MartinMarietta EnvironmentalSystems

c



### THE EFFECTS 

### OF SCREEN SLOT SIZE, SCREEN DIAMETER, AND 

### THROUGH-SLOT VELOCITY 

### ON ENTRAINMENT 

### OF 

### ESTUARINE ICHTHYOPLANKTON 

### THROUGH 

### WEDGE-WIRE SCREENS

Prepared 

### by: Stephen 

### B. Weisberg



### William H. 

### Burton 

### Eric A. 

### Ross Fred 

### Jacobs
Martin

### Marietta Environmental Systems 9200 

### Rumsey Road Columbia, 

### Maryland 21045



### Prepared for: Maryland Department 

### of Natural Resources 

### Power Plant Siting Program 

### Tawes State 

### Office Building

Annapolis, Maryland 21401



### August 1984MartinMarietta EnvironmentalSystems



### FOREWORD
This final report, "The effects of 

### screen slot size, screen diameter, and through-slot velocity on entrainment 

### of estuarine ichthyoplankton through wedge-wire screens," was prepared 

### by Stephen 

### R. Weisberg, William 

### H. Rurton, 

### Eric A. 

### Ross, and 

### Fred Jacobs 

### of Martin Marietta Environmental Systems for Dr. Paul Miller 

### of the State 

### of Maryland 

### Power Plant Siting Program. The study was conducted.fromAugust 1982 

### to July 

### 1983 as 

### part 

### of a program 

### to test alternative-intakescreening devices in 

### the State 

### of Maryland. 

### The work was conducted in its entirety by Martin Marietta Environmental Systems under Contract Numbers P1-83-02 

### and P1-84-02.



### iiMartinMariettaEnvironmentalSystems

MilninMariettaEnvironmentalSystems



### I. 1-1

B, 

### SAMPLING SCHEDULE,.,.....,................. 11-6

111. 111-1 A. 

### COMPARISON OF ENTRAINMENT RATES THROUGH SCREENS 

### OF DIFFERENT SLOT WIDTH AND AN 

### OPEN PORT.o...*....*......r.......u.......... 

### 111-1 

### B. COMPARISON OF ENTRAINMENT RATES THROUGH SCREENS OF 

### DIFFERENT SLOTWIDTH AND A 

### BONGO NET.**.*....*..***o.o..............., 

### 111-9 

### C. COMPARISON OF ENTRAINMENT RATES THROUGH 2-MM 

### SCREENS OF 

### DIFFERENT DIAMETER AND THROUGH-SLOT VELOCITY................,,.,.. 111-11 

### IV. DISCUSSION...,.................................. IV-l



### V. CONCLUSIONS..............................,....,, 

## v- 1

APPENDIX A TEST CONDITIONS FOR EACH NIGHT DURING 

### THE 1983 

### ENTRAINMENT STUDY..................,. A- 1 

### APPENDIX B 

### ANALYSIS OF 

### VARIANCE TABLES FOR THE EFFECT OF 

### SCREEN SLOT SIZE ON 

### BAY ANCHOVY ENTRAINMENT... B-

### z APPENDIX C 

### ANALYSIS OF VARIANCE TABLES FOR THE EFFECT OF 

### SCREEN SLOT SIZE ON NAKED GORY ENTRAINMENT.... 

### c-1

iiiMartinMariettaEnuironmenta(Systems



### TABLE OF CONTENTS (Cont'df

APPENDIX 

### D ANALYSIS OF VARIANCE TABLES FOR THE EFFECT OF THROUGH-SLOT VELOCITY AND SCREEN DIAMETER ON BAY ANCHOVY ENTRAINMENT......,............... APPENDIX E ANALYSIS OF 

### VARIANCE TABLES FOR THE EFFECT OF 

### THROUGH-SLOT VELOCITY AND SCREEN DIAMETER ON 

### NAKED GOBY ENTRAINMENT.,.......,.............

RP-200/ RP-193 PAGE



### D-1



### E-1

iv_ _ ~ MartinMarietta Environmental.Systems



### LIST OF 

### TABLES PAGE 

# - 11-1

11-2

111-1

111-2

111-3

111-4

111-5

111-6

1x1-a

111-9

IV-1

IV-2 Specifications

### of the types of cylindrical wedge-wire screens tested 11-5 Treatment 

### possibi.litLes for seven screen 

### size/ pump speed combinations tested in 1983 11-7 Salinity, dissolved oxygen concentrations, and surface

### water temperature during the studies 

### in 1982 and 1983 111-2 

### Mean density (per 1000

### m3) of bay anchovy 

### collected with each device by 

### size class in 1982 Mean density (per 1000 m3) 

### of bay anchovy collected with each device by 

### size c1a.ss in 1983 Mean density (per 1000 

### m3) of naked goby 

### collected with eisch device 

### by size 

### class in 1982 Mean density 

### (per 1000 m3) of naked goby 

### collected with each device by size 

### class in 1983 Mean density (per 1000 m3) of bay anchovies 

### collected inpaired 

### sets of bongo nets and screened samples Mean density (per 1000 m3) of naked gobies 

### collected in paired 

### sets of bongo nets and screened samples 111-3

111-4

111-7

111-8

111-LO

ItI.-12 Mean density (per 1000 m3) of each bay anchovy size-class collected through screens with different through-slot velocity and 

### screen diameter 111-13 Mean density (per 1000 m3) of each naked goby size-class collected through screens with different through-slot velocity and screen d

### i

### amete1: 

### III--25 Exclusion efficiencies of bay anchovies for three 

### screen sizes, compared to an open port and 

### to canal density IV-2 Exclusion efficiencies of naked gobies for three screen sizes, compared to an open port and compared to canal density IV-3

V

### LIST OF 

### FIGURES

PAGE 

### 1-1 

### Schematic 

### of a bulkhead-mounted screen, with cutaway 

### of wedge-wire configuration 1-2 11-1 

### Location of 

### Chalk Point power plant 11-2 11-2 

### Location of 

### the test facility in the intake canal 11-3 11-3 

### Schematic 

### of test facility used in this study 11-4 IV-1 

### Relationship 

### of standard length to head width for bay anchovy IV-

### 4 IV-2 

### Relationship 

### of standard length to head width

~ 

### for 

### naked goby IV-5

cMartinMariettaEnvironmentalSystems

ABSTRACT
Tests 

### were conducted in the Patuxent estuary from August 1982 

### to July 1983 

### to determine how certain design characteristics of wedge-wire screens affect entrainment of ichthyoplankton through the screens. The study examined the effect 

### of a) altering screen 

### slot sizeL 

### (lmm, 2mm, and 

### 3mm screens) while maintaining 

### a constant thlrough-slot 

### velocity (20 

### cm/sec), b) 

### altering through-slot velocity (9.5 

### cm/sec, 20 

### cm/sec and 40 

### cm/sec) while maintaining 

### a constant screen 

### slot 

### size (2

### mm), and 

### c) altering screen 

### diameter while maintaining constant through-slot 

### velocity (-20 

### cm/sec) and constant 

### slot 

### size (2mm). Size 

### specific responses of 

### two species, 

### bay anchovy (Anchoa mitchilli) and naked goby (Gobiosoma bosci), were examined. In comparison with 

### an open port, screens of 

### all slot sizes reduced entrainment, the effect being highly dependent on fish 

### size. Entrainment through 

### a l-mm screen was reduced 

### for both 

### species when fish reached 5 

### mm in length. For smaller fish, neither species 

### was excluded by.screens. Virtually total exclusion by 

### l-mm screens occurred for both species when fish 

### were 

### greater than 

### 10 

### mm in length. Evidence for two mechanisms of exclusion, physical exclusion and escape by fish 

### fromquickly dissipated flow fields, were apparent. Screen 

### slot size haid a measurable, but small, effect on the number of fish entrained. For 

### small fish, 

### no effect related 

### to slot 

### sizewas found. For 

### large fish, the effect 

### of slot size was the difference between 

### total exclusion produced by the physical barrier of 

### a l-mm screen, and an

J 80%reduction in entrainment found with screens of larger slot size. For fish of intermediate size, the difference in exclusion eEtI.sii2n.:y between a l-mm and 3-mm screen was approximately 25%. The effect of altering through-slot velocity over 

### a fourfold range was found to be significant 

### for naked gobies, but not for bay anchovies. Higher through-slot velocity resulted in greater 

### rates of entrainment for naked gobies. For 

### small gobies, this was apparent over the whole range of through-slot velocities tested. For larger gobies, only the highest thrcughslot velocity increased entrainment. It 

### is suggested that species such 

### as naked gobies, which inhabit 

### areas near the screen, willbe more affected by these changes in flow than willopen 

### water species, such as anchovies, which typically remain outside the influence of the withdrawal field.



# . The effectof screen diameter was found not to be very important, particularly for larger fish. For small individuals, a reduction of the screen diameter was accompanied by a slight reduction in entrainment.
vii

# -- J

. , .:,. .... . MartinMariettaEnvironmentalSystems



### I. INTRODUCTION


### The loss of biota by impingement and entrainment 

### is a potentially major impact which large volume water users can have 

### on aquatic communities. In an effort 

### to reduce such impacts, much research 

### has been conducted 

### to identify costeffective and ecologically sound water-intake modifications (American Society 

### of Civil Engineers, 1982). One promising technology designed to eliminate impingement and reduce entrainment 

### is the cylindrical wedge-wire 

### screen (also referred 

### to as profile wire screens, 

### or Johnson screens). Wedge-wire screens are a passive system, designed to reduce entrainment by physical exclusion and by exploiting hydrodynamics. Physical exclusion occurs when the mesh 

### size of the screen (e.g., 1 mm) 

### is smaller than the organism susceptible to entrainment. Hydrodynamic exclusion results from maintenance 

### of a low through-slot velocity which, because 

### of the screen's cylindrical configuration (Fig. 

### I-I), is quickly dissipated, thereby allowing organisms to escape the flow field. When located where ambient water velocity across the screen exceeds velocity through 

### the screen, their effectiveness 

### in reducing impingement and 

### entrainment 

### is enhanced (Hanson et al., 1978). In situ observations have shown that impingement 

### is virtually eliminated when.wedge-wire screens are used. (Hanson et al., 1978; 

### Lifton, 1979; Rrowne et al., 1981). Furthermore, laboratory studies (Hanson, 1981; 

### Heuer and Tomljanovich, 1978) and field studies (Zeitoun et al., 1981; Lifton, 1979; Rrowne et al., 1981; 

### Delmarva Power and Light, 1982; Weisberg et al., 

### 1983), have shown that fine mesh wedge-wire screens also reduce entrainment. 

### ; Despite the apparent success 

### of wedge-wire screens in reducing entrainment, there has been no attempt to distinguish the 

### relative importance 

### of 

### low through-slot velocity and small slot 

### width on exclusion. Although some studies have examined' 

# i:
the effect of varying screen slot size (Browne et al., 1981; i 

### Zeitoun et al., 1981; Lifton, 1979), and others have examined the effect 

### of altering the hydrodynamic field under laboratory 

# i conditions, (Hanson, et 

### al., 19781, 

### no study has partitioned these 

### two factors under field conditions. Further, it 

### can-be 4 

### assumed 

### that the effectiveness of 

### both mechanisms for exclusion P 

### are influenced by fish size, but only Delmarva Power and Light 

# ; (1982) 

### has examined the effect of fish size in relation to

c 

### either mechanism 

### of entrainment reduction. If wedge-wire screens 

### are to 

### be used for entrainment reduction, then an understanding of these mechanisms would seem to be a 

### necessary t 

### condition for 

### choosing an optimal deployment strategy.

1-1MartinMariettaEnvironmentalSystems

;
.

