ions in the CFE. Brown shri mp were abundant from May through Augu 

with the highest catches occurring in the first month of recruitment

(Figure 5. 10). By the time the brown shrimp catches decreased, pink

shrimp were abundant and remained so through November (Figure 5. 11). Like

brown shrimp, the maximum catch was obtained during the first month of
recruitment. White shrimp were most abundant from July through October

with the maximum catch occurring in the first month of recruitment. The

maximum recruitment of the three shrimp species occurred in Walden Creek

followed by Baldhead Creek.

Blue crab of various sizes were abundant year round in the CFE. The

largest catch of blue crabs occurred in May and was dominated by YOY

recruits in Walden Creek (Figure 5. 12).

Most of the seasonal and length- frequency distributions in 1984 were

similar to previous studies in the Cape Fear and other estuaries (June and

Chamberlin 1959; Dudley and Judy 1973; Chao and Musick 1977; Weinstein

1979b; CP&L 1982 , 1983, 1984).

Time- Series Analysis

All i gator Creek

The abundance of flounder in All igator Creek increased significantly

over the four-year study period (Table 5. , Figure 5. 13). This increase

in All igator Creek is comparable to a general increase of flounder over

the entire estuary. An increase in freshwater flow in recent years (pers.

comm., C. Gunter , United States Geological Survey) may have resulted in

more suitable habitats for flounder throughout the estuary.

The abundance of spot in All igator Creek decreased s igni ficant ly from

1981 through 1984 (Table 5. , Figure 5. 14). This decrease may also be due

to the high freshwater flow during recruitment in 1983 and 1984.

Freshwater flow , as suggested by Copeland et ale (1979), prevents spot

from migrating into the upper reaches of the estuary. The increase in the

abundance of spot in the lower estuary (i.e., Baldhead Creek) also

suggests that the high freshwater flow reduced the recruitment of spot

into the upper estuary.

The abundance of menhaden and bay anchovy in All i gator Creek also

decreased significantly over the four-year study period (Table 5.
Figures 5. 15 and 5. 16). These reductions in abundance are probably

related to freshwater flow or some other environmental factor that prevented menhaden and bay anchovy from uti 1 i zi ng All i gator Creek to the

extent of previous years. Since there was no significant decrease in

numbers of larval menhaden and bay anchovy in the river channel of the

upper estuary, these species may have taken up residence in areas other

than Alligator Creek. Crabs, croaker , and pink shrimp showed no significant upward or downward trends from 1981 through 1984 , whi le brown and

white shrimp were collected in insufficient numbers for analysis

(Tab 1 e 5. 7).

Mott I S Bay

The abundance of flounder in Mott' s Bay increased significantly from

1981 through 1984 (Table 5. , Figure 5. 17). This increase, like the

increase in Alligator Creek, may have been due to low catches in 1981

which were associated with higher salinities (low freshwater flow). From

1982 through 1984, the high freshwater flow lowered the sal inity in the

Mott' s Bay area providing suitable habitat for flounder (Figure 5. 17).

Significant decreasing trends were determined for spot. brown shrimp, pink

shrimp, and white mullet (Table 5. 7, Figures 5. 18- 21). These decreasing

trends appeared to be related to the low freshwater flow in 1981 which

allowed these mesohaline species to inhabit the Mott' s Bay area in large

numbers. With the onset of the high freshwater flow conditions in the

fo 11 owi ng years, the abundance decreased. Further evi dence of th i s

phenomenon is the significant increase in most of these species in the

lower estuary. No significant trend was evident in Mott' Bay for

menhaden, bay anchovy, crabs, croaker , At 1 ant i c s 11 vers i de, or s tr i ped

mullet (Table 5.7). The catches of mummichog and white shrimp from 19$1

through 1984 were too low for time-series analysis to be performed.

Wa 1 den Creek

Analysis on Walden Creek data indicated that significant increases

occurred for croaker, striped mullet, and flounder over the study period

(Table 5. Figures 5. 22- 24). These increases were mainly due to
relatively higher catches in 1983 and 1984, possibly as a result of the

high freshwater flow during these years. The abundance of white shrimp,

bay anchovy, crabs, spot, brown shrimp, pink shrimp, mummichog, Atlantic

silverside, and white mullet remained stable from 1981 through 1984 (Table

7). The menhaden catch, however, decreased significantly over the study

period (Figure 5. 25). This downward trend may be part of a natural multiyear cycle, but the short duration of this study does not allow this to be

accurate ly determi ned.

Ba 1 d he ad Creek

Menhaden , croaker , spot, crabs, brown shrimp, and pink shrimp had

significant increases in abundance in Baldhead Creek (Table 5. 7, Figures

26- 31). These increases, as discussed above, may be due to the high

freshwater flow that occurred in 1983 and 1984. The abundance of bay

anchovy, mummichog, Atlantic silverside and white mullet in Baldhead Creek

did not significantly increase or decrease over the four years of this

study (Table 5.7). The abundances of flounder , striped mullet, and white

shrimp were too low for accurate trend determination.

Return Basin Evaluation

Since the return basin was completed , it has been heavily populated

with fish and invertebrates from the estuary. These organisms entered the

basin by two means: by natural immigration from the estuary and by transportation via the impingement return system. The CPUEs of spot, croaker,

blue crab, and pink shrimp were greater in the return basin than in any

other creek system (Table 5.6). The CPUEs of the remaining species were

s imi 1 ar to the other creek systems.

The seasonal distributions of the populations in the return basin

were similar to those in Walden Creek. As in the natural estuary, the

peak seasonal occurrences of fish and shellfish were related to

recruitment of the individual species. Spot, croaker , menhaden , flounder,

and bay anchovy were most abundant in the winter and spring months. Brown

shrimp were most abundant during the summer months while pink shrimp and

blue crab were most abundant in the fall.
Studies conducted by Pollard (1985) indicated that the populations of

spot and croaker i n the bas in were res i dents. He tagged and re eased

severa 1 thousand spot and croaker and found that the movement from the

basin during residency periods was very limited. However , at the end of

residency periods, the emigration of these fish coincided with the

emigration of the resident fish from the natural habitats.

Cumulative length- frequency distributions were used to determine size

differences between two speci es of fi sh in the return bas in and upper

Walden Creek. A Kolmogorov-Smirnov two- sample test showed significant

differences (P ~ 0. 05) in the cumulative length- frequency distributions

for both spot and croaker. These speci es were generally arger in the

creek than in the basin (Figures 5. 32 and 5. 33). Two factors may have

contributed to the small size of these fish in the return basin. First,

smaller individuals usually populate the upper reaches of tidal creeks.

Since the return basin is located at the headwaters of a tributary creek it is probably being used similarly. Second, the impingement return

system was transporting large numbers of small live spot and croaker from

the fi ne-mesh screens to the bas in where they become part of the

communi ty.

With the high CPUEs, normal seasonal distributions , evidence of residence periods, and length- frequency distributions similar to upper tidal

creeks, it appears that the return bas; n is bei ng ut il i zed as primary

nursery habitat by developing fish and invertebrates.

Summary and Conclusions

The total trawl and seine catches of fish and invertebrates were

slightly greater in 1984 than in 1983. The most abundant species collected in 1984 trawl sampl es was spot, while grass shrimp was the most

abundant species in the seine catch.

Striped mullet, mummichog, and white mullet were weakly related to

salinity and appeared to be associated with mesohaline areas within the

estuary. Atlantic silverside were strongly associated with polyhaline
areas. These species were slightly associated with areas within the

estuary that were lower in sediment organics. There was very little

association between the mullet, mummichog, and Atlantic silverside and

particle sizes of the substrate.

Moderate relationships were noted between the penaeid shrimp, spot,

blue crab, and menhaden and low salinity. These species were also weakly

associated with smaller sediment grain size. No relationship with sediment percent organics and these species was observed. Bay anchovy were

weakly associated with high salinity.

The analysis indicated that spot, blue crab, menhaden, brown shrimp,

and croaker were most closely related to areas in Walden Creek that were

low in salinity and sediment organics. These species were also associated

with the more coarse sediment particles. Flounder , white shrimp, pink

shrimp, and bay anchovy were not associated with salinity or sediment

organi cs. A weak re at i onsh i p was observed between these speci es and

finer sediment particles.

Penaeid shrimp, spot, bay anchovy, blue crab, and menhaden had

strongest preferences for the headwaters of Baldhead Creek. These preferences for the headwater areas also occurred in Walden Creek for spot

blue crab , menhaden, brown shrimp, and croaker. Flounder, white shrimp,

pink shrimp, and bay anchovy were more closely associated with the midcreek stat ions in Wa 1 den Creek.

White mullet and Atlantic silverside were most abundant in Baldhead

Creek, probably as a result of the higher salinity in that area. Spot,

brown shrimp, striped mullet, and mummichog, preferring mesohaline areas,

were collected in their greatest numbers in Walden Creek. The Matt' s Bay

area was selected as preferred habitat by bay anchovy, menhaden, and

croaker, whi 1 e flounder were most abundant in the upper estuary.

In most cases the peak abundance of the se ected speci es of fi sh and

invertebrates occurred during recruitment of the individual species.

Spot , menhaden , croaker, blue crab, striped mullet, and flounder were most
abundant in late winter and spring. Bay anchovy, penaeid shrimp, white

mullet, and Atlantic silverside were more abundant during their respective

summer recru i tments. The abundance of YOY mummi chog peaked in May short 1 y

after spawni ng.

The abundance of all selected fish and invertebrates in Baldhead

Creek remained constant or increased over the pas t four years. The

abundance of all of the selected species, except menhaden in Walden Creek

either increased or remained stable over the past four years. The

abundance of all of the selected species collected in Mott' s Bay, except

for spot, white mullet, and penaeid shrimp, were stable or increased over

time. The decreasing trends of menhaden, spot, brown shrimp, and bay

anchovy in Alligator Creek were probably due to high freshwater flow. The

remaining selected species populations were stable or increased in

abundance over time.

The return basin was used by many fish and invertebrates during

1984. Because of the similarities between the return basin and the

natura 1 estuary, it appears that the construct i on of the bas in produced

24 hectares of primary nursery habitat.

Most species exhibited preferences for selected salinity regimes

substrate makeup, and exhibited spatial and temporal distributions that

were consi stent with past years. These resu lts demonstrate that the

operation of the BSEP has had no adverse impact on the primary nurseries

of the CFE.
Tab 1 e 5. Sediment parameters for the high marsh seine and trawl stations during 1984.

Station

Baldhead Creek

Walden Creek

Mott I S Bay

Alligator Creek

Return Bas i n

Clay = ~ 0. 016 mm

Coarse si lt = 0. 016- 062 mm

Gear

Type

Trawl

Trawl

Seine

Trawl

Trawl

Trawl

Trawl

Sei ne

Trawl

Trawl

Trawl

Sei ne

Trawl

Trawl

Trawl

Sei ne

Trawl

Trawl

Trawl

Trawl

Trawl

Sei ne

Trawl

Seine

Trawl

Trawl

Trawl

Trawl

Trawl

Primary

Grain Size Percent Org an i cs

Fi ne sand

Fi ne sand

Very fi ne sand

Fine sand

Fine sand

Very fi ne sand

Very fine sand

Fine sand

Clay

Clay

Clay

Clay

Coarse s i 1 t

Clay

Very fi ne sand

Very fi ne sand

Very fi ne sand

Very fi ne sand

Coarse s i 1 t

Clay

Clay

Coarse s i 1 t

Clay

Fine sand

Clay

Clay

Clay

Fine sand

Coarse silt

1.35

1.59

1.60

1.60

15.

10.

22.

15.

1.18

1.81

12.

34.

14.

16.

Very fine sand = 0. 062- 125 mm

Fine sand = 0. 125- 250 mm
Tab 1 e 5. Total catch and percent total of the ten most abundant species

collected in the high marsh study during 1984.

Trawl Se i ne

Spec i es Catch Speci es Catch

Spot 62, 182 40. Grass shrimp 30, 396 44.

Grass shrimp 39, 632 25. Spot 13, 826 20.

Bay anchovy 655 Menhaden 10, 915 15.

Brown shrimp 126 Striped mullet 928

Menhaden 564 Bay anchovy 612

Croaker 160 Mummi chog 476

Blue crab 174 White mullet 367

Flounder 447 1.6 Atlantic silverside 225 1.8

Stri ped mu 11 et 237 1.4 Croaker 772 1.1

Pi nk shrimp 737 1.1 Brown shrimp 567

Total 147, 914 95. Total 084 97.
Table 5. Results of the principle component analysis by station for

organisms collected by seines in the high marsh study during

1984.

Principle Component PC 1 PC2

Station Score

558

1.284

0 . 504

661

1.254

1.423

1. 046

1.140

700

575

273

946

Percent of tota 

variation explained 62. 32.

Vari ab 1 es

Mumm i chog

Striped mullet

White mullet

Corre 1 at ions

% Organi cs

973

862

856

512

275

137

0 . 098

":0. 387

191

0. 489

410

776

935

955

119

101

Temperature

Atl anti c si lverside

Sal inity

Grain size

See Appendix B for a detailed explanation of principle component anaysis.
Tab 1 e 5. Results of the principle component analysis by station for

organisms collected in Baldhead Creek by trawl in the high

marsh study duri ng 1984.

Principle Component PC 1 PC2

Station Score

403

192

734

307

1.119

189

713

1.191

156

1.020

605

923

126

247

Percent of tota 

Variation explained

Variables

Brown shrimp

Pi nk shrimp

64. 20.

Correlations

909 270

0 . 899 270

849 419

839 128

789 546

769 0 . 626

359 887

792 522

494 611

0. 688 374

792 522

White shrimp

Spot

Blue crab

Menhaden

Organi cs

Temperature

Bay anchovy

Grain size

Salinity

See Appendix B for a detailed explanation of principle component analysis.
Tab 1 e 5. Results of the principle component analysis by station for

organisms collected in Walden Creek by trawl in the high marsh

study during 1984.

Princi le Com onent PCl PC2 PC3

Station

029

1. 379

1. 033

805

792

441

1.499

1.843

256

Percent of total

variation explained 41. 5

Vari ab 1 

Spot

Blue crab

926

0 . 900

760

O. 708

705

0 . 660

521

161

171

405

714

766

901

Menhaden

Brown shrimp

Croaker

Grain size

Flounder

White shrimp

Pi nk shrimp

Bay anchovy

Sa 1 i nity

Organi cs

Temperature

Score

1.670

1. 734

1. 233

920

663

307

328

0 . 289

111

31.0

Correlation

001

214

525

0 . 444

107

563

0 . 694

0 . 845

772

687

281

183

346

012

670

1. 086

259

565

479

775

216

0 . 500

14.

356

180

195

0 . 445

524

042

287

452

517

313

494

331

174

See Appendix 8 for a detailed explanation of principle component analysis.
Tab 1 e Total catch- per-un it-effort creek system for se 1 ected

species in the high marsh study during 1984.

Baldhead Wa 1 den Matt I Alligator Return

Species Creek Creek Bay Creek Bas i n

Spot 211 135 650

Bay anchovy 156 111

Brown shrimp

Menhaden

Croaker

Blue crab

Striped mullet

Mummi chog

Flounder

Pi nk shrimp

Wh ite mu 11 et

Atlantic silverside

* Seine samples were . not co 11 ected in Alligator Creek and the return

basin.
Table 5. Results of the time-series analysis of high marsh data by creek showing trends in abundance from

1981 through 1984.

Alli ator Creek Mott I s Ba Wa 1 den Creek Baldhead Creek

Species Trend Trend Trend Trend

SpotBay anchovyBrown shrimp

Menhaden

CroakerCrabs

Stri ped mu 11 et

Mummichog

Flounder

Pink shrimp

Wh ite mu 11 

Atlantic silvers ide 

White shrimp

P ;. 0.

01 .:: P .:: 0.001 .:: P .:: 0..:: 0. 001

2 is an adjusted value; see Appendix 

- = decreas i ng trend

+ = i ncreas i ng trend

ID = i nsuffi cent data

NA = analysi~ is not applicable becasue seine hauls were not made
18DEC

El4DECEl5NOU

230CT

020CT

19SEP

21AUG

6 3aJUL

1 aJUL

C 21JUN

U 29tV1V

El9tV1V

18APR

27~

0Stt:IR

14FEB

30JAN

B4JAN

Figure 5.

40 60 80 100 120 140 160

lElliGTH (mm)

Length-frequency distributions of

spot collected in Walden Creek by

trawl in the high marsh study during

1984.

180EC B

B40EC B

E!5NOU B230CT 0

et2IJCT 0

195EP 0

21AUG 018APR a

271'1'1R a

05M'1R 0

14FEB 0

3BJAN a

04JAN B

iii

l 3BJUL

1 BJUL

e 21JUN

P 2sn:1Y

E a~Y

Figure 

100 120 140 160

lENGTH (mm)

Length-frequency distributions of

croaker collected in Mott' s Bay by

trawl in the high marsh study during

1984.
:

LT1

18DEC 

B4DEC 

B5NOU e

23DCr B2DCr 

195EP 

21~UG 111

B9n:JV B

18APR 8

27t1'1R 8

B5tV1R 8

14FEB 

3BJAN B

04JAN 

1'1

31!1JUL

11!1JUL

C 21 JUN

29n:JV

--lilln

Figure 

rL181'1 125 1513 175 2813 225 2513

LENGTH (mm)

Length-frequency distributions of

striped mullet collected in WaldenCreek by seine in the high marshstudy during 1984.

1 SDEC EI

840EC a

85NOU23JCr 0

B2OCT 

19SEP 0

21AUG 030JUL

1 eJUL

21JUN

eSffiVaSffiV a

18APR 

271'1'1R EI05M=IR 0

l'!FED 

30JAN 

04JAN B

Figure SA

1138 125 150 175 200 225 250

LENGTH (mm)

Length-frequency distributions of white

ullet collected in Baldhead Creek by

seine in the high marsh study during 1984.
1BDEC 3-

B4OCC 13-B5NOV B

230CT 0

020CT 0-

19SEP 8-

21AUG ~-38JUL 8

18JUL 8-

21JUN

29MW 5B9t1W 5-

18APR B

271'1'1R 0

051'1'1R 0

14FEB 8

38JAN e

04JAN 5

Figure 5.5

100 125 150 175 200 225 250

LENGTH (mm)

Length-frequency distributions of

flounder collected in Alligator Creekby trawl in the high marsh study during

1984.

18DEC B

B4DEC B

BSNOV 523OCT B

02OCT B

19SEP 8

21AUG B

3BJUL

1BJUL 8

21JUN

29t1W 8B911W 5

18APR B

271'1'1R B

051'f1R B

14FEB 8

30JAN 0

B4JAN 8

Figure 5.

180 125 151'1 175 200 225 250

LENGTH (mml

Length-frequency distributions of

menhaden collected in Walden Creekby trawl in the high marsh study during

1984.
U"1

18DEC 1:1

B4DEC a

B5NOV a230CT 1'1

El20CT 1'1

19SEP a

21AUG 1'1

891'11Y B

18APR 1'1

27~ 0S~ 1'1

30JUL

14FEB ~

3!JJAN 0

1?J4JAN 0

10JUL

C 21JUN

U 2911W

-r1I--,

1'1 21'1 3111 41'1 61'1 9E1

Figure 5.

LENGTH (mm)

Length-frequency distributions of bay

anchovy collected in Walden Creek by

trawl in the high marsh study during

1984.

11'10

18DEC 1:1

84DEC aB5NOU a230CT a020CT a

19SEP 1'1

21AUG 1'1

291'11Y a

B9MW 8

18APR 1'1

27t1'1R a

eSt1'IR a

14FEB a

30JAN 8

64JAN B

1'1

38JUL

HIJUL

21 JUtl

r-r---rll--1 r-.,--1

-, I r T -,

~ I "1--

..--r-r21'1 313 41'1 61'1 81'1 1813

Figure 5.

LENGTH (mm)

Length-frequency distributions of

mummichog collected in Walden

Creek by seine in the high marsh

study during 1984.
18DEC

El4DECElSNOIJ230CT

EJ20CT

195EP

21AUG

30JUL

e 16JUL

U"l

~ 21 JUN

29tf1Y

'-.J

B9tf1'r'

18APR

27rRR

05rRR

14FEB

3E1JAN

04JAN

lEI

Figure 5.

-rr-r---,

70 gel

LENGTH (mm)

Length-frequency distributions of

Atlantic silverside collected inBaldhead Creek by seine in the

high marsh study during 1984.

110 130

18DEC

El5NOV

230CT

020CT e

195EP ~

21AUG3E1JUL

e I ElJUL

C 21 JUN

U 29t1W

El9tf1'r'

18APR

27/"ARBS/"AR

14FEB

31'!JAN

El4JAN

110

Figure 5.

LENGTH (mm)

Length-frequency distributions of

brown shrimp collected in WaldenCreek by trawl in the high marshstudy during 1984.

130
U"1

18DEC 0

8'1DEC IJ

B5NOV ij230CT 0B20CT 0

19SEP 0

21 AUG 03BJUL

1 BJUL

21JUN

29tr1VB9t1\Y B

18APR B

27t1'1R B05t1'1R B

14FEB 0

30JAN 0

IHJAN e

..rfm""1-

108 120 140 160 188 200

Figure 5.

LENGTH (mm)

Length-frequency distributions of

pink shrimp collected in Walden

Creek by trawl in the high marshstudy during 1984.

18DEC 8

B4DEC 0

ElSNOV e

230CT 0

020CT 0

195EP 8

21~UG 8

10JUL 0

29t1\V B9t1\Y e

18APR 8

27t1'1R 0

051'11R 0

14FEB 0

30JAN 0

6"JAtt 

. 3!1JUL

21JUN

,..,..,........n--L

rTl-1.

168 120 140 16B 180 280

Figure 5.

LENGTH (mm)

Length-frequency distributions of

blue crab collected in Walden Creek

by trawl in the high marsh studyduring 1984.
::I

a..

II. 

tHENI/.

::I

a..

LEGEND:

Figure 5.

Figure 5.

TR (P DATE

OBSERVED h..mm----. PRED IC TED

,....... 

YEAR LEVEL

Results of time-series analysis for flounder collected in Alligator Creek in

the high marsh study from 1981 through 1984.

Lt.

JHIP IJAIE

.

IIBStHYfIJ ---00.. PHEIIICIEIJ .-0.' YENH lHf.l

Results of time-series analysis for spot collected in Alligator Creek in the

high marsh study from 1981 through 1984.
::)

t:!

LtGEND:

rR IP DATE

OBSERVED

...... 

YEAR LEIJEL

"""""""" PREDICTED

Figure 5. Results of time-series analysis for menhaden coUected in Alligator Creek

in the high marsh study from 1981 through 1984.

J..

::)

III

EUENDI

IRIP DAlE

m_... PREDICTED

naSEltVED

.... 

TERII LEVU

Figure 5. Results of time-series analysis for bay anchovy collected in Alligator Creek

in the high marsh study from 1981 through 1984.
TR IP DATE

LEGEND: OBSERVED ............... PREDICTED

..,. 

