### CALVERT CLIFFS NUCLEAR POWER PLANT FINFISH SURVIVAL STUDY

FOR 

### BALTIMORE GAS AND ELECTRIC COMPANY

FINAL REPORT



## Denise L. Brei Timothy A. Thoman

Report No. 86-19



### Benedict Estuarine Research Laboratory



## Benedict, MD

Division of Environmental Research Academy of Natural Sciences of Philadelphia 

# 19th and the Parkway

December 23, 1986

### EXECUTIVE SUMMARY

survi val 

### Cliffs Nuclear Power Plant June-August 1986 to compare survival 

## rates overall differences among screen types in 

# finfish. size than did control screens. 

# experimental However, the screen positions rather than screenTABLE OF CONTENTS



### EXECUTIVE SUMMARY 

# ......................................

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

MATERIALS AND METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Finfish Survival Studies 

# .............................

Impingement Study 

# ....................................

Statistical Analyses 

# .................................

RESULTS AND DISCUSSION Finfish Survival Rates 

# ...............................

Sizes of Impinged Finfishes 

# ..........................

Numbers of Impinged Finfish and Blue Crabs 

# ...........

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

LITERATURE C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



### PageINTRODUCTION



# In the
conducted studies to finfish impinged on three different types of traveling 

# at Calvert Cliffs Nuclear Power Plant prevent finfish, other estuarine organisms and debris too large 

### to pass through the 8 x 

### being carried into the screens rotate, screens and into a trough that 

### Bay. FMC single-speed screens are currently used at experimental screen types, Beauderey screens and FMC dual-speed 

### screens were installed (BG&E) at Units 1 and 

### ness at purpose of the study described here was to 

### conversion to 

# significantly operations.

MATERIALS AND METHODS

Finfish Survival Studies



### Survival rates for 

# screens and finfish impinged on the currently used FMC single-speed screens 

### (controls). The screen position 

# position 1
posi tion

### because finfish impingement at these positions tends to be most

similar to that at the positions where the experimental screens 

### were installed Because each type of 

### only one position, this tween screen and position 

# did not impinged at the positions used for 

### and after those 

### of the sampling of impinged animals at CCNPP for 

### and survival rates of 

## screen positions wi Mr. Hixson served that the outermost screen positions and unit 

### individuals. Based on judicious to interpret a difference in survival

impinged finfish or a 

## lower impingement rate at 

### screens than at 

# types. impingement rates are control screens. 

# To diverted from the troughs to large concrete survival pools that 

## measured approximately 9. 

# (Fig. the collections to begin approximately 100 sec after the screen 

### to be amount of time it took for the Unit 1 screens to the unit 1 survival pool. impinged animals were allowed to flow into the pool for 10 

### the duration of each screen procedure was used because the time it took 

### from the 

### more variable screens were 

## manually rotated. Organisms from screens not sampled for

# study

entire pool-filling procedure on days that Unit 2 

# sampled.

Uni t survi val 

### experimental or control screen to be sampled 

### rotation. At water and
screen not 

### than the screens, procedures used at Units 1 and 2 were 

### At the end of 

# into (Callinectes coelenterates and ctenophores were removed and identified to species and total lengths of all dead 

### finfish, up to a maximum of 25 

### each species 5 cm. 

### We attempted to include all fish washed from the screen of interest during 6- 

### 7 successive screen rotations in each 

### However, the samples was often screens were placed in continuous rotation during some portion of the day or 

# of rotations. required continuous rotation of 

# rotated
crete samples from the screens of 

### After the final screen rotation was included in sample, data on environmental parameters were 

### oxygen (D. ) levels were measured with a Y. I. model 57 D. 

# meter. 

# meter. C), water depth and 

# also O. measured at middepth in the in Table 

### Approximately 24 h after pools were 

### and water

# except (Trinectes maculatus) 

# were

identified and classified as live, dead or 

# equilibrium inabili ty 

# water. (haphazardly chosen) individuals of any 

## one species sured to
cm. Trinectes maculatus 

## was not included in this study because previous research indicated that 

## impingement
(Burton, 1976). 

## Sampling was days per through August 

### screens were not in 

### uously rotated. A Beauderey screens, 20 samples from FMC trol screens

Impingement study



### Numbers and kinds of

(Callinectes sapidus) 

### impinged on experimental and FMC single

# speed directly from the 

## August 27-cm stretch-mesh collecting net was placed in the 

### 10-min rotation of each of the six 

### Raw data took to lift the net out of the trough and empty 

# into often
rotates 10 min out of during the 

### and adj number of finfish and blue crabs impinged on 

# hour.

### speed screens at a unit were combined and used as the

against which experimental screens at that unit were 

## Sampling frequency was based on 6- day cycles separated by 

### 2- or 3- 

### day intervals. On h collections 

### were made at each of the two generating 

### not in 

### uni t. 

# screen rotation. The unit to be initial 6- 

# day 6-day periods began at 

### second 

# second sampling periods were scheduled as followed: 

### tions began at 

# first,

ti vely . 