5: 4J -4 3



# . c 

### cu a, k 

### u tn 

### a cu -tJ

3 6 4 

### a -4

.. :i

.... 4 ac 0

l-4I H al k 3 F -4 b.4

1-2MartinMariettaEnvironmentalSystems



### In 'thisstudy, collections were made under field conditions to 

### determine: The 

### effect 

### of Screen slot width on 

### entrainment rate when through-slot velocity 

### is held constant. The effect 

### of through-slot velocity on entrainment rate when slot-width size 

### is held constant. The effect 

### of screen surface area on entrainment rate when both slot-width size and through-slot velocity are held constant. The influence 

### of these factors on different size groups of two common estuarine ichthyoplankton species.MartinhhriettsEnvironrnenteiSystems

11. METHODS

A. 

### STUDY 

### SITE
Tests 

### were conducted 

### at the Chalk Point Steam Electric Station, 

### located 

### on the Patuxent River in Southeastern Prince Georges 

### County, Maryland (Fig. 11-114 The 

### test device 

### was moored midchannel 

### in the Chalk Point intake canal approxi

### mately 25 

### m downstream frolm the mouth (Fig. 11-21. The intake 

### canal 

### is 62 

### m long, 25 

### m wlide, and 

### about 3 

### m deep, and draws 

### its 

### water from the Patuxent River via 

### a canal dredged through Swanson Creek. During the 

### tests, a unidirectional current of 

### about 15 

### cm/sec was maintained in the canal by the operation of the 

### power plant. Test Facility
The model intake 

### test. facility 

### used 

### in this study 

### was a 7.0-m 

### x 5.2-m barge (Fig. 11-31 equipped with 

### two identical 25-horsepower turbine pumps that could be operated at two speeds. In 1982, each pump had a capacity of approximately 7.7 m3/min at high speed and 3.7 m3/min 

### at low speed. Refurbishment of the sumps, prior to 1983 studies', increased withdrawal 

### rate to 12 

### m 

### /min at high speed arid 5.5 m3/min at low speed. Intake orifices were 2-m apart, 35 

### cm in diameter and 1--m below the water surface. Water exited from the barge through identical 25-cm diameter pipes cissociated 

### with each pump. The barge was situated 

### in the canal so that one port was upstream of the other and the axi.s of the screens was perpendicular to the current. The upstream port and the downstream port are referred to 

### as the left and right ports, respectively. Screens
Four types of cylindrical screens: 1-mm, 2-m, and 3-mm screens of nominal diameter, and a 2-mm screen of reduced diameter-were tested. 

### The dimensions of each are shown in Table 11-1. Each screen was mounted on backing plates that inserted into vertical tracks to guide the screen over the intake orifices (Fig. 1-11. The average ve1ocit;y through the open slots of the 1-mm, the larger diameter 2-m, and the 3-mm screens was 20 cm/sec arrd 9.5 cm/sec for high and low pump speeds, respectively, in 1483. Flow diffusers, intended to equalize flow over the screen surface, were present in all screens.

11-1MartinMarietta EnvironmentalSystems

.-.. IMartinMarietta EnvironmentalSystms

ru 0 c 0

m c Q) 

# "I \

a2 -A

L U wl 

# /

'
- 1 1 jMartinMariettaEnvironmentalSystems



## Right

## port 

# 4 Flow 

## Left port


# f Upperd& 

# \Sample

### port 

## Lowerdeck 

## Main

## port

Figure 11-3. Schematic of test facility used in this study

11-4~~ MartinMarietta EnvironmentalSystems



### Table 11-1. 

### Specifications of 

### the types of 

### cylindrical wedge-wire screens 

### tested. Screen Slot 

### Size Diameter (mm) (cm)



### 1 76 

### 2 

### (small) 54 2 

### (large) 76 3 76 

### Wire Percent Length Width Open 

### (cm) (m) 

### Area

86 

### 2 50 

### 46 2 66 61 2 66 55 2 75

11-5MartinMariettaEnvironmentalSystems



### B. SAMPLING SCHEDULE
Auqust 1982

Two samplings were conducted in 

### 1982. All tests were done at night to maximize the number 

### of organisms present and 

### to reduce gear avoidance by 

### visual cues. In tests conducted on 

### 19 August, entrainment through a large diameter 2-mm screen 

### was compared with entrainment through an open p0r.t. 

### Six replicate pairs 

### of samples 

### .were taken. Each pair consisted of 

### a'screened and an unscreened sample. Each condition was tested three times on each port in random order. Towed bongo net samples were taken in the intake canal simultaneously with each sample. In similar tests conducted on 22 August, entrainment through a 

### l-mm screen was compared with entrainment

I_ 

### through an open port. The pumps were run at high speed on both dates.

Summer 1983 Sampling was conducted 11 times (from 12 July to 28 July) in 1983. As 

### in 1982, all samples were coLlected at night. Seven different treatments (Table 11-21 were tested 

### on each port each night. The treatment order was random (theorder 

### of test conditions for each night 

### is shown in Appendix A). Towed bongo net'sampleswere taken in the intake canal simultaneously with each sample.

C. PROCEDURES Ichthyoplankton entrained through the test 

### facility were collected at the two main exit ports (Fig. 11-31 

### using 505-urn mesh plankton nets 1 

### m in diameter by 

### 4.2 m long. In 1982, approximately 100 

### m3 

### ofwater was pumped for each collection. In 1983, 360 

### m3 and 165 m3 

### of water were filtered at high and low pump speeds, respectively. The stepped oblique bongo tows (0.5 

### m 

### diameter, 505um mesh) were taken at the surface and at 1 m 

### and 2 m 

### depths approximately 5-15 m upstream of the test facility.

11-6&rtin firiettaEnvironmentalSystems

Table 11-2. Treatment possibilLties 

### for seven screen size/ pump speed combinations tested in 1983,
ScreenType

Open 

### port 

### l-mm screen 

### 2-mm 

### screen 2-mm screen 2-mm screen 2-mm screen 3-mm screen 

### * Velocity Pump Speed 

### Average ThroughScreen Velocity 

### (cm/sec) 

## * High 

### High 20 

### small

### 1 High 40 small) 

### Low 19 large

### 1 Nigh 20 (large) 

### Low 9.5 High 20

at the orifice of the open port was 400 an/ 

### sec at high pump speed and 190 cm/sec at low pump speed

11-7MartinMariettaEnvironmentalSystems



### Samples from both halves of 

### the bongo nets were combined for processing. Tows took 

### approximately 5 

### minutes and when combined filtered about SO m3 

### of water. The actual volume of 

### water filtered for each canal sample was calculated using a General Oceanics flowmeter installed in the mouth of one side of 

### the bongo net. For each sample, salinity, temperature, and dissolved oxygen were measured at the surface and near the bottom 

### of the intake canal. Salinity and temperature were measured with a Reckman salinometer. Dissolved oxygen was measured with 

### a YSI 

### model 

### 57 meter. All 

### samples were preserved in the field with 5% 

### formalin, in the laboratory, all fishes were sorted by species. Because fin damage precluded measurement of total length, the standard length (SL)

### of each was recorded to the nearest millimeter. Collections in which eggs were too numerous to count were first sorted for larvae: eggs were then counted by sub

### sampling with a Folsom plankton splitter (McEwen et al., 1954).

D. STATISTICAL 

### METHODS Preliminary Analysis

For most analyses in this report, variation in sample density was partitioned using either an analysis 

### of variance (ANOVA)

### or an analysis of covariance (ANCOVA). A 

### major assumption underlying these linear modeling methods is that homogeneity

(equality)

### of variances exists across different treatment groups. The log transformation [lOge(x+l)I was used for all
I 

### tests in this report to 

### meet this assumption. In order to examine size-specific effects of test conditions within species, we analyzed bay anchovy and naked goby data by size category. The categories were selected after determining which size increments would not result in large numbers of 

### empty cells and unequal treatment variances. For bay anchovies, the following size classes were used: C4 

### mm, 5-7 

### mm, 8-10 mm, 11-14 

### mm, and >15

### mm. For naked gobies, the following size classes were used: <4 

### mm, 5-6 

### mm, 7-8 iiirn, 

### and >9

### mm. Comparison of 

### Entrainment Rates Through Screens of 

### Different Slot 

### Width and an Open Port

For 

### data collected in 1982, the hypothesis that no 

### difference existed in the densities of 

### each size class between portsMartinMarietta EnvironmontolSyitamr
(leftand right) 

### or under varying screen conditions (open port, 1-mm screen, 2-mm screen) 

### was tested with 

### a two-way analysis of covariance, using canal density as the covariate. The model used in this analysis 

### was:

where Yijm = 

### mth (m=1, 2...6) observation of pump density taken 

### at the ith

### port (i=l, 21, the jth screen condition 

### (j=l, 2, 3)
D = 

### overall mean ai = 

### effectof the ithport

= effect of the :jth screen condition (ayIij = combined effect of the ithport and the jth screen condition