YEAR LEVEL

Figure 17 Results of time-series analysis for flounder collected in Matt' s Bay in the

high marsh study from 1981 through 1984.

::I

II.

. 2

...I

:::i:

::I

...I

LEGEND:

.

77 -.

. . ! .

TRIP DATE

OBSERVED

...,.. 

YEAR LEVEL

............... PRE D I C TED

Figure 18 Results of time-series analysis for spot collected in Mott's Bay in the high

marsh study from 1981 through 1984.
..I

..:.

LEGEND:

. \

7-:-'-' 7'-

. .. . \.

TR fP DATE

GBS E RVE D

.'~-. YEAR LEVEL

............... PRE DIe TE 

Figure 5.19 Results of time-series analysis for brown shrimp collected in Mott' s Bay

in the high marsh study from 1981 through 1984.

a...

..:

LEGEND:

: . . .......:

TR IP DATE

OBSERVED

..~-. YEAR LEVEL

......-........ PREDICTED

Figure 5.20 Results of time-series analysis for pink shrimp collected in Mott' s Bay in

the high marsh study from 1981 through 1984.
TR IP DATE

OBSERVED

.....

. YEAR LEVEL

Results of time-series analysis for white mullet collected in Mott' s Bay

in the high marsh study from 1981 through 1984.

::::I

;:5

::E

LEGEND: 

Figure 5.

::::I

..J

::E

"-..-......... PRED IC TE D

....

....11-- '---

. r-. --

, ...

\..1

TR IP DATE

OBSERVED ............... PREDICTED

,..........-;a, YEAR LEVEL

LEGEND:

Figure 5.22 Results of time-series analysis for croaker collected in Walden Creek in

the high marsh study from 1981 through 1984.
a..

..I

::t

TRIP DATE

OBSERVED

-*---*- YEAR LEVEL

Results of time-series analysis for striped mullet collected in Walden Creek

in the high marsh study from 1981 through 1984.

LEGEND:

Figure 5.

:; 1.

::J

a..

r:J 1. 0

..I

~ 0.

.. / , , .. ...

TRIP DATE

OBSERVED

* YE~R LEVEL

LEGEND:

PREDICTED

--------------- PRED IC TED

Figure 5.24 Results of time-series analysis for flounder collected in Walden Creek in

the high marsh study from 1981 through 1984.
::I

.... .

:Ii .

:::E

LEGEND:

Figure 5.

::I

:::E

LEGEND:

TR IP DATE

OBSERVED

...-t:.-. YEAR LEVEL

Results of time-series analysis for menhaden collected in Walden Creek in

the high marsh study from 1981 through 1984. 

............... PREDICTED

. .

TR IP DATE

OBSERVED .'-.1.-. YEAR LEVEL

.""".""", PRED IC TED

Figure 5.26 Results of time-series analysis for menhaden collected in Baldhead Creek

in the high marsh study from 1981 through 1984.
::)

t:I

..I

B, 25

0. B0

TR rp DATE

LEGEND: OBSERVED ""'_-..-m.. PREDICTED

...,... 

YEAR LEVEL

Figure 5.27 Results of time-series analysis for croaker collected in Baldhead Creek in

the high marsh study from 1981 through 1984.

::) \ .. ./... :::.

..I

TR (P DATE

OBSERVED

..,.._

YEAR LEVEL

LEGEND;

_............. 

PREDICTED

Figure S.28 Results of time-series analysis for spot collected in Baldhead Creek in the

high marsh study from 1981 through 1984.
TR IP DATE

OBSERVED .--t--. YEAR LEVEL

Figure 5.29 Results of time-series analysis for blue crabs collected in Baldhead Creek

in the high marsh study from 1981 through 1984.

~ 0.

..I

~~ e. 25

e. fie

LEGEND:

a..

LEGEND:

.

TR IP DATE

OBSERVED

..~-. YEAR LEVEL

- I -

............ 

PREDICTED

. .

. ""hm--.... PRED IC TED

Figure 5.30 Results of time-series analysis for brown shrimp collected in Baldhead

Creek in the high marsh study from 1981 through 1984.
LEGEND:

Figure 5.

U 75

513

R 25

; 2

:tJ OJ

..J 1

TR IP DATE

OBSERVED

..---. YEAR LEVEL

.........-.... PRED IC TED

Results of time-series analysis for pink shrimp collected in Baldhead Creek

in the high marsh study from 1981 through 1984.

Hie

.........................

LENGTH

188 128 148 168

LEGEND: RETURN BASIN

....... 

UPPER WAL.DEN

CREEK

Figure 5.32 Cumulative length-frequency analysis of spot collected by trawl in upper

Walden Creek and the return basin in the high marsh study during 1984.
HI0

....

LEGEND:

... ,..........,. 

, .. 'T. , . fT ,~ .. ~ I . . . . . 60 

L ENG TH

100 120 140

RETURN BASIN---....---..... UPPER WALDEN

CREEK

Figure 33. Cumulative length-frequency analysis of croaker collected by trawl in

upper Walden Creek and the return basin in the high marsh study during

1984.

NEKTON

I ntroduct i on

Various species of fish and shellfish spend a portion of their first

year in the marshes of the CFE before mi grat i ng to the ocean as juven i 1 e

and adult members of the nekton community. Operation of the BSEP and

subsequent removal of estuarine water for cooling purposes results in the

potential impingement of these nektonic organisms. Biological monitoring

of the nekton community is conducted to determine if operation of the BSEP

has an adverse effect on these organi sms. The major object i ves of the

nekton program were to monitor changes in the relative seasonal and yearly

abundances, species composition spatial distribution, and size

distribution of the juvenile and adult fish and shellfish in the CFE.

Selected stations were also utilized to investigate the effectiveness of

the diversion structure. Catch- per-unit-effort (CPUE) and lengthfrequency data were used to provi de a measure of these changes. Resu lts

were compared to data collected from 1979 through 1983 to ascertain longterm trends.

Methods

Fourteen stations in the CFE were sampled with a 6. 4-m semiballoon

otter trawl. These stations extended from the freshwater drai nage canal,

approximately 3. 4 km west of Southport, to Alligator Creek , approximately

6 km east of the Brunswick River (Figure 1.2). Detailed descriptions of

sampl ing stations and methodology can be found in CP&L (1984).

Principle component analysis was utilized to examine spatial distributions of species groups. Time-series analysis was employed to examine

long-term trends in yearly abundance of selected species. Bay anchovy,

menhaden , spot , croaker , and weakfish were placed into either the youngof-year (YOY) or juvenile/adult (J/A) size class by examination of their

respective length-frequency distributions (Lagler 1952; Everhart and

Youngs 1981; Ambrose 1983). Sizes for blue crab and penaeid shrimp

species were lumped. The time- series analysis was performed on Stations
1, 4, 7, and 8 combined for the years 1979 through 1984. However, the

analysis for menhaden was performed on Stations 1, 2, 4, 7, 8, and 10 for

the years 1981 through 1984 because of higher catches at Station 10 (CP&L

1982, 1983, 1984). Periods of recruitment and abundance were examined by

inspection of length- frequency distributions fitted to a natural log CPUE

scale instead of a percent scale peymitting direct length and catch comparison between trips.

An evaluation of the effectiveness of the fish diversion structure,

compl eted duri ng November 1982 , was based on catches at Stat ions 5 , 6 , and

13 (inside the structure) and the catches of those stations outside (particularly Station 4). Analysis of variance was performed to examine significant spatial variability between Stations 4 , 5, 6 , and 13; and a timeseries analysis was performed on the combined catch of stations inside the

diversion structure. Statistical analysis of cumulative length-frequency

distributions was employed to investigate size differences of the fish

inside and outside of the diversion structure. Stations 1 , 4, 7, and 10

are channel stations similar to the intake canal and were considered

representative of stations outside the diversion structure. Selected

species utilized for the diversion structure evaluation were J/A menhaden

spot, and croaker (CP&L 1984).

The loge (CPUE+l) was used in all analyses.

05 significance level.

Test were made at the

Results and Discussion

Total Organisms

Bay anchovy, spot, croaker , and menhaden compri sed 81% of the total

catch (Table 6. 1). Grass shrimp, brown shrimp, and blue crab ranked next

in abundance and comprised 17% of the total catch. These species have

hi stori ca lly been the domi nant fi sh and invertebrate speci es co 11 ected in

the nekton program and by other researchers (Birkhead et al. 1979;

Schwartz et a 1. 1979; CP&L 1982, 1983, 1984). Spotted sea trout, stri ped

and white mullet, and southern flounder were four other commercially
important species collected. Since the number of these species collected

has historically been low due to reduced gear efficiency, these species

were not analyzed.

Seasonality, Recruitment, and Time- Series Analysis

Bay Anchovy

The bay anchovy was present in the nekton catch throughout most of

the year (Figure 6.1). The abundance of overwinteri ng adults peaked in

May and June with most individuals at a size of 40 to 50 mm in length.

This peak in abundance may have coincided with peak spawning activity.

Kuntz (1914) reported peak spawning activity during July in North Carolina

waters. Adults declined rapidly after this time and completely

di sappeared by September. The yearly catch of J/A bay anchovi es has

significantly increased since 1979 (Table 6. 2 and Figure 6. 2).

Recruits first appeared in the trawl catch during July at 20 mm in

length and their number peaked during August and September. The catch

increased in 1981 and has remained at that level since (Figure 6. 3). A

significant increasing trend was evident from 1979 through 1984 (Table

2).

Spot

Juvenile and adult spot were abundant in the trawl catch from

February through April (Figure 6. 4). The catch of J/A spot was lower in

1984 than previous years but analysis indi~tes a nonsignificant trend in

abundance (Table 6. , Figure 6. 5). This reflects the cyclic nature in

abundance of J/A spot.

Young-of-year recruits were first collected in February at a modal

length of 20 mm. Recruitment peaked in May and had ceased by the following trip. The catch of YOY spot has fluctuated widely from year to year

resulting in a nonsignificant trend in catch since 1979 (Table 6. , Figure

6).
Croaker

Larger croaker (greater than 100 mm) were present in the trawl catch

from March through June with peak abundance occurring in May (Figure

7). Th i s peak of abundance may correspond to movements into the lower

estuary in spring and a movement out as summer approaches (Haven 1959).

Juvenile and adult croaker catches show a nonsignificant trend since 1979

(Table 6. 2, Figure 6.8) peak catch occurred during 1981 with low

catches occurring in 1979 and 1983.

Young-of-year croaker were continuously recruited from January

through May at lengths of 15 to 20 mm (Figure 6.7). Recruitment in

January was a continuation of recruitment began in the fall of 1983 (CP&L

1984). The maximum period of abundance for the spring recruitment period

occurred from May through June. The fall period of recruitment began in

September and the magnitude was less than that of the spring recruitment

period. Growth of YOY croaker occurred from May through December. Low

catches of YOY croaker in 1981 and 1984 resulted in a significant decrease

in catch from 1979 through 1984 (Table 6. 2, Figure 6. 9).

Menhaden

Juvenile and adult menhaden greater than 50 mm were abundant in the

trawl catch from January through April (Figure 6. 10). These were young

adults that overwintered in the estuary and then moved out during late

spring (Reintjes 1969). The catch of J/A menhaden did not exhibit a significant trend from 1981 to 1984 (Table 6. , Figure 6. 11). Peaks in the

J/A catch occurred every other year.

Because of their small size and cylindrical shape, YOY recruits were

not collected by the trawl until April at 25 to 30 mm in length. Their

abundance in the trawl catch peaked in ate May. The catch of YOY menhaden exhibited a nonsignificant trend since 1981 (Table 6. 2, Figure 6. 12).
Brown Shrimp

Brown shrimp were present in the trawl catch from May unti 1 December

(Figure 6. 13). The peak abundance occurred in June and catches subsequently declined, possibly as a result of commercial shrimping which commenced north of Southport on June 27, 1984. The catch of brown shrimp

exhibited a significant decreasing trend from 1979 to 1984 (Table 6.

Figure 6. 14). A slight increase in catch was seen from 1983 to 1984.

Blue Crab

The blue crab catch consisted of two species, Callinectes sapidus,

and C. similus. The catch of both species was combined for analysis.

Blue crab was present in the trawl catch year round but displayed two

periods of abundance (Figure 6. 15). A small peak occurred in May and

presumab ly coni nci ded wi th emergence of overwi nteri ng juvenil es from the

marsh creek areas as water temperature warmed in the spring (Dudley and

Judy 1973). Juveni les and adults were most abundant from July through

November. The catch of blue crab in 1984 was the lowest among all years

since 1979 (Figure 6. 16). A significant decreasing trend was shown by the

analysis (Table 6.2). Commerical landings of hard blue crab for the Cape

Fear River have dropped from 399 600 kg in 1979 to 234 000 kg in 1983

while commercial landings of hard blue crab have increased statewide from

1979 to 1984 however (Street 1985).

Weakfi sh

Young-of-year weakfi sh recruits first appeared in the trawl catch

during June with a peak period of abundance occurring in August (Figure

17). Inspection of the length-frequency data revealed a second recruitment period in September. Merriner (1976) reported that weakfish first

spawn in Mayor June with a second spawn occurring in late July and August

in North Carolina. A significant decreasing trend in catch of YOY weakfish has occurred since 1979 (Table 6. 2, Figure 6. 18). An upswing in the

catch occurred in 1984.
Pi nk Shrimp

Fewer pink shrimp overwintered during the 1983 through 1984 period

but recruitment and abundance were relatively greater during late summer

and fall than that occurring in 1983 (Figure 6. 19; CP&L 1984). Two

periods of recruitment were seen with the September period exhibiting the

greatest magnitude. Pink shrimp exhibited a significant decreasing trend

in catch from 1979 through 1984 (Table 6. , Figure 6. 20). The 1984 pink

shrimp catch exhibited an increase from the 1983 catch.

White Shrimp

Essentially no white shrimp overwintered from 1983 to 1984 (Figure

21). Temperatures of 4O C or less are detrimental to white shrimp

survival (Musick 1979; McKenzie et ale 1981). Water temperatures reached

this level in the lower CFE during the latter part of January and may have

caused mortal ity or migration of white shrimp from the system (Figure

2). A nonsignificant trend in the catch of white shrimp has occurred

since 1979 which is most likely the result of adverse environmental

conditions (Table 6. 2, Figure 6. 22).

Tota 1 Orqani sms

The catch of total organisms remained stable from 1979 through 1982

and then decreased during 1983 and 1984 (Figure 6. 23). This led to a

significant decrease in catch for the entire study period , 1979 through

1984 (Table 6.2). All finfish species, except for weakfish , exhibited

significantly increasing or nonsignificant trends in abundance. The

decrease in catch of total organisms during 1983 and 1984 reflects the

widely fluctuating catches of penaeid shrimp and blue crab that has

occurred over the past two years. Decreases in abundance of these two

groups of organisms may be linked to severe winter conditions during the

latter part of 1983 and 1984. An increased local commerical fishing

effort for penaeid shrimp and blue crabs would most likely have an effect

on the CPUE for these species. Additionally, there is some evidence of a

detrimental side effect of the shrimp trawl fishery on young finfish

particularly weakfish (Merriner 1973).
Spatial Analysis

Young-of-Year Fi nfi sh

Principle Component Analysis indicates the distribution of YOY finfish was explained by proximity to an inlet and water depth (Table 6.

Figure 6.24). Approximately 89% of the total variation in species was

exp 1 a i ned by these two factors.

Spot, croaker , and weakfi sh d i sp 1 ayed greater assoc i at ions wi th Stations 1, 4, 5, 6, 10 , 11, 13, and 14. All of these stations are deep

channel stations near inlets which are avenues of entry for larvae spawned

offshore. Station 11 near Mott' s Bay is relatively shallow; however, its

proximity to the river channel and to Snow Cut, immediately to the

south , probably produced the association of spot, croaker, and weakfish

with this station. During the period of abundance of weakfish, salinity

regimes ranged from mesohaline (8-16 ppt) to polyhaline (16- 30 ppt)

(Figure 2.1). These stations exhibited oligohaline (0. ppt) to

mesohal ine (8- 16 ppt) sal inity regimes during the periods of abundance of

YOY spot and croaker (Figure 2. 1).

lack of associations of croaker and spot with the upriver areas,

Stations 12 , 15, and 16, was probably due to sustained high current flow

and displacement of the salt wedge downriver during their respective recruitment periods (Figure 2.1). Similiar events were reported for the

Ogeechee River- Ossabaw Sound Estuary in Georgia (Rogers et al. 1984).

Stations 2 and 8, located in the lower river , are broad, flat, sandy

stat ions subject to heavy currents duri ng most of the t i da 1 cyc 1 e wh i ch

would tend to push YOY spot , croaker , and weakfish from these areas.

Weinstein et al. (1980) reported a similar effect for his Spoil Island

Station.

Young-of -year bay anchovy, croaker , weakfi sh , and spot were high ly

associated with the intake canal due to the combination of a continuous

incoming current and the ability of the YOY fish to pass through the

mm mesh screening of the diversion structure (CP&L 1980, 1984). 
appears that they took up res i dence in the intake canal for a peri od of

time. Copeland et ale 0979) made reference to the ability of spot and

croaker to ma i nta in themse ves by tak i ng a pos i t i on near the bot tom of the

intake canal. Th i s abi 1 i ty wou 1 d increase as the spot and croaker became

larger. Higher catches were more strongly associated with Stations 5 and

13 as opposed to 6. Th is was probab ly due to the sha 11 ow depth of Stat i on 6. As incoming flow is restricted vertically by the shallow depth , the

flow velocity increases. Flow velocity then decreases at Stations 13 and

Young-of-year bay anchovy and menhaden displayed greater associations

with Stations 1, 8, 11, 15. and 16. All of these stations, with the exception of Station 1, are shallow shoal areas. Station 1 was on the

average 10 to 2O C warmer than all other stat ions duri ng the wi nter and

spring, possibly due to the dark tannin stained water at this station.

This may have led to the similarity of Station 1 and the shallower stations which would warm more quickly during the spring. A moderately

positive association of temperature with the shallower stations was evident (Table 6.3). Salinity ranged from oligohaline to mesohaline during

the period of abundance of yay menhaden (Figure 2. 1). Weinstein et al.

(1980) reported menhaden as being transitional between oligohaline and

mesohaline areas. Salinity regimes at these stations during the period of

abundance of yay bay anchovy ranged from 01 i goha 1 i ne to pol yha 1 i ne (F i gure

1) .

Juvenile/Adult Finfish and Invertebrate Catch

Juvenile/adult fish and invertebrate distributions were explained by

water depth and a downriver to upriver gradient (Table 6. Figure

25). These two factors accounted for 72% of the variation in the distributions of J/A fish and shellfish. An additional 15% of the variation

was accounted for by the distribution of blue crab which did not exhibit a

downri ver to upri ver preference.

Spot, croaker brown shrimp, and pink shrimp were most closely

associated with Stations 1. 4, 5, 10, 13. and 14. All of these are deep
channel stations located in the lower and midriver areas of the CFE.

These stations exhibited mesohaline to polyhaline salinity regimes of 8 to

23 ppt during the periods of abundance of these four species (Figure

1). Juvenile/adult menhaden were most closely associated with Stations

10 and 14. Both of these are midriver deep stations in the vicinity of

Snow l s Cut. Sal inity regimes during the period of abundance of J/A menhaden ranged from 4 to 16 ppt indicating a preference for the 01 igohal ine

and mesohaline areas of the CFE (Figure 2. 1). Schwartz et ale (1979)

reported similar trends for spot, croaker , and menhaden.

Blue crab was associated with Stations 5 , 10 , 12 , 13 , and 14.

these are deeper stations ranging from the lower to the upper CFE.

All of

Lack of a strong association by bay anchovy to either water depth or

the downriver to upriver gradient indicates that J/A bay anchovy was widespread in its distribution.

Diversion Structure Evaluation

Significantly higher catches of J/A spot, croaker and menhaden

occurred outside the diversion structure as compared to the inside (Table 5). Prior to 1983 , catches of these species inside the intake canal

exceeded catches outside (Schwartz et ale 1979; CP&L 1982). These trends

in the small trawl catch reversed themselves during 1983 with the diversion structure becoming operational during November of 1982 (CP&L 1984).

In addition , results of the time- series analysis (Figures 6. 26 through

28) indicate a highly significant decreasing trend in the catch of J/A

spot, croaker, and menhaden at the intake canal stations since 1981. This

decreasing trend can be attributed to the diversion structure. Spot

catches increased from 1982 to 1983 at the CFE river stations but

decreased in the intake canal during 1983 and steadily declined through

1984. The J/A croaker catches were relatively stable at the river stations whi le they decreased at the intake stations. The menhaden catch at

the intake stations mirrored the fluctuations of the river station but

were significantly reduced over previous years.
Spot of approximately 40 mm or below were capable of passing through

the diversion structure (Figure 6. 29). A Kolmogorov- Smirnov two-sample

test showed that the cumulative length-frequency distribution of spot

inside the intake canal was significantly different from that of spot

outside (P = 0.05). The greatest difference in cumulative percent between

the two distributions occurred at approximately 60 to 70 mm. At this

point. less than approximately 2% of the spot inside the diversion

structure were greater than 60- 70 mm, whereas 10% of the spot outside of

the diversion structure were greater than 70 mm.

The cumulative length-frequency distributions of croaker between

inside and outside of the diversion structure were also significantly

different (P = 0.05). Croaker of approximately 45 mm or less were not

excluded from the intake canal (Figure 6. 30). A greater percentage of 25

to 35 mm croaker were present outs i de of the intake canal. Fi ne-mesh

impingement and entrainment of the smaller size classes of croaker (-:: 45

mm) entering the intake canal may have resulted in this difference. The

diversion structure became effective at excluding larger croaker at

lengths greater than 45 mm. For example, approximately 13% of the croaker

outside of the intake canal were greater than 80 mm , whereas approximately

3% of the croaker ins i de of the intake cana 1 were greater than 80 mm.

The cumulative length- frequency distributions of menhaden present

outside and inside of the diversion structure began to diverge at approximately 80 to 90 mm (Figure 6. 31). The greatest difference in cumulative

percent of the two 1 ength-frequency di stri butions occurred at around 95

mm; however, the two distributions were not significantly different.

These cumulative length distributions were the result of problems

associated with the maintenance of the diversion structure during the week

of January 14-20, 1984. Strong winter storms piled much debris and

detrital material on the diversion screen panels caused damage and blownout screens. Although the catch of menhaden was still greater outs i de, a

arge number of menhaden moved into the intake canal that week thereby

influencing the length-frequency distribution of menhaden present in the

intake canal (Figure 6. 32).
Summary and Conclusions

Nekton monitoring during 1984 showed little difference in

seasonality, abundance, and distribution from previous years. The dominant species collected have remained as such since 1979. Any changes were

minor and were due to gear differences and to the cyclic nature of most

populations. The bay anchovy exhibited a significant increase over the

years 1979 through 1984, while YOY croaker , blue crab, brown shrimp,

weakfish , and pink shrimp exhibited a significant downward trend. This is

most likely related to a combination of the cyclic nature of these species

coupled with severe winter conditions. Brown shrimp, weakfish, and pink

shrimp showed an increase from 1983 to 1984. Spatial distributions for

the dominant species were consistent with past data which indicated that

operation of the BSEP has not imited movement of fi sh and shell fi sh to

and from nursery areas. High springtime freshwater flows seems to have

limited movement of YOY croaker and spot into the upriver areas sampled by

the nekton program, particularly the Alligator Creek area. A change in

spatial distribution of J/A spot, croaker, and menhaden has occurred in

one respect. Historically, the catches of these three species in the

intake canal were among the highest in the CFE. Since operation of the

diversion structure began in 1982, the catch of these species in the intake has been relatively low.

