P. 2

Docke tOW-2002-004 9 DCN #5-430 1 Turnpenny, A. W.H. Fis h Return s a t

Coolin g Wate r

Intake s 

# ffc-W 

# FAWLE Y aqpafi e iras©amd h flailb®iratlffiiii®§ L M 

# Consultancy Report Client : Nuclea

r Electric pi c

For the attention of

: M r C J L Taylo

r CONFIDENTIA

L 2 3 Decembe

r 199 2 

### FIS H RETUR

N A T COOLING WATE RINTAKE S AW H Turnpenn

y

FC R023/9 2P. 3

SUMMAR Y Thi s Report

review s informatio n fromth e UK , US A .an d Europ e relatin g t o fish damag e associate dwit

h impingemen t

o n th e coolin g wate r

intak e screen s o f

powe r stations , type s o f fis h retur n syste muse dan dthei r relativ e success . On th e basi s o f thi s information , outlin e desig n criteri afor drum

- o r band-screen-base dfish return syste mar e presented . CONCLUSION S 1 Impingemen t

o f fish o n coolin g water

intak e screen s cause s avariety o f externall y visibl e injuries , rangin g fromscal e loss , t o mor e seriou s damag e t o eye s an dfins.. Thes e ar e mainl y contac t

injuries . I n specie s possessin g aclose dswimbladde r (eg . co dfamil y an d bass) , interna l damag e t o thi s orga n coul dresul t

frompressur e reduction s associate dwit h raisin g fish t o th e surfac e ove r aperio do f

tim e whic h i s to o shor t t o allo w pressur e adaptation . Thi s i s onl y likel y when th e intak e openin g i s >5 mbelo w th e wate r surface . Larva l o r adul t clupei dfish ma

y suffe r damag e t o th e auditor

y bull asyste mi n offshor e intak e system s wher e th e fish .ar e draw n dow n 2 0 mo r

mor e belo w intak e level . 2 Impinge dfis h ma

y als o suffe

r physiological stress . Thi s ca n b e cause db y exercis e an dexhaustio n withi n th e turbulen t condition s o f

th e screenwell s o f

apowe r station , b y osmoti c imbalanc e resultin g fromdisruptio n o f th e epithelial laye r

b y abrasio n and , durin g period s o f

biocid e application , b y th e toxicit y o f th e biocide . 3 Survival o f

fish for period s o f

on e t o four

day s followin g impingemen t ha s bee n investigate di n oversea s studie s an dvarie s fromzer o t o ahundre dpe r cent , dependin g on species . Demersa l an dinshor e epibenthi c specie s (eg. , flatfishes , bass ) ten dt o b e mos t resilient , wherea s pelagi c specie s (eg . clupeids , anchovies ) ar e mos t delicate . Th e resilienc e o f th e demersa l an depibenthi c fis h ma y b e relate dto both physica l robustnes s an dth e fac t that the y mak e littl e attemp t

t o swim , onc e withi n th e scree n well , an dar e thu s les s subjec t t o exhaustio n an dcontinue dabrasion . 4 I n th e US A an dFrance , fish rescue/return system s hav e bee n develope dt o collec t fish enterin g th e C W intake s an dretur n the mt o th e wild . Th e simples t system s use dcollec t

fish followin g impingemen t

o n th e screen s andattemp t t o minimis e furthe r

handlin g stres s b y carefu l desig n o f

th e associate dbackwas h andhandlin g equipment . Mor e sophisticate d design s preven t

impingemen t

an dguid e fish t o extractio n area s wher e the y ca n b e pumpe d o r lifte dou t

prio r t o return t o th e wild . Th e succes s o f th e mor e elaborat e system s i s moderatel y goo dwhe n measure di n term s o f number s offis h diverte dan dreturne d(eg . 5 0 t o 75 % at Sa n Onofre Nuclear

Generatin g Station ) bu t

thes e figures d o no t

tak e accoun t

o f additiona l mortalitie s du e t o predatio n a t th e outfall , whic h ma

y b e high . I t

i s doubtfu l whethe r an y fish retur n syste mca n hop e t o achiev e >30 % succes s rat e overall , fo r al l species . 5 Effectiv e fish protectio n at wate r intake s require s attentio n first at th e desig n an d sitin g stag e t o ensur e that area s o f hig h fish concentratio n ar e avoide dan dtha t intak e approac h velocitie s ar e kep t belo w th e sustainabl e swimmin g speed s o f th e mos t importan tP. 4

fish species ; secondly , behavioura l deterrent s (eg. , base don sound , ligh t o r bubbl e stimuli ) shoul db e considere da s amean s o f reducin g fish entr

y int o th e intake ; fish retur n system s offe r afinal leve l o f

protection . 6 Desig n criteri afor asimpl e screen-base dfish return systemar e presented . Thi s involve s provisio n o f

fish bucket s o n th e screen s .an d carefu l desig n an dchoic e o f material s t o minimis e handlin g damage . Fis h ar e lifte db y mean s o f th e screen s themselves , bu t additiona l lif

t ma y b e provide di f

necessar y b y th e us e o f

screw-impelle r

fish pumps . A simpl e fish/trash separatio n pi t i s described , thoug h i t

i s recommende dthat

thi s shoul dno t b e use dwher e fish survival i s apriority , o n accoun t o f th e additional handlin g stress . 7 Th e choic e o f

return rout e for

rescue dfish - eithe r

via th e C W disch-arg e o r via a dedicate dfish return pipelin e - depend s parti.ally on cost . Wher e adedicate dretur n lin e ca n b e accomplishe da t

o r belo w th e cos t

o f routin g fish int o th e CW discharge , thi s i s alway s preferable , bein g fre e fromtherma l o r biocid e relate dstresses . Fo r typica l exposur e time s calculate dfo r

passag e throug h CW discharges , includin g exi t o f th e fish fromth e plum e (rang e 17. 5 t o 9 0 minutes) , chlorin e toxicit y i s no t likel y t o kil l fish. Th e effect s o f therma l shoc k ar e les s predictabl e an di t i s recommende dtha

t site-specifi c tri.al s b e performe dt o determin e th e effect s o f

therma l stres s o n fish whic h hav e alread y bee n subjecte dt o th e stresse s o f

impingement . 8 Ther e ma

y scop e for

further reducin g fish damag e b y reducin g thei r residenc e tim e i n screenwells . Thi s might b e accomplishe dby electrical stunning , narcotizatio n (eg . wit h carbo n dioxide ) o r

b y eliminatio n o f

ligh t fromth e screenwel l t o preven t effectiv e orientation . Experimenta l trial s woul db e required .

D r A W H T

y for : FAWLE Y aquati c researc h laboratorie s Ltd Marin e & Freshwate r

Biolog y Uni t Fawley , Southampto n S0 4 1T WP. 5

CONTENT S 1 . INTRODUCTIO N 2 DESCRIPTIO N O F POWE RSTATIO N WATERINTAKE S 3 . STRES S AN D DAMAG E T O FIS H CAUSED B Y IMPINGEMEN T 3. 1 Damag e symptom s o f impinge dfish 3. 2 Post-impingemen t

survival 3. 3 Physiologica l stres s 4 . FIS H RETUR N SYSTEMS : OVERSEA S EXPERIENC E 4. 1 SONG S fish diversio n system 4. 2 L e Blayai s fish/shrim p return system 4. 3 Th e NE P Brayto n Poin t Angle dScree n fish by-pas s syste m 4. 4 Hanfordfish return system 4. 5 Summar

y o f fish recover

y experienc e 5 . DESIG N CRITERI A 5. 1 General layou t 5. 2 Scree n mes h 5. 3 Fis h bucket s an dbackwas h system 5. 4 Tras h hopper s an dfish retur n pip e 5. 5 Fish/tras h separatio n pi t an ddischarg e 5. 6 Limitation s o f

th e desig n 5. 7 Scop e fo r

further reducin g fish damag e 6 . FIS H RETUR N ROUTE S 6. 1 Retur

n via th e C W discarg e 6. 2 Dedicate dfish return pipe s 7 . CONCLUSION S TABLE S FIGURE S APPENDIX : Investigation s o f fish damag e symptom s o n Fawle y Powe r Statio n screen sP. 6

1 . INTRODUCTIO N Th e unintentiona l captur e o f fish i s avirtuall y unavoidabl e consequenc e o f abstractin g larg e flow s o f wate r fromrivers , lakes , estuarie s o r th e sea . Whils t

mos t mode mintak e design s ar e abl e t o tak e advantag e o f establishe ddesig n principle s an dfish protectio n technologie s t o minimis e entrapmen t

o f fish, non e ar e wholl y effectiv e agains t al l specie s an dlif

e stage s o f fish (Turnpenny , 1988) . A possibl e exceptio n t o thi s ar e passiv e screenin g system s usin g fine meshes , wedge-wir e material s o r porou s filtratio n media , bu t whos e us e i s restricte dt o relativel y smal l abstraction s o f < lmV 1 (Turnpenny , 1989) . Th e nee dfo r

fish retur n system s stem s fromth e inadequac y o f primary fish protection . Th e first an dpotentiall y mos t

effectiv e measure s wil l ai mto keep fish awa y fro mth e wate r

intak e poin t altogether : an y fish, onc e withi n th e engineere dsystem , wil l b e at risk o f damag e from th e stresse s o f

passag e an dcontac t

wit h surface s an dmachinery , i n man y case s fro mtoxi c exposur e t o biocides , an dfinally fro mpredatio n at

th e poin t o f return t o th e wild . Fis h return system s wil l thu s have , at best , alimite dsucces s rate . Ther e ha s bee n alimite dexperienc e o f fish return system s i n th e UK , installe dprincipall y at estuarin e site s for

th e return o f

salmo n (Salmo salar) an dse atrou t (S. trutta) smolt s (e.g. , Uskmout h an dOldbury-on-Severn powe r stations) . A numbe r

o f othe r station s (e.g . Dungenes s 'B' , Sizewel l 'A' ) hav e operate dsimple r tras h retur n system s whic h involv e periodi c discharg e o f