### first had begun. 

### in two 6- 

# day from Beauderey screens, 33 samples from unit 1 control 28 samples from FMC dual-speed screens and 35 samples from unit 

# 2 control rates at experimental and control

statistical Analyses


## Survival 

## separately for 

# rates of

each species at each 

### La.
P = 

### Ln. 

# finfishes were 

## calculated

screen as



### where a. = the number of live 

# the total error of p

### total of ~30



### from that screen.

e. p = n where C is the



### Pi = n : N = : n = C 

### (Snedecor and Cochran, 1967). 

# To

screens 

# tion

Z = log i + ~ 

### n. - 

### where d i = the number of dead transformed data were weighted for sample size as f(la. 2 

### -2pLa . n. +p2 

### Ln. 2 

# 1 1

number of samples and



### weight = 1/V

i + 1) (n i + 2) V = i (d i + 1) (n i - d i + 1) 

### Data were analyzed using the SAS GLM 

# 1982). species were where



## species. 

# T-tests and numbers and sizes of impinged 

## used compare

RESULTS AND DISCUSSION

Finfish Survival Rates



### Twenty-nine species of families were collected in the 

### 3) . 

# all 4a-d). per sample are poor

# ever.

midwater species (e. g., bay anchovy (Anchoa mitchilli), 

## Atlan- 

# tic (Brevoortia blueback herring 

## (Alosa

aestivalis)) 

### and highest for 

# g.,

toadfish (Opsanus tau) and flatfishes). 

### Data from Units l and 2 control screens were combined for 

# statistical comparisons of 

# screens. were collected to 

### impinged on 

# screens. 

# fish, (Leiostomus 

# and (Prionotus carol Seven species were 

### dant to 

# dual-speed 

# oyster 

# spot, (Pseudopleuronectes

skilletfish 

## (Gobiesox

strumosus) 

# northern

(Sgmphurus plagiusa). Species included in statistical analyses 

### were those with at least 

# four parison. 

# There were among finfish impinged on the three types of 

### tested in this statistically significant 

### when impinged on 

# trols
screens than on controls 

# arcsin
Rohlf, 1969).Sizes of Impinged Finfishes



### Mean lengths of survival study from each screen 

### Sizes of fish pared in Table 7 for individuals in both the experimental screen of interest and the 

### combined controls. Beauderey screens was larger than that on controls for 7 of the 

# 10 species

(Cgnoscion regalis), 

# spot,

(Peprilus alepidotus), 

### and blackcheek tonguefish. Thus 

### individuals of impinged on presented by larger 

# in
difference in size of skilletfish or northern searobin impinged 

### at Beauderey and control 

### No general differences in 

### between those impinged on control lengths of cantly greater in fish impinged on control 

# of were significantly greater for fish 

### speed screens. screens for lengths of the other fish

Numbers of Impinged Finfish and Blue Crabs



### Numbers of screens at each unit were compared for the 

### species at each unit and 

## and b). control screens for three of the Uni t

### and for all

for which impingements were not significantly different between 

### screen types followed the same 

# ln
screens. column and benthic species. 

### More blue crabs were impinged by Beauderey screens than by 

### unit 1 controls 

### on FMC significant (Table 

### As discussed in the 

# determine . experimental screens than at or screen position.

SUMMARY

1 ) survi val 

## June-August numbers of impinged 

### There were no overall 

### survival rates of 

## comparisons only 2 between experimental and control 

### Beauderey screens than did 

### fish is Beauderey screens may be 

### impinged by 

# screens similar average 

### More fish were impinged by both 

### by FMC impingement rates may be than screen types. the positions that The Academy of conducted at CCNPP 

# rates,

2 )

3 )

4 )