Operation of the BSEP has not adversely affected the population of

nektonic organisms residing in the CFE. Trends in seasonality, distribution, and relative abundance from year to year of most species exhibit

no changes associated with operation of the BSEP. Further, the fish

diversion structure has been successful at excluding larger organisms from

the intake canal.
Tab 1 e 6. 1 Tota 1 number , percent total number , and annual catch-per- unit-effort (CPUE) of the ten most abundant species

co 11 ected in the nekton study duri ng 1984.

Percent

Total

Spec; es Number Total CPUE

Bay anchovy 46. 838 33. 98.

Spot 788 24. 73.

Croaker 20 , 600 14. 43.

Menhaden 10. 752 22.

Grass shrimp 805 18. 50

Brown shrimp 015 10.

Blue crab 551 1.82

Weakfi sh 193 1.57

Pink shrimp 2 , 061 1.47

Hogchoker 1, 104

Total 134 707 96.
Table 6. Results of time-series analysis of nekton river data indicating significant increase (+) or decrease (- ) in CPUE for

1979 through 1984.

Species Trend

Bay anchovy

JjA

yay

Spot

JjA

YOY

Croaker

JjA

YOY

Menhaden

JjA

YOY

Brown shrimp

Blue crab

Weakfi sh

Pink shrimp

White shrimp

Total organisms

p;:. 0.

.( P .( 0.

001 ~ P ~ 0.

p 

~ 0. 001

Time-series analysis for menhaden was run for 1981 through 1984.

is an adjusted value; see Appendix 

JjA = Junvenile and Adult

YOY = Young of Year
Tab 1 e 6. Results of the principle component analysis by station for

young-or-year finfish collected in the nekton study, years

1983 and 1984 comb i ned.

Princi Com onent

Pel PC2

Score

1. 53

1.96 1. 52

1.26

1. 33

1.64

1.21

1.43

1.04

1. 70

57. 31.3

Corre 1 at ions

Station

5 (i ntake cana 1 )

13 (i ntake cana 1 )

6 (i ntake cana 1 )

Percent tota 

variation explained

Vari ab 1 es

Croaker

Weakfi sh

Spot

Bay anchovy

Sa 1 i ni ty

Menhaden

Temperature

See Appendix B for a more detailed explanation of principle exponent analysis.
Tab 1 e 6. Results of the principle component analysis by station for

juveniles/adults collected in the nekton study, years 1983

and 1984 comb i ned.

Principle Component PC1 PC2 PC3

Station Score

5 (i ntake canal) 1.47

1. 25

1.38

1.15

(i ntake cana 1 ) 1 1

.L. .L.L 1. 60

(i ntake cana 1 ) 0. 58

1.03 1.06

Percent of total

vari at i on exp 1 a i ned 49. 22. 15.

Vari ab 1 es Corre 1 at ions

Pink shrimp

Croaker

Brown shrimp

Spot

White shrimp 0. 18

Sal inity

Bay anchovy

Menhaden

Blue crab

Temperature

See Appendix B for a more detailed explanation of principle exponent analysis.
Table 6. Results of analysis of variance and Duncan s multiple range test for selected species

utilized in the evaluation of the BSEP diversion structure during 1984.

Spot

(juveni 1 ejadul t)

Source Value

Trip 82 NS

Stat ion 30. 50***

Trip*station 1. 64 

Trip 1.21 NS

Station 12 . 17***

Trip station 64 NS

Trip 20. 35***

Stat ion 22. 30***

Trip*station 1.81 NS

Duncan s Multiple

Range Test Species ANOVA R

5 13 6

Croaker

(juveni 1 ejadul t)

Menhaden

0'\t-'0'\ (juveni 1 ejadul t) 5 6 13

Station 4 is located outside of the diversion structure and Stations 5, 6, and 13 are located inside

of the d iversi on structure.

Underscores indicate similarity and values decrease from left to right.NS P ~ 0.

0 . 01 ~ P ~ O. 

** 0. 001 ~ P ~ 0.

 

P ~ 0. 001
21IfN

Ff1lI1V

!7UCT

I s.uJi

0 2~

a2.Q.

11alII

lIMY

atltAy

29fEB

11..rAH

15 18 21 24 1:1 38 33 38 39 ~ 4S 48 51 54 fU 68 63 ee 6U it 1S 76

LENGTH (mm)

Figure 6. Length-frequency distributions of bay anchovy collected in nekton trawls

during 1984.
::::I

II..

III

LEGUID :

Figure 6.

::::I

a..

III

..J

Figure 6.

, ., , 

.:Ie

--11

. . 

TR IP DATE

OBSERVED .......-....... PREDICTED *---*--;jI- YE A LEVEL

Results of time-series analysis for juvenile/adult bay anc.llovy collected in

nekton small trawls at Stations 1, 4, 7, and 8 combined for 1979 through

1984.

\ ! 

: I 

. ,

....-1 -

\ /\ .....: ,...

0- :: 

TRIP DATE

LEGEND: OBSERVED

PREOICTED .-.-. YEAR LEVEL

Results of time-series analysis for young-of-year bay anchovy collected in

nekton small trawls at Stations I, 4, 7, and 8 combined for 1979 through

1984.
mJV 

2SSEP .

84SEP

! s.w;

Z 4dl.

82JI.

12J1f

liMY

81/IAY

18AfR

2SIUR

2Sf'E8

86FEB

17dM1

Figure 6.4

.-rrT""r-.

TI.......

.,....,..,

188 IZ8 148 lea 188 288

LENGTH Imm)

Length-frequency distributions of spot collected in nekton trawls

during 1984.
CL.

II 2

:!: ;. .

TR IP DATE

OBSERIJED ............... PRED Ie TED

........_,

YEAR LEVEL

LEGEND:

Figure Results of time-series analysis for juvenile/adult spot collected in nekton

small trawls at Stations 1, 4, 7, and 8 combined for 1979 through 1984.

:!: , . . ....

..J

LEGEND. OBSERVED

....:

I -

TRIP DATE

PREOlcrEO .-.-. YEAR LEVEL

Figure 6. Results of time-series analysis for young-or-year spot collected in nekton

small trawls at Stations 1 4, 7, and 8 combined for 1979 through 1984.
Z-w..

Ill.....

12d11

Z1NY

9!!!AY

!9APR

3NR

Figure 

!800:

Z7lfJV

87!IJV

r'-'l.1

2SSa'

IHSEP

Z9FEB

II6fEB

17JIII 

._

"" ""OU I' .._m'

...... 

1""" "' 1"'" "" 1""""'

,

1"'"

189 12.8 1-18 168 168 28B 2Z8 248

LENGTH (mm!

Length-frequency distn'butions of croaker collected in nekton trawls

during 1984,
TR IP DATE

LEGEND: OBSERVED

,....,. 

YEAR LEVEL

LEGEND:

Figure 6.

::;)

::E

Figure 6.

::;)

TR IP DATE

OBSERVED ..-'f;._,. YEAR LElJEL

Results of time-series analysis for juvenile/adult croaker collected in nekton

small trawls at Stations 1 4, 7, and 8 combined for 1979 through 1984.

............... PREDICTED

I - I , - I 

"'...".""" PRED IC TED

Results of time-series analysis for young-of-year croaker collected in nekton

small trawls at Stations I , 4, 7, and 8 combined for 1979 through 1984.
tIlDE!:

'i8 188 128 1.. 168 188 288 22B Z'i8 ZS8

LENGTH (mml

27MJY

I1lIIY

:: 

Figure 6. 10 Length-frequency distributions of menhaden collected in nekton trawls

during 1984.

IUL

IZ....

Z1MY

81"1"1

28IAR

Z9f'EB

8IIfEB

17.JA11
c:J

LEGEND:

I:)

Figure 6. 11 Results of time-series analysis for juvenile/adult menhaden collected in nekton

small trawls at Stations 1 4, 7, 8, and 10 combined for 1981 through 1984. .

+ 1. 00-

Q,.

c:J

Z 0.

......

TR I P DATE

OBSERUED

YEAR LEIJEL

.....-......... PRE DIe TED

Figure 6. 12 . Results of time-series analysis for young-of-year menhaden collected in nekton

small trawls at Stations 1 , and 10 combined for 1981 through 1984.

50-

25-

25-

LEGEND I

TRIP DAlE

OBSERVED ---_h- PREDICIED .-. -. rEAR LEVEL
g Zw.

~ 9W.

1800:

Z7H)V

17(X:1'

IZJ.It

ZINY

alMAY

1- 

2JJWl -

29ftB ..

96FtJ :.

17JA1f -

18 28 38 48 58 68 78 88 118 1118 118 IZO 138 1-48 158 1fJ! 178 188

LENGTH (mm)

Figure 6. 13 Length-frequency distributions of brown shrimp collected in nekton trawls

during 1984.
0"1

0"1

5 1

;:;- 4 ~I

:J - Q. 3-

CII

(!) .:(

1~1

~ n

.

..J

TRIP DATE

OBSERVED

. 

YEAR LEUEL

LEGEND: PREDICTED

Figure 6. 14 Results of tillIe-series analysis for brown shrimp collected in nekton ('mall

trawls at Stations 1 4, 7, and 8 combined for 1979. through 1984.
24d1.

e -

Z7JIJV

rnm 

 .

J"\..r1

I~ 

h -

 

1- 

112.11.

12d11

2'f8.AY

IWR

2SIIAR

Z9F9

86fEB

17.w1

.. .. ... ...

-18 88 188 128

LENGTH (mm)

1-18 168 168

Figure 6. 15 Length-frequency distributions of blue crab collected in nekton trawls

during 1984.
0"\

....

~ 2.

(!J

1.0

LEGEND:

11"\

TRIP DATE

OBSERVED --_u-- PREDICTED

.

... 

YEAR LEVEL

Figure 6. I 6 Results of time-series analysis for blue crab collected in nekton small trawls at Stations 1, 4, 7, and 8 combined for 1979 through 1984.
ISU

G Z4.JI.

P 82.0.

IZdlt

2NJV

I7tf1t

170:1"

ZUlU

8111AY

IWR

2I!W1

29fIB

86ftB

17.JA11

... ......... ,....... ,.. .....

,........ "I

188 118 ' III 138 I" 158

LENGTH (mm)

Figure 6. 17 Length-frequency distributions of weakf"lSh collected in nekton trawls

during 1984.
(:)

0'\

I""i

c:(

~iLEGEND:

(\ \ ! (\

lilt:

1', 

TRIP DATE

OBSERlJED

.-~-. YEAR LEVEL

PREDICTED

Figure 6. 18 Results of time-series analysis for young-or-year weakfish coUected in

nekton small trawls at Stations 4, 7, and 8 combined for 1979 through

1984.
?:

,.:

2'MN 

z.:

8'MN 

z.:

meT t

z.:

,.:

2SSEP .

z.:

,.:

am .

z.:

, s.u; 

~ 2.a ro 

BlJ.l. !

E '

!2J.!1

.

'Wi

ZIMY

II HAY

,.:

Z9FEB .

z.:

88FEB &

z.:

,.:

'7JA11 "

185 lIS IZS

LENGTH tmm)

Figure 6. 19 Length-frequency distributions of pink shrimp collected in nekton trawls

during 1984.
.....

c..

--;, 2

...J

c:(

LEGEND:

11 :r-'

,~.I "

:: 

r n

TRIP DRTE

OBSERUEO

* YE H R L E IJE L

PRED IC TED

Figure 6.20 Results of time-series analysis for pink shrimp. collected in nekton small

trawls at Stations 1 4, 7, and 8 combined for 1979 through 1984.
I SMJ&

G 21d1.

p et.u.

12dIt

ZM1t

81lfN

11U:T

2SSEP

84SEP

21&'

eUfAY

IWR

2IJW!

2SfEII

8IIFEB

17 .IAN

189 118 128 138 I" 158

LENGTH (mm)

Figure 6.21 Length-frequency distributions of white shrimp collected in nekton trawls

during 1984.
;:)

III

TR IP DATE

OBSERVED

.

. YEAR LEUEL

Results of time-series analysis for white shrimp collected in nekton small

trawls at Stations I, 4, , and 8 combined for 1979 through 1984.

LEGEND:

Figure 6.

............ 

PREDICTED

;:)

III 2

TR IP DATE

OBSERVED

..-t---. YEAR LEIJEL

LEGEND:

.......... 

PREDICTED

Figure 6.23 Results of time-series analysis for total organisms collected in nekton small

trawls at Stations 1 , 7, and 8 combined for' 1979 through 1984.
Deep 

Figur~ 6.

PC1

Croaker Proximity to Weakfish an inlet Spot

I PC2

Shallow 

Principle component ordination of the nekton young-or-year f"milSh data for 1983 and 1984 comQined. Each axis represents a continuum along an

environmental gradient. Solid lines encircle station groups with similiar

species distributions as detennined from cluster analysis. Species listed

have str~ng associations with the gradient See Appendix B for more

explanation.
Brown Shrimp

Pink Shrimp

PC,

Spot

Croaker

jDeepl

Menhaden

Downriver

Figure 6.

Upriver 

I Shallowl

Principle component ordination of the nektonjuvenilefadult data for

1983 and 1984 combined. Each axis represents a continuum along an

environmental gradient. Solid lines encircle station groups with similiar

species distributions as detennined from cluster analysis. Species listed

have strong associations with the gradient. See Appendix B for more

explanation.
:::E

LEGEND;

, Figure 6.

Diversion Structure

Completed

, 

TR I P 0 A TE

""'..m_-... PREDICTED

Results of tim~series analysis for juvenile/adultspot collected in the intake

canal (Stations 5, 6, and 13), by the nekton trawl for 1981 through 1984.

:::E

LEGEND:

Figure 6.

OBSERVED

.,...--.t- YEAR LEVEL

Diwrsion Structure

Completed

TR IP DATE

08 S E R lJE D

.-....-.t- YEAR LEVEL

nm_"nn_-- PRE 0 

leT 

Results of tim~series analysis for juvenile/adult croaker collected in the intake

canal (Stations 6, and 13), by the nekton trawl for 1981 through 1984.
LEGEND:

DivenJon Structure

Completed

'+ 3

;:)

CI.

CI 2

of(.

:ii

TR fP DATE

OBSERVED

..~-. YE~R LEVEL

""""""'" PREDICTED

Figure 6.28 Results of time-series analysis for juvenile/adult menhaden collected in the

intake canal (Stations 5, 6, and 13), by the nekton trawl for 1981 through

1984.

M 75

. L

I sa

~ 25

HHJ

..................... .......

n--" ._m

......................

80 100 120

LENGTH (mm)

INSIDE

140 1 6 EI 18 EI 200

LEGEND: ............... OUTSIDE

Figure 6.29 Cumulative length-frequency analysis of spot collected by the nekton

trawl inside (Stations 5, 6, and 13) and outside (Stations 1 , 4, 7, and 10)

the diversion structure during 1984.
HHI

.., ...

M 75

"nn

.... ,

100 125 151:)

LENGTH (mm)

LEGEND: - INSIDE

.............,....,.. 

175 2 !':Jfj 225 250

""-m..m.. OUTSIDE

Figure 6.30 Cumulative length-frequency analysis of croaker collected by the nekton

trawl inside (Stations 6, and 13) and outside (Stations 1 4, 7, and 10) the dive~ion structure during 1984. 

100

... 

~- 25

...,....,......,,, .. 

" I

LEGEND:

HJ0 125 150

LENGTH (mm)

INSIDE

Figure 6.

"".............m......................-----------------.....

, , ,,

175 20B 225 2SEI 275

"""-nm... OUTSIDE

Cumulative length-frequency analysis of menhaden collected by the nekton

trawl inside (Stations 5, 6, and 13) and outside (Stations 1, 4, 7, and 10)

the diversion structure during 1984.
0"\

+:0

L I~

g WlL

82JIl

12JlII

21mY

81mY

100"

2!.HIHB

mill

INSIDE

1mE(

2i'IIIJJ

8ml))

170n

2SSEP

845EP

OUTSIDE

18Of(

2i'111JJa8i'IIIJJ

170(11

2SSEP 884SEP

l$AlIi

24JlL 482JIL

12JII

E limY 8

almY

I00Pl/

2!HB

eifEl

ml'fl

.....,

188 128 118 Iii 188 28B 2(8 218 268

LENGTH (mm) .

Figure 6. 32 Length-frequency distributions of menhaden collected by the nekton trawl inside (Stations 5, 6, and 13) and outside (Stations 1 , 4, 7, and 10) the diversion structure during 1984.

28 48 68 88' 188 128 148 Iii 188 288 228 218 268

LENGTH (mm)
ENTRAINMENT

I ntroduct i on

Studies to determine the species composition, seasonality, and

abundance of entrained larval and postlarval fish, penaeid shrimp, and

portunid crabs at the BSEP have been conducted by CP&L as part of its

long-term monitoring program since September 1978. Prior to that

entrainment studies were conducted by NCSU from May 1974 through August

1978. In addition , the results of studies conducted since July 1983 are

used to determine the effectiveness of flow minimization and fine-mesh

screens on reduci ng entra i nment.

To determine reductions in entrainment due to fine Jmesh screens, a

speci a 1 study was imp 1 emented whereby samp 1 es were co 11 ected from the

two types of intake screens (9. 4- and 1-mm mesh) during comparable time

periods. Three such comparative studies were completed; one each in

November 1984, December 1984, and January 1985.

Methods

The collection gear, sampling methods, and sample processing have

remained unchanged since 1982. For further discussion, .refer to . CP&L

(1983).

The ideal conditions under which to measure reduction in entrainment due to fine-mesh screens would be to have each unit operating a

different screen type simultaneously. However , due to plant operating

restrictions, this was accomplished only during the December study.

During the November and January studies, the samples were collected from

the two types of screens in two consecutive 24- hour periods.

In all three studies, the samples were collected according to approved entrainment samp 1 i ng procedures. The November and December

studies had additional samples collected at 0600 and 1800 hours.

Because of an overlap in operation of screen type, the 0300 samples were

de 1 eted from the ana lys is for the Janu ary study.
ANOVAs were performed testing week, period, and tide effects as

well as all two-factor interactions. All ANOVAs and DMR tests were

performed on loge transformed numbers and densities. Results are

presented at the P ~ 0. 05 significance level.

Results and Discussion

Domi nant Speci es

In 1984 the dominant organism entrained was Gobiosoma spp. which

comprised 24% of the mean density of all organisms entrained. Croaker

ranked second with 16% , while spot and Anchoa spp. ranked third and

fourth, respectively, at 15% each. The other top-ranked species, in

decreas i ng order of abundance, were bay anchovy, portun i d mega lops

Penaeus spp. postlarvae, silversides, blennies, Microgobius spp.,

menhaden, and Gobionellus spp. (Table 7. 1).

Seasona 1 i ty and Abundance

The seasonal ity or periods of abundance for the selected species

analyzed remained the same as in previous years (Table 7. 2; Figures

11).

Croaker reached a peak density of approximately 1896/1000m3 in midJanuary. Flounder achieved a peak density of 12/1000m in late

February. Menhaden peaked at 151/1O00m in early April, mullet at

26/1000m3 in late February, spot at 1857/1000m3 in mid-March , anchovies

at 1179/1000m3 in late June, 

Gobionellus spp. at 163/l000m3 in mid-March

Gobiosoma spp. at 2028/l000m3 in late May, and seatrout at 13/1000m3 in

early June. Of the shrimp, pink and white shrimp had a peak abundance

of 186/1000m 3 in mid-September and brown shrimp peaked at 108/1000m3 in

late June (Table 7. 2).

Number Entrained

Entrainment rates were computed by multiplying the mean density per

day by the mean flow per day. The mean daily flow of cooling water
through the BSEP ranged from 1. 5 x 106 m3 in April to 4. 5 x 106 m 3 in

September and early October (Table 7. 3).

The rate of total fish entrained ranged from 6. 6 x 10 /day in midJanuary to 2. 2 x 1O /day in mid-November. For the species analyzed,

croaker were entrained at a maximum rate of 5. 8 x 1O /day in midJanuary, flounder at 3. 7 x 10 /day in late February, menhaden at 3. 1 x

/day in mid-March, mullet at 7. 7 x 10 /day in late February, spot at

5 x 1O6/day in mid-March, anchovies at 2. 6 x 1O /day in late June,

Gobionellus spp. at 3. 9 x lO /day in mid-March, and Gobiosoma spp. at 4.

x lO6/day in early June. Pink and white shrimp had a maximum entrainment rate of 5. 1 x lO /day in late September and brown shrimp of 2. 4 x

/day in late June (Table 7. 3).

Diel Patterns

ANOVAs performed on all species analyzed showed that entrainment

densities were significantly different between day and night. In all

cases, DMR tests ranked nighttime densities greater than daytime densities. This was consi stent with previous years I data (CP&L 1983) (Figure

12).

Entrainment Special Study

When all data from the three study periods were combined, only

anchovi es, croaker , spot, Gobionellus spp., and total fi sh appeared in

sufficient numbers to be analyzed accurately.

All species, except spot, were entrained in larger numbers and

densities at night. The ANOVA for spot numbers and densities showed no

significant difference between periods.

All species, except Gobionellus spp., were entrained in larger

numbers and dens i ties through the standard-mesh (9. 4-mm) screens. The

ANOVA and DMR test for Gobionellus spp. densities showed no significant

difference between screen types. However, Gobionellus spp. numbers were

significantly higher through the standard-mesh screens.
For the three study periods combined, a total of 153 fish was

entrained through fine-mesh (l-mm) screens for mean density of

99/1000m A total of 973 fish was entrained through standard-mesh

screens for a mean density of 543/1000m These figures represent an 84%

reduct ion in total number and an 82% reduct i on in mean dens ity 

entrained organisms due to fine-mesh screens. For the species analyzed,

anchovy dens it i es were reduced 69%, croaker dens it i es 88% spot

densities 58%, and Gobionellus spp. densities 70% (Table 7. 4).

Flow Minimization

In June 1981 , plant operations enacted a partial flow minimization

regime whereby the amount of water withdrawn from the estuary for

cooling purposes was reduced (Figure 7. 13). In July 1983, a more

drastic flow-reduction schedule was employed. This schedule called for

a maximum flow of 915 cubic feet per second (cfs) (25. 9 cubic meters per

second (cmsJ) during three-pump operation and a maximum allowable flow

of 605 cfs (17. cms) during two-pump operation. The delineation

between two- pump and three-pump operat i on was dependent on intake water

temperature. At water temperatures 65O F (18. C) and above

(approximately the end of April), three- pump operation was allowedn

below that (approxmiately the end of November) only two-pump operation

was used. A further restriction required that two of the three traveling screens on each unit must be equipped with fine mesh.