= combined effect of the jth screen condition and YjB canal density

, ai8 = combined effect of the ithport and the

. canal density (ayIij6 = combined effect of the 

### ithport and the jth screen condition and canal density Xjm = mth observation of bongo net density taken at the 

### same times as the jth screen condition X = 

### overall mean canal density 6 = pooled regression slope of pump density on 

### canal density Eijm = 

### error associated with the mth pump density observed at the 

### ith port and the jth screen condition. Thie 

### errors are assumed normally distributed with common mean 0 and variance 

### u2.



### For data collected in 1983, the hypothesis that no difference existed in the densities of each size class under varying conditions (open port, lmm screen, large diameter 2mm screen

11-9MartinMariettaEnvironmentalSystems



### at high pump speed, and 3-mm 

### screen) was tested with a blocked one-way analysis of 

### covariance, using canal density as the covariate, and the 22 

### date-port combinations as blocks. The 

### model used in this 

### analysis was:

where'ij = 

### observation of pump densit taken at the 

### ith block (i=l,2. .22) 

### the jTh 

### screen condition (j=l,2, 

### 3, 4)
p = 

### overall mean ai = 

### effect of block 

### i

= 

### effect of the 

### ith screen condition yi B = 

### combined effect 

### of the jth

### screen condition and the canal density Xij = 

### observation 

### of net density taken at the 

### ith block and the jth 

### screen condition X = 

### overall mean canal density B = 

### pooled regression slope of pump density on canal dens

### ity Eij = 

### error associated with pump density observed at the 

### ith port and the jth screen condition. The errors are assumed normally distributed with common mean 0 

### and variance 02.


### When interaction terms were found to 

### be insignificant, they were excluded from the model and a new fit was made that did not include the insignificant terms. When a significant screen-condition effect was found, pairwise comparisons 

### of the adjusted treatment means for the various screen conditions were made (Snedecor and Cochran, 1980). 

### If the covariate was found to be insignificant (i.e., slope 

### not significantly different from zero) or if interaction terms involving the covariate were found to be significant (implyingunequal slopes across treatment groups), ANOVA 

### models, similar to the model above without the covariate terms, replaced the ANCOVA 

### model. If 

### the screen effect was significant 

### in the ANOVA 

### model, Duncan's new multiple range test (Ott, 1977) 

### was used for comparisons among treatments.

11-10MartinMariettaEnvironmentalSystems



### Due to the high degrlee 

### of exclusion caused by screens, or to 

### the low numbers of fish in certain 

### size categories present in the intake canal, Cochran's t'estfor equality of 

### variance showed that in some cases unequal variances across treatment groups remained even after transformation. When the assumption 

### of homogeneity 

### of variance could not be met with transformation, the Friedman rank sum statistic (Conover, 1971) was used. In this test, the the observations are ranked within blocks and ranks are then summed over treatments. For the 1982 data, port (left, right) was used as the blocking factor; for 1983, date-port combinations were used. When treatment differences were significant, pairwise comparisons 

### of the treatment mean ranks were made (Conover, 1971). The critical values for each pairwise comparison were determined using a type I error of alpha/2m (wherem 

### is the number 

### of comparisons to be made) to account for increases in the Type I error from multiple hypothesis testing. The overall alpha was set at 0.05, 

### and most individual comparisons were conducted at a'=0.009. 

### Comparisons 

### of Intake Facility Collections and Net Collections
The null hypothesis of no difference in density between samples collected in the canal with bongo nets and samples collected through screens on the intake facility was tested using paired t-tests. Th.ehypothesis was tested separately for each screen condition (1-mm, 2-mm, and 3-mm screens). Com

### parisons were made using data from both years. Comparison 

### of Entrainment.Rates Throuqh Screens of Different Diameter/ThroUah-Slot Velocitv The hypothesis of 

### no difference in the densities of each size class when using screens 

### of different diameter and through.- slot 

### velocities (smalldiameter 2-nun screen at high and low 

### pump speeds, large diameter 2-mm screen at high and low pump speeds) was tasted using a blocked one way analysis 

### of covariance. Port-day combinations were treated as a blocking factor and canal density as 

### the covariate. The model used in the analysis was identical to 

### the one used to test for the effect of different slot 

### widths, except that screen diameter/through-slot velocity was 

### substituted for screen slot 

### size. As 

### with the earlier analysis, when interaction terms were insignificant, they were excluded from the model, and a new ti4 

### was made which did not include the insignificant terms. When a significant screen condition effect was found, pairwise comparisons of 

### the adjusted treatment means under varying test condj Lions 

### were made. When 

### the covariate was found 

### to be insignificant, or 

### the covariate by screen condition interactions was found to 

### be signi

### ficant (indicating unequal slopes across treatment groups),

11-11MartinMariettaEnvironmentalSystems



### the ANCOVA 

### model was replaced by a blocked one-way ANOVA. 

### Significant differences found using the ANOVA 

### model were tested using Duncan's new multiple range test. When low numbers resulted in unequal variances across treatment groups that could not be corrected for 

### by transformation, Friedman's rank sum statistic, described earlier, was used. In this case, date-port was used as the blocking factor and screen diameter/through-slot velocity condition was the main effect. When treatment differences were Significant, pairwise comparisons 

### of the treatment mean ranks were made (Conover, 1971). 

### The critical values 

### for each pairwise comparison were determined using a Type 

### I error 

### of alpha/2m with alpha set at 

### 0.05.

## -- ~~~ MartinMariettaEnvironmentalSystems



### ILII. RESULTS



### - The mean values for salinity, dissolved oxygen, and temperature during,the 1982 and 1983 study periods are presented in Table 111-1. 

### In 1982, salinity ranged from 7.3 .- 

### 11.3 ppt 

### with a mean value of 9.0 ppt. Lower salinities were recorded in 1983 

# (x= 7.2 

### ppt). Mean water temperature was higher in 1983 than in 1982 

### (29.1 vs 27.13OC). 

### Dissolved oxygen concentrations were 

### close to saturation in

### both years. The species 

### of organisms captured by the model intake facility and by nets towed in the discharge canal were similar in both 1982 and 1983. Ni3ked goby (Gobiosoma bosci) and bay anchovy (Anchoamitchilli) were the most abundant larval and juvenile fish during the study,with hogchoker (Trinectes maculatus) and silverside (Menidiamenidia) larvae captured occasionally. Grass shrimp (Palaemonetes spp.), 

### mysid shrimp

(Neomysisamericana), and an unidentified isopod 

### of the family Cymothoidae dominated the macroplankton. Amphipods (mostly Leptocheirus) and crab zoea were collected occasionally.

A. 

### COMPARISON OF ENTRAINMENT RATES THROUGH SCREENS OF , 

### DIFFERENT SLOT 

### WIDTH AND AN 

### OPEN PORT

Screens had the effect of lowering entrainment rate, relative to 

### an open port, for all but the smallest size category of both species and their eggs. The degree of entrainment reduction was dependent on fish size, with larger ichthyoplankton more successfully excluded. Screen slot size had some effect on entrainment rates, but the effect was not large. Anchovies
Tables 111-2 and 111-3 show the mean density 

### of anchovies, captured by size class under each screen condition in 1982 

### and 1983, 

### respectively. The size distribution 

### of anchovies present in the ambient waters (asmeasured by the bongo net collections and the open port) varied between years. Eggs and smaller larvae were prevalent in July 1983, 

### whereas in August 1982 no eggs 

### were found and the larger size classes predominated. The data for bay 

### anchovy met the assumptions of parametric statistics for 

### most size classes. However, it 

### was necessary to use 

### nonparametric methods for size class 2 (5-7 

### mm) in 1982,



### 111-1MartinMariettaEnvironmentalSystems



### rable 111-1. 

### Salinity, dissolved oxygen concentration, and surface water temperature during the studies in 

### 1982 and 1983.

Salinity

(ppt)

9.0 7.3-11.3 7.2 4.6-9.9 Dissolved Oxygen Temperature (ppm) 

### ("C) 

### 7.6 27.8 

### 4.3-10.5 25.9-28.9 6.9 29.1 5.5-9.6 27.1-31.5 -982 Mean Range 1983 Mean Range

111-2MartiriMariettaEnvironmentalSystems

Table 

### 111-2. Mean density (per 1000 m3) of bay anchovy collected with each device by size 

### class 

### in 1982.


### l-lNn Screen 0.0 

# 1 OoO 

# I 0.0 0.0
0.0
0.0



## - 8-10 mm 1.5 0.0



### - 11-14 IWI 

### 152.9 31.1 10.5 0.0



## - > 15 mm 

# I 57.3 

### 15.0 1.5


## - 2f469*4

111-3MartinMariettaEnvironmentalSystems

Table 111-3. Mean density 

### (per 1000

### m3) of 

### bay anchovy 

### sizeclass

Size Class Eggs



## - <4m

5-7 

### mm
8-10 

### mm

11-14 

### mm



### - > 15 mrn collected with each device by 

### in 1983. Bongo

Net I Open Port 3

### -mm Screen 

### 2-mm Screen 

### 1-mm 

### Screen 19610 

### 2341 1707 18435 10966

6.0 9.6 13.6 21.0 

### 9.2

37.6 

### 20.1 11.3 

### 9.2 10.8



### 11.2 7.7 2.6 

### 1.6 

### 1.0

3.5 

### 1.3 0.3 0.0 0.0

9.3 

### 3.3 

### 0.5 0.4 0.0

111-4MartinIMariettaEnvironmentalSystems

for 

### size class 4 

### (11-14 mi) 

### in both years, and for size class 5 (> 

### 15 

### mm) in 1983. 

### Except for class 3 (8-10 

### mm) 

### in 1983, use 

### of canal density as a covariate was ineffective for bay anchovies. Table 8-1 

### presents the results of ANOVA 

### for anchovy eggs. 

### No significant screen effect was found. Although there was a large difference in the mean number 

### of eggs entrained through the open port and the 1 and 2-mm screens, however this difference was small relative to the large variability associated with capture of eggs. There was no observed effect 