th e accumulate dbiological an dothe r debri s to th e sea , wit

h n o deliberat e attemp t

t o secur e th e survival o f

livin g organisms . Th e inclusio n a t th e yet-to-be

commissione d Sizewel l 'B ' powe r stetio n o f

th e facilit

y t o direc t

tras h eithe r

t o basket s o r int o th e C W discharge , thereb y providin g th e opportunity fo r fish return , i s t o b e welcomed . Ther e has , indeed , bee n littl e encouragemen t b y th e regulatory authoritie s i n Englan dan d Wales , wit

h th e Ministr y o f

Agriculture , Fisherie s an dFoo d(MAFF ) on th e on e han d generall y i n favou r

o f th e retur n o f

impinge dmaterial s t o th e se afo r th e benefi t

o f fisheries, an dth e Nationa l River s Authority (NRA ) o n th e other , reluctan t t o licenc e discharge s containin g impinge ddebris . I t i s t o b e hope dtha

t th e argumen t

wil l b e decide dultimatel y i n term s o f

whic h ca n b e show n t o b e th e mos t environmentall y beneficial . Oversea s authoritie s hav e bee n les s reticen t abou t encouragin g th e developmen t o f fis h retur n systems . I n th e Unite dStates , th e prospec t o f compensatio n bein g levie dagains t fish losse s (Loeffelma

n an dTamms , 1991) , an dth e requiremen t unde r Sectio n 316(b ) o f

th e Federa l Wate r Pollutio n Contro l Ac t

t o implemen t

effectiv e environmenta l protectio n system s (Langford , 1983 ) ha s encourage dth e developmen t o f primary (fis h deterrence ) an dsecondar y (fis h return ) fish protectio n system s for wate r intakes . I n Europe , th e Frenc h powe r industry , a s par t

o f it s nuclear

expansio n durin g th e '70 s an d'80s , investigate dawid e rang e o f fish protectio n system s an dha s implemente dafish andshrim p return syste mon at

leas t on e estuarin e site , L e Blayais , o n th e Girond e (Travad e et al., 1983) . Th e objectiv e o f

thi s Report

i s to revie w researc h int o th e natur e an dfrequenc y o f fis h stres s FAWLE Y aquati c researc h laboratorie s Lt dP. 7

an ddamag e symptom s associate dwit h fish impingemen t

andreturn i n estuarin e an dmarin e powe r statio n coolin g wate r

(CW ) system s and , fro

marevie w o f

th e limite ddat afrom existin g fis h return systems , t o summariz e desig n criteri afor acost-effectiv e fish retur n syste msuitabl e for

estuarin e an dcoastal powe r stations . 2 DESCRIPTIO N O F POWE RSTATIO N WATE RINTAKE S Detail s o f intak e syste mdesig n diffe r fromplan t

t o plan t but , i n general , th e coolin g wate r system s o f

estuarin e an dmarin e powe r station s confor

mto on e o f

tw o types : onshor e o r offshore . Th e essentia l difference s betwee n thes e tw o type s o f intak e ar e illustrate di n Figur e 1 . In bot h types , wate r

i s pumpe da

t th e landwarden dfro

madeep screenwell , whic h i s fe d b y gravit y fromth e se ao r estuary . In th e offshore design , wate r enter s th e screenwel l via a n offshore intak e opening , on o r abov e th e bed , whic h feed s int o on e o r mor e concrete - o r steel-line dpipe s sun

k belo w be dlevel . Hydraulically , th e offshore intak e operate s o n th e manomete r

principle . Th e onshor e desig n differ s i n tw o chie f respects : firstly, th e wate r i s canalised , rathe r

tha n piped , s o tha

t afre e surfac e exists ; secondly , th e passag e distanc e and tim e fo r fish fro mintak e t o screenwel l i s muc h reduced . Bot h type s normall y featur e a foreba y area , aheado f

th e screenwell , whic h introduce s astorag e volum e int o th e system . Th e exclusio n o f

fish , wee dan dother

debri s i s normall y achieve db y at leas t tw o level s o f screening . Th e primary coars e screens , o r tras h racks , ar e locate dat th e mos t upstream poin t o f th e intak e syste man dserv e t o exclud e bulk y item s suc h a s driftwoo dan dbarrels . Th e tras h rack s typicall y hav e bar s space da t ~ 10c mpitch . Smalle r

items , includin g fish, ar e remove db y finer , mobil e screens . Th e scree n apertur e i s commonl y ~ 1cmsquare , forme dfromwove n stainles s stee l wir e o r punche dstainles s panels ; Electricit e d e Franc e hav e adopte dfiner

(2-3m maperture ) woven plasti c o r wir e mes h on som e recentl y buil t stations . Th e characteristic s an dmesh siz e o f th e screenin g surfac e ma y hav e som e bearin g o n fish damage , an dwil l als o determin e th e size s o f fish excluded . Turnpenn y (1981 ) examine dth e relationshi p betwee n mes h siz e an dfish exclusion , an dasummar y o f th e findings for

commo n inshor e Britis h specie s i s give n in Figur e 2 . Any smal l fish no t retaine db y th e mesh , includin g egg s andichthyoplankton , wil l pas s throug h th e coolin g syste man db e returne dt o th e wild , thoug h wit h variabl e survival prospect s (Langford , 1983) . Th e mobil e screen s t o whic h th e fine mes h panel s ar e attache dar e usuall y o f th e dm mo r ban dtype . Ban dscreen s compris e fla t panel s o f scree n mes h affixe dt o vertica l belt s i n th e manne r o f a'caterpillar ' trac k

(Figur e 3) . Th e water

i s filtere dfromoutsid e t o in , fish an d othe r debri s becomin g impinge don th e inne r vertical wal l o f

mesh . Th e screen s ar e continuousl y o r

intermittentl y rotated , s o tha t th e foule dsurfac e i s raise dabove wate r leve l an dimpinge dmaterial s fal l b y gravit y ont o ledge s o r

scoop s fittedhorizontall y alon g th e botto mo f eac h scree n panel . Upo n reachin g apoin t clos e t o th e to p o f

th e rotatio n path , pressurise dbackwas h jet s (1- 4 bar pressure ) spra

y water throug h th e screen , washin g debri s of f int o acollectio n troug h o r 'tundish' , whenc e th e flow o f backwas h wate r

carrie s th e materia l int o acollectin g pi t line dwit h amesh basket . FAWLE Y aquati c researc h laboratorie s Lt dP. 8

Th e principl e o f

dm mscreen s (Figur e 4 ) i s simila r t o tha t o f ban dscreens , bu t

her e th e mes h panel s ar e affixe dt o arigiddm mwhic h rotate s continuously . Photograph s showin g detail s o f th e dmmscree n an dbackwas h systema t Fawle y powe r

statio n ar e include di n th e Appendix . A thir dtyp e o f

fine scree n whic h i s les s commonl y use di s th e Detfordstrainer . I t i s a pressur e straine r

whic h comminute s th e debri s an dpasse s i t throug h th e C W system . Strainer s offe

r n o opportunity for

fish return . I n Britain , straine r system s ar e fittedat

Isl e o f Grai n an dBra d wel l powe r stations . At mos t powe r stations , chlorine , whic h i s toxi c t o fish, i s injecte dint o th e coolin g wate r intake s clos e t o th e prim.ar y screens . It s purpos e i s t o preven t th e accumulatio n o f

attache d biofoulin g organism s (i n th e UK , principall y th e mussel , Mytilus edulis) whic h coul d otherwis e reduc e flo w rat e an ddamag e hea t exchanger s (Whitehous e et a/. , 1985) . Wher e lon g inle t tunnel s exist , additiona l injectio n point s ma y b e fittedat

interval s alon g thei r

lengt h t o compensat e for

chlorin e decay . I n France , chlorin e i s injecte dat aconcentratio n o f

1 mgl " ' ; i n Britain , dosin g i s normall y designe dto achiev e aconcentratio n o f 0. 2 mg l" 1 at

th e condense r inlet , whic h ma

y requir e > 1 mg" 1 a

t th e injectio n point , especiall y for lon g inle t tunnels . Chlorin e i s usuall y applie donl y i n th e warme r season s o f

activ e musse l growth (water temperatur e >9-10°C ) . 3 . STRES S AN D DAMAG E T O FIS H CAUSE D B Y IMPINGEMEN T 3. 1 Damag e Symptom s o f Impinge dFis h Ther e ha s bee n anumber o f investigation s o f

damag e suffere db y fish a s aresul t impingemen t

o n mobil e dmmo r

ban dscreens . Th e mos t

relevan t o f thes e t o Sizewel l i s th e previousl y unreporte dstud y o f fish damag e symptom s observe db y th e autho r an dcolleague s a t Fawle y Powe r

Station , Hampshire . Thi s i s reporte di n full i n th e Appendix . Th e study describe s damag e symptoms , includin g los s o f scales , splittin g o f

fins , haemorrhagin g o f

eye s an dfins, an dprotrudin g o r bulgin g eyes . Th e specie s o f fish examine dwer e bas s (Dicentrarchus labrax), herrin g (Clupea harengus), sprat (Sprattus sprattus), pollac k

(Pollachius pollachius), pou t (Trisopterus luscus), whitin g (Merlangius merlangus) an dsandsmel t (Atherina presbyter). N o flatfish specie s wer e include di n th e study , owin g t o thei r

scarcit y in th e catc h at

Fawley . O f th e fish examined , ove r 90 % exhibite dsign s o f physica l damage . Th e commones t symptom s wer e fin damag e (splittin g and/o r haemorrhaging ) an dscal e loss , thoug h ey e damag e wa s als o commo n (Tabl e 1) . Thes e condition s ar e al l potentiall y harmfu l t o th e fish , eithe r throug h directl y impaire dfunctio n o f th e damage dpart , o r

throug h consequentia l physiological disturbanc e o r diseas e (se e th e Appendi x for afuller discussion) .