### ogists believed had the



# effort to
sizes for analyses of survival

LITERATURE CITED 

# Burton, and quantitative survival 

# crabs. 2-1 to 11. 2-49 in 

## semi-annual environmental monitoring report for Calvert Cliffs Nuclear Power 

### Plant, March Baltimore, Maryland.


### Cox, D. 

### London , England. Chapman and Hall,



## SAS s guide: 

# sti tute, 

# statistics. SAS InSnedecor, G. W. and 

# 6th ed.

Sokal, R. and Co., San Francisco 

### W. H. FreemanrL.JL~ +m mr;"L"I'J I. ,6112..JL2J L2Ja2J all cr'---- :~"'r"-'". II-'I-'Un i tSurvivalPool--t jI"" C~-.t..- C. (1",i;Figure 1.Power PlantUnit 2 Screensw/Position NumbersUnitw/I'osit ionEmbaymentChesapeake BayUnit ISurvivalPoolDiagram of CCNPP.rotating screensshown.Approximate relative locations ofsurvi val

### Table 1. Dates on which survival pools were filled for 1986 the finfish survival study and the mean number 

## sample. Prior to ples from the desired screens at Unit



### Sample Dates



### Beauderey Screens Unit 1 controls (FMC single- 

### speed 

### screens) FMC dual- 

### speed



### screens Uni t 2

(FMC single- 

### speed 

### screens)

June June June 12 June 10



### July July 

### July July

Augus t Augus t Augus t Augus t

X (SE) number of rotations per sample: 

### 3(0. 4(0. 

### 6(0. 0(0.

### Table 2. Dissolved oxygen , salinity and temperature of water in survival pools. F = , E = data taken approximately 24 h late!, on the day the pool was emptied. data are presented as



### Screen 

### Dissolved Oxygen (mg' L - 1 

## Salinity (ppt) Water 

### Temperature

Beauderey 7 . 6:tO . 2 5 . 6iO . 7 

### 14. 

### 2iO. 13. 25 . 6iO . 9 

### 24. 

### 5iO.

FMC dual- 

### speed 

### nO. 

### nO. 14. 

### 2iO. 13 . 9iO . 3 

### 26. 4iO. 24. 7iO.

Uni t 1 

### control 7 . 6iO . 3 

### 5. 9iO. 14. 

### 2iO. 14. 25 . BiO . 4 24. 2iO . 4

Unit 2 

### control 

## aO. 4 . 3iO . 14. 3iO . 3 13. 5iO. 3 25 . 9iO . 5 24. 3iO .

### Table 3. Finfish species collected from experimental and control screens for the 1986 finfish survival study at CCNPP. Hogchokers 