### of screen size on entrainment 

### of anchovies 

### in size class 1 (< 4 mm). ANOVA 

### performed 

### on 1983 data showed screen effectto be insignificant for this size class (Table B-2). 'In 1982, 

### no anchovies of this 

### size class were captured through the intake facility (Table 111-2). 

### There was a statistically Significant effect of screen size 

### on entrainment of size class 2 

### (5-7 mm) bay anchovies in 1983, 

### but not in 1982, In 1983 

### the open port collected approximately twice as many.orgalnismsas any 

### of the screens (Table 111-2). 

### Entrainment through the open port was significantly different from entrainment through all screens (Table B-3), 

### but no difference could bs detected among the different screens. In 1982, no size class 2 

### (5-7mm) 

### anchovies 

### were captured through either the 

### 1 or 2-mm 

### screens (Table 111-2). 

### However Friedman's Test did not show these screens to reduce entrainment significantly 

### (x2 = 

### 3.6, p = .17), 

### as only 5 

### individuals 

### of this 

### size class dere collected through the open port in 1982. 

### The effect Df 

### screen size on 

### size class 3 

### (8-10 mm) bay anchovies was significant in 1983, 

### but not in 1982. 

### In 1982, no 

### size class 3 

### anchovies were captured through the 1 mm screen, and the few captured through the open port and 2 mm 

### screen were insufficient to allow detection of a screen effect (Table B-4). 

### In 1983, significantly more anchovies of this size class were collected through the open port than through any 

### of the screens (Table B-5). 

### There were no significant differences 

### in entrainment for the different screen sizes (Table B-5). 

### In both years of the study, there was a significant screen effect for 

### the 

### 11-14 

### mm size class of anchovies. Friedman's test conducted with 1982 

### data showed that the number 

### of anchovies collected through the open port was significantly greater than that through the l-mm 

### screen (

## x2 = 

### 12.2, p 

## < .01). 

### However, entrainment through the open port was not significantly different from 

### entrainment through the 2-mm screen, nor was 

### the l-mm 

### screen different from the 2-mm 

### screen. Friedman's test on 

### 1983 data showed significant differences between the open port 

### and all screen sizes 

### (x2 = 

### 22.4, p 

### < .Ol), 

### but no 

### differences among screens (Table B-6). 

### Anchovies of this 

### si-zeclass were

III-sMartinMariettaEnvironmentalSystems

not captured through 

### a 1-mm screen in either year, and in 1983 none were captured through the 2-mm screen. The open port captured many times 

### more size class 5 (> 15m) hay anchovies in 1982 than the 1 

### or 2-mm 

### screens (Table 111-2). Differences in numbers 

### collected under the different 

### test conditions 

### were significant (Table 

### B-7). In 1983, no anchovies of this size 

### class were collected through the 1-mm screen (Table 111-3). Friedman’s 

### test showed 

### a significant 

### screen effect 

## (x2 = 29.97, 

### p 

## < .01). The open 

### port collected a significantly greater number of anchovies than 

### were entrained through any screen, but no significant difference inentrainment among screens of different 

### sizeswas found.

Naked Gobies
Tables 111-4 and 111-5 present the mean number 

### collected through screens of each 

### size for the four naked goby size 

### classes in 1982 and 1983, respectively. 

### As with bay anchovies, 

### more individuals 

### of small 

### sizewere present in ambient 

### waters in July 1983 than inAugust 1982. 

### More individuals of 

### large 

### sizewere present in the 1982 

### study (asmeasured by bongo net and open 

### port collections) than in 1983. Parametric methods 

### were found 

### to be appropriate for all naked goby analyses except that for the 1983 

### size class 4 (> 9 

### mm) data. Canal density 

### as a covariate 

### was found 

### to be appropriate for 

### size classes 1 ((4 

### mm) and 2 (5-6 

### mm) in both years, but 

### not for 

### size classes 3 (7-8 mm) and 4 ( > 

### - 9 

### mm) in either year. No significant screen effect 

### was found for size 

### class 1 (C 4 mm) in either 1982 (Table C-1) 

### or 1983 (Table C-2). In 1982, the mean number of individuals captured through the 1-mm screen 

### was less than 10%of that 

### collected through the open port (Table 111-4): however, this 

### was found 

### to be statistically insignificant using ANOVA (p = .63, Table C-1). In 1983, the mean number of individuals captured through the open 

### port varied by 

### less than 5%from the mean value of fish captured through any of the screens (Table 111-S): these differences 

### were also statistically insignificant (TableC-2). The effect of screen 

### slot 

### sizewas found 

### to be significant for 5-6 mm naked gobies in 1983 (Table C-3), but not in 1982. 

### rn 1983, the 

### 1-mm screen captured significantly fewer individuals of this size 

### class (250%)than the open port (TableC-3). The 1-mm screen collected significantly fewer individuals than the 2-mm 

### or 3-mm screens. The numbers collected through the larger mesh screens did not differ significantly from those collected through the open port (Table C-3). In 1982, the 1-mm screen

111-6MartinMariettaEnvironmentalSyttenk

'able 

### 111-4.

Size 

### Class 

### (mm3 < 4


## - 5-6
7-8
> 9



### - Mean density 

### (per 

### 1000 m3) of naked goby collected with each device by size 

### class 

### in 1982. Bongo



### Net Open 

### Port 2-mm 

### Screen 

### l-mm Screen 95.3 

### 17.2 13.5 1.5



### 117.6 22.9 19.5 

### 6.0

95.5 

### 38.5 16.5 5.8



### 342.3 201.5 

### 64.6 35.8

111-7MartinMariettaEnvironmentalSystems



### 1-mm Screen

562.5

66.5

3.9

~ 111-8MartinMariettaEnvironmentalSystems



### also collected less than half the number of 5-6 

### mm individuals collected through the open 

### port (Table 111-41, but the 

### screen effectwas not found to be significant (Table C-4). Tables C-5 and C-6 show results of ANOVA 

### �or the 7-8 mm 

### size class in 1982 and 19183, respectively. The 

### screen 

### effect was significant, and the open 

### port 

### collected a significantly greater number of individuals than 

### all screens in both years. The 

### 1-mm screen 

### collected significantly fewer individuals than the 2-mm screen in 1982 (Tables 111-4 and C-51, and significantly fewer than the 2 

### or 3-mm screen in 1983 (Tables 111-5 and C-6).The screen effect

### waLs found 

### to be significant for the 

### > 9 

### mm 

### size class in both 

### yeairs of the study. In 1982, both the 1 and 2-mm screened samples contained significantlty fewer gobies than the open 

### port, but 

### no difference between the screened 

### samples was found (Table C-7). In 1983, the open 

### port also collected significantly 

### more gobies of this 

### size than each 

### of the screens according 

### to results of the Friedman's 

### test 

## (x2
= 39.50, p 

### < .01). As in 1982, the effect of the 1-mm screen did not differsignificantly from the effect of the 2-mm screen in 1983 

### tests; however, significantly fewer gobies 

### were entrained through the 

### 3-mm screen.



### B. COMPARISON OF ENTRAINMENT RATES THROUGH SCREENS OF DIFFERENT SLOT WIDTH AND A 

### BONGO NET
The pattern of exclusion by screens 

### was very 

### similar when compared 

### to bongo nets 

### or when 

### compared with open 

### ports. Screens had the effect of reducing entrainment, relative 

### to density measured with 

### a bongo net, for 

### allbut the smallest size category of each 

### species and for 

### eggs. The degree of entrainment reduction increased with fish size, and was affezted only 

### to 

### a minor degree by screen 

### slot size. Bay Anchovies
Canal density and densities of concurrent screened samples of each bay anchovy 

### size class 

### are presented in Table 111-6. There was no significant difference in density of eggs for screens of any slot size 

### relative 

### to canal density. For the 1-mm and 2-mm 

### screens, mean density in the canal exceeded the screened density three 

### to four fold, but these differences were insignificant due 

### to the high variability associated with ambient egg density.

111-9MartinMariettaEnvironmentaiSystems

rn rn rn C c r: c 

# I C C rD 

# . c m 19 

# . m 

# . m 

# . II 0 m 4 N 0 0 

### cn I+ 

# I ifi P d d

\o 19 

# . m cv

# . 19 m 

# . -3 Ln I- Q\ 0 N v d N 4 I-



# - 

# - - 

# ­

m rn C C e 

## * * m In P a 

# . -3 m 

# . Ln 

# . m .Fp W II cv N m a3 d d

I+ 0 W N I- 

# . a\ 

# . m 

# . ln -3 in 

# . 4 0 W Iln m 4 w P 9



# - -

# - ­

m ([I C v) W C 

### * c c c V W N Ln W 0 m a, m 2= 0 l- W 0 0 0 u 4 E 0 L W u -=$ C N W 0 P d 0 a, W h 0 m m P. N W a, -Y m cv d W ln w -d 73

I_ h 7 4 LI C ([I
-4 ln u4 -Y P d -r( I c 

# 2 2 2 u
VI Ln VI 0 -4 cn t-.1 I 

# - -k
111-1cMartinMariettaEnvironmentalSystems

Although the density of bay anchovy size 

### class 1 (< 4 mm) in screened samples always exceeded canal density, none-of the differences werl? statisti-callysignificant. For all other size classes, tile density in the canal was always higher than that of screene(lsamples,, All the comparisons 

### were statistically significant, 

### exzept 

### for that 

### between 3-mm screen der,sity and canal density for size

### class 4 (11-14 

### mm) anchovies. In this comparison, the density through the 

### screen was only about 10% of 

### the density 

### estimated from the 

### bongo net collections, but 

### low numbers of fish

### were taken with both devices, which probably accounts for the 

### lack of significance.

Naked Gobies
Table 111-7 shows the mean density of naked gobies 

### for each 

### size class collected in screened samples compared with canal densities. All cornparisons of bongo net samples and screened 

### samples for naked gobies 

### were statistically significant, but the direction of the difference

### was dependent on fish size. The density of gobies in

### size class 1 (< 4 mm) 

### was always greater in screened 

### samples than in the-canal samples. However, for 

### allother 

### size 

### categories, the canal samples had 

### a considerably higher mean density than screened samples.

C. COMPARISON OF ENTRAINMENT RATES THROUGH 2-MM SCREENS OF DIFFERENT DIAMETER AND THROUGH-SLOT VELOCITY
The four combinations of screen diameter velocity 

### were not found 

### to affect entrainment but did affect that of naked gobies. Density in our samples generally increased with higher velocity, but was dependent on fish size. Bay Anchovies and through-slot of bay anchovies, of naked goby

through-slot

Table 111-8 shows the mean density for each bay anchovy size category collected through 2-mm screens of different diameter and through-slot velocity. The assumptions of parametric 

### statistics were 

### met for 

### all 

### size classes except size 

### class 

### S.(>15 mm). The canal density 

### was a significant covariate with homogeneous slope only 

### for size class 3 (8-lorn). Tables D-1 through D-5 show ANOVAS for eggs and fish of size classes 1-4. 

### In none of these cases was the effect of throughslot velocity or screen diameter significant. For size 

### class 5 (> 15 mm), Friedman's test showed that effects of through-slot

111-11MartinMariettaEnvironmentalSystems



# I-+-i

i I I I I I I I

111-12 

# I___~ MartinMariettaEnvironmentalSystems

rable 111-8. 