FAWLEY aquati c researc h laboratorie s LtdP. 9

Th e type s o f

fish damag e i n th e Fawle y stud y ca n b e describe da s contac t injuries , cause d b y physica l contac t

wit h th e dm mscreens , trough s an dbackwas h system . Lo w pressur e effects , whic h ca

n lea dt o simila

r ey e damag e symptom s (Turnpenny , Davis , Flemin g an d Davies , unpublishe ddata ) ca n b e mle dou t

i n thi s case , a s th e fis h ar e at all time s belo w a fre e atmospheri c surfac e at Fawley . 3. 2 Post-Impingemen t Survival A few studie s o f

th e survival rate s o f

marin e o r

estuarin e specie s i n th e perio dshortl y afte r impingemen t

hav e bee n reported , thoug h n o attemp t wa s mad e t o measur e thes e i n th e Fawle y study , du e principall y t o th e difficult y of obtainin g goo dcontro l data . Thi s als o i s ashortcomin g o f

some o f th e investigation s i n th e literature, Clark an dBrownwel l (1973) , fromstudie s i n th e USA , refe r t o hig h rate s o f

mortality , not immediatel y after

impingemen t

but afte r adela y o f afe w hour s o r

more . The y mentio n flounde r (Pleuronectidae) , alon g wit h "certai n othe r

botto mspecies " a s bein g abl e t o surviv e impingemen t

wher e exposur e tim e an dother condition s ar e favourable . Thes e finding s ar e give n mor e scientifi c substanc e i n th e environmental monitorin g studie s arisin g fromth e Calvert

Cliff s nuclea r statio n i n Maryland , US A (Burton , 1976) . Impinge d fish wer e remove dt o laboratory aquari aan dthei r survival monitore dove r

a9 6 h perio d post-impingemen t

(Figur e 5) . A s migh t

b e expected , delicat e clupeio dspecie s suc h a s th e anchov y (Anchoa sp. ) an dmenhade n (Brevortia sp. ) mostly die dove r thi s period , wherea s th e mor e robus t

littora l specie s suc h a s th e spo t (Leiostomus sp. ) an dpipefishe s (Syngnathus sp. ) showe dgoo dsurvival . Unfortunately , thi s experimen t wa s compromise db y lac k o f contro l dat ausin g unimpinge dfish, s o tha t whil e hig h survival rate s ar e meaningful , lo w surviva l rate s mus t

b e regarde da s unsubstantiated . A mor e rigorous analysi s o f impinge dfish survival wa s conducte da s par t o f th e Hudso n Rive r (Ne w York ) powe r

plan t investigation s (Muessi g et al., 1988) . Thes e author s di dus e experimenta l control s an dth e finding s the y presen t ar e adjuste dfor

contro l fish survival. Figur e 6 give s asimplifie drepresentatio n o f thei r finding s for

familie s o f

fish commonl y presen t at U K powe r stations . Thi s give s aclea r pictur e o f

decreasin g surviva l rat e wit h th e progressio n fro mlittora l an depibenthi c specie s suc h a s th e soles , throug h th e demersa l specie s suc h a s bas s an dco dfamilies , t o th e pelagi c clupeid s an danchovies . Thi s progressio n concur s wit

h th e tren di n physical robustnes s o f th e animal s a s befit s thei r habits . Th e onl y surpris e amongs t thes e result s i s th e apparen t sensitivit y o f th e eels , afamil y generall y renowne dfor

it s toleranc e o f

hostil e environmental conditions . I n France , Travad e an dBorde t (1982 ) monitore dpost-impingemen t surviva l o f

estuarin e fish an dshrimp s a t

L e Blayai s powe r

station . The y place dfish an dshrim p specie s int o five categorie s o f

resistance , a s show n i n Tabl e 2 , base do n survival rate s 24- h post-impingement . A s i s seen fro mTabl e 2 , th e finding s ar e broadl y consisten t wit h thos e fromth e U S studies , FAWLEY aquati c researc h laboratorie s Lt dP.1 0

5 thoug h th e hig h resistanc e attribute dt o ee l i n th e Frenc h stud y i s mor e credible . I t shoul db e note dtha t

i n th e Frenc h study , th e backwas h je t pressur e wa s 3. 5 bar , compare d wit h atypica l pressur e o f

—1 ba r o n U K powe r stations . Travad e andBorde t reporte d comparativ e trial s o f

3. 5 ba r versus 1 ba

r backwas h pressur e an dshowe dthat , whils t th e sensitiv e specie s di dno t

benefit , ahighe r

proportio n o f

th e shrimp s an d'resistant ' fish specie s wer e enable dt o survive . I t i s no t mad e clea

r i n an y o f

thes e studie s whethe r

chlorin e o r

alternativ e biocide s wer e bein g applie da t

th e tim e o f

th e experiments . 3. 3 Physiologica l Stres s Fis h mortalitie s du e t o impingement , whethe r o r no t precipitate db y physica l injuries , ar e ultimatel y du e t o physiological stress . A number o f possibl e contributory cause s ca n b e identified , including : exhaustio n

asphyxiatio n osmoti c stres s biocid e toxicit

y pressur e chang e Exhaustio n Fis h ma y spen dlon g periods , hour s o r eve n days , swimmin g withi n th e screenwel l o f a powe r statio n (Turnpenn y an dUtting , 1981 ) an da s aresul t ma y b e exhauste db y th e tim e that the y ar e impinged . I n physiological term s thi s signifie s a n accumulatio n o f

lactat e i n th e blood , generatin g a

n oxyge n debt . Thi s oxyge n deb t ma y tak e u p t o 2 4 hour s o f

restin g t o repay (Batt

y an dWardle , 1979) , durin g whic h tim e th e fish i s unabl e attai n maximu m swimmin g performanc e an ds o i s at increase drisk

o f predation . I t

i s no t clea r whethe r exhaustio n per

se i s likel y t o caus e death . I t i s noticeabl e tha

t certai n type s o f

fish , particularl y flatfish, mak e n o visibl e attemp t t o swimonc e withi n ascreenwell . Thi s ha s als o been note dby othe r worker s (Clar

k an d Brownell , 1973 ) an dma

y contribut e toward s th e highe r survival o f

flatfish species . Th e sam e ma y b e tm e for

othe r inshor e epibenthi c species , many o f whic h hav e n o sustaine d swimmin g ability (Turnpenny , 1988) . Th e consequence s o f

fish no t resistin g th e flo w b y swimmin g ma y no t b e restricte dt o th e FAWLEY aquati c researc h laboratorie s LtdP.1 1

reductio n o f

oxyge n debt : protracte dresidenc e in th e turbulen t water s o f

ascreenwel l wil l undoubtedl y increas e th e chanc e o f contac t injurie s and , where biocide s ar e present , wil l increas e th e exposur e period . Asphyxiatio n Fis h ar e likel y onl y t o becom e asphyxiate dwhen the y accumulat e wit h othe r debri s i n tras h baskets . On th e screen s themselves , concentration s o f fish ar e rarel y adequat e t o mak e asphyxiatio n possible . Osmoti c Stres s Th e osmoti c concentratio n o f fish bloo dlie s somewhere betwee n tha t o f fres h an dsal t

water , equivalen t t o abou t 15% o i n herrin g (Clupea harengus), fo r exampl e (Blaxter

an dHunter , 1982) . Damag e t o th e epithelium , an dscal e loss , brea k dow n th e interfac e betwee n thes e tw o medi aan dca

n leadt o osmoti c dismption . In th e author' s experienc e wit h clupeid s particularly , thi s i s mos t

seriou s i n hypersalin e condition s sinc e osmoti c wate r los s fromth e fish lead s t o dehydration . Thi s ca n occu r withi n les s tha

n on e hour . I t

i s norma l practic e a t th e Fawle y laboratory , when sein e nettin g for marin e fish, t o transfe r

themimmediatel y after captur e int o half-strengt h se awater , wher e the y ar e hel dfor 2 4 hour s befor e bein g returne dt o full-strengt

h se awater . Thi s perio dallow s th e majorit y t o recove r

fro m superficial damag e an drestor e osmoregulator y function . Hyposalin e condition s can als o jeopardiz e survival . I n th e Hudso n Rive r study , wher e th e salinit y rang e wa s 0. 1 t o 2 %o, Muessi g et al. (1988 ) foundfish survival t o b e increase dat th e highe r salinit y value s i n thi s range . Lo w temperatures , belo w 3°C , wer e als o linke dwit h hig h mortality rate s due , th e author s suggest , t o impairmen t o f osmoti c functio n a t

lo w temperatures . Biocid e Toxicity A s chlorin e i s th e chie f

for mo f biocid e use dat

Britis h powe r

stations , discussio n wil l b e limite dt o chlorine . Typica l value s for

th e acut e (24-48h ) media n lethal toxicit

y o f chlorin e ar e a s follow s (Emberto n an dTurnpenny , 1981) :

FAWLEY aquati c researc h laboratorie s Lt dP.1 2

7 Famil y LC 5 0 (m g 1 ) Cyprinida e 0.0 3 - 0.2 3 Salmonida e 0.05-0.1 3 Pleuronectida e 0.0 3 - 0.2 5 Gasterostida e 0.09-0.1 3 Anguillida e 0.2 5 - 0.3 0 Thes e LC 50 s ar e wel l belo w th e applie ddose s at mos t powe r station s an dtherefore , whe n chlorin e i s bein g applied , ther e i s asevere risk o f chlorin e toxicity , especiall y fo r thos e specie s whic h exten dthei r residenc e i n th e screenwell s b y swimming . I t fortuitou s that

mos t o f th e fish ar e caugh t

at time s o f th e yea r when th e CW tunnel s ar e no t chlorinate d(se e Figur e 10) , thu s th e conflic t wil l occur

onl y durin g th e warme r

months , whe n fe

w fish ar e impinged . Pressur e Chang e Pressur e change s associate dwit h th e intake s o f

C W system s aris e onl y i n offshore intak e systems , especiall y wher e dee p tunnel s ar e employed . In suc h systems , fis h draw n i n a t intak e leve l ar e subjecte dt o pressur e increas e a s the y follo w th e descendin g lim b o f th e intake , an dpressur e decreas e a s they ris e toward s th e surfac e at th e inshor e end . Onshor e intakes , havin g asurfac e fre e t o th e atmosphere , impos e n o suc h pressur e change s on fish, thoug h pump suctio n ma

y draw fish dow n by afe w metre s withi n th e screenwel l itself . Depth , an dhenc e pressur e chang e ar e normal feature s o f lif e t o whic h fish ar e physiologicall y adapte d(se e Davies , 198 8 review) . A n increas e i n dept

h o f 10 mi s equivalen t t o approximatel y 1 atmospher e ( 1 bar ) pressur e increase . Muc h o f th e fish's body i s fluid an dthu s wil l no t

suffe r volum e change s a s aresul t o f dept h changes . However , th e gase s i n th e swimbladde r