To determine reductions in entrainment due to flow minimization , a

comparison using observed entrainment numbers was made between historical flows (pre-January 1981; Hogarth and Nichols 1981) and the observed

flows.

For the peri od from January 1981 through June 1983, the mean number

of total fish entrained per day was 3. 6 x 10 6 and the average plant flow

was 843 cfs (23. cms). Using the historical mean flow of 1149 cfs

(32. 5 cms), the mean number would have been 4. 9 x 10 The percent

reduction in number entrained per day was 26. 5% (Table 7. 5).
During the period from July 1983 through November 21, 1983 , the

mean number of total fish entrained was 1. 3 x 106 with an average plant

flow of 818 cfs (23. 2 cms). The mean number using the historical flow

of 1185 cfs (33. 6 cms) would have been 1. 8 x 10 The percent reduction

between the historical and observed numbers was 27. 8% (Table 7. 5).

From November 22, 1983, through April 1984 , intake water temperatures were be 1 ow 65 o f (18. 3 a C); therefore on 1 y two- pump opera t i on was

permited and the corresponding traveling screens had to be fine mesh.

However, some samples were collected during times of debris filter

cleaning when a third pump (standard mesh) was activated as allowed by

the permit. The number reported has been adjusted to reflect only finemesh entrainment. These periods of three-pump operation are also the

reason that the observed plant mean flow is h i gher than the perm it ted

605 cfs. The estimated hi storical mean number for 1105 cfs (31. 3 cms)

was 9. 7 x 10 , and the observed mean number for 610 cfs (17. 3 cms) was

4 x 105 This represents a 44. 3% decrease in entrainment due to flow

minimization. By applying the 82% decrease in density due to fine-mesh

screens calculated from the entrainment special study (Table 7. 4), the

estimated historical number for 1105 cfs through standard mesh screens

is 5. 4 x 10 The difference between th i s and the observed mean number

of 5. 4 x 105 for 610 cfs through fine-mesh screens represents a 90%

decrease due to both mod i f i cat ions (Tab 1 e 7. 5).

For the peri od from May 1984 through October 29, 1984 , the observed

number was a 28. 6% reduction from the estimated historical number.

The period from October 30, 1984, through April 18, 1985, was

another time of two-pump, fine-mesh screens only operation. Again, we

see a 90% decrease in number entrained due to both flow minimization and

fi ne-mesh screens.

Summary and Conclusions

In 1984 , studies were conducted to determine the species composition seasonality, and abundance of entrained larval and postlarval
fish, penaeid shrimp, and portunid crabs. The results were also used to

determine the effectiveness of flow minimization and fine-mesh screens

on reducing entrainment.

The domi nant organ i sm entra i ned in 1984 was Gobiosoma spp. It

compri sed 24% of the mean dens i ty of all organi sms entrained. The other

top-ranked speci es, in decreas i ng order of abundance, were croaker

spot, Anchoa spp., bay anchovy, portunid megalops, Penaeus spp.

postlarvae, silversides, blennies, Microgobius spp., menhaden, and

Gobionellus spp.

The periods of peak abundance for all species analyzed remained the

same as in previous years. The pattern of diel variation also remained

the same--night densities were significantly greater than day densities. For all species, the greatest daily average of numbers of organisms entrained occurred during the period of peak abundance.

speci a study was conducted on three occas ions to compare

entrainment densities and numbers between standard-mesh screens and

fi ne-mesh screens.. For all speci es analyzed, except spot, the die 

vari at i on was the same as for entrainment. Except for Gobionellus spp.

significantly higher densities of entrained organisms occurred through

the standard-mesh screens. Overall, there was an 82% reduction in

densities and an 84% reduction in numbers due to fine-mesh screens.

Estimates of the historical mean number entrained per day based on

observed values were used to determine the reduction in entrainment due

to flow minimization. The percent reduction ranged from 26. 5% to 47. 4%.

There was also an estimated 90% reduction between historical and

observed estimates due to the combined effectiveness of fine-mesh

screens and flow minimization.
Tab 1 e 7. 1 Mean density and percent total of fish, penaeid shrimp,

and portunid crabs entrained, September 1978-August 1984.

Speci es

Gobiosoma spp.

Croaker

Spot

Anchoa spp.

Bay anchovy

Portunid megalops

Penaeus post 1 arvae

Si lversides

Blennies

Microgobius spp.

Menhaden

Gobionellus spp.

September 1978 -

August 1983

Dens ity Percent

September 1983 -

August 1984

Dens i ty Percent

373

170

164

191

177

235

145

22.

10.

10.

11.0

10.

14.

143 24.

16.

15.

15.

1.0

1.0

1.0

1.0

7 -
Table 7. Entrainment densities (mean per day) at the BSEP from September 1983 through Apri I 1985.

Samp I e Total Gob i 0- Gob i 0-

Date Fish Croaker Flounder Menhaden Mu Ilet Shr I mp Spot Anchovy nellus soma Seatrout

06SEP83 398. 52, 77 . 190.

13SEP83 241 . 185. 26. 22. 75.

20SEP83 170. 43. 39. 66.

27SEP83 148. 113. 50. 60.

040CT83 69. 17. 31. 20.

IlOCT83 99. 11. 44. 32. 18.

180CT83 27 . 23. 14.

250CT83 92. 30. 17. 30.

01NOV83 62. 13. 21. 23. 13.

08NOV83 85. 17. 19. 55.

15NOV83 19. 10. 10 .

22NOV8329NOV83 21. 17. 00 '

06DEC83 34. j 4 .

-.J 13DEC83 77 . 52. 15.

20DEC83 240. 134. 15.

27DEC83 191. 129. 50.

04JAN84 283. 249. 20.

10JAN84 332 277 33.

18JAN84 172. 895. 185, 46.

24JAN84 046. 882. 161,31 JAN84 235. 176. 44.

07FEB84 583. 120. 11. 422, 14.

14FEB84 137. 14. 105.

21FEB84 372 . 46. 10. 15. 271. 10.28FEBB4 485. 15. 12. 26, 373. 26.

06MAR84 581 42. 434.

13MARB4 201 20. 131 10. 19.

20MAR84 281. 55. 128. 24. 856. 23. 163.

27MARB4 465. 32. 59. 331. 22.

03APRB4 221 . 23. 26. 133. 15.

10APR84 629. 52. 151. 366. 13.

17APRB4 398. 152. 33. 121. 33.

25APRB4 302. 153. BO. 13. 29.
Table 7.2 (continued)

Samp I e Total Gobio- Gob i 0-

Date Fish Croaker Flounder Menhaden Mullet Shrimp Spot Anchovy nell us soma Seatrout

01 MAY84 521 222. 10. 62. 17 . 16.08MAY84 591. 139. 47. 58. 24. 55.

15MAY84 654. 50. 12. 358. 65.

22MAY84 066. 10. 471. 11. 300.

29MAY84 098. 762. 026.

05JUN84 919. 11. 494. 24. 282. 13 .

12JUN84 181. 399 736.

19JUN84 707. 22. 809. 787.

26JUN84 308. 108. , I 78 . 044

02JUL84 671. 24. 274. 265.

IOJUL84 745. 14. 292. 376.

17JUL84 161. 42. 47. 60.

24JUL84 423. 60. 319. 67.

'-I 31 JUL84 335. 63. 261 . 33.

07AUG84 140. 35. 98. 21. I.D 14AUG84 66. 29. 49.

21 AUG84 278. 40. 189. 60.

28AUG84 222. 90. 137. 34.

04SEP84 84. 50. 44. 24.

18SEP84 90. 14. 17. 23. 25.

25SEP84 141 39. 25. 13.

020CT84 193. 31. 36. 89.090CT84 261. 104. 99, 53.

160CT84 335. 288. 27 . 18.

230CT84 198. 1 54 . 11. 34.300CT84 78. 65.

06NOV84 68. 56.

13NOV84 29. 19.19NOV84 19.

27NOV84 52. 33. 14.

04DEC84 29. 19.

11 DEC84 213. 040. 11. 65,

19DEC84 26. 16.

26DEC84 25. 15.
Table 7. 2 (continued)

Samp I e Total Gob i 0- Gob i 0-

Date Fish Croaker Flounder Menhaden Mullet Shr imp Spot Anchovy nell us soma Seatrout

02JAN85 38. 33.09JAN85 210. 118. 39. 34. 10.

16JAN85 104. 63. 29.

24JAN85 256. 175. 69.

31 JAN85 257. 106. 127.

06FEB85 190. 57. 125.

13FEB85 328. 95. 227

20FEB85 271. 93. 166.27FEB85 73. 12. 51.05MAR85 310. 39. 246.

13MAR85 696. 28. 11. 25. 623.

20MAR85 344. 49. 71. 278.

27MAR85 436. 34. 25. 46. 343.

--..J 03APR85 129. 15. 10. 44. 47.

IOAPR85 478. 20. 151 34. 162. f-'

17APR85 485. 35. 61.
Table 7 Entrainment rates (mi II ion number per day) at the BSEP from September 1983 through Apri I 1985.

Sample

Date

Mean f low

(Mi II ion

cubicm Flounder Menhaden

TotalFish Croaker

......

'-JI-'

06SEP83 4.478 1.785 0.000 0.000 0.000

13SEP83 4.478 1.083 0.000 0.000 0.000

20SEP83 4.478 0.763 0.000 0.000 0 00027SEP83 4.478 0.666 0.006 0.000 0.000 o4o~l8r---.r:418-----(r~311 0 ~OOO 0 ~OOO 0.000 110CT83 4.478 0.446 0.051 0.000 0. 000 180CT83 3.719 0.104 0.005 0.000 0. 000 250CT83 3.719 0.344 0.115 0.000 0.000

6lNOV83 

.. 

480 - 0.092 0.019 O~OOO - - 0.000

08NOV83 2.929 0.249 0.052 0.000 0. 000

15NOV83 3.156 0.060 0.032 0.000 0. 000

22NOV83 2.398 0.022 0.008 0.000 0.000

29NOV83 2.398 0.051 0.042 0.000 0. 000

(y6DFC1n----- 39r-~- O~OB.

)

O~ozr -- cf:ooo - 0. 005

13DEC83 2.398 0. 186 0 126 0.000 0. 000

20DEC83 2.796 0.672 0.375 0 000 0. 000

27DEC83 2.398 0.460 0.310 0.000 0.000 04JA~2.3 8--

- D~()8 r- ---- 599- ()OO--- O~.(roo 10JAN84 2.961 0.985 0.822 0.000 0.000

18JAN84 3.037 6.598 5.758 0.000 . 015

24JAN84 2.961 3.099 2.613 0.007 0. 000

31JAN84 2.961 0.696 0.522 0.000 0. 000

07Fm84----L.9or- T~12~- 0. 358 :oT6-m".-O:OO8 14FEB84 2.961 0.408 0.044 0.000 0.000

21FEB84 2.961 1. 102 0. 137 0 030 0. 000 28FEB84 2.961 1.437 0.045 0.037 0. 014

06MAR84 - 2~2~----1~28if----o~69-

004 ----- o:oli

13MAR84 2.398 0.484 0.050 0.012 0.013

20MAR84 2.398 5.470 0.134 0.020 0. 308

27MAR84 1 .556 0. 725 050 002 0. 093

03APR84

()-:328- 0.035 0----- 0-;040--- 10APR84 1.480 0.932 0.078 0.003 0. 224

17APR84 1.480 0.590 0.226 0.000 0. 050

Mullet

000000000000

0 :000

000

000000000000

000000000000

000000005

O~(JOo

000006000007

0:034

013045077

6:054

006059000 

0-:066--

000000

Shrimp

Gob i oneil us Gob i 0- soma Seat rout Spot Anchovy

237 0.000 0.349 0.035 0.851 0.024 833 0.000 0. 121 0.100 0.337 0.018 196 0.000 0. 177 0.039 0.299 0.000 509 0.000 0.224 0.034 0.270 0 000 078 0.000 0. 141 

;029----" 92---- 0:000 - 200 0.000 0. 144 0.084 0.028 0.000 088 0.000 0.020 0.054 0.000 0.000 128 0.000 0 064 _(). ~15 - 0.000 0.000 032 0.000 0.034 0.019 0.000 0.000 058 0.000 0. 163 0.023 0.000 0.000 032 0.000 0.009 0.009 0.000 0.000 000 0.000 0.005 0.009 0.000 0.000 005 0.000 0.005 _JJ.Oo.~n 

(). D.QO_

_JJ_ OOQ. 000 0.000 0.034 0.013 0.000 0.000 000 0.000 0.038 0.000 0.000 0.000 000 0.000 0.244 0.042 0 000 0 000 000 0.010 0. 122 0.005 0.000 0.000 

Cf-:-()()O----0~O()5-----o.04-r--()-:-0()0~ 

D:(JOlr~~OOO 000 0.044 0.099 0.000 0.000 0.000 000 0.564 0.141 0.000 0.000 0.000 000 0.478 0 000 0 000 0 000 0.000 000 0. 133 0.006 0.000 0.000 0.000

000 1 252 0.043 - 0:000-----0:000--0:000- 000 0.311 0.005 0.000 0.000 0.000 000 0.804 0.032 0.000 0.000 0.000 000 1. 105 0.079 0.021 0.000 0.000

000 962 004- ---0:006--- 0:660

0:000---- 000 0.315 0.024 0.046 0.000 0.000 028 4.452 0.057 0.391 0.000 0.000 010 0.516 0.004 0.035 0.000 0. 000

~Oi2--- ir:198- 0:o66----0:02:f obd 0. 000 000 0.542 0.020 0.014 0.000 0 000 005 0. 180 0.050 0.012 0.000 0.000
Table 7 3 (continued)

Sample

Date

Mean flow

(Mi II ion

cub i c m.

yc;",v-1Jc.ktl'1~C;$rr.

C'tY'o,c""", "(Ii' Total

Fish

i\tlt.L"It;'c...

Croaker f\tlc..1~'c.. Flounder Menhaden

......

'-.J

25APR84 1 . 480 ___ 448 __

_Q.l~__ 9QP__~_Q._QQ_ 01MAY84 2,239 1 168 0.498 0,000 0.013 08MAY84 2.239 1.325 0.311 0,000 0.000 15MAY84 2.239 1.466 0. 114 0,000 0.000

22MAY84 2.239 2.387 0.013 0.000 0.00029MAY84 480 4.585 0.004 O O~Q_ Q,-~QQ- 05JUN84 - 239 

8- 0.003 0.000 0 000

12JUN84 1.480 1 749 0.000 0.000 0. 000

19JUN84 2.268 6. 140 0.000 0,000 0. 000 26JUN84 2.239 5. 168 0.000 0.000 0 000

02JUI84 2.239 ~O4 - :000 --- O~OOO 0. 000

10JUL84 2.239 1 668 0.000 0.000 0.000

17JUL84 2.355 0.379 0,000 0,000 0. 000 24JUL84 2.239 0.948 0.000 0 000 0. 000

31JUL84 2.239 0.751 0.000 0 000 0. 000

n____ --- u

_

u_-- 

07AUG84 2.239 0.314 0.000 0 000 0 000

14AUG84 2.239 0.149 0.000 0 000 0. 000

21AUG84 2.239 0.624 0.000 0.000 0. 000

~~UG~"---_ ___ ~~- 0. 000 ..o_Q~- .o..!.OOQ --D4SEP84 2.239 0.189 0.000 0 000 0 000

18SEP84 2.588 0.233 0 036 0.000 0. 000

25SEP84 - 156

__

- 0.447 0._ 126 - 0.000 0. 000 020CT84 3.719 0.719 0. 117 0.000 0. 000

090CT84 3.719 0.973 0.389 0.000 0. 000

160CT84 3.532 1. 186 1 020 0 000 0. 000

230CT84 3.719 0.738 0.575 0.000 0. 000

300CT84 579 0 124 0 104- O OQQ Q... QQa. 06NOV84 1 .480 0. 102 0.083 0.000 0. 000

13NOV84 2.398 0. 122 0.072 0.000 0. 000

19NOV84 1 635 0 036 0 013 0.000 0.000

27NOV84 2.961 0. 156 0. 100 0.000 0.000

040EC84 - -

07 ------O~O48-----o-=6ob

0 :006 - 

110EC84 2.961 3.592 3.081 0.033 0,000 190EC84 2.961 0.080 0.050 0.000 0.005

(YIv

(;

Mullet

000

000

000000000

..9_C&...._-

000

000000000004000000000000

000000000000

OOC000000

000000000000OOC)

000000000

000

6~ooo

000

000

Y-h-rf mp

007 0, 119 023 0. 139 009 0. 106 010 0, 027 023 0. 007

Q... OQCL- - O. QQG - - 025 0 000 005 0,000 050 0. 000 242 0. 000 055 0. 000 031 0. 000 100 0. 000 136 0. 000

0 . 14 .3.._- o.~OO() u 079 0, 000 067 0. 000

091 0 000 202 0. 000 ' 12 0, 000 045 0. 000 079 0.000. 135 0. 000 017 0, 000 011 0 000 043 0. 000

009 0 000 -

010 0 000 083 0. 000 005 0. 000 000 0. 000

cf. 060 6;600 000 0 000 000 0. 000

P'M;".-

..~ f- Gob i oneil us

r -

Gob i 0-

Spot Anchovy soma Seatrout

020 0.043 0.000 0.000 039 0.036 0.000 0.000 131 0.055 0 124 0. 003 802 0.013 0. 190 0. 004 055 0.026 0.673 0. 000

_

J, 115L- - - - 0_ .QOJL____ QQ2-

___

.Q9_ 106 0.056 0 633 0, 031 591 0.002 1 090 0 005 837 0.000 4,053 0. 007

..2....6.39_____0...o.Ol.--- 2 .338--- 0....00.0 615 0.003 0.595 0. 003 654 0.000 0.842 0. 017

113 0 006 0 142 0. 013 714 0.010 0, 151 0.0\6

- 0 5~6 0.042 - 0 ()76 - 0.003 220 0.007 0.048 0. 003 111 0.010 0.017 0, 000 425 0.003 0, 136 0 013 306 0.019 0,078 0. 009 ci:099- O03 

0 :OS4 

- 0:000 060 0,065 0.014 0 004 236 0.-04.1 D._ODD 0.010 333 0.186 0.011 0.000 370 0. 197 0.011 0. 000 096 0.065 0.000 0. 000

127 0 029 0 000 0.000

003 0 01.4 0 000- 0.000 009 0,003 0.000 0. 000 005 0.046 0.000 0. 000 009 0.009 0.000 0.000

013 0 044 0 000 0 000 

_____n_n______

005 0.012 0.000 0. 000 221 0. 193 0.000 0. 000 005 0.015 0.000 0.000
Table 7. 3 (continued)

Sample

Date

Mean flow

(Mi II ion

cubic m. Croaker Flounder Men haden Anchovy

Total

Fish Mullet

Gob i oneil us Gob i 0- soma Seat rout Shr imp Spot

......

-...J

26DEC84 2.961 0.077 0.046 

_ 

_

02JAN85 2.961 0. 114 0.099

09JAN85 2.961 0.623 0. 352

16JAN85 2.961 0.310 0. 188

24JAN85 2.961 0.760 0. 51931 JAN85 003 0.773 0. 319

06FEBB5 2 . 61-- 563- Tid

13FEB85 2.961 0.974 0. 283

20FEB85 2.961 0.804 0. 27627FEBB5 961 0.217 0.022

MAR85 

2--:96 r

O:-gnr o:TT1---- 13MARB5 2.454 1.708 0.069

20MAR85 2.961 1 021 0. 147

27MAR85 961 294 0. 10303APRB5

835 -~237----- 029

10APR85 2.398 1. 147 0.05017APR85 2.398 3.561 0.013

000

6~o60

005

005005000606- -

000000006

0:010 -

022000

028

- 6.006 - -

000000

000 0.000 0.005 Q.QQ.---- !.!_n_SJ.. Q------ C!PO 

Q... _

0:000 :00-6------0;605

0:000 - 011 0.000 0.000 0. 000 000 0 118 0.000 0. 102 0.030 0.006 0.000 0. 000 000 0.005 0.000 0.087 0.019 0.005 0.000 0. 000 000 0.026 0.000 0.204 0.005 0.000 0.000 0. 000 008 - 0 024 0.000 0.383 0.015 0.000 0.000 0 000 000 0.005 - 0.000-- - - 0~371 (j~Or6 - 

()

~odo M6 - ---0:000 000 0.006 0.000 0 674 0.012 0 000 0.000 0. 000 000 0.006 0.000 0.492 0 018 0 000 0 000 0. 000 000 0.037 0.000 0. 152 0.000 0.000 0.000 0. 000 

O:OT6-- o:6T5

o:ciTs-- - --0:729 - --- 01'6--- 00- 000

0;-6- 028 0.000 0.062 1.531 0.017 0.006 0.000 0.000 014 0 014 0.210 0.825 0.000 0.007 0.000 0. 000 076 0.000 0. 139 1.018 0.000 0.051 0.008 0. 000

020 0 006 0:OB 0:0Bo

0:005

o:oatr- o:m)O ~OOO 363 0.004 0.083 0 390 0.010 0.005 0 000 0. 000 084 0.005 0. 148 0.036 0 009 0.005 0.005 0.000
Tab 1 e Reduct i on in entrainment by number and mean dens ity

(#/lOOOm ) for selected species for the three special study

periods.

Gobionellus Total

Anchovies Croaker Spot spp. Fi sh

Number

9. 4-mm screens 690 125 973

1-mm screens 153

Reduct i on 68% 90% 71% 67% 84%

Dens ity

9. 4-mm screens 387 543

1-mm screens

Reduct i on 69% 88% 58% 70% 82%
Table 7. Comparative reductions in entrainment of total organisms due to flow minimization.

Observed Hi storical

Time Period Dens i ty Flow Number/Day Flow Number/Day Percent Reduction

(#/1000 m (cf s)

January 1981-June 1983 1759 843 3 . 6 x 10 1149 4 . 9 x 10 26.

July 1983- November 21, 1983 632 818 1. 3 x 10 1185 1.8 x 10 27.November 22, 1983-Apri 1 1984 359 610 4 x 10 1105 9.7 x 10 44.

November 22 , 1983- Apri 1 1984 1994 610 0 x 10 1105 4 x 10 44.

May 1984-0ctober 29, 1984 705 884 1.5 x 10 1205 1 x 10 28.

-..J October 30 , 1984-Apri 1 18 , 1985 289 580 1 x 10 1105 8 x 10 47.

c 1606 3 x 10 4 . 3 x 10 October 30, 1984-Apri 1 18, 1985 580 1105 46.

Adjusted for fine mesh only.

Estimated number of total organisms entrained/day.

Calculated increase in entrainment without fine-mesh screens based on results of special study (Table 12).