### Mean density 

### (per 1000 

### m3) of each bay anchovy 

### size class collected through screens with different through-slot velocity and 

### screen di

### amet

### er

# .

screen Diameter Pump Speed rhrough 

### Slot Jelocity (

### cm/sec)

Fish Size 

### (mm) 8-10

11-14
>15



### - Low
9.5 22229

23.7


### 15.7

1.9

0.0 Small Small

20 19 40 18435 24752 3358

21

### .o 32.3 8.8

9.2 16.3 13

### .O
1.6 3.3 3.3
0.0 0.3 0.5
0.4 

# 1 0.8 

# 1 0.8

I

LMartinMarietta EnvironmentalSystems



### velocity and screen diameter were insignificant (

### ~2 = 

### 3.0, p = .39). 

### These findings are supported by the data in Table 111-8, 

### which show no consistent pattern 

### of large differences in 

### entrainment rates for different test conditions. It 

### appears that 

### for bay anchovies, neither screen diameter nor through-slot velocity, within the range tested, affected entrainment through the screens. Naked Gobies
Table 111-9 

### shows the mean density for each naked goby size class collected through 2-mm screens of different diameter and through-slot velocity. For all size categories, the assumptions necessary for use 

### of parametric statistics were met. The covariate was found to be significant only for size classes 1 ( < - 

### 4 

### mm) and 2 (5-6 

### mm). Unlike results obtained for bay anchovies, the through-slot velocity and screen diameter effect was significant for every naked goby size class (Tables E-1 

### to E-4). 

### There were some minor differences in rank order for different test conditions, but the small screen at high pump speed always captured the greatest density of gobies. 

### For size categories 1 ( 

### < 4-mm) 

### and 2 (< 5-6-mm) 

### gobies, the magnitude 

### of difference betweer? this and other screen conditions was relatively small (C 

### 50%). For 

### goby size categories 3 (> 

### 7-8-mm) 

### and 4 (>9-mm), 

### the difference increased to 

### more than 100% 

### (Table 111-9). 

### ANOVA 

### done 

### on size category 1 (< 4 mm) 

### showed that screens 

### of both large and small diameter collected significantly mor2 

### individuals per volume filtered when operated at high pump speed than at low pump speed (Table E-11, 

### while collections from screens 

### of different sizes, used with the same pump speed, 

### did not differ. For size class 2 (5-6 

### mm), 

### both high purne 

### speed conditions entrained a greater density of gobies cha~ 

### the large screen at low pump speed (Table E-2 

### and Table 111-9). 

### No 

### other significant differences were found within this size group. 

### For size classes 3 (7-8 

### mm) 

### and 4 

## (29 mm), 

### the density of 

### fish collected through the small screen operated at high speed was significantly greater than the density under all other conditions, and no other significant differences were found (TablesE-3 

### and E-4).

111-14MartinMariettaEnvironmentalSystems

Table 111-9. Mean 

### density (per 1000 

### m3) of each naked goby 

### size 

### class collected through screens

### with different through-slot 

### velocity and 

### screen di

### amet

### er

# .
Screen 

### Diameter 

### I Large 

### I Larqe Sma11 Srna1.1 Pump Speed Low High Low High Through-Slot Velocity 

### (cm/sec) 9.5 20 

### 19 

### 40 <4 400.5 513.4 424.8 598.6 

## I I



## - >9 

### 4.7 4.4 3.6 

### 11.4

### -- MartinMariettaEnvironmentalSystems

IV. DISCUSSION 

## -
Do Screens Reduce Entrainment Relative 

### to an Open Port?

Entrainment 

### rates of bay anchovy eggs and of larvae 4 ITUII 

### in length 

### or less, were not significantly affected by screens. However, approximately 

### 50%

### of the 5 

### to 7 

### mm bay anchovies 

### were excluded in comparison with an open 

### port. Individuals 

### greater than 7 

### mm long 

### were increasingly excluded with 

### size. For anchovies 

### greater than 10 

### mm 

### in length, 

### almost 100%exclusion by a l-mm screen 

### was noted. In the 

### case 

### of naked gobies, fish 4 

### mm in length 

### or less were not excluded by screens when entrainment 

### rates were compared 

### to those for an open port. Exclusion began 

### to occur for fish 

### of 5 

### to 6 

### mm, and exceeded 90%for gobies 7 

### mm or longer when using 

### a 1-mm screen. Tables IV-1 and IV-2 show screening efficiency 

### for each size 

### class 

### of bay anchovy and naked goby, respectively. The degree of physical exclusion should be expected 

### to increase 

### as fish

### grow larger. Figures IV-1 and 

### IV-2 show the relationship between body length and head width for bay anchovies and naked 

### gobies, respectively. Physical exclusion by screens might 

### not be expected for fish of both species 4 mm in length 

### or less, since their average head width 

### is less than 0.5 

### mm. On the other hand, fish 

### greater than 8 

### mm long 

### are close to, or exceed, 1 

### mm inwidth and should not be entrained through 1 

### mm 

### slot width screens. Data from the study support this. For bay anchovies, only 

### a single individual above 8 mm 

### in length was ever caught through a l-mm screen, and the exclusion efficiency of a l-mm screen was 95%for naked gobies larger than 7 mm. Swimming performance and ability 

### to avoid flow fields 

### also increase with fish size, and probably contributed 

### to exclusion of larger fish. Hanson (1981)'observed that striped bass under 7 

### mm in total length 

### (TL)do not possess sufficient swimming ability to avoid screens under laboratory conditions, whereas larger fish do. In our study, individuals of either species 4 

### mm (SL) in length or less 

### were not excluded by screens. Bay anchovy eggs possess no swimming ability and were not excluded by l-mm screens according to both this study and the study of Browne et al, (19811, even though the eggs exceed 1 mm in diameter. In cont.rast, individuals larger than 4 mm were excluded by all 

### screens in our study, even though they could easily pass through screens with 2 and 3-mm slot width.

IV- 1MartinMariettaEnvironmentalSystems

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IV-2MartinMarietta EnvironmentalSystems



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IV-4MartinMariettaEnvironmentalSystems



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IV-5MartinMarietta EnvironmentalSystems

Other studies have 

### also shown that fish 

### size is an important determinant of screening efficiency. In flume studies conducted by Hanson (19811, yellow perch of less than 8 

### mm (TL) were 

### not excluded by a l-mm screen. Exclusion efficiency increased with increasing fish 

### size and 

### became 100%when yellow perch reached 13

### mm (TL). A 

### similar pattern, with 

### total exclusion at 11 

### mm (TL), 

### occurred for striped

### bass. In field studies with 

### a 

### l-mm screen, exclusion of 

### striped bass 

### was insignificant 

### for individuals 

### less than 10 

### mm 

### (TL),but 

### was greater than 90% 

### for individuals larger than 

### 11 

### mm, Delmarva Ecollogical laboratory (1980). They 

### also found 

### similar 

### size related patterns 

### for other fish 

### species. This was the only other study inwhich the effect of fish 

### size on screening efficiency in the field has been examined. However, in 

### several field studies 

### it has



### . been noted that the maximum 

### size of fishentrained through 

### l-mm 

### screens 

### is less than that 

### collected through open 

### ports or towed nets 

### (Dames and 

### Moore, 1979; Otto

### et 

### al., 1981; Zeitoun et 

### al., 1981). In the present 

### study, fish 

### size

### was found 

### to be important in determining the effectiveness of 

### wedge-wire screens. In many other studies of reduction 

### inentrainment through 

### wedge-wire screens, the effect of fish size has not been examined, which may help 

### to ex?lain why apparent inconsistencies inconclusions 

### were reached by previous researchers. 

### Dames and 

### Moore (1979) and 

### Delmarva Power and Light (1982) both found 

### close to 100% exclusion 

### of bay anchovies in comparison 

### to Browne 

### et al., (1981) who found only 61%exclusion. The mean 

### size of anchovies 

### was not given in the first

### two studies, and may have been large. 

### In contrast, the mean 

### size of anchovies 

### collected through the open port inthe study 

### of Browne 

### et al., 

### was only 4.2 

### nun 

### (TL). In the 

### case of naked 

### gobies, Dames and 

### Moore (1979) found 56%exclusion efficiency through 

### a l-mm 

### screen, while Browne 

### et 

### al., (1981) found no significant difference between collection through 

### a l-mm screen and through an open port. Again the 

### small mean 

### size of gobies entrained through the open 

### port in the 

### later study (4.8 

### mm) may have led 

### to their 

### lesser estimate of exclusion.

Do Screens Reduce Entrainment Relative 

### to Canal Density?

Tables IV-1 and IV-2 show screening efficiency compared to canal density for 

### 1, 2 and 3-mm screens. The pattern of exclusion 

### is very 

### similar 

### to that observed when screens were compared with an open port, i.e., screens effectively reduced entrainment, though the magnitude was dependent on fish size. For bay anchovies, entrainment of eggs 

### or individuals less than 5 mm 

### in length was not significantly affected by screens. Individuals larger than 5 

### mm were excluded 

### in comparison to either open port 

### or canal density, though the magnitude of exclusion was greater in relation 

### to canal density. For anchovies IV-6MartinMariettaEnvironmentalSystems

laryer'than 14 mm, the exclusion efficiency of all screen sizes tested exceeded 99%

### .in 

### relation to canal density. Naked gobies of 4 

### mm in length 

### or less were captured in significantly 

### greater numbers in screened samples than in bongo net samples. The attraction through the screens indicated by these data could be due 

### to this 

### species' habitat preference 

### for structures. Naked gobies 

### were often observed during the study swimming in 

### or near the biofouling community that developed 

### on the 

### barge. This behavior would tend 

### to cause underestimates of ambient 

### density when measured by the bongo net, which 

### was towed upstream of the barge. For gobies greater than 4 

### mm in length, screens significantly 

### reduced entrainment in relation 

### to canal density. For 

### gobies 

### larger than 6 

### mm, exclusion 

### was always 

### greater than 90%. 

### In our study, 

### as well 

### as in others, towed net samples have 

### almost always been shown 

### to contain 

### more ichthyoplankton than unscreened port samples. This 

### is not surprising, since an unscreened 

### port 

### creates a flow field which ichthyoplankton can
. detect and avoid (Hocutt 

### and Edinger, 1980). Bongo nets, on the other hand, 

### are 

### an active collection method and 

### are generally towed at speeds which make avoidance by 

### smaller ichthyoplankton unlikely. When calculating screening efficiency, the use of towed net 

### samples 

### as a 

### control will therefore result in exclusion efficiences higher than those found when using unscreened ports. We have presented exclusion efficiency using both methods as reference points. For 