( agas-fille dstmctur e whic h function s a s abuoyanc y controlle r an d auditory resonator ) wil l expan dan dcontrac t wit h pressur e decreas e an dincrease , respectively . Ga s conten t in th e swimbladder

ca n b e adjuste deithe r

b y secretion

/ resorptio n b y th e blood , o r

b y gulpin g o r

expellin g ga s via th e gut . Gadi dfis h (co dfamily ) an d others , includin g bas s (Dicentrarchus labrax), posses s th e former mechanis man dar e know n a s physoclists . Physoclist s requir e lon g period s to adjus t ga s volum e an drising fas t i n a wate r column ma

y mptur e th e swimbladder . Fo r exampl e co d(Gadus morhua) an dsaith e (Pollachius virens) requir e fiv e hour s for swimbladder

adjustment

fo r every halvin g o f hydrostati c pressur e (Tytle r an dBlaxter , 1973) . I t

ha s bee n show n experimentall y tha t for shorte r timescale s tha

n this , mos t

physoclist s ca

n withstan dup t o ahalvin g o f th e acclimatio n depth , but

n o more , before th e swimbladder rupture s (Turnpenny , unpublishe d data) . Physostomes , thos e specie s whic h regulat e ga s volum e via th e gut , ca n los e ga s withi n second s an ddepressurisatio n i s les s o f aproblem . Benthi c specie s suc h a s th e FAWLEY aquati c researc h laboratorie s Lt dP.1 3

8 flatfishes posses s n o swimbladder andar e thu s no t

subjec t t o thi s problem . Swimbladde r damag e wil l leadt o immediat e buoyanc y contro l problem s whic h wil l leav e fish les s manoeuvrabl e an dpossibl y mor e vulnerabl e t o predation . Th e risk o f swimbladde r

damag e for

physoclist s withi n offshore intak e system s i s no t a s grea t a s migh t b e expected , sinc e althoug h fish ma y b e subjecte dt o rapi dascen t (up t o 30 min 30-4 0 s at some sites) , they wil l hav e bee n expose dt o acomparabl e pressur e increas e in th e descendin g lim

b o f th e tunne l at

th e offshore en dafe

w minute s previously . Ove r thi s perio d the y wil l no t

hav e hadtim e t o adap t physiologicall y t o th e pressur e change : thus , th e swimbladde r

wil l b e compresse do n descen t an dwil l simpl y expan dt o it s initia l volum e o n reascent . An associate dphenomeno n ha s bee n describe din herrin g (Blaxter an dHoss , 1979) . In thi s specie s an dothe r

clupeids , th e swimbladder i s connecte dt o th e auditor y bull asyste mvia a ga s duct . In fish o f

1 2 to 1 5 c min length , increasing th e pressur e rapidl y from1 t o 3 ba r (equivalen t

to 2 0 mdept

h increase ) cause s mptur e o f th e pro-oti c membran e withi n th e bulla . Smalle r fish ar e les s sensitiv e t o thi s effect , thoug h larva l herrin g o f < 3 0 m mlengt h ma y b e at risk sinc e th e swimbladde r

ha s no t ye t bee n forme dandhenc e the y hav e n o adaptiv e capacity . Th e functio n o f th e bull ai s primaril y auditory , thoug h pressur e discriminatio n ma y als o b e afunction . Othe r form s o f pressure-relate ddamag e ar e know n amongs t fish. Haemorrhagin g o f th e eye s i s frequentl y ascribe dt o pressur e reductio n effect s (Davies , 1988) , thoug h ou r ow n studie s at Fawle y hav e indicate dtha t mechanica

l damag e i s mor e commonl y th e caus e an d that thi s sympto mcause db y lo w pressur e i s onl y foundunder some o f th e mor e extrem e condition s associate dwit

h passag e throug h low-headhydroelectri c turbines . I t i s unlikel y t o occu r a s aresul t

o f pressur e change s o f

th e rang e an dspee dfoun din CW intak e systems . I n conclusion , swimbladder damag e i s onl y likel y t o occu r amongs t physoclistou s species , an dthe n onl y wher e fish ar e taken froma n initial wate r

dept h at th e intak e openin g o f greate r tha n 5 m(i.e. , a

t apressur e o f

0. 5 ba r abov e atmospheric ) an dbrough t u p t o th e surface . Larva l o r

adul t clupei dfish ma

y b e risk o f damag e t o th e bull asyste min coolin g system s wher e th e fish ar e draw n dow n 20 mo r mor e belo w intak e level . 4 . OVERSEA S EXPERIENC E O F FIS H RETURN SYSTEM S Variou s technologie s hav e bee n incorporate dint o intake s an dscreenin g system s t o reduc e fish damage , an dt o improv e th e prospect s for fish returne dto th e sea . Experienc e o f marin e system s ha s bee n gaine dmainl y i n th e USA , b y Ne w Englan dPowe r (NEP) , Souther

n Californi aEdiso n (SCE ) andBattelle , an din Franc e b y Electricite " d e Franc e ( E d e F) . Fou r system s wil l b e describe dbriefly : in-plan t fish diversio n scheme s operate dat Sa n Onofre Nuclea r Generatin g Statio n (SONGS) , Souther n California , an da

t Brayto n Point ,

FAWLE Y aquati c researc h laboratorie s Lt dP. M

Massachusetts ; afis h return syste moperate di n Franc e at L e Blayai s Powe r

Statio n o n th e Girond e Estuary ; finally, afreshwater fish recovery systema

t Hanfordo n th e Columbi a River . 4. 1 SONG S Fis h Diversio n Syste m Th e SONG S fish retur n syste m(Lov e et al., 1987 ) accommodate s aflow rat e 5 2 mV 1 take n from1 k mlon g offshore tunnels . Th e wate r enter s aforeba

y an dfish ar e guide db y a syste mo f concret e guid e vane s (flow-straighteners ) an dplasti c louvres . Th e guidanc e principl e i s base don fish avoidanc e o f water turbulenc e generate db y th e louvr e slat s (se e Turnpenny , 1988) . Th e louvre s themselve s are fitte dt o atravellin g b.an d screen , s o tha

t the y ar e self-cleaning . O n encounterin g th e louvres , fish swimalon g th e fac e o f the mt o aquie t zone , whic h i s aconcrete-line dbasi n measurin g 4. 9 mx 4 m . A fis h lift , comprisin g a metal baske t

wit h awater-tigh t

lowe r hal f an dperforate duppe r

half , i s activate dperiodically . Upo n reachin g th e upper limi t o f it s trave l th e baske t

tips , spillin g th e fish int o asluic e channel . Simultaneously , additiona l water flushe s th e channel , dischargin g th e fish via a pipelin e whic h enter s th e se aat 6 mdepth , some 40 0 moffshore . Test s t o examin e th e efficienc y o f th e SONG S systemsho w variabl e diversio n capability . Thes e hav e bee n reporte dregularl y i n annual environmental review s o f th e plant' s operatio n sinc e 198 4 (Southern Californi aEdiso n Company , 198 5 et seq.), an dtypicall y rang e from aroun d90 % for

th e to p specie s (eg . norther n anchovy ) t o one-thir dfor les s responsiv e specie s (eg . queenfish) . Annual average s for al l specie s hav e bee n aroun d75 % in goo d years , fallin g t o 50 % i

n les s successful years . Th e reason s for thi s variability ar e no t

clear . Experiment s hav e als o bee n conducte dt o measur e 96- h survival rate s o f returne dfish, b y placin g a n encirclin g ne t

aroun dth e fish outfall . Thes e survival s ar e extremel y variabl e (n o figures published) , dependin g o n specie s an dsiz e o f fish an dindicat e that , overall , arathe r smal l percentag e o f

fish ar e abl e t o surviv e 'rescue' . I t i s further note db y th e researchers , that fish emergin g fromth e outfal l ar e ofte n subjec t t o heav y predatio n pressur e b y school s o f predatory fish. Th e ne t benefit s o f

th e SONG S systemar e therefor e no t a s hig h a s th e diversio n efficienc y figures woul dimply . 4. 2 L e Blayai s Fish/Shrimp Retur n System Th e syste moperate db y E d e F at L e Blayai s (Travade , 1982 ) i s intende dt o cop e primaril y wit h shrimp retur n bu t

i s effectiv e i n reducin g mortalit y o f mos t fish caught , thoug h no t delicat e specie s suc h a s sprat , herrin g andshad . Th e syste mi s amodificatio n o f standard dm mscree n technology , an duse s lo w pressur e ( 1 bar ) backwas h jet s t o remov e organisms , followe db y ahig h pressur e (3. 5 bar ) je t t o remov e more consolidate ddebris . Th e screen s themselve s ar e fitte dwit h afin e mesh (2- 3 mm ) plasti c mes h wit h help s t o reduc e impingemen t

damage . A rotatin g troug h edg e als o help s to reduc e damag e t o fish. Th e trough s fro meac h dm m FAWLE Y aquati c researc h laboratorie s Lt dP.1 5

1 0 sectio n fee dvia plastic-line dgulley s int o acommo n discharg e pip e fromwhic h th e organism s ar e flushe dbac k

t o th e estuary . Th e systemi s apparentl y effectiv e an deas y t o maintain . However , E d e F biologist s suspec t (F . Travade , pers . comm.) , fro mthei r observation s at th e outlet , tha

t predatio n pressur e frompiscivorou s bird s andfish i s high , .an d thu s th e ne t benefi t o f th e syste mi s reduced . 4. 3 Th e NE P Brayto n Poin t Angle dScree n Fis h Bypas s Syste m Thi s study i s describe db y Davi s et al. (1988) . Th e equipment wa s fitte dt o Uni t