### Trinectes maculatus were also impinged but were not included in the study.

FAMILY SCIENTIFIC NAME COMMON NAME 

### Anguillidae 

### Anguilla rostrata American eel 

### Clupeidae Alosa aestivalis Alosa pseudoharengus Brevoortia tgrannus 

### blueback herring alewife Atlantic menhaden 

### Engraulidae Anchoa mitchilli bay anchovy 

### Ophidiidae Ophidion marginatum striped cusk- 

### eel Batrachoididae Opsanus tau oyster toadfish 

### Gobiesocidae 

### Gobiesox strumosus 

## skilletfish
Gadidae Urophgcis regia spotted hake 

### Cyprinodontidae Cgprinodon variegatus sheepshead minnow 

### Poeciliidae Gambusia affinis mosquito fish 

### Atherinidae Menidia menidia 

## Atlantic silverside

Syngna thidae 

### Sgngnathus fuscus northern pipefish 

### Triglidae Prionotus carolinus 

### northern sea Percichthyidae Morone saxatilis striped bass 

### Sciaenidae Menticirrhus americanus



### Cgnoscion regal is Cgnoscion nebulosus 

### Leiostomus xanthurus 

### southern kingfish weakfish spotted seatrout 

### spot Bothidae Paralichthgs dentatus Scophthalmus aquosus summer flounder windowpane 

### Pleuronectidae Pseudopleuronectes americanus winter flounder 

### Soleidae Trinectes maculatus 

### hogchoker 

### Cynoglossidae Sgmphurus plagiusa 

### blackcheek tonguefish Tetraodontidae Sphoeroides maculatus northern puffer 

### Blenniidae Chasmodes bosquianus Hgpsoblennius hentzi striped blenny feather blenny 

### Gobiidae Gobiosoma bosci naked goby 

### Stromateidae Peprilus alepidotus 

## harvestfish

### Table 4a. Survival rates of finfishes impinged in 1986 on Beauderey screens at CCNPP Unit



### number of number of indi vidua 1 samples on in samples 

### which per- 

### included in 

### Percent 

### survival cent survival calculation of 

### Species SEi, is based*'" 

### percent survival

Alosa aestivalis 1. 0 Anchoa mitchilli
Anguilla 

## rostrata 1.0 Brevoortia tgrannus 1. 9 Chasmodes bosquianus 

### 100. 

### 1.0

cynoscion regal is 

### 31.6 Gambusia affinis 

### 100. 

### Gobiesox strumosus 100. Gobiosoma bosci 

### 100. 

### 1.0 

### Leiostomus xanthurus 45. 20. 122. 51. 7 Menidia menidia 

### 1.5 

### Opsanus tau 97. 

### 1.4 Paralichthgs dentatus 

### 44. 1. 8 Peprilus alepidotus 18. 

### 41.0 12. 

### Prionotus carolinus 51.0 1. 3 

### 277. 

### 249. Pseudopleuronectes americanus 78. 11. 11. Scophthalmus aquosus 100. 1. 0 Sphoeroides maculatus 

### 87. 1. 3 Sgmphurus plagiusa 

### 47. 15. 

### 12. 

### Syngnathus fuscus 33. 

### 1.5 Urophgcis regia 11. Unknown 

### 1.0

*Standard errors for survival rates are calculated for all species 

### represented by a total of at least 30 individuals and found in at least 3 **The survival rate of a species is calculated using all samples that included at least one individual of that species.

### Table 4b. Survival rates of finfishes impinged in 1986 on FMC dual- 

### speed screens at CCNPP Unit



### number of number of 

### individuals samples on in samples which per- 

### included in Percent 

### survival cent survival calculation of 

### Species is based 

### percent survival

Alosa pseudoharengus 

### 1.0 Anchoa mitchilli 

### 89. 

### 84.

Brevoortia 

### tgrannus 1.6 Chasmodes bosquianus 

### 89. 

### Cgnoscion' 

## regalis 21.4 1.5 Gambusia affinis 100. 

### Gobiesox strumosus 98. 23. 13.

Gobiosoma 

## bosd 93. 

### Leiostomus xanthurus 91. 0 

### 22. Menidia menidia 

### 12.

Morone 

## saxatilis 100. 

### 1.0 Ophidion marginatum 100. 

### 1.0

Opsanus 

### tau 96. 

### 1.0 25.

Paralichthgs 

### dentatus 89. Peprilus alepidotus 

### 36. 

### 1.4 

### Prionotus carolinus 38. 

### 1.9 Pseudopleuronectes americanus 

### 47. 

### 11.2 Scophthalmus aquosus 

### 1.0 Sphoeroides maculatus 

### 66. 

### 1.5 Symphurus plagiusa 

### 65. 12. Sgngnathus fuscus 

### 22. 

### 1.5 Urophgcis regius 75. 

### 1.6

### Table 4c. Survival rates of finfishes impinged in 1986 on Unit 1 control screens at CCNPP.



### munber of 

### number of 

### individuals samples on in samples 

### which per- 

### included in 

### Percent 

### survival cent survival calculation of 

### Species is based 

### percent survival

Alosa aestivalis 17. 