### most fish size 

### classes, the conclusion reached inour study would be the 

### same using eithermethod, though the magnitude of exclusion would vary. The open 

### port method 

### is the 

### more conservative approach and 

### is our 

### recommended method for estimating entrainment reduction. However, the towed net method should not be discounted. Several authors have shown that ichthyoplankton estimates increase with increasing boat speed up 

### to about 8 

### m/sec (Thayer 

### et al. 1983; Colton et al. 1980; Clutter and Anraku, 1968). Since 

### our 

### tows were conducted at a boat speed of approximately 0.5 

### m/sec., they may still produce underestimates of actual numbers present in the ambient waters.
Did Screen Slot SizeAffect the Numbers Collected?
In this study, fewer individuals of both species were entrained through the l-mm 

### screen than through the 2 

### or 3-mm screens. For 

### most size 

### classes of naked gobies these differences were significant. However, for 

### several size classes of bay anchovies, the difference in entrainment rates among different screens was not significant. Examination of the data indicates that the lack of statistical significance may be an artifact of low numbers. For example, not a single anchovy in the 11 to 14 mm size class 

### was entrained through a l-mm screen in our IV-7MartinMariettaEnvironmentalSystems

tests. Total exclusion by 2 

### or 3-mm screens.

### was 

### not observed. However, because of low ambient anchovy.abundance, and the 70-80% exclusion offered b;y 2 and 3-mm screens, sufficient samples containing no anchovies were 

### collected through the 

### larger 

### screens 

### so that these results could not be 

### statistically distinguished from those for the 

### l-mm screen. 

### In other studies that have compared entrainment through screens of different 

### slot size, the mean number olf individuals 

### collected through the 

### larger 

### screen has always been greater. In the study by 

### Dames and 

### Moore (19791, the difference in fish 

### collected when using 

### a 1 and 

### 2-mm screen

### was only 8%. However, Browne 

### et 

### al. (1981) found, on the average, 80%greaterentrainment of naked gobies and bay anchovies through a 

### 2-mm 

### screen than through 

### a l-mm 

### screen. Zeitoun 

### et 

### al. (1981) found, 

### on the average, that 40%

### more individuals 

### were entrained through 

### a 

### 2-mm screen than through 

### a 9.5-mm screen. Thus, 

### a consistent trend has been found 

### in a11 studies; larger mesh screens entrain

### more organisms but the differences 

### are not statisticallysignificant. There 

### are twopossible explanations 

### for the lack of 

### statistical significance. First, thismay be due 

### to low numbers captured, 

### as was the 

### case with bay anchovies in our study. With 

### low numbers variance 

### tends 

### to increase 

### and small differences 

### become difficult 

### to detect. Secondly, in all of the studiesmentioned above, fishof different size 

### classes were grouped 

### together for analysis. However, different sizegroups behave differently with respect 

### to 

### screen size. Small individuals may not be affected by changes in 

### slot size if they can pass through the 

### smallest 

### slot sizes (e.g., the fish

### < 4 

### mm size in our study). Similarly, large i'ndividuals will-not be a�fectedby changes 

### in screen 

### slot size if they 

### are so large 

### as 

### to be physically excluded by all 

### scrzens or possess sufficient swimming ability 

### to avoid entrainment through 

### screens of 

### all sizes. When analysis is conducted on data that 

### is pooled over several size groups, the increased variance may obscure significant patterns that occur only within a limited size range.
Did Screen Diameter Affect the Numbers Captured?


### Screen diameter appeared 

### to have little effect 

### on the 

### number of ichthyoplankton entrained. The effect of screen diameter 

### on the number of individuals captured was determined by c.omparing the large diameter 2-mm 

### screen 

### at high pump speed with 

### results for the small diameter 2-mm screen at low pump speed. Both 

### screens had the same through-slot velocity. 

### For bay anchovies there was no 

### statistical difference. For naked gobies, only for the smallest category was there a significant difference. In the latter 

### case, the large screen at high pump speed collected approximately 20%more fish.

IV-8MartinMarietta EnvironmentalSystems

Did Throuqh-Slot Velocity Affect the Numbers Captured?
The effect of through-slot velocity on the density of individuals collected can be discerned by comparing effects 

### of screens of identical diameter and 

### slot width size, but 

### of different withdrawal 

### rates. In our study, such 

### a comparison was made 

### twice: between the effects of high and 

### low pumping 

### rate when the large diameter 2-mm screen 

### was used (20 

### cm/sec and 9.5 

### cm/sec through-slot velocity, respectively), and the 

### effects of high and 

### low pumping 

### rate when the 

### smalldiameter 

### 2-mm 

### screen rate was 

### used (40 

### cm/sec and 19 

### cm/sec, respectively). The density of bay anchovies did not differ when 

### collected through screenswith different through-slot velocity. The number of bay anchovies 

### collected through 

### 2-mm screens, particularly 

### for the larger 

### size classes, was 

### low. No consistent differences 

### in the mean density of individuals 

### collected under different conditions 

### were apparent (Table 111-81, though the 

### low numbers may have hampered our ability 

### to detect significant differences. For every naked goby size 

### class, the greatest density was found in samples taken 

### at the highest through-slot velocity (Table 111-9). Significant differences 

### were observed for the 

### smallest size 

### class of 

### gobies between 9.5 

### cm/sec and 20 

### cm/sec., 

### as well 

### as between 19 

### cm/sec and 40 

### cm/sec. For the 

### two largest goby size 

### classes, significant differences 

### were found only between 19 

### cm/sec and 

### 40 

### cm/sec. This pattern suggests that the swimming abilityof 

### smaller gobies 

### is sufficient 

### to overcome through-slot velocities of 9.5 

### cm/sec, but not of 

### greater withdrawal 

### rates, and that 

### larger gobies can 

### overcome velocities as great 

### as 20 

### cm/sec but not 

### as great 

### as 40 

### cm/sec. In tests of screen slot 

### size, swimming ability was undoubt5,5iy important in reducing entrainment of both species through 

### screens with 

### slots too large 

### to exclude them physically 

### (i.e.! 2, and 3-mm screens). Therefore, it 

### is surprising that entrainment of bay anchovies 

### was not affected by changes in the 

### flow field. The through-slot velocities we chose 

### to test may havs Seen 

### too low 

### to affect anchovies, but high enough to affect naked gobies. Hanson et al. (1978) used anchovies in 

### tests with through-slot velocities that were higher than those we used, and found 

### little effect 

### on the fish. However, anchovies used 

### in tests 

### by Hanson et al. were larger than those inour studies and it is unlikely that the anchovies inour study could escape currents of 40 cm/sec. Further, maximum swimming speed of 

### most larval fish, including anchovy (Webb and Corolla, 1981) and goby (Logachev and Mordvinov, 1979) species, is generally less than 10 

### cm/sec (e.g., Blaxter, 1969; Hettler, 1978; Hartwell and Otto, 1978; Turnpenny and Bamber, 1983). Even 15 mm anchovies would not possess enough swimming ability to escape the 40 

### cm/sec through-slot velocity used in our tests.

IV-9.. MartinMarietta EnvironmentalSystems

A 

### better explanation for differences in response to throughslot velocity may include differences in behavior: 

### of the two species, along with the differences in swimming ability. Naked gobies tend 

### to prefer structures and were observed swimming very 

### close to the screen, as if feeding on detritus drawn toward it. Anchovies were not observed to move as 

### close 

### to the screen on a regular basis. The through-slot velocities used in this test were qui.cklydissipated by the screen's circular configuration. In our attempts at measuring flow, water withdrawal 

### was indistinguishable from ambient flow at 

### a distzance of less than 10 cm from the screen surface. Gobies, because they swim close to the screen, should be more affected by khis change 

### in their local environment than anchovies, which generally remain outside this flow field.

IV-10MartinMariettaEnvironmentalSystems



### V. 

### CONCLUSIONS



### In this study we have shown that the effectiveness of wedge-wire screens in reducing entrainment 

### is dependent on fish 

### size. Evidence for exclusion by maintenance of low through-slot velocities as well as by physical exclusion, were-apparent. A l-mm screen reduced entrainment 

### of both species when they reached 

### 5 

### mm in length. Below that size, no exclusion by screens was apparent. Above 10 

### mm 

### in length, virtually total exlusion by 

### l-mm screens occurred for both species. Screen slot size had an effect on the number of fish entrained, but the effect was not large. A 

### l-mm screen was found to 

### represent a barrier for 100% 

### of the larger fish, while Screens with larger slots excluded 5 

### 80% 

### of the ichthyoplankton relative to an open port. Altering through-slot velocity over 

### a four-fold range affected entrainment of naked gobies but not 

### of bay anchovies. Due to the circular configuration of the screens, inward flow vectors quickly dissipate. We suggest that species such as 

### naked gobies, which inhabit areas near the screen, will be 

### affected more by these changes in flow than will open water species such as anchovies, which typically remain outside the influence 

### of the withdrawal field. The effect 

### of screen diameter was found to 

### be rather unimportant, particularly for larger fish. For 

### small individuals there was a slight reduction in entrainment with a lower withdrawal rate.

V-lMartinMariettaEnvironmentalSystems

VI. REFERENCES



### - American Society of Civil Engineers. 1982. Design of 

### Water Intake Structures for Fish Protection. 163 pp. ASCE, NY, NY. 

### Blaxter, 

### J.H.S. 1969. Swimming Speeds 

### of Fish. FA0 Fisheries 

### Report 62:69-100. Browne, M.E., 

### L.B. Glover,, D.W. 

### Moore and D.W. Ballengee, 1981. In-situ 

### biological and engineering evaluation of fine-mesh profile-wire cylinder 

### as power plant intake screens. pp. 36-46. In: Advanced Intake Technology for Power Plant Cooling 

### Water Systems, Proceedings of the Workshop of Advanced Intake.Technology. P.B. Dorn, and J.T. Johnson, eds., San Diego, CA. Clutter, R.I. and 

### M. Anraku. 1968. Avoidance of samplers. pp. 57-76. In: Zooplankton Sampling. Monographs on OceanographicMethodology 2. D.J. Tranter, ed. Colton, J.B., J.R. Green, R.R. Byron and 

### J.L. Frisella. 1980. Bongo net retention 

### rates as effected by towing speed and mesh 

### size. Can. 

### J. Fisheries Aquat. Sci. 37:606-623. Conover, W.J. 1971, Practical Nonparametric 

### Statistics. John Wiley and Sons. New York, New York. Dames and 

### Moore, 1979. Seminole Plant Units No. 1.andNo. 2 316b Study and Report. Report 

### to Seminole Electric Cooperative, Inc, Delmarva 

### Ecological Laboratory. 1980. Ecological Studies of the Nanticoke River and Nearby Area. Vol. 11. Profile Wire Studies. Report 

### to Delmarva Power and, Light Company. Delmarva Power and Light. 1982. Vienna Power Station. Prediction of aquatic impacts of the proposledcooling 

### water intake. A 316b demonstration. Hanson, B.N., W.H. Bason, B.E. Beitz and K.E. Charles. 1978. A practical intake screen which substantially reduces the entrainment of early life stages of fish. pp. 392-407.



