llOGICAL EVALUATION OF 

ANDLING COMPONENTS 

JATER INTAKE SCREEN !. 

DESIGNED TO PROTECT LARVAL FISH 

Division of Water Resources 

Tcnncssce Vnllcy Authority 

N o r r is. Tc ti n c:iscc 3 7 8 2 8 
A RIOLOCICAL EVALUATION OF FISH HANDLINC COMPONENTS OF A WATER 

IIiTAKE SCREEN DESIGNED TO PROTECT LARVAL FJSH 

Prepared by 

IldultI A. ~l~l~llll.~!l~lli?Jlt I1 

John H. Heucr 

Division of Water Resourc-i!s 

l’carlricssoc Vi11 1 (’y AuLlior i Ly 

Norris, Tennessee 37828 

I 
ABSTRACT 

Larval fish survival associated with all aspects of fish 

handling on a laboratory model center-flow screen was evaluated. The 

fish handling components which were evaluated included: (1) impingement 

diiriition, (2) tritvc-1 rroin Llir air-wntcr intcrfncc to thc: spilling 

position, and (3) spilling into a fish return trough. Relatively large 

larvae OC scvural species (paddlefish, iior!Aiern pikc, wliitc sucker, nnd 

~~1~~!1~~1~.! 

condit ons. Two small, fragile larvae, striped bass and striped bass x 

white bass hybrid, showed very low survival under nearly all conditions, 

while intermediate survival was exhibited by the redbreast sunfish, 

largemouth bass, bigmouth buffalo, and walleye. Plultifactor analysis 

of variance of the results from tests of four :;pecies showing 

intcrmediate survival showed that impingement dL,ration had the grcatest . 

rc:il\ fj?!l) #!l'~yixl !![E!] yyiy!!! I!w!lpc I!o!irly iI! 1 c!xl+ritiwni-ttl 

.. 

effect on survival, followed by air exposure. Spilling appeared to have .. 

little effect on survival. The important species and critical life 

stages of fish at a proposed intake will determine both the biological 

feasibility of a prototype impinge-releasr rcrecn systcm and the extent 

: 
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A BIOLOGICAL EVALUATION OF FISH HANDLING COMPONENTS 01: A WATER 

INTAKE SCREEN DESIGNED TO PROTECT LARVAL FISH :I f 

INTRODUCTION 

Investigations of screening technologies to protect fish at 

power plant cooling water intakes have been conducted by TVA since 1976. 

The aim of these studies has been to develop screen systems capable of .. -. 

. i 

, . . .., .. . 

, . :'I ** protecting all post-hatch life stages. Since it is generally txue.that .- .4 ., 

.. 

the larvae represent the most fragile phase of a fish's life cycle, .. . 

these studies have concerned protection of these earliest life stages. 

.. 

Screens which protect larvae will also afford protection for ttir larger, 

.. 1 One screening concept under invrsti gation ~ses contj nuoilsly . I 

. moving fine mesh screens to filter the fish from the water as it passes 

through the screens at the intake pumping station. Following if short 

impingement time, which is dependent on screen travel .peed arid Lhr 

aniount of submerged screen, the fish are lifted from the water in sc-rperl .. 

panels and spilled into a fish return trough which carries them back LO . 

the source water body. This "impinge-release" conccpt can be appl icd to 

horizontal (submerged) as well as vertical (emergent) traveling screens. . 

Features common to each scrr'en include smal I opcniiig nicBsti, coriLiritic,i~s 

screen rotation to minimize impingement time. and provisioris to rtturn 

the fish to the source water body. 

.. 

in i976 a series of laboratory tests was conducted to evaluate 

the potential for this concept (Tom1 janovich et al. 1976). Tw+, ohjectivcs 

of that study were to: (1) determin? the srnallcst size srreeii opening 

~it+c~ilrcl Lo reL;tiii Cisli lurviit!, 111111 (21 c~vri111riL~~ tht, !2iri;viv,iI rtitt- (11 I titretained, i.e., impinged, larvae. The study showed that a scrCen ~prriing 
2 

of 0.5 inn1 was requircd to rc1L;tin the sniallest larvae tested and that 

imI>ingeiiicnt durati-ons of up to four minutes rcsul ted in initial survival 

between 75 arid 100 percerit. These results suggested that the concept was 

viable ant1 that future studies should be directed at developing 3 prototype screen. 

Ol>j e r t i vcs . ... . .- - . 