### 58. 

### 53.

Anchoa 

## mitchilli 18. 

### 65. 36. Brevoortia tgrannus 12. 16. 10. Chasmodes bosquianus 

### 66. cgnoscion nebulosus 100. 

### 1.0 Cgnoscion regalis 

### 26. Gambusia affinis 

### 100. 

### Gobiesox strumosus 100. 

### 1.2 Gobiosoma bosci 

### 100. 1. 7
Hgpsoblennius 

### hentzi 1. 0

Leiostomus 

### xanthurus 61.1 99. 

### 27. Menidia menidia 10. Menticirrhus americanus 1. 0
Ophidion 

### marginatum 1. 0
Opsanus 

### tau 96. 

### 1.5

Paralichthgs 

### dentatus 35. 1. 9 Peprilus 

### alepidotus 10. 

### Prionotus carolinus 44. 23.

Pseudopleuronectes 

### americanus 46. 

### 11.6 Scophthalmus aquosus 

### 40. 1. 7 Sphoeroides 

### maculatus 87. 

### 1.1

Sgmphurus 

### plagiusa 45. 

### 11.1 

### Sgngnathus fuscus 44. 1. 8 Urophgcis 

### regia 35. 

### 1.1

### Table 4d. Survival rates of finfish impinged in 1986 on Unit 2 control screens at CCNPP.



### number of number of 

### individuals samples on in samples 

### which per- 

### included in 

### Percent 

### survival cent survival calculation of 

### Species is based 

### percent survival

Anchoa mitchilli 

### 1.3

Anguilla 

## rostrata 100. 

### 1.0 Brevoortia tgrannus 

### 1.3 Chasmodes bosquianus 

### 100. 

### 1.0 cgnoscion nebulosus 

### 1.0 Cgnoscion regalis 

### 13. 11. Cgprinodon variegatus 100. 

### 1.0 

### Gobiesox strumosus 91. 7 

### 1.1 Gobiosoma bosci 91. 7 

### 1.5 

### Leiostomus xanthurus 82. Menidia menidia 1. 0 Ophidion marginatum 

### 50. 

### 1.0

Opsanus 

### tau 94. 1. 7 

### 18. Paralichthgs dentatus 75. 

### 1.3 Peprilus alepidotus 1. 0 

### Prionotus carolinus 35. 18. 11. Pseudopleuronectes americanus 

### 90. 16. 10. Sgmphurus plagiusa 

### 56. 

### 11.8

Sgngnathus 

### fuscus 75. 

### 1.0 Urophgcis regia 100.

### Table 5. Statistical comparisons of survival rates of finfish impinged in 1986 on a) Beauderey and control screens and b) FMC dual- 

### speed and control screens. Onlyspecies of interest are included in means or statistical comparisons. Mean vival calculated for all samples containing )4 individuals of that 

### species.

Species 

### X percent survival (number of samples) 

### Beauderey combined 

### screens 

### controls p)F 

### 8(7) 0(8) 427 

### 41.2(9) 70. 

### 4(18) 017 100. 

### 0(7) 95. 

### 4(19) 542 44 . 4 (6) 

### 48. 

### 5(14) 1. 65 216 Brevoortia 

### tgrannus 

### Leiostomus xanthurus Opsanus tau prionotus carolinus



### X percent survival (number of samples) FMC dual- 

### speed combined 

### Species 

### screens 

### controls p)F

Anchoa mitchilli 

### 0(8) 8(16) 008 

### Gobiesox strumosus 97. 

### 4(7) 100. 

### 0(11) 119 

### Leiostomus xanthurus 84 . 5 (9) 70. 

### 4(18) 060 

### Opsanus tau 97. 

### 3(14) 95. 

### 4(19) 133 prionotus carolinus 45 . 9 (9 ) 48 . 5 (14) 808 Pseudopleuronectes americanus 

### 53. 

### 2(4) 65 . 1 (7) 435 Sgmphurus plagiusa 

### 80. 7 (9) 

### 56. 

### 2(10) 507Table 6a-d,Total lengths of finfish collected for the finfish survival study at CCNPP, June-August 1986.(n = number of fish measured in each category.Beauderey ScreensTotal LengthLive IndividualsDead IndividualsLOE IndividualsSpeciesAlosa aestivalisAnchoa mitchilliAnguillarostrata33,10.Brevoortia tgrannus16.17.Chasmodes bosquianusCgnoscion regalis11. 71.5Gambusia affinisGobiesox strumosusGobiosoma bosci1.0Leiostomus xanthurus12110.18111,1. 0Menidia menidia1.0Opsanus tau12.Paralichthgs dentatus11,22.Peprilus alepidotusprionotus carolinus11.11.11.5Pseudopleuronectes americanus1.4Scophthalmus aquosusSphoeroides maculatus13.1.2Sgmphurus plagiusa11.11. 4Sgngnathus fuscus16.17.1.5Urophgcis regia12.15.Unknown Fish18.Table 6a-d (continued).Total lengths of finfish collected for the finfish survival study atnumber of fish measured in each category.en =FMC Dual-Speed ScreensTotal Length(cm)Live IndividualsDead IndividualsLOE IndividualsSpeciesAlosa pseudoharengusAnchoa mitchilliBrevoortia tgrannus16.1. 7Chasmodes bosquianus1.3Cgnoscion regalisGambusia affinisf-IGobiesoxstrumosus100Gobiosoma bosciLeiostomusxanthurus11.216311.Menidia menidiaMoronesaxatilis17.Ophidion marginatum15.Opsanustau10.paralichthgs dentatus19.1.022325.Peprilus alepidotusPrionotus carolinus11. 611. 713.1.0Pseudopleuronectes americanus20.ScophthalmusaquosusSphoeroides maculatus11.11.31. 3Sgmphurus plagiusa11. 911.211.5Sgngnathusfuscus20.16.1.3Urophgcis regia16.1.116.Table 6a-d.(continued). Total(n = number of fish measured in each category.Unit 1 Control ScreensTotal LengthLive IndividualsDead IndividualsLOE IndividualsSpeciesAlosa aestivalisAnchoa mitchilli234Brevoortia tgrannus16.15.135Chasmodes bosquianusCgnoscion nebulosusCgnoscion regalisGambusia affinisGobiesox strumosusGobiosoma bosciHgpsoblennius hentziLeiostomus xanthurus3192301.0Menidia menidia10.Menticirrhus americanus32.Ophidion marginatum18.Opsanus tau11.109Paralichthgs dentatus17,23.Peprilus alepidotusPrionotus carolinus11.10111.413213.Pseudopleuronectes americanus1.4Scophthalmus aquosusSphoeroides maculatus14.1.1Sgmphurus plagiusa11. 710.Sgngnathus fuscus17.16.Urophgcis regia15.16.Table 6a-d.(continued). Total(n = number of fish measured in each category.Unit 2 Control ScreensTotal LengthLive IndividualsDead IndividualsLOE IndividualsSpeciesAnchoa mitchilliAnguilla rostrataBrevoortia tgrannus16,Chasmodes bosquianuscgnoscion nebulosusCgnoscion regalisCyprinodon variegatusGobiesox strumosusGobiosoma bosciLeiostomus xanthurusMenidia menidia10.Ophidion marginatum18.17.Opsanus tau113Paralichthgs dentatus18.19.Peprilus alepidotusPrionotus carolinus10.11.Pseudopleuronectes americanusSgmphurus plagiusa10.10.Sgngnathus fuscus15.15.Urophgcis regia17.Results of t-tests comparing sizes of finfish impinged in 1986 experimental and control screens at C = control screens , D = FMC dual- 