4 o f th e powe r station , whic h ha s adesig n flow o f 17. 3 mY 1

. Th e behavioura l principl e i s simila r t o tha t o f th e SONG S system , i n tha t ban dscreen s ar e used , aligne dat a n angl e (25° ) t o th e incomin g flow, bu t

i n thi s system , ther e i s n o louvr e assembl y i n front o f th e ban dscreens . Th e fish ar e by-passe dt o aslo t at th e downstrea

mendo f th e screens , wher e Hidrosta l Mode l L12 F 3 0 c mdiamete r

screw-impelle r

centrifuga

l pump s ar e used , rathe r

tha n afish-lift, t o return fish t o th e sea . I n addition , th e band-screen s ar e fittedwit h bucket s t o maintai n i n wate r an y fish that

ar e impinged . Thes e ar e then washe dof f wit h a"low-pressure " (detail s no t supplied ) backwas h spra y t o adedicate dfish return pipe . Th e efficienc y o f

th e systemha s bee n evaluate dandsurvival rate s 4 8 h after handlin g measured . Diversio n efficienc y wa s 76% , thoug h allowin g for mortalities , onl y abou t

on e thir do f fish enterin g th e systemwer e returne dlive , via th e diversio n syste mbac k t o th e sea . Thi s compare s wit

h abou t 20 % expecte dsurvival for th e return o f

impinge dfish. 4. 4 HanfordFis h Retur n System Thi s freshwate r

fish recovery syste mwa s investigate db y Battell e (Pag e et al., 1979 ) a t HanfordGeneratin g Projec t (HGP ) on th e Columbi aRiver . Th e systemuse s travellin g ban d screen s fitte dwit

h fish buckets . Thes e ar e backwashe db y first alow-pressur e spra y t o remov e fish, the n ahig h pressur e spra y t o remov e debris . Th e syste mi s therefor e muc h th e sam e a s that

use dat L e Blayais , bu t

adapte dfor

ban drathe r

tha n dm mscreens . Effort s wer e mad e t o minimis e scree n penetratio n by fish, b y usin g afine scree n mes h (3. 2 m maperture ) an dfittin g sponge-rubbe r seal s aroun dth e edge s o f th e scree n t o preven t

leakage . T o measur e th e 9 6 h survival rate s o f fish recovere db y th e system , th e fish wer e sluice dvia a1 5 c mPV C pip e t o aswimmin g pool . Survival o f salmo n fr

y wa s 95% , wit

h 'virtuall y n o laten t mortality' . Survival for

al l fish specie s (unspecified ) wa s 85% . Th e author s make n o commen t

abou t survival rate s o

n returnin g fish t o th e wild . Thi s aspec t wa s apparentl y no t investigated .

FAWLE Y aquati c researc h laboratorie s Lt dP.1 6

1 1 4. 5 Summar

y o f Fis h Recover

y Experienc e Althoug h i t

ha s bee n show n tha

t fish rescu e system s ca

n remov e fish fromwate r

intake s wit

h les s damag e tha

n i s cause db y conventional tras h screenin g equipment , th e efficienc y o f suc h system s i s ope n t o questio n andi n some case s lower tha n publishe dfinding s sugges t whe n additional mortalit

y du e t o predatio n pressur e o n returne dorganism s i s take n int o account . Tw o basi c type s o f

fish return systemca

n b e distinguished : thos e whic h rel y upo n travellin g dmmo r ban dscreen s t o remov e th e fish fromth e C W flow , an dthos e whic h us e by-passe s t o guid e fish alon g th e scree n fac e t o some for mo f fish lift . O

f th e two , th e screen-base d systemi s much th e simpler , requirin g littl e modificatio n t o conventional tras h screenin g equipment . I t

i s difficul t

t o make useful comparison s o f fish survival s betwee n th e tw o system s becaus e o f

th e different

fish specie s involve di n th e studie s reported . Comparativ e trial s a t Brayto n Poin t

indicat e tha

t th e survival s ar e somewha t lowe r (20 % versus 30% ) wit

h th e screen-base dsystembu t th e smal l increas e in survival wit h th e by-pas s syste mwoul dno t appea r t o justif y th e greatl y increase dcost . Wit h eithe r typ e o f system , ne t

survival s o f

returne dfish ma

y b e low , althoug h som e o f th e more robus t

specie s ma

y surviv e well . 5 . DESIG N CRITERI A FO RA SCREEN-BASE D FIS H RETUR N SYSTE M Wit h th e reporte dsucces s o f

fish exclusio n method s (acousti c detenen t method s fo r

exampl e reportedl y givin g 6 0 t o 100 % fish diversio n fo r relativel y smal l capita l investment : Loeffelma n et ah, 1991) , acost-efficient approac h woul db e t o instal l primary protectio n o f thi s typ e a s th e mai n lin e o f defence , backe du p by ascreen-base dfish return system . Thi s woul db e base do n conventional dm mo r ban dscreen equipment , fromwhic h th e fis h woul d b e remove dan dreturne dt o th e wil dvia eithe r th e main C

W discharg e o r

adedicate dfish retur n channel . I n thi s Section , th e main element s an ddesig n criteri ao f suc h alow-cos t

fish return ar e described . Th e exampl e use demploy s ban dscreen s bu t shoul dwor

k equall y wel l wit

h dm m screens , s o lon g a s the y provid e sufficien t lif t t o creat e adequate fall o n th e fish retur n path . Th e desig n propose dals o include s arudimentar y fish/trash separator , thoug h i f consent s ca n b e gaine dwithou t

providin g thi s facility , th e degre e o f fish handlin g wil l b e reduce dan d fish ar e likel y t o b e returne din ales s damage dstate . 5. 1 General layou t A sketc h o f

th e genera l layou t

i s give n in Figur e 7 . Th e principl e i s a s follows . Materia l (fish , othe r

organisms , trash ) i s filteredb y th e ban dscreen s andfall s int o collectin g bucket s containin g wate r

a t th e botto mo f

eac h scree n panel . O n reachin g th e backwas h point , thi s material i s flushe dou t

int o hopper s feedin g th e tras h retur n pipeline . Th e heigh t

t o whic h th e screen s lif

t material an dth e height

o f th e backwas h hopper s i s designe dt o allo w gravity FAWLEY aquati c researc h laboratorie s LtdP.1 7

1 2 fal l o f th e material alon g th e pipelin e to th e trash/fis h separatio n pit . Thi s material i s conveye di n th e backwas h water , augmente db y a n additional carrie r

flo w fromapumpe d suppl y t o ensur e goo dpipelin e flushing. Additiona l lif t ca n b e provided , i f

necessary , usin g afish pump . I n thi s case , th e C

W discharg e i s useda s th e rout e fo r returnin g fish bac k

t o th e estuary o r se a(thoug h se e Sectio n 6) . Th e fish/trash separatio n pi t i s locate dalongsid e th e CW discharg e seal-pit . Wate r an dmaterial arrivin g fro mth e bandscreen s i s discharge dove r a se t o f slopin g tines , allowin g coars e materia l t o slid e alon g th e bar s an dint o tras h basket , whic h i s hoiste dou t

periodicall y for

emptying . Smalle r materia l drop s throug h th e tine s an dint o th e bas e o f th e pi t wit h th e wate r

flo w an d i s discharge dint o th e adjacent sea l pit . 5. 2 Scree n Mes h Figur e 2 show s scree n mes h size s require dfor th e exclusio n o f

variou s fish specie s and different sizes . Th e scree n mes h siz e fitte dt o th e dm mo r ban dscreen s shoul db e smal l enoug h t o preven t 'target ' fis h penetratin g th e mesh . Fo r example , ames h siz e o f < 8 m mi s require dt o exclud e bas s >5 0 m

mlength . Reductio n o f

mes h siz e t o 3- 4 m

mwoul dhel p reduc e fish damag e further , but i t shoul db e note dthat

smal l mes h size s wil l increas e th e risk o f screen blockage , especiall y by ctenophore s ('comb jellies') . Thi s ha s been afrequen t proble min Franc e (F . Travade , pers . comm.) , wher e smal l mes h size s ar e used , bu t n o proble mi n Englan dan dWales , wher e a n 8-1 0 m mmes h siz e standardha s been adopted . 5. 3 Fis h Bucket s an dBackwas h System Collectin g trough s attache dt o th e ban dscreen fac e shoul db e o f th e 'fis h bucket ' typ e (Figur e 3) . Th e requirement s ar e that : (a) th e trough s shoul dretai n wate r u p t o th e poin t

i n th e cycl e wher e th e organism s ar e flushedout ; (b ) th e backwas h je t pressur e at

th e poin t o f fish remova l shoul db e kep t at o r belo w 1. 0 bar . Th e fish bucket s shoul db e constmcte do f epoxy - o r

plastic-coate dmil dsteel , t o giv e bot h hig h strengt

h .an d lo w fish abrasio n characteristics . 5. 4 Tras h Hopper s an dFis h Retur n Pip e Ther e i s arequiremen t

t o avoi dabrasio n o f

fish o n th e return pathway . Thi s i s bes t met b y usin g smoot

h face dplasti c pipewor

k an dgulley s o f

GR P o r PV C constmction . A minimu m interna l diamete r

o f 3 0 cmi s recommende dfor th e fish return pipeline .