Calculated number that would have been entrained without fine mesh or flow minimization.

NOTE: Difference between b and d is a 90% reduction in entrainment because of flow minimization and

fine-mesh screens.
I R. 8

~ S.c:J

........

--J

~ 2.

DATE

Figure 7. Density of total fish entrained at the BSEP from May 1974 through August 1984.
'-J

'-J

CI)

11).

....I

::iii:

Figure 7.

OAT(

Density of croaker entrained at the BSEP from May 1974 through August, 1984.
" 2

in 

CIO

t:J

,.....--..J

::!:c( , w '

DRH

Figure 7. Density of flounder entrained at the BSEP from May 1974 through August 1984.
3-;

Ci) aJ 

..J

....

-...J

DA J(

Figure 7.4 Density of menhaden entrained at the BSEP from May 1974 through August 1984.
.......

ii)

II)

t.:J

..J

on J(

Figure 7. Density of mullet entrained at the BSEP from May 1974 through August 1984.
...J

"-J

I-~

I I 

ORa

Figure 7. Density of shrimp entrained lit the BSEP from May 1974 through August 1984.
...... ..... !:::

..J.

c:(

. 3

OAT(

Figure 7. Density of spot entrained at the BSEP from May 1974 through August J 984.
18.

--..J

ii)ffi 5.

.:( 2.

OArr

Figure 7. Density of anchovy entrained at the BSEP from May) 974 through August 1984.
...

-.J ..J

1':-

OAf(

Figure 7. Density of Gob;one/lus spp. entrained at the BSEP from May 1974 through August 1984.
18. 8'"

7. 5

-....J

ffi 5.

~ 2.

OAf(

Figure 7.10 Density of Gob;osoma spp. entrained at the BSEP from May 1974 through August 1984.
.......

r'0

...1

. I

. Dna

Figure 7.11 Density of seatrout entrained at the BSEP from May 1974 through August 1984.
J0"" "1

1 200B--I11000

10ee0

90130

.......

1')

aEIO"";

::;.

I;; 713138

::J

.E 6000~ seee1.11

40ee

3eee213130

1 B0E1

, ) . ,

I' , , I II 

r I , II I' I

J I ,, I

'II I . 

~I ( I I I' 

I.. \J \-J

\..

YEAR

DAY

----- NIGHT

Figure 7.12 Entrainment day/night mean densities for total fish, September 1974 through August 1984.
-...J

CXJ

JANUARY

1981

I ~

Figure 7.

JUNE

1981

.(

91 5 cIs

JUI Y NOVEMBER 1983 1983 MAY 1984 OCTOBER 1984 APRIL 1985

~ I

FINE MESH

Ie "nd "1

915 cis

I FINE 

MESH I

915 cIs

FINE MESH I'" and "

605 cis

I FINE MESH I

605 cis

Time line depicting initiation dates of the Brunswick Steam Electric Plant modifications and maximum

flow lunit from June 198 t through April 1985.
SURVIVAL STUDIES

Introduction

Survival studies were initiated in early 1984 to determine what percentage of organi sms impi nged on the travel i ng screens and transported

down the return flume are returned to the CFE alive. Specifically, these

studies examined survival by species and size class in addition to speed

and mesh size of the traveling screens. Emphasis was directed towards

those species that are consistently dominant in either the larval or

juvenile/adult impingement programs.

Methods

The logistics of collecting organisms from the intake traveling

screens during plant operation produced many unexpected variables in the

data set. Percent survival was examined for as many species and size

classes as time, laboratory space! and species availability allowed.

Co 11 ect i on

Imp i nged organ isms were washed off the screens into the two- trough

fiberglass return sluiceways. Collections were made at the end of the

37- km flume where it emptied into the 3. 24- hectare return basin (Figure

1.3). At first an oversized "plankton bucket" was used to collect the

smaller organisms. The bucket, similar in shape to the cup on a larval

net, measured 1.5 m tall by 27. 9 cm in diameter , with 1-mm mesh screening. Several 15-second samples were usually taken. Beginning in May, a

larval table similar to one used by McGroddy and Wyman (1977) was utilized

that allowed for a longer sampling duration while decreasing mortality

associated with collection. Water from the return flume flowed through a

lO. 2-cm diameter PVC intake pipe onto the table where it spread out and

reduced velocity. The organisms were then funneled into a relatively

undisturbed collection basket. The table was used for the duration needed

(usually 3 to 10 minutes) to obtain statistically sufficient numbers. The

larger juvenile and adult organisms were collected with a 9. mm bar-mesh
net fitted on a frame that conformed to the shape of the return fl ume.

Sampling duration was limited to approximately three minutes.

Contro 1 organi sms were co 11 ected from the intake canal us i ng several

different gear types. Initially for collection of the smaller size

classes, a 1-m diameter 505- )..Im mesh net with the oversized II plankton

bucket II was used. After June 10, 1984 , a similar net with 1-mm mesh was

utilized. Smaller juveniles were collected with a 3. 2-m two-seam trawl

with a body of 4-mm bar mesh and a cod end of 2-mm knitted mesh.

Occasionally when control organisms were scarce or larger size classes

were needed, a 6. m semiballoon otter trawl with a 18. 1-mm bar-mesh webbing and a 6. mm bar-mesh cod end was used. To keep mortality associated

with collection at a minimum, all tows were as short as possible, usually

between one and three mi nutes (McCoy and Brown 1967). After each co 11 ection, organisms were transported to the laboratory for sorting and stocking into holding tanks.

Holding Facilities

The survival laboratory was located at the end of the return flume

adjacent to the return basin. Water from the intake canal was pumped

through an aeration tank to various size flow-through tanks to maintain

water quality as close to ambient as possible.

Housed in the laboratory were ten 92. liter round black tanks equipped with overflow valves and modified bottoms which allowed for flushing

of dead organisms and removal of poor quality water. Eight l1S.4- liter

glass aquaria were used for shellfish and those organisms such as flounder

and young-of-the-year mullet not requiring the round tanks (person. comm.,

W. F. Hettler, National Marine Fisheries Service). Four 769- liter tanks

were used for larger juvenile and adult organisms. Small portunid megalops and postlarval penaeid shrimp were held in 3. liter plastic buckets,

whi le juveni le crabs were held in individual SOO-ml cups to prevent cannibal ism.
Stocking and Monitoring

At the laboratory, organisms were placed on a lighted sorting table

and the targeted organisms sorted by species and size class. Efforts were

made to stock at least 30 1 ive organi sms per repl icate which were held for

a minimum of 96 hours to determine latent mortality. Live and dead organisms were then sorted and counted. During the 96- hour holding period

tanks were monitored hourly and any dead organisms were removed and measured. Water quality parameters (temperature and salinity) were checked

initially and at the end of 1, 3, 6, 9, 12, 18, 24, 36, 48, 60, 72, 84,

and 96 hours (Taft et ale 1981). The tanks were drained and all live and

any dead organi sms were counted and measured after 96 hours.

Definitions, Calculations, and Analyses

Initial mortality refers to those organisms that died before reaching

the laboratory. Latent mortality describes those organisms that died

after stocking. The summation of the two results in the total mortality. For reporting purposes, a percent total mortality and percent.

survival were calculated using the following formulae:

Initial Mortality + Latent Mortality Percent Total Mortal i ty x 100 Number of Organ isms Co 11 ected

Percent Survival = 100 - Percent Total Mortality

Occasionally more live organi!ms were collected than could be stocked. In

these cases, the atent mortality percentages were app 1 i ed to all 1 i ve

organisms prior to calculation of percent total mortality.

12.. f+I~

;

The intake travel ing screens rotate approximatel ~ 75 cm per 

slow-screen operation and between 2. 5 and 4 times faster during fastscreen operation. To examine the effect of screen speed on survival

analysis of variance (ANOVA) was performed on two size classes of croaker

and one size class of spot using the general linear models procedure of

the Statistical Analysis System. The model examined date, screen speed

and their interaction as factors with replicate nested in screen speed.
For all statistical analysis, a significance level of 5% (P ~ 0. 05) was

used. Prior to any analysis, an arcsine square root transformation was

mad~ to achieve uniform variance of the percentage data.

Results and Discuision

In assessing any stress-related effects on larval and postlarval

organisms, special handling methods and/or acclimation periods are usually

required (Hoss et a1. 1974 . 1977). The organisms sensitivity to handling

and holding often results in a reduced survival prior to any experimental

test i ng. To ascertain that fact, contro 1 organi sms were collected and

held. The survival percentages obtained from those controls are presented

along with the experimental percentages. No adjustments were made for

this mortality associated with collection or holding; therefore, the survival rates reported are conservative.

Total Organisms

Forty 96- hour survival studies were conducted from early February

1984 through the middle of April 1985; however , techniques for collection

handling, and holding were not standardized until late March 1984. From

the remaining 34 sampling dates, 15 taxa and over 21, 000 organisms were

collected and used in obtaining the survival percentages presented (Table 8. 1). Included among the 15 taxa collected are members of the commercially and/or recreationally important families found in the CFE:

drum , flounder mullet, herring, penaeid shrimp, and portunid crab. Other

taxa examined included members of the anchovy, sole, and searobin families.

Survival studies conducted during fast-screen operation resulted in

the collection of over 6600 organisms comprised of 14 taxa. Croaker and

striped mullet were placed in two groups for calculation of percent survival. Croaker 25 mm or greater in length were considered Group 2, while

striped mullet were grouped by young-of-the-year and juveni le/adult categories. During slow-screen operation, only 9 taxa but over 6200 organisms

were co 11 ected. Again. both croaker and spot were separated by size group
(Table 8.2). Almost 8800 organisms, including 14 taxa, were collected as

contro 1 s with every taxa represented except for menhaden (Tab 1 e 8. 3).

Croaker , spot, and striped mullet were again grouped to obtain more realistic and accurate estimates of the survival for each respective size

class.

Species Accounts

Croaker

Croaker were collected on 24 different dates including 21 occasions

during fast-screen operation and 18 times during slow- screen operation.

On a 11 but two dates, control organi sms were co 11 ected. Altogether , over

6000 croaker were collected for analysis, and almost 3000 were stocked and

examined for survivability at 96 hours.

Croaker exemplify the problems encountered in obtaining a particular

survival figure for any species. Results indicated poor survival of the

smaller sizes (9- 13 mm) during slow-screen operation but good survival of

these same sizes collected during fast- screen operation (Table 8.4). 

the organisms increased in size, survival also increased (Figure 8. 1).

The younger organisms collected from late October through December consistently showed less than 10% survival during slow-screen operation , while

those collected during fast-screen operation (12-mm fish) showed a survival ranging from approximately 10% on November 13 to almost 57% on

December 4. The effect of screen speed was less evident with the larger

size classes.

Controls consistently showed a mean survival over 90%. However on

October 15 , November 5, and January 23, unusually low mean survival percents were observed i nd i cat i ng a phys i ca 1 response by the fi sh to certa 

conditions. The low survival experienced by experimental organisms from

the first two dates does not reflect plant- induced mortal ity but mortal ity

from either " outside environmental conditions (fish stressed prior to

impingement) or from poor water quality during holding. The poor results

on January 23, 1985, reflects the extremely cold temperatures (3.

experienced during that week of collection.
Two additional dates showed low survival. On June 17 and 24 , 1984

the larger size classes (41-45 mm) collected during both screen speeds

displayed low survival. The possibility of exposure of these organisms to

ch lori ne in the spray wash water was thought to be the cause of the low

survival. It has been documented that three-minute exposure to chlorine

concentrations as low as 0. 13 ppm causes high mortality (Hoss et al.

1977) .

The results of ANOVA indicated that smaller organisms (~ 25 mm) collected during fast-screen operation showed significantly higher survival

than those collected during slow-screen operation. No significant difference in survi va 1 was seen between screen speeds for the arger organi sms

(:: 25 mm).

Overall during fast-screen operation, approximately 29% of all

smaller croaker survived the impingement process, while at least 36% of

the large croaker were returned alive. During slow-screen operation, only

10% of the smaller sizes survived, while 36% of Group 2 survived. Controls exhibited approximately 20% mortality for the smaller sizes but only

2% for the arger croaker.

Spot

Spot were analyzed on 14 dates involving 12 trials during slow- screen

operation and 8 trials during fast operation. Over 3500 experimental spot

were co 11 ected wi th an add i t i ona 1 2300 contro 1 s co 11 ected.

Results indicated that as size increased so did survival (Figure 8.2). Mean survival ranged from ~ 1. 0% on March 4 with 18-mm fish to

almost 77% on 88-mm fi sh on January 17, 1985 (Tab 1 e 8.5). Survi va 1 of

spot collected during fast- screen operation was consistently higher than

those collected during slow-screen operation. The low survival on June 17

again reflects the possibility of exposure to chlorine in the screen wash

water.
Results of the ANOVA indicated that small spot (0:: 25 mm) collected during fast-screen operation showed significantly higher survival than

those collected during slow-screen operation. The mean survival computed

for all dates during fast-speed operation was 31% compared to only 8% during slow-screen operation (Table 8.2). Small control organisms displayed an average mortality of 20% compared to 2% for the larger 

sizes.

Penaeid Postlarvae

Postlarval penaeid shrimp (9- 14 mm) exhibited high survival off the fine-mesh screens. Survival averaged 80% during slow-screen operation and

over 90% during fast-screen operation (Table 8.6). Controls indicated approximately 10% of the mortality was associated with the 

handling and holding of the organisms.

Pink and White Shrim

Due to the difficulty in identifYing young penaeid shrimp at species level the without additional handling, pink and white shrimp were combined during collection and analyzed as one group. Overall , they showed excellent survival regardless of size class or screen speed. Sur- vival ranged from a low of 81.

2% with 51-mm shrimp collected during slowScreen operation to a high of 100% on two dates in 

October with shrimp of

approximately the same length collected during fast-screen operations (Table 8.6). Control data indicated high survival with approximately 8%

mortality associated with collection and holding.

Brown Shrim

Survival data on the brown shrimp were obtained only on the larger size cl asses wi th mean engths rangi ng between 72 and 143 mm. Three stud- ies were conducted during slow operation and two during fast operation (Table 8. 6). Overall , survival was slightly better during slow-screen operation than during fast (approximately 90% to 70%). However , two fac- tors influenced the percent survival on those 

collected during fast-screen operation. First, during the middle of August , molting occurred and
resulted in impingement of soft- bodied shrimp. This probably caused more

physical damage and a resultant lower survival. In addition , chlorine was

detected in the screen wash water on August 19, possibly causing some

stress to organi sms and lowered survi va 1 even more.

CoDtrol organisms showed a lower percent survival on the average than

the experimental organisms. This was, however, an artifact of the collection gear. The trawl used in collecting larger shrimp from the intake

canal occasionally became filled with silt, consequently clogging the

gills of the shrimp and causing some latent effects. When this was compounded with molting, organisms became stressed and an even lower survival

resulted. Survival percentages ranged from approximately 63% in August to

over 83% in June (Table 8.6). It appeared that plant impingement had

little effect on the survival of brown shrimp.

Blue Crab

Callinectes sapidus and C. similis were combined as Callinectes spp. during

collection, holding and, for analysis. These abundant and commercially

important species were held during nine dates. Experimental data for all

cases indicated excellent survival regardless of ife stage or screen

speed (Table 8.7). Survival ranged from over 82% to 100% for experimental

organisms with control survival ranging from 77% to 100%.

The survival of the megalop life stage of the blue crab collected

from the fine-mesh screens was examined on four different occasions (twice

at each screen speed) during October and November 1984. During these four

studies, 159 megalops were collected during fast-screen operation, 203

during slow operation, and 363 were collected as controls. A mean survival of 86% was obtained for all three groups indicating that neither

screen speed nor impingement had any effect on survival of blue crab megalops.

Juvenile blue crab consistently showed a mean survival over 85%

(Table 8.7) Five studies were conducted during September and October on

blue crab that averaged 22 mm. The average survival for those trials was
approximately 92%. Screen speed showed no effect on survival. Control

organisms displayed similar results with mean survival ranging from 85% to

100%. Again, the observed mortality may be associated with collection and

holding of the organisms rather than the actual impingement process.

Weakfish

In addition to croaker and spot of the drum family, weakfish was also

collected and held during four survival studies. All experimental organisms were collected during fast-screen operation. Survival was extremely

poor during the two dates in August and September; however, controls also

displayed low survival indicating a possibility of stressed organisms

prior to impingement or just confirming the delicate nature of weakfish

(Table 8.8). An improvement in survival (35%- 37%) was seen in October as

the organisms increased in size. Likewise, control organisms also

improved dramatically with over 94% of the individuals collected living

the full 96 hours. However , the few numbers collected prevent any conclusive statement of survival for weakfish.

Bay Anchovy

Bay anchovy showed no survival from the intake travel ing screens

during either fast- or slow-screen operation. A total of 845 anchovies

was collected from the return flume representing two size classes (20- and

33-mm mean length). Both groups showed no survival. Bay anchovies collected for control purposes also showed poor survival documenting the

inabil ity to collect 1 ive anchovies. Of 60 control anchovies collected

only 29% survived the 96- hour holding period which confirmed the statement

Stickney (1983) made concerning the mere removal of the bay anchovy from

the water which caused " almost instant mortality.

Striped Mullet

The survival of two different age classes of striped mullet was examined. Postlarval mullet (25 mm) showed a mean survival of 67. 6% collected

during fast- screen operation, while control mullet of this size exhibited
excellent survival of over 95%. Juvenile/adult striped mullet (150 mm)

showed excellent survival for experimental (91. 9%) as well as for control

organ isms (100%).

Flounder

Results from the only survival study conducted on flounder indicated

that postlarvae survived the impingement process extremely well. Collected during fast-screen operation, 13-mm flounder exhibited over 90%

mean survival. Control flounder indicated 5% of this can be contributed

to co 11 ect i on and ho 1 ding.

Menhaden

Few large menhaden were available for collection during survival

stud i es. Of the 32 menhaden co 11 ected with a mean ength of 95 mm, a

15. 6% mean survival was seen. No controls were collected, thus no determination of the percent mortality associated with collection and holding

was made.

Miscellaneous Species

Blackcheek tonguefish, searobin , and hardback shrimp were also collected in sufficient numbers for analyses.

Collectively, a total of 110 blackcheek tonguefish was collected

during fast-screen operation on three separate dates resulting in an overall mean survival of 83% (Table 8.9). Of 116 control organisms , 113

(97. 6%) remained alive at the end of the 96- hour studies. Mean lengths of

experimental and control organisms were 62 and 50 rom, respectively.

Four 96- hour survival studies were conducted on searobin from September 24, 1984, through October 19 , 1984. A total of 132 experimental

organisms with mean lengths between 21 and 27 mm was collected during

fast-screen operation. Searobin exhibited excellent survival with over

89. 0% survival. Control organisms indicate approximately 4% of this mortality is associated with collection and holding (Table 8. 9).
On October 29, 1984 , 123 hardback shrimp were collected during slowscreen operation. Survival for the two replicates averaged only 22.

(Table 8.9). No data from organisms exposed to the fast-screen operation

were obtai ned. Contra 1 s, as expected , showed exce 11 ent survi va 1. Th is

poor experimental survival is unexplainable considering the high survival

of the related Penaeus spp. Additional data are needed to conclusively

state survival percentages for hardback shrimp.

Throughout the study period, additional species not reported were

collected. These incidental species included mummichog, skilletfish

black drum, blenny, stargazer , and pipefish. Occasionally these species

were held for 96 hours, even though sufficient numbers were not collected

to statistically substantiate the high survival percentages obtained.

Summary and Conclusions

Intensive efforts were made to obtain accurate estimates of the percent survival for selected commercially and recreationally important

species and size classes of fish and shellfish that were commonly impinged

or entrained by the BSEP. Overall, 15 different taxa were examined

including over 21, 000 organisms of which 10 700 were held for 96 hours.

Approximately 6200 organisms were collected during slow-screen operation,

6600 during fast- screen operation , and almost 8800 for controls.

Thirty- four dates from April 1984 through April 1985 provided sufficient information to conclude that most shellfish survived the impingement process extremely well. Penaeid shrimp survival was consistently

over 80% , while megalop and juvenile stages of blue crab constantly exhibited over 85% survival. Experimental percentages were equal to or exceeded control percentages for these organisms indicating little or no

plant effect on survival. In addition, the commercially important

flounder and striped mullet showed excellent survival , while the abundant

sole and searobin indicated good survival.

Croaker and spot showed varying degrees of survival with survival

usually increasing with size. The smaller size classes for both species

showed a higher percent survival collected during fast-screen operation.
Weakfish and hardback shrimp, along with numerous other species, were

collected in too few numbers to conclusively state any trend of

survival. Menhaden showed poor survival , while the bay anchovy showed no

survi val.

Survival studies indic~te that the intake modifications return a

considerably high percentage of organisms impinged back to the CFE

alive. Numerous commercially important species, including most shellfish

species, were shown to be minimally, if at all, affected by impingement

and their subsequent return.
Table 8. Mean lengths of organisms examined during 96- hour survival studies at the BSEP during 1984 and 1985.

Pink/White Brown. Penae i d Blue Portun i d Sea- Bay Tongue- Hardback

Date Croaker Spot Shr i mp Shrimp Post larvae Crab Weakfish Mega lops robi n Anchovy fish Flounder Mullet Shr i mp Menhaden

01 APR 8408 APR 84

30 APR 84

06 MAY 84

10 JUN 84

17 JUN 84

24 JUN 84

08 JUL 8422 JUL 84

05 AUG 84

13 AUG 84 13219 AUG 84 141

27 AUG 84

17 SEP 84

24 SEP 8401 OCT 8408 OCT 84

........

1 5 OCT 84

29 OCT 84

05 NOV 84

1 3 NOV 84

26 NOV 8404 DEC 84

10 DEC 84 12-27**17 DEC 84

07 JAN 85 13-29**

17 JAN 85

23 JAN 85 176

04 FEB 85

18 FEB 85

04 MAR 85

18 MAR 85

01 APR 85

15 APR 85

number

of tr i a I s

*Blue crab mega lops were not measured

**Two size c I asses were he I d on these dates.
Table 8. Survival percentages for organisms coilected during fast- and slow-screen operation at

the BSE? duri ng 1984 and 1985.

Percent

TaKon Screen Number Number n I I a Collected Speed Tr i als Collected Stocked Marta I i ty Morta I i ty Survival

Croaker--Group 2903 1285 39. 52. 28.

--Group 2 584 338 36. 43. 36.

Spot--Group 1349 620 19. 61.

Pink and wh i te shrimp 264 219 92.

Brown shr imp 25. 69.

Penae i d post larvae 188 120 90.Blue crab 170 92.Blue crab megalops 159 11. 88.

Weakf I sh 282 191 19. 82. 12.

Sea rob i n 132 124 89.

Blackcheek tonguef ish 110 15. 79.Bay anchovy 249 114 54. 100.Str i ped mu II et--Group 19. 67.

--Group 2 91. 1--&

4'0 Flounder 90.

Menhaden 83. 15.

Croaker--Group 2105 772 60. 77.