'I'iie piirpose of the present :;turly was to evaluate larval fish 

survival associatcti with a11 aspects cf fish h;iiid:irig on a laboratory . 

screcsn. 'rht.sr data uil 1 hc used to opl imizc xurviviil of fish by 

niodi.fying any components of thc screcn which cause significant niortality 

to thc 1.arvoe. This report dcscri bes ihr prototype screen wli i ch was 

ctiosc?n for laboratory tests, the laboratory model test scrt-clri, and the 

tc'st clcsigri. It also prcsents thf. results of tests coridiicted during 

1978 arid icictnti f.ics remaining areas of study that riced to be adrlrcssetf 

iri ortlcr to devclop a final prototype 4esign. 
showed very low stirviva1 with and without temperature control. 

the refrigeration unit, very little useful information would have been 

obtained exrcpt €or the ti;irdjr species. 

Without 

S UM!lIARY 

1. Ten larval fi.sh specics, ranging in age from 3 to 16 days and total 

length from 5.0-14.0 mm were tested in 1977 and 1078 on a laboratory 

model fine mesh traveling screen. The objective of the test was to 

evaluate the effect of several fish handling components (impingement, 

exposure to air, and-spilling into a fish return trough) on survival 

of the larvae. 

2. No significant differences in effect of various fish handling coiiiponents 

were shown for four relatively large, hardy species of larvae. 

Paddlefish, northern pike, white sucker, antl channel catfish, which 

were among the youngest (three to six days of age), but largest 

larvae showed high average initial and 24-hour survival (>97 percent 

ancl >S9 pel-cc!it , rt~spc~ctively) under all test conditjons. 

.J. 9. Two specicis (striped bass antl striped bass x white bass hybrid) 

showed relatively iow ;!vt?rage survival under most test condiLions , 

~:>hicti .?lsr! precl utfed evaluating the effect of screen components 

on surviv;il . Con: r.oL survival for thcsc specics ais0 was low and 

ti i glil y VA L- i gj ti i t: . 
29 

4. Redbreast sunfish, largemouth bass, bigmouth buffalo, and walleye 

larvae showed survival intermediate between the other two groups. 

This intermediate group of four species was used to evaluate the 

fish handling components. 

The following items concern the intermediate group species: 

5. Impingement showed the greatest effect on survival and was significant ' 

CONCLUSIONS 

The objective of this study was to provide the necessary information 

to identify components of an impinge-release screen system which need to be 

modified in order to optimize fish survival. It wa!; obvious from initial 

results that the amount of modification needed will be dependent largely 

on the species and life stages to tic protected. 

6. Air exposure had a significant effect on initial and/or 24-hour 

adjusted survival for all four species. 

usually associated with least air exposure. 

Highest survival was 

7. The effect of spilling fish into the return trough was not 

significant in tests which included air exposure for any of 

the four species. In tests which did not include air exposure 

("impingement only" and "impingement plus spi.11 from a wet 

screen") an apparent effect of spill was observed for three ., . ..il 

species. 

8. Two-way interaction effects among the three variables did not 

appear to be important. 
30 

The large range in survival among species tested suggests that 

a similar pattern would be found in the natural environment using a 

prototype screen. Consequently, an average survival rate for larval 

fish would not be meaningful. 

species was related to size differences for a given age among species. 

Much of the range in survival among 

If a species that has relatively large larvae is to be protected, 

little or no modification to the basic fine mesh screen may be needed. 

However, if small, fragile larvae, such as striped bass, require piotection, 

considerable modification may be required to provide optimum protection. 

To date, tests discussed tiere have shown only limited success in protecting 

the very fragile species using this impinge-release concept. However, 

high control mortality in tests with these species suggests that the 

._ 

... 

: .. 

laboratory studies have not adequately described the effect of the 

screen on survival. . 

.. . : 

For species of intermediate hardiness it appeared that 

providing a water trough to the screen panel, limiting the impingement . 

time to four mirutes or less, and providing low pressure sprays for fish 

renioval would significantly increase survival. 

Additional testing is required €or fragile to moderately hardy 

species in order tu .~dequately identi.fy the need for and evaluate screen 

systcm modifi.cations. Specific areas which need to be addressed include: 

(1 j deterrni.ning optimum spray velocities and volumes, (2) evaluating the 

effect of screen clc>g:ging on flow pattern as it may influence fish remcval 

and survival, and (3) determining optimum screen panel configuration for 

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. .. 

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