FAWLEY aquati c researc h laboratorie s Lt d1 3

Shar p bend s i n th e retur n pipelin e shoul db e avoided . Experienc e elsewher e ha s show n that fish tr y t o swi mbac k

upstreami f

the y encounte r

turbulence . A minimu mben dradiu s o f 3 mi s recommende dt o avoi dthi s problem . Th e volum e o f

wate r use dfor fish return nee dno t

full y floodth e pipelin e but shoul d maintai n aminimu mdept

h o f 1 0 c malon g it s whol e length . Th e us e o f asecondar

y pumpe d carrie r suppl y t o augmen t

th e backwas h wate r

supply i s recommended . 5. 5 Fish/Tras h Separatio n Pi t an dDischarg e I t i s recommende dthat

tw o suc h pit s b e provide dto allo w fo r uninterrupte dfunctio n whe n tras h basket s ar e remove dfor emptying . A suitabl e mean s o f divertin g flow fromon e t o th e othe r woul dthe n nee dt o b e provided . Fish/tras h separatin g tine s shoul db e fixedat 10-1 5 c mcentre s (Figur e 8) . A 1 0 c mpitc h wil l allo w th e majorit

y o f fish t o fal l through , thoug h a1 5 c mpitc h woul db e require dt o allo w large r

flatfishes suc h a s flounder t o penetrate . Som e experimentatio n ma y b e require d t o achiev e th e optimu mspacing . This , would , however increas e th e proportio n o f undesirabl e anthropogeni c materia l bein g returne dt o th e estuary . Th e provisio n o f a n optiona l soli d cove r tha t ca n b e fittedove r

th e tine s i s to b e recommended , a s amean s o f disablin g th e fish return systeman dallowin g al l material t o ente r th e tras h baskets . Th e slop e o f

th e tine s shoul db e aroun d15 ° t o th e horizontal (Figur e 8) . Th e discharg e fromth e separatio n pits(s ) shoul dente r th e CW discharg e seal pi t via a n outlet i n th e sid e wall . Thi s arrangemen t i s preferabl e t o direc t

injectio n int o th e outfal l tunne l a s i t provide s bette r

acces s fo r

removin g blockages . Th e interio r o f th e pi t an dth e discharg e pipelin e shoul db e coate do r o f plasti c constructio n t o minimis e fish abrasion . Interior , vertica l an dhorizonta l comer s shoul db e rounde d(minimu m3 0 c mradius ) t o ensur e a smoot h wate r flow. I t ma y b e necessar

y t o elevat e th e bas e o f

th e pi t abov e dec k

leve l t o preven t

backin g u p o f wate r fromth e sea

l pi t o n extrem e hig h tides . Thi s shoul db e take n int o accoun t whe n calculatin g th e require dfal l fromth e scree n hoppers . 5. 6 Limitation s o f

th e Propose dDesig n I t i s envisage dthat

many o f th e fish returne dfromth e screen s wil l b e deado r moribun dan d unlikel y t o recove r

upo n retur n t o th e estuary . Nevertheless , i t i s expecte dtha

t alarg e numbe r o f th e mor e valuabl e species , includin g juvenil e bass , eels , sol e an dothe r flatfish , a s wel l a s crustacean species , woul dsurviv e return t o th e wild , at leas t whe n th e syste mwa s no t bein g chlorinated , makin g th e scheme worthwhile . Th e effec t o f returnin g deado r

moribun dfish to th e wil dma y b e o f concern . Floatin g fish attrac t predators , notabl y gull s (bu t als o large r

fish) which , in populate dareas , ca n becom e anuisanc e t o loca l residents . However , i t woul db e unusua

l for larg e quantitie s o f

fis h t o FAWLEY aquati c researc h laboratorie s Lt dP.1 9

1 4 b e emergin g fromth e discharg e at an y on e time : th e fish woul demerg e individually , a t th e sam e rat e a s the y ar e becomin g impinged . I t woul dunde r

thes e circumstance s b e asimpl e matte r t o disengag e th e fish retur n systeman ddiver t al l th e material t o th e tras h baskets . Th e likelihoo do f

dea dfish becomin g washe dashor e an dattractin g publi c criticis mi s generall y negligible , o n accoun t o f natura l predator s an ddetritivores . 5. 7 Scop e fo r

Furthe r Reducin g Fis h Damag e Protracte dresidenc e o f

fish i n scree n well s i s amajo r contributo r

t o damag e symptoms , especiall y for

large r specimen s o f

strongly-swimmin g species . I t als o increase s physiologica l stresse s associate dwit

h exhaustio n o r

biocid e toxicity , thereb y puttin g th e fish mor e at risk frompredatio n upo n bein g returne dt o th e wild . In-plan t fish by-pas s system s hel p t o reduc e th e residenc e tim e but , otherwise , designer s o f fish return system s seemt o hav e pai dn o attentio n t o thi s problem . Ther e ma y b e littl e scop e for

reducin g th e residenc e tim e o f fish withi n screenwell s but som e experimentatio n coul dprov e worthwhile . Possibl e experiment s include :

- us e o f pulse delectri c fields t o stun fish (health and safety implications may preclude this)

- n.arcotizatio n o f

fish b y pulse dinjectio n of , eg. , carbo n dioxid e int o th e screenwell s

- exclusio n o f

ligh t fromscreenwell s t o confus e fish orientation . Non e o f thes e appear s t o hav e bee n teste dan dsimpl e experiment s o n a n existin g screenwel l might quickl y yiel dresults . 6 FIS H RETUR N PATHWAY S Two option s exis t

for th e retur n o f

fish andothe r

organism s t o th e sea : the y ca n b e returne d via adedicate dretur n pipelin e o r the y ca n ente r b y th e mai n coolin g wate r discharg e a t

th e seal pi t o r surg e shaft . 6. 1 Return via th e CW Discharg e Th e mai n reaso n for

adoptin g thi s rout e woul db e to sav e on cost . Wher e i t woul db e mor e costl y t o rout e material via th e CW disch.arg e tha n to constmc t

adedicate dreturn pipeline ,

FAWLE Y aquati c researc h laboratorie s Lt d1 5

becaus e for

exampl e o f

th e lengt h o f th e pip e mn , then adedicate dfish retur n discharg e wil l alway s b e preferable , owin g t o th e potentia l physiologica l stres s impose db y chlorin e toxicity and/o r elevate dwate r

temperatur e i n th e CW discharge . Thi s Sectio n examine s th e risks associate dwit h biocid e toxicit

y an dtherma l stress , b y considerin g exposur e level s an dtime s i n relatio n t o dose-respons e data . Exposur e Time s withi n th e C W Discharg e Le t u s assum e tha t

th e fish ar e t o b e discharge dfromth e fish recovery syste mt o th e C W syste mvia aseal pi t

o r asimila r chamber . Th e tim e o f

exposur e t o th e C W effluent wil l compris e thre e elements ; first , th e tim e take n to leav e th e sea l pi t (tj) ; secondly , th e transi t tim e alon g th e discharg e culvert (t 2 ) ; finally, th e tim e taken for th e fish t o swimou t

o f th e plum e (t 3 ) . Th e time , t , for

th e fish t o leav e th e sea l pi t depend s on th e mixin g characteristic s o f th e wate r enterin g th e pi t

wit h respec t t o th e wate r

containe di n th e pit , an dwhethe r o r no t th e fish activel y swi mt o maintai n thei r positio n i n th e flow. Becaus e th e fish wil l ten dt o avoi d bein g displace ddownstream , asimpl e calculatio n o f th e dilutio n rat e o f

th e sea l pi t content s wil l no t suffic e an dth e questio n mus t b e resolve dempirically . Th e clearanc e o f fish from screenwell s offer s aclos e analogy . Fro mexperiment s carrie dou t a t Dungenes s 'A ' powe r statio n (AW H Turnpenny , unpublishe ddat ahel din th e FAWLE Y arl Nuclear Electri c Archive) , i t

wa s show n that

marke ddead

fish (adul t

sprat : Sprattus sprattus) wer e cleare d a t arat e o f 60 % i n 8. 5 minutes . I t wa s estimate dfromexponentia l decay pattern s whic h followe dth e entry o f

pulse s o f liv e sprat s fro

mth e se athat

liv e fish wer e cleare dat arat e o f 60 % pe r

hour , thoug h som e fish remaine di n th e screenwell s fo r u p t o five hour s (Turnpenn y an dUtting , 1980) . N o dat awer e obtaine dfor othe r species , bu t

i t ca n b e assume dtha

t flatfis h an dothe r

epibenthi c specie s woul db e cleare da t arat e somewher e betwee n that

o f deadfish an dtha

t o f liv e sprats . Fo r

th e presen t

purpose , th e followin g averag e clearanc e rate s (t, ) wil l b e assumed , assumin g epibenthi c fish an dshrimp s t o resis t impingemen t

onl y slightl y longe r

tha n deadfish: Pelagi c an ddemersa l fish t , = 6 0 mi n Epibenthi c fish an dshrimps ; t , = 1 5 min . Th e transi t

time , t 2 , alon g th e CW culvert , depend s on th e wate r velocity an dlengt

h o f culverts . I t

i s assume dthat

i n th e absenc e o f

light , organism s wil l no t orientat e effectivel y i n th e tunnel s an dtherefor e wil l move , o n average , a t th e .sam e rat e a s th e water . Typically , at full CW discharge , desig n velocit y i s 2 ms 1 , reducin g t o hal f thi s a t period s o f

reduce d generatin g load . Th e lengt h o f th e CW culvert s rang e fromperhap s 20 0 mt o 100 0 m , givin g arang e o f

value s o f

t j fromhal f

t o ful l loado f approximatel y 2 t o 1 7 minutes . A t Sizewel l 'A' , fo r

example , th e culvert

lengt h i s - 20 0 m , puttin g t 2 i n th e rang e 2- 4 minutes .

FAWLEY aquati c researc h laboratorie s Lt dP.2 1

1 6 Th e time , t 3 , take n for

fish t o swimou t

o f th e plum e depend s o n thei r swimmin g spee d relativ e t o widt

h o f th e plume . A

n orde r o f magnitud e estimat e wil l suffic e for thi s purpose . Assumin g a

n averag e fish lengt

h o f 1 0 c mand , conservatively , astead y swimmin g spee do f 1 body lengt

h pe r secon d(se e Turnpenny , 1988) , afish woul dtak e 50 0 second s t o swi m fro mth e centr e t o edg e o f a10 0 mplume , perpendicula r t o th e plum e axis . Sinc e th e fish ma y swi mi n any directio n withi n th e 180 ° sector , th e averag e tim e t o escap e ca n b e calculate dusin g th e averag e valu e o f th e sin e o f

th e angl e betwee n th e fish an dth e plum e betwee n th e fish an dth e plum e fo r 0 t o 180° , whic h i s 0.64 . Hence , th e average tim e fo r th e fish t o exi t

th e plume , assumin g i t

swa mi n astraight

lin e at an y randomly-selecte dangl e woul db e 500/0.6 4 = 78 0 second s (1 3 minutes) . A 100 mplum e widt h i s larg e compare d wit h therma l plume s i n flowing wate r condition s a t

mos t coastal sites , an dthi s wil l b e take n a s th e uppe r

limi t for th e tim e tha

t i s likel y t o b e spent

by afish in th e plume . A 2 0 c mfish i n a1 0 mplum e would , b y th e same calculation , spend2 5 second s i n th e plume , whic h wil l b e taken a s th e lowe r

limit . Th e sumo f

t , + t

2 + t 3 give s th e overal l exposur e time , a s follow s Minimu mMaximu m ^ (seal pit ) 1 5 mi n 6 0 mi