--Group 2 597 420 15. 57. 35.

Spot--Group 1806 767 39. 87.

Group 2 333 219 27. 61. 28.

Pink and white shrimp 81.

Brown shr i 249 241 89.Penaeid postlarvae 131 119 15.

Blue crab 92.

Blue crab mega lops 203 135 11. 86.Bay anchovy 596 90. 100.

Hardback shr imp 123 66. 34. 22.

= Fast-screen operat i on.

S = Slow-screen operat i on.

N umber organ isms that were found dead in collection gear f number collected

Number of organ isms that died after be i ng stocked in tanks f number stocked

lOO - ((a) (Number collected) + (b) (Number stocked) + (b) !Other live organisms collected but not stocked)) '"

number co I I ect ed
Table 8. Survival percentages for control organisms call ected for survi va studies the

BSEP during 1984 and 1985.

Number Percent

Taxon Number Number Initial Latent Tota 1

Collected Trials Collected Stocked Marta 1 i ty Morta 1 i ty Survi va 1 c

Croaker--Group 1 1392 1095 14. 77.

Group 2 2550 611 1.8 97.

Spot--Group 1 1361 895 12. 80.

Group 2 973 213 98.

Pi nk and white shrimp 561 347 92.

())

Brown shri 323 304 23. 72.

,....

Penaeid postlarvae 115 112 89.

Blue crab 238 100 94.

Blue crab megalops 362 231 86.

Weakfi sh 155 116 40. 51.0

Searobin 104 1.9 1.0 96.

B 1 ackcheek tonguefish 444 116 97.Bay anchovy 20. 56. 29.

Striped mullet-- Group 1 95.

Group 2 100.

Flounder 95.

Hardback shrimp 90.

~Number of organi sms that were found dead in co 11 ect i on gear f number co 11 ected.

Number of organi sms that died after be i ng stocked in tanks f number stocked.

100 - ((a) (number collected) + (b) (number stocked) + (b) (other live organisms collected

but not stocked)) f number collected.
Tab 1 e 8. Mean percent 96- hour unadjusted survival va 1 ues for croaker

held during survival studies at the BSEP during 1984 and 1985.

Mean Percent Survival

Size (SL) Experimenta 

Date Range (mm) Mean (mm) Slow Fast Control

08 APR 84 11- 23. 66. 86.

30 APR 84 13- 39. 98.

06 MAY 84 14- 33. 54.

10 JUN 84 22- 43. 97.

17 JUN 84 31- 10. 9* 93.

24 JUN 84 32- 20. 10. 97.

08 JUL 84 39- 70. 33. 95.

22 JUL 84 . 46- 76. 50. 100.

05 AUG 84 53- 62. 100 .

15 OCT 84 18. 52.

29 OCT 84 81.8

05 NOV 84 17. 48.

13 NOV 84

26 NOV 84 21.4 80~ 3

04 DEC 84 57. 90.

10 DEC 84 17. 26. 87.

20- 96.

17 DEC 84 41. 7 87.

07 JAN 85 12. 56. 87.

20- 51.1 100.

23 JAN 85 37. 38.

04 FEB 85 10- 33. 87.

18 FEB 85 37. 84.

04 MAR 85 15. 52. 98.

18 MAR 85 24. 88.

15 APR 85 22. 100 .

*Results possibly reflects chlorine present in screen wash water.
Table 8. Mean percent 96- hour unadjusted survival val ues for spot held

during survival studies at the BSEP during 1984 and 1985.

Mean Percent Survival

Size (SL) Experimenta 

Date Range (mm) Mean (mm) Slow Fast Contro 1

01 APR 84 15- 15. 68. 89.

08 APR 84 15- 84.

30 APR 84 12- 11. 5 91.0

06 MAY 84 14- 19. 33.

10 JUN 84 27 - 37. 97.

17 JUN 84 28- 98.

17 JAN 85 74- 124 76. 100.

23 JAN 85 11- 14. 47.

04 FEB 85 11- 13. 86.

18 FEB 85 12- 26. 48.

04 MAR 85 14- 94.

18 MAR 85 14- 12. 41.2 83.

01 APR 85 15- 34. 91.2

15 APR 85 12- 18. 82.

*Resu 1 possibly reflects chlorine present in screen wash water.
Table 8. Mean percent 96-hour unadjusted survival values for penae i d

shrimp held during survival stud i es at the BSEP dur i ng 1984 and

1985.

Mean Percent Survival

Size (TL) Exper i menta 

Speci es Date Range (mm) Mean (mm) Slow Fast Contra 

Pink and

Wh i 13 AUG 84 34- 97. 96.

Shrimp 19 AUG 84 31- 83. 75.

17 SEP 84 19- 81.2 98.

24 SEP 84 27- 91.2 94.

01 OCT 84 23- 100. 97.

08 OCT 84 22- 100. 91.6

15 OCT 84 23- 91.7 93.

Brown 10 JUN 84 42- 107 93. 83.

Shri mp 17 JUN 84 44- 118 81.0 79.

24 JUN 84, 46- 13 5 94. 68.

13 AUG 84 69- 175 132 76. 69.

19 AUG 84 115- 185 141 61.4 63.

Penaei d 01 APR 85 10- 60. 89. 84.

postlarvae 15 APR 85 100. 91.8 94.
Table 8. Mean percent 96- hour unadjusted survival for blue crab held

during survival studies at the BSEP during 1984 and 1985.

Life Stage

Mean Percent Survival

Experimenta 

Date Slow Fast Control

01 OCT 84 81.8 96.

08 OCT 84 88. 94.

29 OCT 84 86. 78.

05 NOV 84 85. 77.

17 SEP 84 92. 95.

24 SEP 84 94. 89.

01 OCT 84 85. 100.

08 OCT 84 100. 100 .

15 OCT 84 87. 85.

Megalops

Juveniles

Table ~. Mean percent 96-hour unadjusted survival for weakfish held

, during survival studies at the BSEP during 1984 and 1985.

Mean Percent Su rv i val

Size (SL) Exper i menta 

Date Range (mm) Mean (mm) Fast Contro 

05 AUG 84 15- 37.

24 SEP 84 16- 21. 3

01 OCT 84 18- 37. 94.

08 OCT 84 25- 35.
Table 8. Mean percent 96-hour unadjusted survival for miscellaneous species held during survival studies at the BSEP during 1984

and 1985.

Speci es Date

Size 

Range (mm) Mean (mm)

B 1 ackcheek

tonguefish 27 AUG 84

08 OCT 84

15 OCT 84

Searob i n 24 SEP 84

01 OCT 84

08 OCT 84

15 OCT 84

Hardback

shrimp 29 OCT 84

18-

22-

22 -

13-

12-

15-

14-

18-

Mean Percent Survival

erimenta Fast Control

79.

80.

89.

95.

99.

97.

84.

90.

90.

91.9

100.

95.

100 . a

93.

22. 90.

*Hardback shrlmp collected during slow-screen operation.
,......

Xa20 Xa66 1 BB-J X a 36 X 5 45

X ~ 77

X=56

X a 

813 ,

x - 15

513

x = 12 x = 12

413

.... \ /\ /

A. 

/ \ ,/ .

.f 

\\

;

/

. . 12 X - 12

X . 11

x = 14

II 

\ / \

x-1~1 , , l' I X~x--' Il I X I :k-

. /~ X 

X'" 1\ .... ;of-- 

..

....

-1 

APR84 MAY84 JUN84 JUL84 AUG84 SEP84 OCT84 NOU84 DEC84 JAN85 FEB85 NARB5 APR85 NAY8S

DATE

X-x-X FAST LEGEND: SPEED CONTROL

++

+ 

SLOW X = MEAN STANDARD LENGTH

Figure 8. Mean percent survival of croaker during survival studies conducted at the BSEP during 1984 and 1985.
1 1210

--+tttt JIlIlIlIlIlI -t*----+------+JT~

It!

\/ : : 

/II

t+ 

4- \i 1\ Ilil if 

I 1II11I -4- II 1I1I1 \ I tt4. 8121 !i 

/ \

'1111 II I! \ I 1. / 11 11' II li / \1 11 I III /I

II 

1* ,I 

/ ,

. J ",1 / II \ i III E=I . I 1\ il II 1 I, 1/ \~ I I

1121

2121 100 120

LE-:NQ TH (MM) LEGEND: STUDY -I--+---f- CONTROL 0 0 0 FAST

SLOW

Figure 8. Survival/mortality comparisons of spot by size class collected during fast and slow screen operation at the BSEP during 1984-1985 survival studies.
IMPINGEMENT (Larval)

Introduction

With the initiation of fine-mesh screen operation , many of the

larval and postlarval organisms that would previously have been

entrained were impinged and returned to the CFE. A larval impingement

program was begun in January 1984 to provide an estimate of the total

number of larvae and postlarvae being impinged. Survival percentages

applied to these estimated numbers gave an assessment of the success of

fine-mesh screens.

Methods

Samp 1 e Co 11 ect i on

To collect the impinged larval - and postlarval organisms, a 505-um

mesh plankton net, 1 m in diameter, was placed in the nekton return

flume such that the entire water column was filtered. Five-minute

samples were collected on mid and slack tides over one 24- hour period

per ca endar week.

Samp 1 e Ana lys is

Due to the arge number of organi sms co 11 ected , many of the samp 1 es

were subsampled; however , at least 25% of the total sample weight was

retained for processing. Samples were processed in the same manner as

entrainment samples except that only minimum and maximum lengths were

recorded for each species (CP&L 1983).

Incidental collection of organisms large enough to be considered

juveniles or adults required the enforcement of length limits. Only

fish 2 40 mm were identified with the exception of eels, pipefish , and

leptocephalus larvae which were kept only if they were 2 100 mm. The

portunid crab cutoff imit was set at 2 24 mm.
Processing of larval impingement samples was very time- intensive.

All collections made in January were processed and analyzed. After

January at east two samp 1 i ng tri ps per month were processed and

analyzed. Three-way analyses of variance and Duncan s multiple range

test were performed to examine month , period, and tidal factors. ANOVAs

were performed on loge transformed numbers, and . results are presented at

the P ~ 0. 05 significance level.

Results and Discussion

Domi nant Spec i es

A total of 5. 7 x 108 organisms representing 99 taxa was impinged

during 1984. Croaker and spot were the dominant species comprising

22. 9% and 20. , respectively, of the total catch. Of the other commercially and/or recreationally important species, portunid megalops

ranked third (20. 4%), Anchoa spp. fourth (10. 0%), bay anchovy fifth

(6. 9%), Penaeus postlarvae sixth (5. 6%), Gobiosoma spp. seventh (3. 0%),

and menhaden eighth (2. 9%). Portunid crabs and Gobionellus spp. ranked

ninth and tenth, respectively, with a combined percentage of approximately 3. 0% (Table 9. 1).

Seasona 1 i ty and Abundance

The typi ca 1 wi nter and summer peaks ; n abundance observed in

entra i nment were also observed in arva 1 imp i ngement. The wi nter peak

consisted of menhaden spot, croaker, mullet, flounder, and brown

shrimp--all ocean- spawned species. Portunid megalops is an early 1 ife

stage of the blue crab which spawns near the mouth of the river in the

higher saline areas during the summer. Its period of peak abundance

occurred during the late summer and fall months and is considered a

winter species. The summer peak consisted of such ocean- spawned species

as seatrout and pink and white shrimp and of the estuarine-spawned

species of anchovies, Gobionellus spp. , and Gobiosoma spp.
Menhaden were present in impi ngement from January through May and

were impi nged in greatest numbers from ate March to mi d-April. Spot

and croaker were impinged from January through mid-June with spot being

impinged in greatest numbers in late March and croaker during mid to

late January. Mullet and flounder were impinged from January through

April and they both achieved greatest impingement during late January

through early March. Brown shrimp were present in impingement from midFebruary to late June, had their greatest impingement during late

March, and reached a second peak in ate June. Portun i d mega lops

appeared in impingement from early April through December and had their

highest impingement from late August to late November.

Of the summer species, seatrout were impinged from mid-May to early

October and had their greatest impingement during early to mid- June.

Pink and white shrimp were present in impingement from mid-August

through early November with their greatest impingement occurring from

late August to early October. Anchovies and both genera of gobies were

present throughout the year. Anchovies reached peak impingement during

June as did Gobiosoma spp. Gobionellus spp. had two periods of high

impingement--one during late March to early April and the other from

late September through early October (Table 9. 2).

All seasonality and peak abundance patterns observed in arva 1

impingement closely follow the patterns seen in both the entrainment and

river larval fish programs.

Diel Patterns

ANOVA and DMR test results showed that for all species

significantly greater numbers were impinged at night. This is

consistent with the pattern seen in entrainment.
Tidal Patterns

Except for seatrout, penaeid shrimp, Gobionellus spp., and portunid

megalops, ANOVA results showed no significant difference among tidal

stages for numbers imp i nged.

According to the DMR test rankings, the most penaeid shrimp,

GobioneZlus spp., and portunid megalops were impinged during high slack

tides and the most seatrout were impinged during low slack tides.

Survival Estimates

In most cases, survival studies were conducted with organisms collected from two different intake screen rotation speeds. To obtain an

overall percent survival of impinged larval and postlarval organisms

returned to the estuary, all survival tests from slow screen rotation

for size classes whose mean length was ~ 40 mm were used. The same was

done for corresponding size classes from fast screen rotations. These

percentages are presented in Table 9. 3 by speci es and screen speed.

month ly est imate of total number imp i nged for each speci es

studied was calculated by expanding the known number collected for the

hours sampled by the total hours in that month. These monthly estimates

were then combined and are presented as the total number impinged in

Tab 1 e 9.

In 1984 an estimated 1. 3 x 108 croaker were impinged. If they had

been impinged on slow-rotating screens, 1. 6 x 10 would have been

returned to the estuary alive. If they had been impinged on fastrotating screens, 3. 8 x 10 7 would have been returned alive. Total spot

impingement was 1. 2 x 10 If these were impinged during slow rotation,

1.1 x 10 would have returned to the estuary alive. If they were

impinged during fast rotation, 3. 7 x 107 would have survived. Similar

fast/slow survival estimates were calculated for the other species

studied and are presented in Table 9.3. The eight taxa tested for
survival represent 79% of the total impingement catch. Of these, 49%

would have been returned al ive to the estuary if the screens had been on

fast rotation. This corresponds to 39% of the total larval organisms

impinged being returned to the estuary.

Summary and Conclusions

In 1984 a larval impingement program was initiated to provide an

estimate of the total larvae and postlarvae being impinged by the

BSEP. A total of 5. 7 x 108 organ isms represent i ng 99 taxa was imp i nged

with croaker and spot dominating the catch. The seasonalities of those

commerciallyjrecreationally important species were much the same as

those observed in the entrainment and river larval fish programs.

All species were impinged in greater numbers at night. Penaeid

shrimp, Gobionellus spp., and portunid megalops showed significantly

higher impingement catches during high slack tides and seatrout showed

significantly higher catches during low slack tides. . For all other

species analyzed, there was no significant difference in impingement

catches among tidal stages.

Overall , percent survival estimates for slow- intake screen speeds

ranged from 8. 9% for spot to 86. 3% for portunid megalops. Survival

estimates from fast screen rotation ranged from 12. 6% for weakfish to

90. 2% for Penaeus postlarvae. Bay anchovy showed no survival at either

speed. The eight taxa tested for survi va 1 represented 79% of the total

impingement catch. At fast screen rotation , 49% of these organisms

would have been returned alive to the estuary which corresponds to 39%

of the total larval organisms impinged being returned to the estuary.
Tab 1 e 9. Ranking by percent of total impingement of species collected in the BSEP larval impingement program during 1984.

Rank Spec i es Percent of Total Imp i ngement

Croaker 22.

Spot 20.

Portunid megalops 20.

Anchoa spp. 10.

Bay anchovy

Penaeus postl arvae

Gobiosoma spp.

Menhaden

Portunid crabs 1.6

Gobionellus spp. 1. 5
Table 9. Total number of selected species collected by trip in larval impingement during 1984.

Penaeus Gobionell us Gob j osoma Portun i d

Trip Date Anchovy Menhaden Seatrout Spot Croaker Mullet Flounder SPP. SPP. SPP. Mega lops

12 JAN 84 835 933 884 2471 7 JAN 84 310 751 899 148 159

24 JAN 84 932 505 93, 644 198 999

31 JAN 84 470 581 602 736 336

07 FEB 84 032 126 345 780 797 83121 FEB 84 332 421 27 , 356 495 405 692 250

06 MAR 84 016 267 294 476 862 820 148 213

20 MAR 84 460 603 264 083 133 393 807 364

03 APR 84 152 888 501 987 151 369 333

10 APR 84 649 919 341 838 114 877 708

01 MAY 84 955 176 574 104 765 443

15 MAY 84 982 107 705 145 176 605 309

12 JUN 84 581 809 354 295 121 '-0

19 JUN 84 701 360 650 142 518 '-.J

26 JUN 84 981 147 172 205

10 JUL 84 520 311 458 139

24 JUL 84 531 184 436 345 631

07 AUG 84 894 717 105 214 191

1 4 AUG 84 150 567 156 749

21 AUG 84 718 144 174 719 327

28 AUG 84 176 103 545 246 143 508

18 SEP 84 526 139 282 697 488 285 262

25 SEP 84 536 287 423 505 130 83102 OCT 84 699 108 997 325 087 302 830

09 OCT 84 999 317 776 110 292 134

16 OCT 84 682 751 695 618 100 673

06 NOY 84 328 220 886 377 72327 Nay 319 383 193 848 891

04 DEC 84 451 017 249 010

20 DEC 84 860 683 114 306 130
Table 9. Overall percent survival and number of larval impinged organisms returned alive to the Cape Fear

Estuary.

Speci es

Total

Number Imp i nged

vera II Percent ~urV1va 

~ l Screen Screen Speed Speed er urned Al l ve as Screen Screen Speed Speed

'-0

CroakerSpotBay anchovyPenaeus postl arvaeFlounder

Mullet

Portuni d mega lops

Weakfish

Anchoa spp.MenhadenOther organi sms (89 taxa)

1.3 X 10

1.2 x 10

9 x 10

2 x 107 x 10

1.6 x 101.2 x 10

5 x 10

7 x 10

1.6 x 10

0 x 10

29.

30.

90.90.

67.

88.

12.

12.

77 .

86.

8 x 10

7 x 10

9 x 10

2 . 4 x 10

1.1 x 101.1 x 101.1 x 10

1.6 x 101.1 x 10

5 x 10

1.0 x 10

7 x 5 x 108 (79%)a

1 x 108 (72%)b

Tota 1 organi sms

Tota 1 organi sms tested

Tota 1 organi sms tested

(excluding bay anchovy)

Not tested

a Percent of total organlsms implnged that were tested.

b Percent of total organlsms imp1nged that were tested excluding bay anchovy.

c Percent of a that were returned a 1 i ve.

d Percent of b that were returned al ive.

2 x 108 (49%)c

2 x 108 (54%)d
10. IMPINGEMENT (Juvenile and Adult)

10. I ntroduct i 

Impingement studies have been conducted at the BSEP since January 19,

1974, when water was first pumped through the plant. Objectives of the

past and present studies addressed the determination of numbers, weights,

species composition, and length frequency of organisms impinged at the

BSEP.

The 1984 juvenil e and adu It (J/A) imp i ngement study was conducted

with the permanent fish diversion structure in operation. The diversion

structure, as descr i bed in Append i x A and the 1981 annua 1 report (CP&L

1982), prevented arger organi sms from enteri ng the intake canal except

when screen panels failed as a result of biofouling and/or debris

buildup. During the repair of failed screens, sections of the diversion

structure were opened all owi ng access of organ isms to the intake cana 1 .

Except for these short periods, most J/A fi sh and she 11 fi sh were excl uded

from possible impingement during 1984.

10. Methods

Samples were collected for one 24- hour period each week during 1984

with only two exceptions. The data for the first week in January were

omitted due to the use of an experimental sampling procedure which was not

comparab 1 e with the subsequent samp 1 i ng scheme and the second week in

September was not sampled because of Hurricane Diana. During these two

months, data were expanded based on three week s of samp 1 i ng instead of the

normal four or five weeks.

The 1984 samples were taken by placing a steel-framed collection

basket in each sluice. The baskets were fitted with a 9. 4-mm plastic

webbing similar to the screens on the original intake traveling screens.

Contro 1 valves were opened so screen wash water flowed freely i n both

sluiceways. As a basket filled with organisms and debris, a third basket

was set in the flume to guarantee continuous filtration of the screen wash

10-
water while the basket was emptied. A sample was completed at sunrise or

sunset to be day/night specific. Samples were returned to the laboratory

for sorting, identifying, enumerating, measuring, and weighing of

organisms. Up to 50 individuals of the 13 selected species (Table 1.2)

were measured from each samp le. Monthly estimates and expans ion factor

calculations were identical to those described in the 1982 annual report

(CP&L 1983). This report uses 1977- 1982 as comparable past data. The

data for 1983 was only recorded for the first six months , whi le the second

six months was used to develop the new J/A impingement program. Data are

reported in both numbers and densities. Total numbers refer to the 1984

data set, while densities are used when comparing 1984 to past years.

Converting all years of data to densities enables comparisons, regardless

of plant operation (flows). The 1984 data reported in densities can

objectively compare the effects of the fine-mesh screens, diversion

structure, and most importantly flow minimization to past J/A impingement

data.

. Organisms ;;: 25 nun were considered incidental catches and were not

recorded in the J/A program, while larval impingement (Section 9. 0) did

not record organisms ~ 40 mm. To resolve this 16-mm overlap between

programs, the 1977- 1982 J/A impingement data were examined for catches

below 40 mm. Historically, 2. 0% of the 1977- 1982 catch was ;;: 40 mm

whereas 60. 3% of the 1984 J/A impingement was ;;: 40 mm (Table 10. 1). The

addition of fine-mesh screens, the effect of the diversion structure, plus

the change in the sampling gear in 1984 dramatically skewed the catch

towards smaller organisms. An adjustment of the data set was needed for

two reasons: (1) the 25-40 mm organisms were being expanded and

documented in both larval and J/A impingement and (2) the data set would

have to be comparable to past years so trends could be determined. Thus,

organisms ~ 40 mm are considered part of JjA impingement.

Fish ~ 41 mm, shrimp ~ 41 mm, crabs ~ 25 mm, and eels and pipefish ~

101 mm were included as the JjA impingement catch. Occasionally groups of

organisms were recorded below and above the cutoff limits. On such

occasions the values remained in the J/A analysis and reportings. Lengthfrequency plots include data with no cutoff limit to show the entire

10-
length frequency ~ 25 mm. A reference line was included in all lengthfrequency plots at 40 mm to divide larval versus JjA impingement.