### - In: Fourth National. Workshop on Entrainment and Impingement. L.D. Jensen, ed., Ecological Analysts, Inc.,, Melville, NY.

VI-1-- 

### ---
-- MartinMarietta EnvironmentalSystems

Hansori, R.N. 1981. Studies of larval Striped bass 

### (Morone

_l_l_ 

### - saxatilis) and yellow perch (Perca flavcscens) exposed t o 

## ___---- - a Imm slot proEile-wire screen model intake, pp. 22-35. In: P.B. Dorn, and J.T. Johnson, eds. Advanced Intake Technology for Power Plant Cooling Water Systems, Proceedings 

### of the Workshop 

### of Advanced Intake Technology. 

### San Diego, CA. Hartwell, S.I. 

### and R.G. Otto. 1978. Swimming performance of juvenile menhaden 

### (Brevoortia tyrannus). Trans. Am. Fish. SOC. 107:793-798. Hettler, W.H. 1978. 

### Swimming speeds of juvenile estuarine fish 

### in a 

### circular flume. Proc. S..E. 

### Assoc. Game Fish Corn. 31:392-398. Heuer, J.H. and D.A. Tomljanovich. 1978. A study on the 

### protection of fish larvae at

### water intakes using wedgewire screening, pp. 169-194. 

### In: Larval 

### Exclusion Systems For Power Plant CoolingWater Intakes. R.K. Sharmer and J.B. Palmer, eds., Argonne National Lab., Argonne, IL. Publ. 

### no. ANL/ES-66. 

### Hocutt, C.H. and J.E. Edinger. 1980. Fish behavior in flowfields. 

### pp. 143-181. In: Power Plant Effects on Fish


## - and Shellfish Behavior. C.H. Hocutt, J,R. Stauffer, Jr., J.E. Edinger, 

### L.W. Hall, Jr. 

### and R.P. Morgan 11, eds., Academic Press, 

### NY. Lifton, W.S. 1979. 

### Biological aspects of 

### screen testing 

### on the St. Johns River, Palatka, Fla. pp. 87-96. In: Proceedings 

### of Passive 

### Screen Intake Workshop, Johnson Division UOP Inc., St. Paul, MN. Logachev, V.S. and Y.E. Mordvinov. 1979. Swimming speed and activity 

### of larvae of round goby and some predatory crustacea.ns 

### of the Black Sea. Sov. J. Mar. Biol, 5:227-229. McEwen, 

### G.F., M.W. Johnson and T.R. Folsom. 1954. A statistical analysis 

### of the performance of the Folsom plankton sample splitter based upon test observations. Arch. Meteorol. Geophys. Bioklimotol., Ser. A. 7:502-527. Ott, L. 1977. An Introduction to 

### Statistical'Methods and 

### Data Analysis. Duxbury Press. North Scituate, MA, Otto, R.G., 

### T.I. Hiebert and V.R. 

### Kranz. 1981. The effectiveness of a 

### remote profile-wire screen intake module 

### in reducing the entrainment of fish eggs and larvae. pp. 47-56. In: Advanced Intake Technology for Power Plant Cooling Water Systems, Proceedings of the Workshop of Advanced Intake Technology. P.B. Dorn and J.T. Johnson, eds., San Diego, CA.

VI-2MartinMarietta EnvironmentalSystems



### Snedecor, G.W. and W.G. 

### Cochran. 1980. Statistical Methods. Iowa State University 

### Press. Ames, IA. Thayer, G.W., D.R. 

### Colby, M.A. 

### Kjelson and M.P. Weinstein. 1983. Estimates of larval-fish abundance: Diurnal variation and influences of sampling gear and towing speed. Trans. Am. 

### Fish. SOC. 

### 112:272-279. Turnpenny, A.W.H. 

### and R.N. 

### Bamber. 1983. The critical swimming speed 

### of the sand smelt (Atherina presbyter Cuvier) in relation to capture at a power station cooling water intake. J. Fish Biol. 23:65-73. 

### Webb, P.W. and R.T. Corolla. 1981. Burst swimming performance of Northern Anchovy, Enqraulis mordax, larvae. Fish. Bull. 79:143-150. Weisberg, S.B., F. 

### Jacobs, W.H. 

### Burton, and R.N. 

### Ross. 1983. Report on preliminary studies using the wedge wire screen model intake facility. Report 

### NO. PPSP-CP-83-1. Prepared for State of Maryland, Power Plant Siting Program. ?re?c;&:Ci 

### by Martin Marietta Environmental Center, Baltimore, MD. 

### Zeitoun, I.H., J.A. 

### Gulvas and J.Z. 

### Reynolds. 1981. Effectiveness of 

### small mesh cylindrical wedge-wire screens in reducing fish larvae entrainment at an offshore and an onshore location of Lake Michigan, pp. 57-64. 

### In: Advanced Intake Technology for Power Plant CoolingWater Systems, Proceedings of the Workshop of Advanced Intake Technology. P.B. Dorn, and J.T. Johnson, eds.I San Diego, CA.

VI-3MartinMariettaEnvironmentalSystems



### APPENDIX A

TEST CONDITIONS, SURFACE SALINITY, TEMPERATURE, AND DISSOLVED OXYGEN FOR EACH NIGHT DURING THE 1983 

### ENTRAINMENT STUDY

A-1MartinMarietta EnvironmentalSystems

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A-2MartinMariettaEnvironmentalSysms

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A- 4m MartinMariettaEnvironmentalSystems



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A- 5MartinMariettaEnvironmehtalSystems

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A- 7MartinMariettaEnvironmentalSystems



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A- 8MartinMariettaEnvironmentalSystems

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A- 9~~
MartinMarietta EnvironmentalSystems

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A-10MartinMariettaEnvironmentalSystems

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### a 3 0 d II cll cMartinMarietta EnvironmentalSystems

Tah1.e H-1. Two-way analysis oE variance for- 1983 data an bay anchovy eggs using date-port as a hlockinc factor and screen size (open, 

### l-mm, 2-m, and 

### 3-mml 

### as the main effect

~~ Effect DF 

## ss F 

### P Blocking 

### Factor 21 209.29 0.99 .49 Screen 

### 3 37.15 1.03 .30 Error 63 636.49



# -MartinMariettaEnvironmentalSystems

Ta

### ble B-2. Two-way analysis of variance for 1983 data 

### on size 

### class 1 (2-4 

### mm) bay anchovy using date-port as 

### a blocking factor and screen size (open, 

### 1-mm, 2-mm, and 3-mm) as the main effect

~~ Effect 

### DF 

### ss F 

### P Blocking 

### Factor 

### 21 42.801 

### 2.99 c.01 Screen 3 2.789 

### 1.37 .26 

### Error 63 42.89

B-3MartinMarietta EnvironmentalSystems



### Table E-3. 

### Two-way analysis 

### of variance for 1B83 

### data on size class 2 

### (5-7 mm) 

### bay anchovy using 

### date-port as a blocking factor and screen size (open, 1-mm, 

### 2-mm, and 3-mm) 

### as the main effect

Effect 

### DF 

## ss F P Blocking Factor 21 38.432 4.02 

### <.01

.. 