n t j (outle t tunnel ) 2 mi n 1 7 mi

n t 3 (plume ) 0. 5 mi n 1 3 mi

n Tota l tim e 17. 5 min 9 0 min Chlorin e Concentratio n Chlorin e concentratio n (a s total residual oxidant : TRO ) at th e sea l pi t ca n b e expecte dt o remai n clos e t o th e 0. 2 mgl" 1 targe t concentratio n at

th e condensers . Typically , thi s woul d declin e t o aroun dhal f

thi s valu e o r

les s withi n th e firs t

100 mo f th e plum e (Davies , 1992) . Chlorin e Dose-Respons e Curve s Figur e 9 summarise s exposur e time s require dfor 50 % mortalit

y a t different chlorin e concentration s fo r

aselectio n o f

eigh t marin e an destuarin e fish species . Als o show n i s th e are aenclosin g chlorin e an dexposur e tim e minima an dmaxima for typical CW discharges , a s detaile dearlier

i n thi s Section . I t i s show n tha

t th e exposur e tim e an dconcentratio n envelop e for C W discharge s fall s wel l belo w th e acutel y letha l zon e for thes e fis h species . I t

ca n b e conclude dfromthi s informatio n tha t

th e chlorin e wil l no t

b e acutel y toxi c t o mos t

fish durin g passag e fromth e CW sea l pi t o r surg e shaf

t t o th e poin t

o f exi t fro mth e plume , unde r

typica l statio n desig n an doperatin g conditions . I t shoul db e recalle dtha

t i n th e U K chlorinatio n i s normall y limite dt o relativel y lo w period s o f fish impingement , when th e wate r temperatur e i s > 10°C . Figur e 1 0 show s th e monthl y catc h o f impinge dfish at

Fawle y powe r

statio n ove r

a1 2 mont

h perio dan dth e associate d FAWLEY aquati c researc h laboratorie s Lt dP.2 2

1 7 seasonal temperatur e profile . Durin g th e perio dwhen chlorin e woul dhav e bee n applied , i n thi s cas e May t o November , th e catc h represente donl y 13 % o f th e annua l catch . Typicall y at Britis h stations , les s tha

n 20 % o f th e annual impingemen t total i s impinge ddurin g th e chlorinatio n period , s o tha t fo r 80 % o f fish chlorin e toxicit

y wil l no t b e a n issue . Temperatur e i n CW Discharge s Temperatur e rises (At

) at th e CW discharg e relativ e to th e CW inle t a t U K station s ar e generall y in th e rang e 8 to 12°C , occasionall y reachin g 15° C a t som e nuclea

r site s (Langford , 1990) . Thi s A

t i s adde dt o aseasonal temperatur e profil e which , i n Britis h coasta l waters , range s fromamea n winte r temperatur e o f

5 t o 8°C t o amea

n summer temperatur e o f 1 4 t o 17° C (MAFF , 1981) . Thus , th e seasona l maximu mdischarg e temperature s wil l normall y fal l withi n th e rang e 1 3 t o 20° C fo r winte r an d2 2 t o 29° C i n summer . Th e seasonal profil e show n i n Figur e 1 0 i s typical o f souther n Britis h waters . Fis h Toleranc e o f

Therma l Shoc k Therma l discharg e effect s on fish hav e bee n reviewe drecentl y b y Langford(1990) . Al l fish can adapt , i n time , t o temperatur e change , thoug h th e capacit y t o adap t

depend s upo n th e rat e o f chang e an di s bounde dat hig h temperature s b y th e ultimat e lethal temperatur e (ULT) , beyon dwhic h n o further

adaptatio n i s possible . Toleranc e o f temperatur e increas e i s related , first, t o th e temperatur e increas e relativ e t o th e temperatur e t o whic h th e fish hav e bee n acclimatize dand , secondly , t o proximity t o th e ULT . Fe w fish species , eithe r

temperat e o r

tropical , hav e ULT s abov e 38°C . Fo r Europea n species , ULT s rang e from2 2 t o 32° C i n salmonids , t o 3 3 t o 42° C i n non-salmonid s (Alabaste r an dLloyd , 1980) . Thus , i t i s conceivabl e tha

t discharg e temperature s ma y reac h th e UL T fo r

som e salmomds , thoug h no t for non-salmonids . Therma l shoc k i s therefor e likel y t o b e th e mai n issu e for mos t fish species . Despit e th e extensiv e literatur e on temperatur e effect s o n fish (Langford , 1990) , ther e i s surprisingl y littl e coverag e o f U K marin e an destuarin e fish, an deve n les s relatin g specificall y t o shor

t ter mexposure . Th e littl e informatio n whic h i s availabl e relate s mainl y t o larva l an djuvenil e fish expose dt o combine dtemperature , chlorin e an dmechanical stress , an dindicate s hig h mortalit y o f mos t specie s (GESAMP , 1984) . Publishe dinformatio n may , i n an y case , hav e littl e relevanc e t o fish whic h hav e alread y bee n stresse db y impingemen t

an dsubsequen t

handling . In th e absenc e o f

relevan t thermal shoc k

data , i t woul db e advisabl e t o conduc t empirica l trial s wit h th e specie s o f

interest , base do n th e A

t o f th e statio n i n questio n an dth e compute d exposur e time . I t

woul db e preferabl e t o conduc t suc h trial s usin g fish that hav e bee n impinged .

FAWLEY aquati c researc h laboratorie s Lt dP.2 3

1 8 6. 2 Dedicate dFis h Retur n Pipe s Adoptio n o f

adedicate drout e for

fish return obviate s any problem s associate dwit h chlorin e o r therma l stress . Th e general desig n criteri aar e a s set ou t in Sectio n 5.4 . Th e outfal l fro mth e fish return pip e shoul db e locate dsuc h a s t o minimis e th e chanc e o f re entrapment . I t

shoul dpreferabl y b e submerge dat al l state s o f

tid e but , i f

not , shoul db e arrange ds o that

i t discharge s int o wate r

rathe r tha n adryin g are ao f

se abed . 7 CONCLUSION S 7. 1 Impingemen t

o f fish o n coolin g wate r

intake screen s cause s avariety o f externall y visibl e injuries , rangin g fro mscal e loss , t o mor e seriou s damag e to eye s an dfins.. Thes e ar e mainl y contac t

injuries . I n specie s possessin g aclose dswimbladder (eg . co dfamil y an d bass) , interna l damag e t o thi s orga n coul dresul t

fro mpressur e reduction s associate dwit h raisin g fish t o th e surfac e ove r aperio do f

tim e whic h i s to o shor t t o allo w pressur e adaptation . Thi s i s onl y likel y when th e intak e openin g i s >5 mbelo w th e wate r surface . Larva l o r adul t clupei dfish ma

y suffe r d.amage t o th e auditor

y bull asystemi n offshore intak e system s wher e th e fish ar e draw n dow n 2 0 mo r mor e belo w intake level . 7. 2 Impinge dfish ma

y als o suffe

r physiological stress . Thi s ca n b e cause db y exercis e an dexhaustio n withi n th e turbulen t condition s o f

th e screenwell s o f

apowe r station , b y osmoti c imbalanc e resultin g fromdismptio n o f th e epitheli d laye r

b y abrasio n and , durin g period s o f

biocid e application , b y th e toxicit y o f th e biocide . 7. 3 Survival o f

fish for period s o f

on e t o four

day s followin g impingemen t ha s bee n investigate di n oversea s studie s andvarie s fromzer o t o ahundre dpe r cent , dependin g o n species . Demersa l an dinshor e epibenthi c specie s (eg. , flatfishes , bass ) ten dt o b e mos t resilient , wherea s pelagi c specie s (eg . clupeids , anchovies ) ar e mos t delicate . Th e resilienc e o f th e demersa l an depibenthi c fish ma y b e relate dt o bot

h physical robustnes s an dth e fac t tha t the y make littl e attemp t

t o swim , onc e withi n th e screen well , an dar e thu s les s subjec t t o exhaustio n an dcontinue dabrasion . 7. 4 I n th e US A an dFrance , fish rescue/return system s hav e been develope dt o collec t fish enterin g th e C W intake s an dreturn the mt o th e wild . Th e simples t system s use dcollec t

fish followin g impingemen t

o n th e screen s andattemp t t o minimis e further

handlin g stres s b y carefu l desig n o f

th e associate dbackwas h an dhandlin g equipment . Mor e sophisticate d design s preven t

impingemen t

an dguid e fish t o extractio n area s wher e the y ca n b e pumpe d o r lifte dou t

prio r t o return t o th e wild . Th e succes s o f th e mor e elaborat e system s i s moderatel y goo dwhen measure di n term s o f number s o f

fish diverte dan dreturne d(eg . 5 0 t o 7 5 % a t

Sa n Onofre Nuclea

r Generatin g Station ) bu t

thes e figure s d o no t

tak e accoun t

o f additiona l mortalitie s du e t o predatio n at th e outfall , whic h ma

y b e high . I t

i s doubtfu l whethe r an y fish return systemca n hop e t o achiev e >30 % succes s rat e overall , for al l species .