10. Results and Discussion

10. Species Composition

The total JjA impingement during 1984 included 5, 128 817 organisms

representing 116 taxa and weighing 16 890 kg (Table 10. 1). Total

impingement density was reduced in number by 43% and in weight by 67% when

compared to the 1977- 1982 mean catch (Table 10. 2) Bay anchovy were the

most abundant species totaling 59. 0% of the catch. Menhaden (12. 8%), blue

crab (5. 6%), Atlantic silverside (4. 0%), blackcheek tonguefish (2. 6%), and

croaker (2. 1%) were second, third, fourth, and fifth, respectively. Pink

shrimp (1.8%), spot (1.7%), brown shrimp (1.6%), and white shrimp (1.0%)

rounded out the top ten species (Table 10. 3). Each of the remaining 106

taxa was represented by ~ 1% of the total expanded catch.

10. Oiel Patterns

The catch at night comprised 78% of the total J/A impingement. The

lowest night impingement rate (47%) was recorded during May, while the

highest night catch 92% was recorded during October (Figure 10. 1).

Percentages of day versus night impingement calculated by weight were

similar to the numerical percentages. Both number and weight percentages

are consistent with data reported in the 1982 annual report (CP&L 1983).

10. Flow Rates

Flow rates in 1984 were below the mean flow of previous years (1977-

1982). Mean monthly intake flow rates in 1984 ranged from 45. 4 x 10

jmonth in April to 110. 0 x 106 m jmonth during October. Mean monthly

flow rates for previous years ranged from 85. 9 x 106 m jmonth in June to

117. 6 x 106 m jmonth during January (Figure 10. 2). The lower flow rates

during 1984 are attributed to the flow-minimization program which in turn

reduced impi ngement.

10-
10. 4 Length-Frequency D is tr i but ions

Length- frequency data was collected to examine the size distribution

of certain species from the impingement catch. Seatrout , mullet , and

flounder were not impinged in sufficient numbers for length-frequency

distribution analysis. All length- frequency plots include organisms

between 25 and 40 mm, even though that size group is not being reported as

JjA impingement.

The modal length of bay anchovy decreased from previous years by up

to 25 mm, especially in the first six months. The reduced modal length

may be attri buted to the fi ne-mesh screen and new samp 1 i ng procedure

(Figure 10. 3).

Menhaden spot, and croaker length distributions for juvenile

organi sms were s imil ar to previous years, although numbers were reduced

(CP&L 1982 , 1983). Unlike previous years, adult menhaden were essentially

absent except in January and February when catches were attributed to the

failure of the diversion screens in mid- January (Figure 10. 3). Catches of

adu It spot al'1d croaker did not increase duri ng those months and rem a i ned

low throughout the year (Figure 10. 4).

Length data for penaeid shrimp are similar to past years (CP&L 1982,

1983) . Brown shri mp peaked in numbers duri ng Ju ly and in s i ze duri ng

August. White shrimp peaked in number during September and in size during

November. Pink shrimp had scattered distributions throughout the year

peak i ng in abundance duri ng October.

10. Estimated Survival Adjustments

The JjA survival studies tested ten of the most frequently impinged

species (Section 8.0). Bay anchovy was tested but showed practically no

survival. The remaining nine species and estimated survival of the

remaining nine species are presented in Table 10.

10-
The application of the survival study results to the J/A impingement

data documents a probability of survival for organisms which were impinged

(Table 10. 4). An estimated total of 813, 372 organisms weighing 7, 174 kg

were impinged and returned to the estuary alive in 1984 (Table 10. 4).

When the survival estimates are subtracted from the J/A impingement, only

220 kg of spot, 197 kg of croaker, 266 kg of blue crab, and 158 kg of all

penaeid shrimp were actually lost to the estuary because of impingement

during 1984 (Table 10. 4).

The application of the survival study results to the impingement

totals reduces the loss to impingement in number by 15. 9% and weight by

42. 5% of the 1984 expanded J/A imp i ngement catch. Casual observat ions of

the survival studies and impingement sampling showed many live individuals

of additional species initially survived the return system. Those

additional species have yet to be tested, thus the reduced percentages are

a documented minimum and future studies should show additional survival.

10. Summary and Conclusions

The 1984 J/A impingement catch consisted of 5 128,817 organisms

weighing 16,890 kg. Bay anchovy (59%) was the most abundant species,

while menhaden was the second most abundant species. Total impingement

density was reduced in number by 43% and in weight by 67% when compared to

the 1977- 1982 mean catch. The diversion structure probably excluded most

of the J/A menhaden spot, and croaker, which historically dominated

impingement catches at the BSEP (CP&L 1982, 1983). Bay anc.hovy was not

excluded by the diversion structure and thus dominated the 1984 J/A

impingement. Three out of four organisms were impinged at night.

Length- frequency plots generally showed typical distribution of YOY

organisms but with the substantial reduction of year and older

individuals. The smaller organisms ~ 40 mm could pass through the

diversion screens and populate the intake canal , while larger individuals

were generally excluded. The smaller organisms freely entered the canal

and possibly establish residence until the time of their natural migration

out of the estuary. Their size would limit them from exiting through the

10-
diversion screens and their only departure route then would be through

impingement and the nekton return system. However , survival studies show

that essentially all of the penaid shrimp and blue crab can be returned to

the open estuary a 1 i ve.

An estimated total of 813, 372 organisms (15. 9%) weighing 7, 174 kg

(42. 5%) were returned alive to the estuary. The tested survivability was

appl ied to J/A impingement total s resulting in the loss of only 266 kg of

blue crab, 158 kg of penaeid shrimp, 220 kg of spot, and 197 kg of croaker

during 1984. The southern district of North Carolina reported prel iminary

landings of 446 265 kg of blue crab , 1 211 731 kg of penaeid shrimp,

133, 871 kg of spot, and 164 167 kg of croaker during 1984 (Street 1985).

Additionally, private individuals harvest unknown quantities of blue crab

and penaeid shrimp for personal usage. When J/A impingement is compared

to such 1 and i ngs, one can see that what was cropped by the BSEP was

ins i gn if i cant.

10-
Table 10. A summary of expanded juvenile/adult impingement at the BSEP

duri ng 1984.

Number of organi sms

Weight (kg)

Number of shellfish

Weight of shellfish (kg)

Number of finfish

Weight of finfish (kg)

Number of mi sce 11 aneou s

Weight of miscellaneous

Total number of taxa

Total taxa of finfish

speci es

species (kg)

128, 817

16, 890

587 048

5, 689

531, 733

11, 161

10, 036

116

102

Tab 1 e 10. A summary of expanded juvenile/adult imp 1 ngement by year at

the BSEP.

Imp i nged Number Impinged Weight (kg)

of Organisms per of Organisms per

Total Million Cubic Total Million Cubic

Number Meters of Water Weight (kg) Meters of Water

Year Impinged Entra i ned Imp i nged Entra i ned

1977 16, 355, 569 124 593 98, 730 743

1978 18, 859 331 124 289 131 570 865

1979 11, 147 099 91, 060 61, 374 464

1980 697 879 79, 647 67, 701 523

1981 9 , 736 , 795 74, 286 270 514

1982 810 886 204. 162 76. 494 709

1984 926, 485 167, 346 20 , 628 256

1984

;:. 40 128, 817 66, 398 16, 890 210

1977- 1982 116 341 636

mean

1984 % reduct i 

10-
Tab 1 e 10. summary of juven 11 e/ adu 1 mp; ngement spec; es the

BSEP during 1984.

Total Tota 1

Rank Speci es % of catch Number Weight (kg)

Bay anchovy 59. 023, 433 950

Menhaden 12. 653, 960 186

Blue crab 286, 626 227 Atlantic silverside 203, 697 585

B 1 ackcheek tonguefi sh 131, 575 192

Croaker 110 199 445

Pink shrimp 1.8 92, 551 172

Spot 1.7 89, 252 544

Brown shrimp 1.6 83 , 662 878

White shrimp 1.0 52, 529 327

10-
Table 10. Estimated survival of juvenile and adult organisms impinged during 1984.

Number of Estimated Estimated

Percent** Survi val Number Weight (kg) Number Weight (kg) Species Survi va Tests Impi nged Impi nged Surv; ved Survived

Penaeus spp. (pi nk and whi te) 92. 145, 080 499 133 764 460

81 ue crab 93. 286, 626 227 268, 569 961

Stri ped mull et 92. 19, 691 475 18, 116 437

Brown shrimp 86. 662 878 368 759Blackcheek tonguefish 79. 131, 575 192 96, 774 153

Spot 59. 89, 252 544 105 324

Croaker 55. 110, 199 445 61, 381 248

(:)

35. 277 Weakfi sh 20, 790

Menhaden 15. 653 960 186 102 018 809

Bay anchovy 023, 433 950

At 1 ant ic s i 1 vers ide 203, 697 585

Other species (104 taxa) 370, 852 842

Total 128, 817 16, 890 813 , 372 174

% Survival 15. 42.

Exc 1 ud i ng bay anchovy 105, 384 38.

Excluding bay anchovy and others not tested 530, 835 53.

*Not tested.

**Percent survival calculated using only juvenile and adult-size classes.
100

..... (:) ......

DAY

ill NIGHT

Figure 10.

MONTH

Day Inight comparison of juvenile/adult impingement at the BSEP during 1984.
140 

120

1 0 0 i""----- -

......

1977- 1982

\ /

---t" 

\ / /

Jon Dee

Figure 10.

Feb Mar Rpr May Jun Ju Rug Sep De 

\:,

No\)

MONTH

Mean monthly rates of water entrained at the BSEP, January-December, 1977- 1982 and 1984.
BA Y ANCHOVY

JIt

rEB

... ......

N = 274 760

N = 389 675

N = 128 620

N = 73953

N = 19732N - 30 668N = 4.422

.N =

N '" 9 067

N = 28 561

N = 31 931

N = 269,869

8 5

un,," 1m)

N = Number Sampled MENHADEN

58.421

10746

N = 23 957

47361

N = 1655N = 384

N = 174

N =

N - 784

N = 336

N =.

N =

JlR

822

II lIt 1lI

fIBIII

II'f

ItC

III III 141

U~1H (ltI)

Figure 10. 3 Length-frequency distributions of bay anchovy and menhaden impinged at the BSEP, January-December, 1984. Organisms greater than 40mm are considered juvenile and adult.
.......

.AI 8

c-a

rug 8

tI1/ 8

c-a

IQ) A

'ill

mY 8

RJII8

UL 8

roi 8

ocr 8/OJ 8IIC 8

SPOT CROAKER N = Number Sampled

N = 1 430

339

= 9 647

438 N = 2 229

N = 147 N = 609

N = 5,510 N = 1,381

N '" 9 984 N = 4.445

R 11

" J1

N = 7 332

N '" 4 332 N = 8.443

N = 5

741 N = 836

N = 590 282

198 286

N = 682

1111 128 141 lIB 188 281

W'II/Im,

N = ,. 373

88 II 13)

lOtllll (1ft)

118 1(1 III

Figure 10.4 Length-frequency distributions of spot and croaker impinged at the BSEP, January-December, 1984.

Organisms greater than 40mm are considered juvenile and adult. 

11.0 REFERENCES

Allen, G. H., A. C. Delacy, and D. W. Gotshall. 1959. Quantitative sampling of marine fishes: A problem in fish behavior and fishing

gear. Pages 448- 509. in E. A. Pearson (eds. ). Proc. 1st International Conference on Waste Disposal in the Marine Environment.

Pergamon Press, New York.

Ambrose, J., Jr. 1983. Age determination. Pages 301- 324 in L. A. Nielson and D. L. Johnson (eds). Fisheries techniques. American

Fisheries Society, Blacksburg, VA.

Birkhead, W. S. , B. J. Copeland , and R. G. Hodson. 1979. Ecological

monitoring in the lower Cape Fear River estuary, 1971- 1976. North

Carolina State University, Raleigh , NC.

Bousfield, E. L. 1955. Ecological control of the occurrence of barnacles

in the Miramichi Estuary. Natl. Mus. Can. Bull. 137:1- 69.

CP&L. 1980. 1979 monitoring program. BSEP Cape Fear studies, Supplement I. Carolina Power & Light Company, New Hill , NC.

1982. Brunswick Steam Electric Plant, annual biological

monitoring report, 1981. Carolina Power & Light Co., New Hill

NC.

1983. Brunswick Steam Electric Plant, annual biological

monitoring report, 1982. Carolina Power & Light Co. , New Hill

Nc.

1984. Brunswick Steam Electric Plant, annual biological

monitoring report, 1983. Carolina Power & Light Co. , New Hill

NC.

Chao, L. N.. and J. A. Musick. 1977. Life history, feeding habits , and

functional morphology of juvenile sciaenid fishes in the York

River estuary, Virginia. Fishery Bulletin 75:657- 702.

Copeland, B. J., and R. G. Hodson. 1977. Larvae and postlarvae in the

Cape Fear Estuary, NC, 1976- 1977. Report No. 77-5 to Carolina

Power & Light Company. North Carolina State University, Raleigh,

NC.

Copeland, B. J., R. G. Hodson , and R. J. Monroe. 1979. Larvae and postlarvae in the Cape Fear River estuary, NC, during operation of the

Brunswick Electric Plant, 1974- 1978. North Carolina State University, Raleigh, NC.

Dudley, D. L., and M. H. Judy. 1973. Seasonal abundance and distribution

of juvenile blue crabs in Core Sound. NC. 1965- 1968. Chesapeake

Sci. 14: 51- 55.

11-
Everhart, H. W., and W. D. Youngs. 1981. Principles of Fishery Science

2nd ed. Cornell University Press, Ithaca , NY.

Geaghan, J. P., and M. T. Huish. 1980. Distribution and diversity of

fish and crustacean communities in the Cape Fear River estuary,

North Carolina, 1977- 1979. North Carolina State University,

Raleigh, NC.

Haven D. S. 1959.

Copeia 1:25- 30.

Migration of the croaker Micropogon undulatus.

Hodson , R. G. 1979. Utilization of marsh habitats as primary nursery

areas by young fish and shrimp, Cape Fear Estuary, NC. BSEP Cape Fear Studies, Volume VIII. North Carolina State University,

Raleigh, NC.

Hodson , R. G., C. R. Bennett, and R. J. Monroe. 1981. Ichthyoplankton

sampler for simultaneous replicate samples at surface and bottom. Estuaries 4(3): 176- 184.

Hogarth , W. T. , and K. L. Nichols. 1981. Brunswick Steam Electric Plant intake modifications to reduce entrainment and impingement

1 os ses. Caro 1 i na Power & Light Company, New Hi 11 , NC.

Hoss, O. E., W. F. Hettler , Jr., and L. C. Coston. 1974. Effects of

thermal shock on larval fish: Ecological implications with respect to entrainment in power plant cooling systems. Pages 357-

371 in J. H. S. Blaxter (ed.

). 

The early life history of fish.

Springer Verlog, Berlin, West Germany.

Hoss D. E., L. E. Clements, and D. R. Colby. 1977. Synergistic effects

of exposure to temperature and chlorine on survival of young- ofthe-year estuarine fishes. Pages 345- 355 in F. J. Vernberg, A.

Calabrese, F. P. Thurberg, and W. B. Vernberg (eds.

). 

Physiological repsonses of marine biota to pollutants. Academic Press, New

York.

Huish , M. 1., and J. P. Geaghan. 1979. A study of adult and juvenile

fishes of the lower Cape Fear River near the Brunswick Steam Electric Plant, 1975- 1976. North Carolina State University, Raleigh

NC.

Ingram, R. L. 1965. Facies maps based on the megascopic examination of

modern sediments. J. Sed. Petrol. 35(3):619-625.

June, F. C., and J. L. Chamberlin. 1959. The role of the estuary in the

life history and biology of Atlantic menhaden. Pages 41- 45 in P. Idyll (ed). Proceedings of the Gulf and Caribbean Fisheries

Institute, 11th Annual Session. Miami Beach , FL.

Kuntz, A. 1914. The embryology and larval development of Bairdella chrysura and Anchoviamitchilli. Fish. Bull. 33:1- 19.

11-
Lagler , K. F. 1952. Freshwater fishery biology. lishers, Dubuque, IA.

Wm. C. Brown Co. PubLawler, J. P., H. Y. Chen, T. L. Englert, and T. B. Vanderbeek.

Mathematical modeling of biological impact on the Cape Fear

ary due to operation of the Brunswick Steam Electric Plant.

Cape Fear Studies, Volume XX. Lawler, Matusky, & Skelly

neers, Pear 1 River, NY.

1980.

EstuBSEP

E ng i -

McCoy, E. G., and J. T. Brown. 1967. Migration and growth of commercial

penaeid shrimps in North Carolina. N.C. Dept. of Natural and

Economic Resources, Division of Commercial and Sports Fisheries.

Raleigh , Nc.

McGroddy, P. M., and R. L. Wyman. 1977. Efficiency of nets and a new

device for sampling living fish larvae. J. Fish. Res. Board Can.

34:571- 574.

McHugh , J. L. 1967. Estuarine nekton. Pages 581- 620 in G. H. Lauff (ed). Estuaries. Am. Assoc. Ad. Sci. No. 83. Washington, DC.

McKensie, M. D., J. Whitaker , C. Bearden, D. Theiling, D. Ligo, R. Rhodes,

E. Schroeder , and K. Swanson. 1981. Profile of the penaeid

~hrimp fishery in the South Atlantic. South Atlantic Fishery

Management Council , Charleston , SC.

Merriner , J. V. 1973. Assessment of the weakfish resource, a suggested

management plan and aspects of life history in North Carolina.

Doctorate thesis. North Carolina State University, Raleigh, Nt.

1976. Aspects of the reproductive biology of the weakfish

Cynocion regalis (Sciaenidae), in North Carolina. Fish. Bull. 74:

18-26.

Musick , J. L. 1979 Assessment of Georgia shrimp and crab resources.

Georgia Department of Natural Resources, Contributing Serial No.

30.

Norcross, L. B., and R. F. Shaw. 1984. Oceanic and. estuarine transport

of fish eggs and larvae: A review. Am. Fish. Soc. 113:153- 165.

Pollard, L. W. 1985. Brunswick Steam Electric Plant, movement of fish

from the nekton return bas in. Caro 1 i na Power & Light Company.

New Hi 11 , NC.

Reintjes, J. W. 1969. Synopsis of biological data on the Atlantic menhaden, Brevoortia tyrannus. S. Fish and Wildl. Serv. , Circ. 320.

Rogers, S. G. , T. E. Targett, and S. B. Van Santo 1984. Fish nursery use

in Georgia salt-marsh estuaries: The influence of springtime

freshwater conditions. Trans. Am. Fish. Soc. 113:595- 606.

11-
Schwartz, F. J., P. Perschbacher L. Davidson K. Sandov J. Tate,

M. McAdams, C. Simpson , J. Duncan , and D. Mason. 1979. An ecological study of fishes and invertebrate macrofauna utilizing the

Cape Fear River estuary, Carol ina Beach Inlet, and adjacent Atlantic Ocean, 1978. BSEP Cape Fear Studies, Volume XV. Report to

Carolina Power & Light Company. Institute of Marine Sciences.

University of North Carolina, Morehead City, NC.

Stickney, R. R. 1983. Care and handling of live fish. Pages 85- 94 

L. A. Nielson and D. L. Johnson (eds). Fisheries techniques.

American Fisheries Society, Blacksburg, VA.

Street, M. 1985. Status of North Carolina commerical catch. Tar Heel

Coast. Vol. 20, No. 1. North Carolina Division of Marine Fisher- i es. Department of Natural Resources and Community Development,

Morehead City, NC.

Taft III , E. P., T. J. Horst, and J. K. Downing. 1981. Biological evalu- ation of a fine-mesh traveling screen for protecting organisms.

Pages 159- 168 in P. B. Dorn and J. T. Johnson (eds). Proceedings

of the workshop of advanced intake technology. San Diego, CA.

Wang, J. C. 5., and R. J. Kernehan. 1979. Fishes of the Delaware estuaries: A guide to the early life histories. Ecological Analysts,

Inc. , Towson , MD.

Weinstein, M. P. 1979a. Larval retention study, Cape Fear River , 1978.

BSEP Cape Fear Studies, Volume X. Lawler , Matusky & Skelly Engineers, Pear 1 River , NY.

1979b. Shallow marsh habitats as primary nurseries for fishes and shellfish, Cape Fear River , North Carolina. Fish.

Bull. 77:339-357.

Weinstein, M. P., S. L. Weiss, R. G. Hodson, and L. R. Gerry. 1979.

Retention of three taxa of postlarval fishes in an intensively

flushed tidal estuary, Cape Fear River, North Carolina. Fish.

Bull. 78:419-436.

Weinstein , M. P., S. L. Weiss, and M. F. Walters. 1980. Multiple determinants of community structure in shallow marsh habitats, Cape

Fear Estuary, NC. Mar. Biol. 58:227- 243.

11-
APPEND IX A

BRUNSWICK STEAM ELECTRIC PLANT

INTAKE MODIFICATIONS AND FLOW MINIMIZATION

DIVERSION STRUCTURE

The 4. km intake canal intersects Walden Creek in the area of Snow '

Marsh. In the fall of 1982, a diversion structure was installed at the

mouth of the intake canal where it intersects Walden Creek (Figure A- 1).

This structure was intended to prevent juvenile and adult fish from

entering the canal and thus reduce impingement.

The diversion structure consists of concrete pilings driven into the

bottom across the mouth of the canal. The entire device was constructed

in a V-shape with the apex pointing away from the plant so that tidal

flushing would keep the screening relatively clean. In the event that

trash became impinged on the screens, it would wash off at the change of

the tide.

Panels are constructed of 9. 4-mm mesh copper-nickel screens mounted

on copper- nickel frames. Sheet metal pilings with cathodic protection

extend the full length of the diversion structure and provide relief from

underwashing. Vertical guideways that allow the installation of two

screens, one directly behind the other, extend upward from the sheet

piling to a walkway that extends the full length of the structure. The

walkway allows access to each screen and facilitates their removal for

cleaning or replacement. Because impingement of organisms and trash

aga i nst the screens presents a prob 1 em, the daub e-screen system is u sefu 1

as it allows one panel to always be in place while the other is pulled up

for cleaning or maintenance.
FINE-MESH SCREENS

In June of 1983, fine-mesh (1-mm) polyester screens were placed over

two of the four 9. mm intake traveling screens on each unit. The NPDES

permit requires that these screens be run at all times. Except for

periods when detritus loading, drive chain, or pump problems prevented the

operation of these screens, this was the case.

The flow-minimization regime resulted in only fine-mesh screens being

run during those periods when the intake water temperature was less than

65O F as a five-day average. When the water temperature was greater than

65O F, two fine-mesh and one 9. mm screens were operated.

The effectiveness of fine-mesh traveling screens in reducing entrainment is discussed in Section 7.

FLOW MINIMIZATION

Tables A- and A- present the flow-minimization regime from

June 1, 1981, through the permit expiration date. Prior to this time, the

cooling-water flow was approximately 1105 cfsjunit except the period May

through October when the flow was 1205 cfsjunit.
Cool ing water flow (cubic feet per second)/unit for the BSEP from

June 1, 1981 through June 30, 1983.