### Screen 3 6.308 4.62 

### .os Error 63 28.666



### Duncan's New 

### Multiple 

### Range Test For Screen Effect: open l-ItUn 

### 3-mm 

### 2-mm port screen screen screen

iMartinMariettaEnvironmentalSystems



### Table B-4. Two-way analysis of variance 

### for 1982 

### data on size 

### class 3 (8-10 

### mm) bay anchovy using 

### port (left, 

### right) 

### and screen 

### size (open, 1-mm, and 

### 2-mm) as main 

### effects

- 

### Effect 

### DF 

### ss F 

### P Port 

### 1 0.00 

### 0.03 .86 

### Screen 2 

### 0.06 0.38 

### .69 

### Error 19 1.50

B-5 IMartinMariettaEnvironmentalSystems

Table 8-5. Two-way analysis of covariance for 1983 data on size

### class 3 (8-10 

### mm) bay anchovy using dateport 

### as a blocking factor, screen 

### size (open 

### port, 1-mm, 2-mm and 3-mm) 

### as a main effect, and canal 

### density as the covariate
Effect DF 

## ss F P Port 21 7.152 1.37 .17 Screen 3 9.963 13.32 

### c.01 Covar

### iate 1 1.040 4.17 .05

1 Error 62 15.45 Multiple Comparisons 

### For Screen Effects: Open 1

### -mm 2-mm 3-mm Open Port X 

### <.01 <.01 <.01 1

### -mm X .70 .18 2-mm 

### X .33 3-mm X

B- 6MartinMariettaEnvironmentalSystems

Table 6-6. Two-way analysis 

### of variance for 

### 1983 

### bay anchovy data on 

### size class 4 (11-14 

### mm) using date-port 

### a5 a blocking factor and screen size 

### (open 

### port, 

### 1-mm, 2-mm and 3-mm) 

### as the main effect
Effect DF 

### ss F 

### P Blocking Factor 

### 21 1.28 1.28 .22 

### 1.43 10.00 <.01 Screen 3
ErrOK 

### 63 3.00
Duncan's New Multiple Range Test For Screen Effect: Open 

### 3-mm 2-mm l-lWtl Port Screen Screen Screen

I



### B-7MartinMariettaEnvironmentalSystems <



### Table B-7. 

### Two-way analysis of 

### variance for 1982 

### data on size class 5 (> 

### 15 mm) 

### bay anchovy using port 

### (left, right) 

### and screen size (open, 1-mm and 2-mm) 

### as main effects

Effect DF 

## ss F P Port 

### 1 1.15 3.lo7 

### 0.10 

### Screen .- 2 

### 11.32 15.17 

### <.Ol Error 19 7.09



### Duncan's New Multiple Range 

### Test For Screen Effect: Opeh 2-mm l-IIUll 

### Port Screen Screen

B- 8MartinMariettaEnvironmentalSystems

APPENDIX C

ANALYSIS OF VARIANCE TABLES FOR THE EFFECT OF SCREEN SLOT SIZE ON NAKED GOBY ENTRAINMENT



### c-1MartinMariettaEnvironmentalSystems



### Table C-1. 

### Two-way 

### analysis of 

### covariance 

### for 1982 

### data 

### on size class 1 (< 

### 4 mm) 

### naked gobies using port (left, right) and screen 

### size (open, 1-nun 

### and 2-mm) as

### main effects 

### and canal density 

### as the covariate

Effect DF 

## ss F P i Port 

### 1 2.09 

### 9.79 .01 Screen 

### 2 0.20 

### 0.48 .63 

### Covariate 

### 1 2.98 14.01 <.01 

### Error 18 

### 3.83

c-2MartinMariettaEnvironmentalSystems

Table C-2. Twci-way 

### analysis of 

### covariance far 1983 

### data on 

### size class 

### 1 (< 

### 4 mm) 

### naked goby 

### using date-port as a 

### blocking Tactor, screen size (open 

### port, 

### l-mm, 2-mm 

### and 3-mm) as the main effect, and canal 

### density 

### as the covariate

Effect Blocking Factor Screen Cavariate Errar 

### DF 

## ss F 

### P 

### 21 34.082 

### 4.59 

## < .01

3 1.095 1.03 .38 

### 1 

### 2.771 7-83 

### < .01 

### 62 

### 21.935MartinMariettaEnvironmentalSystems

Table C-3. Two-way analysis of covariance 

### for 1983 data 

### on size

### class 2 

### (5-6 

### mm) naked 

### goby using date-port 

### as a blocking factor, screen 

### size (open port, 

### l-mm, 2-mm and 

### 3-mm) 

### as the main effect and canal density 

### as the covariate

Effect DF 

## ss F P Blocking Factor 21 29.717 2.71 <.01 Screen 3 7.829 4.99 

### <.01 Covariate 

### 1 

### 38474 

### 6.65 

### .01 Error 62 32.405 Multiple Comparisons For Screen Effect: Open 

### l-mm 2-mm 3-mm Open X 

## <.01 .ll .13 1

### -mm X 

### 003 .03 2

### -mm 

### X .98 

### 3-mm XMartinMarietta EnvironmentalSystems

*rableC-4. Two-way analysis of covariance for 1982 data on size 

### class 2 (5-6 mm) naked gobies using port 

### (left,right) and screen 

### (open, l-mm, and 2-mm) 

### as main 

### effects



### Effect 

### DF 

### ss F 

### P Fort 

### 1 0.90 2.,74 .12 

### Screen 2 

### 0.19 0

### "29 .75 

### Covari

### ate 1 5.26 16.02 Error 18 5.91

c-5MartinMariettaEnvironmentalSystems

Table 

### C-5. Two-way analysis 

### of variance for 1982 data on 

### size class 3 (7-8 

### mm) naked gobies using port 

### (leEt, right) and screen 

### size (open, 

### 1-mm, and 

### 2-mm) 

### as 

### main effects
Effect DF 

## ss F 

### P Port 

### 1 1.30 5.20 .03 

### Screen 2 5.25 10.53 

### C.01 

### Error 19 4.74
Duncan's New Multiple 

### Range Test For Screen Effect: Open Port 2-mm 1-REll

C-6MartinMarietta EnvironmentalSystems

*r;lt)icC-6. Twc~wayanalysis OF variance for 19133 data On size c3.ass 3 (7-8 mrn) naked qohies using date-port. as a blocking factor and screen size (open port, 1-mm, 

### 2-mm alnd 

### 3-mm) as themain efjfect



### Effect 

### DF 

### ss F 

### P Blocking Factor 21 25.980 2.53 

### <.01 Screen 

### 3 44.658 30.46 

## <. 01 Error 

### 63 30.788

Duncan's New Multiple Range Test For Screen Effect:



# - Open Port 

### 3-mm 

### 2-mm 1-mm

c-7MartinMarietta EnvironmentalSystems

Table c-7. Two-way analysisof variance 

### for 1982 data on 

### size class 4 

### 0 9 rnm) naked gobies using port 

### (left,right) and screen size (open port, 

### 1-mm, and 2-mm) 

### as main effects
Effect DF 

## ss F P Port 1 

### 1.41 3.46 .08 Screen 

### 2 13.21 16.25 

## <.01 

### Error 19 

### 7.72

Duncan's New Multiple Range Test For Screen Effect: Open Port 

### 2-mm l-llllll

C-8MartinMarietta EnvironmeptalSystems

APPENDIX D

ANALYSIS OF VARIANCE TABLES FOR THE EFFECT OF THROUGH-SLOT VELOCITY/SCREEN DIAMETER ON BAY ANCHOVY ENTRAINMENT



### D-1MartinMariettaEnvironmentalSystems

Tab

### le D-1. 

### Two-way analysis 

### of variance 

### for bay anchovy eggs 

### using date-port as 

### a blocking 

### factor and 

### screen diameter and through-slot velocity as the 

### main effect

Effect 

### DF 

## ss F P Blocking Factor 21 308.07 1.20 .28 

### Velocity 3 

### 44-44 

### 1.21 

### .31 Error 63 770.15

D-2. . .. MartinMariettaEnvironmentalSystems

-~



### Table D-4. Twg-way 

### analysis of 

### covariance for bay anchovy size class 3 

### (8-10 mm) 

### using date-port as 

### a blocking factor and through-slot velocity and screen diameter 

### as the main effect
Effect Blocking Factor
Ve

### loc

### ity Csvariate Error 

### DF 

## ss F P 21 10.59 1.70 

### .OS

3 1.06 1.19 .32 

### 1 1.14 3.83 

### .OS 62 18.44

D-

### 5Martin.Allariette.Environmentd Systems



### Table D-5, 

### Two-way analysis of 

### variance for bay anchovy size class 4 

### (11-4 

### mm) using date-port as 

### a blocking factor and through-slot velocity and screen diameter as the main effect


### Effect DF 

## ss F P 

### Blocking Factor 

### 21 0.64 0.87 .63 

### Ve1

### ocity 3 

### 0.23 2.23 .09 

### Errar 63 2.21

D-6MartinMariettaEnvironmentalSystems



### APPENDIX E



### ANALYSIS 

### OF VARIANCE TARLES FOR 

### THE E'FFECT

### OF THROUGH-SLOT VELOCITY AND1 SCREEN DIAMETER ON NAKED GORY 

### ENTRAINMENT

E-1MartinMarietta EnvironmentalSystems

Table E-1. Two-way analysis 

### of covariance 

### for 

### sizeclass 1 ((4 nun) naked goby using date-port 

### as 

### a blocking 

### factor, screen diameter and through-slot 

### velocity 

### as the main 

### effect, and canal density 

### as the covariate

DF 

## ss F 

# - P 

### Factor 21 

### 23.88 

### 3.41 <.01 

### 3 3.35 3.35 .02 

### 1 6.87 20.56 <.01 

### 62 20.08 Comparisons For Main Effect: Effect Blocking 

# I Velocity

Covaria

### te Error 

## I 

# 1Multiple
1 

# i Log SL 

### SH 

### Means SL 

## - 1.19 

### X 

### .03 

# ISH

- 0.79 

### X

LL 

## - 1.15 

### LH 

## - 0.78

SL

## - Small Screen/Low Pump Speed SH 

## - Small Screen/High Pump Speed LL 

## - Large Screen/Low Pump Speed LH 

### - Large Screen/High 

### Pump Speed LL LH


### .83 .02 .04 

### .93

X .03 

### X

E-2MartinMariettaEnvironmentalSystems

Table E-2, 

### Two-way analysis of covariance for naked goby size

### class 2 (5-6 

### mm) data using date-port 

### as a blocking factor, through-screen 

### slot velocity and 

### screen diameter as the main effect, and canal density as 

### the covariate
Effect DF 

## ss

- 

### F 

### P Blocking Factor 

### 21 

### 32.54 1.76 

### .04 Velocity 

### 3 7.63 2.89 

### .04 Covar

### ia te 1 

### 7.76 8-81 

### <.01 Error 

### 62 54.63


### Multiple Compa'risons For Main Effect: SL SH LL LH Log Means 

### SL

## - 2.92 X 

### .12 23 .46
SH 

## - 2.47 

### X <.01 .39 LL 

## - 3.27 

### X .05 LH 

## - 2.71 

### X

SL 

### - Small Screen/Low Pump Speed SH

## - Small Screen/High Pump Speed 

### LL 

## - Large Screen/Low Pump Speed LH 

## - Large Screen/High Pump Speed



### E-3 

# AMartinMariettaEnvironmentalSystems

Table 

### E-3. 

### Two-way analysis of 

### variance for 

### size class 3 

### (7-8

### mm) naked goby data using date-port as a blocking factor and screen diameter and through-slot velocity 

### as the main effect

Effect 

### DF 

### ss F 

### P Blocking Factor 

### 21 21.36 1.30 .21 

### Velocity 3 

### 21-00 8

### -93 

## < .01 

### Error 

### 63 49.41



### Duncan's New Multiple Range Test 

### For Main Effect:

Small Screen Large Screen Large Screen Small Screen High Speed 

### High Speed Low Speed Low Speed

E-4-- MartinMariettaEnvironmentalSystems

Table E-4. Two-way analysis oE variance �a~- 

### size class 4 (> 9 

### mm) naked goby data using 

### date-port as a 

### biocking factor, and screen diameter 

### and 

### through-slot velocity 

### as the

### main effects


### Effect Rlocking Factor 

### Velocitry 

### Errar 

### DF 

### ss F P 

### 21 16.53 1.58 e08

3 6.84 4.58 

## < '01 63 

### 31.35

Duncan's New 

### Multiple 

### Range Test 

### For Main Effect:



### - Small Screen 

### Large 

### Screen Large 

### Screen Small 

### Screen High Speed High Speed 

### Low 

### Speed 

### Law Speed