### speed screens. 

### Table 7a-b.

Beauderey Screens vs. Controls



### Species p::.t Screen type impinging individuals with largest average size

Anchoa 

## mitchilli

Brevoortia 

### tyrannus Cynoscion regalis

Gobiesox 

### strumosus

Leiostomus 

### xanthurus

Opsanus 

### tau Peprilus alepidotus 

### Prionotus carolinus Pseudopleuronectes americanus Symphurus plagiusa 001* 001 003* 538 025 022* 008 201

O. 047i~ 008

FMC Dual-Speed Screens vs. Controls



### Species p::.t Screen type impinging individuals with largest average size

Anchoa mitchilli

Brevoortia 

### tyrannus Cynoscion regalis

Gobiesox 

### strumosus Gobiosoma bosci

Leiostomus 

### xanthurus

Opsanus 

### tau

Paralichthys 

### dentatus Peprilus alepidotus 

### Prionotus carolinus Pseudopleuronectes americanus Sgmphurus plagiusa 756 330 OlP' 389 570 001 345 658 732 012 O. 048* 001
*Approximate t-tests were used where variances were significantly heterogeneous (SAS Institute , 1982).Table 8.Number of finfish and blue crabs impinged per hour in 1986 on experimental and control screens atCCNPP. a) Unit I, b) Unit 2.05)Beauderey vs. Unit 1 Control ScreensSpeciesX ! 1 SE number of individuals impinged per hourBeauderey screenst or approximate tp)tAnchoamitchi11iLeiostomusxanthurusOpsanustauPrionotus caro1inusTrinectesmacu1atusAll finfishCa11inectes sapidus8!1.618 . 4!3 . 65. 9!1. 714.0!4.98. 4!54 . 2151. 3!55, 339 . 0!4 . 61. 6!O, 57 . 1!2 . 01.5!O,10. l!6 .17.5!6.39 .1!10. 126.4:t4. 145t73t44t53t1. 48t00t019009019600 fiS0 . 140 fiS054043FMC Dual-speed vs, Unit 2 Control ScreensSpeciesX :t 1 SEFMC dual-speed screenst or approximate tp)tAnchoami tchi11 iLeiostomusxanthurusOpsanustauPrionotus caro1inusTrinectes maculatusAll finfishCa11inectes sapidus4 .1:t1. 55 .8:t1.3 . o:to . 97 . 9!2 . 215 . 8!3 . 841.4!6.25 .6:t3. 30 . 8!0 . 3nO.nO.1. no .8. 6!2 . 915. n3.19.6:t3.11t46t75t1.5335t1.170440330200100 . 132 ns002246 ns*Approximate t-tests were used where variances were significantly heterogeneous (SAS Institute, 1982).