Flow

Intake water temperature 1 es s than

65O F as a 5-day average

Reactor power 1 eve 1 40% or greater

Reactor power level less than 40% for

48 hours or more

915

605

Intake water temperature between 65O F and 85O

as a 5-day average

Reactor power 1 eve 1 40% or greater

Reactor power 1 eve 1 1 es s than 40% for

48 hours or more

915

605

Intake water temperature 85O F or greater

Reactor power evel 40% or greater

Reactor power 1 eve 1 1 es s than 40% for

48 hours or more

1105

835
Cooling water flow (cubic feet per second)/unit for the BSEP from

July 1, 1983 through the permit expiration date.

Flow

Intake water temperature ess than

6so F as a 5-day average 605

Reactor power 1 eve 1 40% or greater

Reactor power level less than 40% for

48 hours or more

605

400

Intake water temperature between 65O F and 85O

as a 5-day average

Reactor power level 40% or greater

Reactor power level less than 40% for

48 hours or more

915

605

Intake water temperature 8so F or greater

Reactor power evel 40% or greater

Reactor power level less than 40% for

48 hours or more

1105

835
ACCESS ROAD

:PFigure A- Location of diversion structure, sluiceways, and return basin at the Brunswick Steam Electric Plant.

APPENDIX B

STATISTICAL EXPLANATION OF TIME- SERIES AND

MULTIVARIATE ANALYSES

DATA TRANSFORMATIONS

Fisheries and environmental data can be considered as collected on

several levels: sample, replication, space, and time. For many statistica 1 ana lyses , the data were accumu 1 ated over one or more of the above

levels and a "mean 'l calculated to represent the distribution of values.

The distribution of numbers at any collection level tends to be

skewed toward the lower ranges of values. Application of the In(X+1)

transformation to individual samples helps to normalize the base data.

This transformation was applied to the lowest collection level , the sample, to ensure that distributional parameters calculated at higher levels

would still maintain the assumptions of normality (means of normally di~-

tributed data will be normal). Calculation of means across several levels

of collection will further stabilize the normality assumptions. The above

procedure was applied to all data before time- series or multivariate analyses were performed.

II. TIME- SERIES MODEL

Form of the Mode 

The concept of independent error terms inherent in typ i ca 1 regres s ion

techniques are often violated in the analysis of environmental data. Most

general linear models (GLM) assume that the observations within a single

data series measured at fixed intervals of time are statistically independent. Time correlations of data occur when an observation at some present

time can be predicted from past values of the same series. Application of

strictly linear models to this data will typically violate the assumptions
of independence and can lead to an invalid predictive model. Data exhibiting consistent measurable cycles over time are considered periodic.

Trigometric functions are easily used to approximate periodic behavior. 

function obeying sine-cosine type periodicity is specified as follows:

f(t) = A sin (At + 

where: = amp itude

= frequency, the number of times the function repeats itself in

a period of length 2n

= time

= phase angle, determines the points (- ~ plus integer values

of ~) where the function is zero.

Using standard trigonometric identities, a more useful paramaterization is written:

f(t) = B 1 cos At + B2 sin At

where: 1 = A siM

2 = A cos~

Based on the above

developed as follows:

relationship, GLM time-series model was

' = y, + r ' COS (2~t/P ) + B Sin (2~t/P, ) + E j=l 'J 

where: = 1 to the number of years of data (N)

k = the number of periodicities selected to fit all years

P = periodicity (= 2~/A)
The total number of terms in the model is N+(N*k)+1. The model

requires a data series measured at equally spaced intervals of time with a

constant number of observat ions per year. Res i dua 1 s from the correct 

selected model will be independent and normally distributed , exhibiting no

testable periodicity.

The time-series model paramaterization does not allow the inclusion

of an intercept term. Therefore, the correlation of determination (R

reported in this report has been reformulated. The model and total sums

of squares (reported R2 numerator and denominator, respectively) are not

adjusted for the mean of the dependent variable. The result is an R

which is slightly inflated over the standard formulation of R

comparison of the two formulations of R resulted in an R2 of 0.

(standard value) and 0. 88 (reported value).

Model Advantages

The funct i ona 1 form of the above mode 1 allows for ana lys is of the

following:

Statistical testing of selected periodicities within each

year.

Comparisons of s~lected periodicity effects between years.

Comparisons of year level terms (Y i) between years.

Abundance measurements of most fish species under study in this report vary in number or density and distribution between years. Therefore

calculation of a mean value based on a yearly sampling protocol is highly

dependent upon distributional constraints imposed by changing spawning

times, year-class abundance, and temperature and salinity differences over

time. Comparisons of these means between years may not be good indicators

of fish abundance or year-class strength. The year- level terms in the

time-series model serve as a yearly indication of abundance after adjusting for environmental effects which impose selective periodicities on
the distribution of fish. Year- level terms in the model are comparable

with each other but are not comparable to yearly mean densities reported

in the text. Sta tis t i ca test i ng of the presence or absence of

significant periodicty between years provides a testable means for

biological or environmental interpretation.

Ana lys i s Steps

Development and evaluation of any time-series model proceeded with

the following steps:

Spectral analysis of the In(X+1) data including statistical

tests for periodicity.

Selection of dominant or "most explainable " periodicities

based on the results of (1) above.

Fitting the time- series model.

Fitting the time~ series model without the year- level terms

(but including an intercept).

Spectral analysis of the residuals from (3) above, including statistical tests for periodicity, to evaluate model

fit and residual assumptions.

Linear regression on the residuals of (4) above to test for

significant linear trends over time.

Most species of fish were initially fit with 1- and 6-month

periodicities. In most cases, this model fit well and met the assumptions

of independent and random mode 1 errors. However, in those cases when

other periodicities were dominant and explainable or the error assumptions

were violated, the model was rerun using a second set of selected periodicities.
Spectra 1 Ana 1 ys 

Spectral analysis techniques are used to define the periodicities for

model formulation as well as testing model residuals. In spectral analysis! the fourier transform is used to decompose the data into sine and

cosine waves of different ampl itudes and wavelengths:

X(t) = (a /2) + E (ak COS w t + bk Sin w k=l

where: X(t) = data at time t (t = 1 

. . 

. N)

= N/2 (even N) or (N- l)/2 (odd N) = number of periodicities

which are determi ned

2X (set to zero for analyses in this report)

= cosine coefficients

= sine coefficients

21T kIN

The periodogram ordinate is defined as:

k = N (a

2 + b )/2

and represents the sums of squares for each of m frequenc i es. Select i on

of those frequencies with the greatest periodogram ordinates for inclusion

into the model will result in the best model fits. The larger periodogram

ordinates also represent the most important biological and environmental

frequencies. The distribution of periodogram ordinates for data or residuals with no periodicity will be relatively flat. Fisher s Kappa and

Bartlett' s Kolmogorov- Smirnov statistics were used for statistically testing the presence or absence of periodicities in both the data and residuals. Application of these tests to model residuals was used to test for

the assumption of residual independence.
Linear Trends

After application of the properly constructed time-series model, the

model residuals will generally show no significant periodicities (as

tested by Fisher s Kappa and Kolmogorov-Smirnov statistics). Linear regression can then be applie~ to these residuals without violation of the

standard error assumptions. The year- level terms are removed from the

standard model to allow for trends over time (otherwise, the slopes would

always be flat). The regression results provide a statistical test for

significant linear increases or decreases across all years.

III. MULTIVARIATE ANALYSES

Overvi ew

The multivariate analyses presented in this report are a composite of

principal component analysis, correlation analysis, cluster analysis, and

graphical techniques coupled with comprehensive biological interpretation. Principal component analysis (PCA) is a multivariate technique for

examining the relationship among quantitative variables. The effect of a

PCA analysis is to take a location by species matrix of mean In(X+1)

values and reduce it into a location by component matrix where the number

of components is smaller than the number of spec i es. Each component has

an associated eigenvalue giving the amount of variation in species

accounted for by the component and an eigenvector giving the weighting of

each species on the component. The eigenvectors are orthogonal , so the

principal components represent jointly perpendicular directions through

space of the original variables. Successive components account for

unique, progressively smaller portions of the total variation in

speci es. Ideally, 2 or 3 components wi 11 account for the majori ty of the

variation in species contained in the original data matrix. Correlation

analysis can be used to measure the amount of association of a species

with a component. Those species that vary widely over locations can have

high positive or negative correlations with the components. Note that

high correlations are dependent upon geographic distribution and not

magnitude of abundance. Principal components can be computed from a
variety of matrix transformations including the sum of square and cross

products, covariance, and correlation matrices. In this report, the

correlation matrix was uti ized. The effect was to adjust each species by

its mean and standard deviation , thus eliminating species magnitude and

variance as a measure of importance.

The multivariate analyses proceeded as indicated in the following

outl i ne:

Development of a location by species matrix where the

number of speci es is 1 ess than or equal to the number of

locations.

Development of a " location by environmental indicator (temperature, sal inity, grain size) matrix.

PCA of (1) above, producing a location by component matrix.

Correlation of individual species from (1) above with each

component.

Correlation of individual environmental indicators from (2)

above with each component.

Cluster analysis of (1) above.

Bivariate plot of component scores plotting locations with

species and environmental indicators as axis labels; also

on the plot is an overlay of the cluster results.

Interpretat ion

Interrelations of locations as defined by multivariate distributions

of species can be examined by bivariate plots of each location on the

scores of the first two principal components. The score of a location on

a component is the sum of the products of the transformed abundance of
each species times its corresponding eigenvector. Locations with similar

species associations wi 11 form a cluster on this graph. Cluster analysis

of the original location by species matrix , with squared euclidean distance as a measure of interlocation similarity, was also used to help

identify location groupings. Although cluster and PCA analysis are very

different techni ques, concordance among the resu ts strengthens the i nterpretation of the data. Biological and environmental gradients along the

components were exami ned with Spearman s rank corre 1 at i on coeffi ci ents.

Variation along the component is related to those species and environmental indicators with high positive or negative correlations with that component. Environmental indicators were standardized to mean zero and

standard deviation one before correlation analysis. It is important to

note that the correlations test linear relationships between variables.

The assumption of linearity between biological and environmental variables

is usually not met which affects significance testing of the correlation. However , the relative level of the correlation is an indication of

variable relationship and creates a basis for further biological interpretation.

The final step in the multivariate analysis is the comprehensive

biological interpretation. PCA, correlation, and cluster analysis serve

to define the geographical gradients of species and environmental variables. However , the biological and ecological evaluation of these relationships is left to the individual analyst.
APPENDIX C

RIVER LARVAL FISH AND TUCKER TRAWL

GEAR COMPARISON STUDY

INTRODUCTION

The river larval fish (RLF) program utilized only surface and bottom

samples (Section 3. 0) to assess river larvae densities. The discrete depth (DO) sampling program (Section 4.0) utilizes a Tucker trawl and

bottom sled to sample the 6 or 7 different depths over the water column

, 3, 5 , 7, 9, and 11 m). In order to determine which method provided

the best estimate of larval densities, a special study was conducted to

compare larval fish densities using RLF gear and DD trawl gear simultaneou s ly.

METHODS

Sample Collection

The samples were taken at Tucker trawl Station 34 for one complete tide (approximately 12. hours) on two separate nights (April 7- and

April 9- , 1984). At the start of each tidal stage , surface and bottom

larval fish samples were taken, followed immediately by a complete set 

(1, 3, 5, 7, 9, and 11 m) of DO trawl samples, followed by another set of

surface and bottom larval fish sample. This same sample scheme was repeated through each of the 8 tidal stages: high slack, high out, mean

out , low out, low slack, low in , mean in, and high in.

The collection gear and sample preservation was the same used in the

regular RLF and DO sampling programs. For further discussion , see CP&L

(1983) .
Data Analysis

Since the objective was to determine if there was a significant difference in the densities estimated by the two gear types, a paired t-test

was conducted to see if the two means (determi ned by each gear) were

equal. The t- tests were performed on loge transformed densities. Results

are presented at the P 2 0. 05 significance level.

RESULTS AND DISCUSS ION

Paired t-test results by round and with rounds combined (Table Cshowed mixed results. Salinities may have had some effect on the results

as they were lower during Round 1 than Round 2 (Figure C- 13).

Clupeidae

Clupeidae in Round 1 showed a significant difference between gears

with RLF catching higher densities. RLF surface nets caught higher

densities than DO trawls, and both bottom nets caught similar densities

with the 3- , 5- , and 7-m depths falling far below the straight line

between surface and bottom (Figure C-2). Comparisons by tidal stages also

followed the same pattern throughout the eight tidal stages (Figure

3). Past studies have shown that clupei ds tend to move to the surface

at night, so the curve for the DO trawl is quite representative of the

larval distribution of Clupeidae for all depths except the surface. The

RLF gear actually samp 1 ed the surf ace, whereas the DD trawl samp 1 ed

1 meter below the surface; therefore, the DO trawl gear showed lower

densities. Round 2 data showed no significant difference between gear

types but an examination of the density plots (Figure C- 2) show much the

same pattern as Round 1 for the upper half of the water column , but the

lower half of the water column was a different pattern. The OD trawl gear

caught more larvae in the bottom half of the water column , thereby

ba 1 anci ng out the compari son.
When results of both rounds were combined. the data showed a significant difference between gears, with the pattern the same as shown for

Round 1. Mean densities of RLF were similar for both rounds, but DO trawl

mean densities were lower in Round 1 than Round 

Croaker

Croaker in Round showed no significant difference between gear

types but an examination of the plots by tide and round show the DO trawl

gear caught more larvae at most depths (Table C- , Figures C- 5 and C- 6).

Round 2 croaker data showed a significant difference between gear

types with the DO trawl gear again having higher densities, although both

gear types caught higher mean densities than in Round 1 (Figure C- 5). 

examining the comparisons by tidal stage (Figure C- 6). they followed the

same pattern as the overall round. With salinity at zero, there were no

croaker present but as the sal inities increased (at the bottom of the

water column) densities increased, thereby weighting the bottom densities

of DD trawl gear. The same was true in Round 2 to a greater degree as

salinities were slightly higher . so densities at the bottom portion of the

water column increased proportionally.

When both rounds were combined , the data showed a significant dif-:-

Ference between gear types (Figure C- 4) with DO trawl gear showing much

higher densities at the bottom of the water column (7 , 9 and 11 m) during

both rounds.

Spot

Spot showed no significant difference between gear types in either

Round 1 . Round 2 , or combined rounds (Table C- 1). The density by tidal

stage and round show the larval fish gear collected higher densities at

the surface and the DO trawl gear collected higher densities at the bottom

(Figures C- , C-8, and C-9).
Total Fish

Total fish in Round 1 showed a significant difference between gear

types with RLF catching higher densities (Table C- , Figure 11). This

was explained by the fact that clupeids were the most abundant species

caught, so total fish results were heavily weighted by Clupeidae (Table 1). Plots by round and tidal stages of total fish (Figures C- ll and

12) and Clupeidae (Figures and C-3) showed the same patterns for

both. Combined round results were again like Clupeidae, showing no significant difference between gear types (Table Figure C- 10).

SUMMARY

Allen et ale (1959) summarized many other studies in which efficiencies of various gears were compared. The overall conclusions to be drawn

from their rev; ew are:

Most gears do not capture all fish exposed to them.

The proportion of the vulne;,rable fish captured by the gear may

not be consistent and certainly varies by species.

As a consequence, absolute abundance data cannot be obtained from monitoring surveys with most sampl ing gear.

In looking at the overall results of the t-test, it is apparent that

the RLF sampling technique, of sampling just surface and bottom, did an

adequate job of gathering information for estimating densities of larval

fish in the water column. It is also apparent that the RLF surface nets

were more efficient at sampl ing the surface than the DO trawl. On the

other hand, it appears that the DD trawl sled was more efficient at

sampling the bottom; but when the results are averaged over all species

and rounds, there was no significant difference in gear types.
Table C- Results of paired t-test on larval densities co 11 ected in the

gear comparison study conducted during 1984.

Standard Error

Taxon Round Mean of Mean PR )0 It!

Difference

Clupeids 1.174 270 003

Clupeids 079 O. 301 O. 80 1

Croaker 546 334 1.63 146

Croaker 1.023 323 016

Spot . 1 229 352 535

Spot 141 351 O. 699

Total 878 252 010

Total 0 . 004 323 992

Clupeids 1 & 2 627 241 020

Croaker 1 & 2 784 233 004

Spot 1 & 2 044 245 860

Total 1 & 2 437 228 1.92 075

Not significant -

01 " " 0.

0 . 00 1 " P " 0.

P " 0. 001

Indicates discrete depth

mean ln (density + 

Indicates discrete depth

mean ln (density + 

P ;. 0.

mean In(density + 1) " river larval fish

mean In(density + 1) )0 river larval fish
DEPTH 1m)

Figure Co

LARVAL FISH GEAR 

/

4 4.6 4. 8 5.

MEAN LOGe (DENSITY +1)

Clupeid density profiles for the gear comparison stud y with rounds combined, April 7- , 1984.
DEPTH (m)

ra!

133

137

DEPTH (m)

rat J

93 1

rae; ~

" t

1 1

Figure CROUND '" 1

LARVAL FISH GEAR

-4 e; 

MEAN LOGe (DENSITY +1)

ROUND '" 2

LARVAL FISH GEAR

lJ 

I" "'" 0""'"'"'

,.. 

I""'"'" 0""""""" 0"" . .. . .. I"'" 

.. 

-4 

MEAN LOGe (DENSITY +1)

Clupeid density profiles for the gear comparison study showing rounds

1 and 2, April 7-10, 1984. 
3 ~ 

::. .

B 11 

,...

DEPTH 1m)

B 11

B 11

811

Tidal Stage

LO = Low out MI c Mid LS = Low Slack MO = Mid out

LI = Low 

Clupeid density profiles for the gear comparison study by tidal stage, April 7- , 1984.

+:0

:::

0 '

= TUCKER TRAWL

x - - x = LARVAL FISH GEAR. MEAN OF REPS

0 = LARVAL FISH GEAR. INDIVIDUAL REP

Figure CLO'

,...

! 0 

"t0 '+

,.- 0

f.+.-

o"-' 

oto 0 

0 0

j.-fe 

'"'to o

MEAN LOGe (DENSITY +1) HO = High out

HS = High slack HI = High In
\,0

DEPTH (m)

e 1

LARVAL FISH GEAR 

TUCKER TRAWL

11, S

, 

, 

,

,. 

.

,.

,

6. B

Figure C1.9 1. 5 2. B ~. 0 4. S MEAN LOGe (DENSITY +11 Croaker density profiles for the gear comparison study with rounds combined, April 7- , 1984.
ROUND = 1

DEPTH 1m)

9:3

137

1 1

;3 

... 

MEAN LOGe (DENSITY +11

ROUND = 2

DEPTH 1m)

1211

1213

1215 TUCKER TRAWL

LARVAL FISH GEAR ""'

1217

1219

..... ,.. .... ... ,......... ,......... ,.........

:3 

... 

MEAN LOGe (DENSITY +1)

Figure C- Croaker density proIt1es for the gear comparison study showing rounds

1 and 2, April 7- 10, 1984.
DEPTH 1m)

LS .

B 11

HS HO ~/

. 

:1-

B 11

+x 0

......

B 11

:T '-..

:

1-. 0 " B 11

I . I . I . I . I ' 

= TUCKER TRAWL

MEAN LOGe (DENSITY +1) Tidal Stage x- - x = LARVAL FISH GEAR - MEAN OF REPS LO = Low out MI = Mid HO = High out 0 = LARVAL FISH GEAR - INDIVIDUAL REP

LS = Low slack MO = Mid out HS = High slack

= Low HI = High in

Figure Croaker density profiles for the gear comparison study by tidal stage, April 7- , ) 984.
DEPTH 1m)

f--'

f13

f1S

TUCKER TRAWL

2. (1

Figure Ci;: LARVAL FISH GEAR 6 4. MEAN LOGe (DENSITY +11 Spot density profiles for the gear comparison study with rounds combined, April 7- , 1984.
DEPTH Iml

ge;

Ii!JS

1 1

DEPTH 1m)

a 1

Figure CROUND'" 1

i LARVAL 

FISH GEAR

,... .. ,. .... ,....,.... ..... .....,.., ....... ,.

MEAN LOG" (DENSITY +11

ROUND = 2

TUCKER TRAWL

MEAN LOG (DENSITY +1)

Spot density prof'tles for the gear comparison study showing rounds

1 and 2, April 7- 10, 1984.
DEPTH (m)

LS I LI 

B 11

:

\

t\ 

/ 

1 HO

, 

,,

8 11 0 o "i- 00 "iLO . ~ LS '

...... 

..,.. :

,

~:t

"1-

B 11 0 '+

HS r0 . B 11 c0J.

Tidal Stag LO = Lowout MI '" Mid in

LS = Low slack MO = Mid outLI = LQW 

Spot density profiles for the gear comparison study by tidal stage, April 7- , 1984.

 

... 

 

TUCKER TRAWL

x - - x = LARVAL F ISH GEAR - MEAN OF REPS

0 = LARVAL FISH GEAR - INDIVIDUAL REP

MEAN LOGe (DENSITY +11 HO = High out

HS = High slack HI = High in

Figure C-
.......

U"1

DEPTH 1m!

1J9

LARVAL FISH GEAR l..-/ 1'15

5. G

MEAN LOGe (DENSITY +1)

Figure C- IO. Total fish density profiles for the gear comparison study with rounds combined, April 7- 10, 1984.
DEPTH (m)

,!t

1 I

LARVAL FISH GEAR

IS 

MEAN LOGe (DENSITY +1)

DEPTH 1m)

137

1 I

TUCKER TRAWL

.,..., .., ...,..

I; 

MEAN LOGe (DENSITY +1)

Figure C- 11. Total fISh density pror1les for the gear comparison study showing rounds

1 and 2, April 7- , 1984.
I--'

-....J

DEPTH 1m)

B 11

B 11

B 11 .

B 11

:+: 0 

-1---

:

0-..

........

Z\+

-- + = TUCKER TRAWL

)( 

)( 

LARVAL FISH GEAR - MEAN OF REPS

0 = LARVAL, FISH GEAR - INDIVIDUAL REP

0 o

0 '+

.......

-it1o

-+0 

f-.

o~o~

..

-f--

11 2

Tidal Stage

LO = Low outLS = Low slack

LI = Low 

MEAN LOGe (DENSITY +1)

() 

MI = Mid 

MO" Mid out

Figure C- 12. Total fish density profiles for the gear comparison study by tidal stage, April 7- 10, 1984.

HO = High out

HS = High slack

HI = Highin

DEPTH 1m)

LO . LS .

B 11 -

1 -

5 -

I '+

7 -

\

B 1'

...... 

:,

.......

B 11

. 

.. .... .... 

.. 

:,

B 11

1 Ii) 1 (i) 3 EJ (i) 113 213 413

Tidal Stage

LO "" Low out MI = Mid in HO = High out

LS = Low slack MO = Mid out HS = High slackLI = Low In HI = High in

Figure C- 13. Salinity profiles by tidal stage during the gear comparison study, April 7- , 1984.

MEAN LOGe (DENSITY +1)