FAWLE Y aquati c researc h laboratorie s Lt dP.2 4

1 9 7. 5 Effectiv e fish protectio n at wate r intake s require s attentio n first a t th e desig n an d sitin g stag e t o ensur e tha t area s o f hig h fish concentratio n ar e avoide dan dthat intak e approac h velocitie s ar e kep t belo w th e sustainabl e swimmin g speed s o f th e mos t importan t fish species ; secondly , behavioural detenent s (eg. , base do n sound , ligh t o r bubbl e stimuli ) shoul db e considere da s amean s o f reducin g fish entr

y int o th e intake ; fish return system s offer afinal leve l o f

protection . 7. 6 Desig n criteri afor asimpl e screen-base dfish return systemar e presented . Thi s involve s provisio n o f

fish bucket s o n th e screen s an dcarefu l desig n an dchoic e o f material s t o minimis e handlin g damage . Fis h ar e lifte db y mean s o f th e screen s themselves , bu t additiona l lif

t ma y b e provide di f

necessar y b y th e us e o f

screw-impelle r

fish pumps . A simpl e fish/tras h separatio n pi t i s described , thoug h i t

i s recommende dthat

thi s shoul dno t b e use dwher e fish survival i s apriority , on accoun t o f th e additional handlin g stress . 7. 7 Th e choic e o f

return rout e for

rescue dfish- eithe r

via th e CW discharg e o r via a dedicate dfish return pipeline

- depend s partiall y o n cost . Wher e adedicate dreturn lin e ca n b e accomplishe da

t o r belo w th e cos t

o f routin g fish int o th e C

W discharge , thi s i s alway s preferable , bein g fre e fro mtherma l o r biocid e relate dstresses . Fo r typical exposur e time s calculate dfor

passag e throug h CW discharges , includin g exi t o f th e fish fromth e plum e (rang e 17. 5 t o 9 0 minutes) , chlorin e toxicit y i s no t likel y t o kil l fish. Th e effect s o f therma l shoc k ar e les s predictabl e an di t i s recommende dtha

t site-specifi c trial s b e performe dt o determin e th e effect s o f

thermal stres s o n fish whic h hav e alread y bee n subjecte dt o th e stresse s o f

impingement . 7. 8 Ther e ma

y scop e for

further reducin g fish damag e b y reducin g thei r residenc e tim e i n screenwells . Thi s might b e accomplishe db y electrical stunning , narcotizatio n (eg . wit h carbo n dioxide ) o r

b y eliminatio n o f

ligh t fromth e screenwel l t o preven t effectiv e orientation . Experimenta l trial s woul db e required .

FAWLE Y aquati c researc h laboratorie s Lt dP.2 5

2 0 REFERENCE S Alabaster , J S an dLloyd , R(1980) . Wate r Qualit y Criteri afor

Freshwate r

Fish . Butterworths , Londo n an dBoston . Batty , RS & Wardle , C S (1979) . Restoratio n o f glycoge n fromlacti c aci di n th e anaerobi c swimmin g muscl e o f

plaic e Pleuronectes platessa L. . J . Fis h Biol . 15 , p p 509-519 . Blaxter , J H S & Hunter , J R(1982) . Th e biolog y o f clupeoi dfishes. Adv . mar . Bio l 20 , p p 3-223 . Blaxter , J H S an dHoss , D E (1979) . Th e effec t o f rapi dchang e o f

hydrostati c pressur e on th e atlanti c herrin g Clupe aharengu s L . I I Th e respons e o f th e auditory bull asyste m i n larva e in juvenile . J . Exp . Mar . Biol . Ecol . 41 , p p 87-100 . Burton , D T (1976) . Impingemen t Studie s II : Qualitativ e andquantitativ e survival estimate s o f impinge dfish an dcrabs . In : Semi-annua l Environmenta l Monitorin g Report , Calvert Cliff s Nuclea r Powe r Plant , Pacifi c Ga s andElectric , Marc h 1976 . Clark , J an dBrownwell , W (1973) . Electri c powe r plant s i n th e coastal zone : environmenta l issues . Am . Littora l Soc , Spec . Publ. , 7 , America n Littora l Society , Highlands , N J 07732 , USA . Davies , J K

(1988) . A revie w o f

informatio n relatin g to fish passag e throug h turbines : implication s t o tidal powe r scheme . J . Fish . Biol . 3 3 (Suppl . A) , p p 111-126 . Davis , RA , Matousek , J A , Skelly , M J & Anerson , M R(1988) . Biological evaluatio n o f Brayto n Poin t

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i n relatio n t o th e cultur e o f

eel s (Anguilla anguilla L. ) i n heate deffluents . CEGB Report No . RD/L/2112N81 . Langford , TE L (1983) . Electricity Generation s an dth e Ecolog y o f Natura l Waters . Liverpool , Universit

y Press , 34 2 pp . Langford , TE L (1990) . Ecologica l Effect s o f Therma l Discharges . London , Elsevier , 46 8 pp . Loeffelman , P H an dTamms , K M (1991) . Environmental aspect s an dcomplianc e cost s o f hydropowe r

regulation . In : Proceeding s o f th e Specialit

y Conferenc e o n Energ y in th e '90s . Sponsore dby th e Am . Soc . Civ . Engrs. , p p 243-249 . Love , M S , Sandhu , M , Stein , J , Herbinson , K T , Moore , RH , Mullins , M , an dStephens , FAWLE Y aquati c researc h laboratorie s Lt dP.2 6

2 1 J S , Jr . (1987) . Analyse s o f diversio n efficienc y andsurvivorshi p o f th e Sa n Onofre Nuclear Generatin g Statio n fish return system . Unpublishe dreport , Southern Californi aEdiso n Co , Rosemead , USA . MAF F (1981) . Atla s ofth e Sea s aroun dth e Britis h Isles . Ministry o f Agriculture , Fisherie s an dFood , Lowestoft , NR3 3 OHT , England . Mattice , J S an dZittel , H E (1976) . Site-specifi c evaluatio n o f powe r plan t chlorination . J.Wat . Pollut . Contr . Fed. , 48(10) , p p 2284-2308 . Muessig , P H , Hutchinson , J B Jr , King , L R , Ligotino , RJ .an d Daley , M (1988) . Surviva l o f fishe s afte

r impingemen t

on travellin g screen s at

Hudso n Rive r

powe r plants . Am . Fish . Soc . Mon . 4 , p p 170-181 . Page , T L , Gray , RH , Saroglia , GM & Bronzi , P (1978) . Comparativ e fish impingemen t o f Italia n an dUnite dState s Wate r Intakes : Proceeding s o f

aWorkshop . Battell e Pacifi c Nort

h Wes t Laboratory , Repor

t No . BN-SA-1040 . Souther n Californi aEdiso n Company (198 5 t o 1991) . Sa n Onofre Nuclear

Generatin g station : Marin e Environmenta l Analysi s andInterpretation . Report o n 198 5 Data . Repor t No . 85-RD-37 . 198 6 Data . Repor t No . 86-RD-31 . 198 7 Data . Report No . 87-RD-31 . 198 8 Data . Report No . 88-RD-35 . 198 9 Data . Report No . 89-RD-ll . 199 0 Data . Report

No . 90-RD-50 . 199 1 Data . Report No . 91-RD-10 . Travade , F (1982) . Survi e de s organisme s entraine d su r le s filtre s rotetif

s d e laCentral e d

u Blayais . Electricit e d e France , Report No . HE/3 1 - 82.04 , AR D - E3A08 . Travade , F an dBordet , F (1982) . Etude s experimentale s relative s au x entrainment s d'organisme s dan s le s prise s d'ea u d e laCentral e d u Blayais . Resultet s d e 198 1 - Perspectives . Electricit e d e France , Repor t No . HE/31-82.05 , 1 7 pp . Travade , F , Bertran dY an dCoulon , G (1983) . Etud e comparativ e d e deu x system s d e recuperatio n d'organism s entraine s dan s le s prise s d'ea u d e lacentral e du Blayais . Electricit e d e France , Report No . HE/31.83.17 , 3 2 p p + figure s + plate s + tables . Turnpenny , AW H (1981) . A n analysi s o f mesh size s require dfo r

screenin g fishes a t

water intakes . Estuarie s 4(4) , p p 363-368 . Turnpenny , A W H & Utting , N J (1981) . Tidal factor s i n fish impingement , CEG B Interna l Publicatio n RD/L/2109/N8 . Turnpenny , AW H (1988) . Th e behaviourial basi s o f fish exclusio n fro mcoasta l powe r statio n coolin g wate r

intakes . CEGB Researc h Report No . RD/L/3301/R88 . Turnpenny , AW H (1988) . Exclusio n o f salmoni dfish fromwate r intakes . CEG B Researc h Report

No . RD/L/3371/R88 . FAWLEY aquati c researc h laboratorie s Lt dP.2 7

2 2 

### Tytler , P , Blaxter , J H S (1973) . Adaptio n b y co dan dsaith e t o pressur e changes . Neth . J . SeaRes . 7 , p p 31-45 . Whitehouse , J W , Khdanski , M , Saroglia , M G an dJenner , H A (1985) . Marine Fouling an dPowe r Stations . A collaborative Researc h Workin g Grou p Report , CEGB , EDF , ENEL , KEMA .

FAWLE Y aquati c researc h laboratorie s Lt dP.2 8

2 3



### Table 1 Percentag e o f Eac h Fish Specie s Exhibitin

g Differen t Damag e Symptoms followin g Impingemen

t o n Fawle y Powe r Statio n Screens . Specie s Bas s Herrin g Sprat Pollac k Pou t Whitin g Sandsmel t Scal e Los s 3 5 8 0 9 1 5 2 5 8 4 1 1 5 Ey e Haemonhag e

0 6 0 2 8 3 3 1 6 1 1 4 7 Bulgin g

Ey e 0 7 4 1 7 1 3 0 7 Fi n Damag e

9 4 8 9 10 0 8 3 8 7 10 0 9 9

FAWLE Y aquati c researc h laboratorie s Lt d2 4

Tabl e 2 Post-Impingemen t Survival Rate s Recorde dfo r Variou s Specie s a

t L e Blayai s Powe r Statio n o n th e Girond e Estu.ar y (Travad e an dBorde t

(1982) . Damag e Resistanc e Ver y resistan t

specie s Resistan t specie s Les s resistan t

specie s Sensitiv e specie s Ver y sensitiv e specie s 24-hou r Surviva l 100 % 60-80 % 50 % 10 % 0 % Specie s

Eel , adul t flounder,lamprey,bas s Juvenil e flounder, sole , adul t mullet , sticklebac k Palaemon longirostris, Crangon crangon Gobie s Shad , sprat , herring , anchovy , smelt , juvenil e mullet , juvenil e pipefishe s

FAWLE Y aquati c researc h laboratorie s Lt d

# FIGUR E 1 Compariso n of th e Mai n Feature s of Offshor e an d Onshor e Intake System s (Sectiona l views ) (a) Offshor e Intak e Wate rSurfac e

Intak e Structur e Coars e Scree n Descendin g Lim b / Se a Be d

CW Inle t Tunne l Foreba y 

# i Ascendin g Lim b 

## (b ) Onshor e Intak e Wate rSurfac e

Se a Be d Wate r Intake Foreba y Coars e Screen Ic oP.3 1

SCREE N MES

H SIZ E - m

m Fig . 2 Squar e scree n mes h aperture s require d fo r excludin g fis h o f differen t specie s an d sizes .P.3 2

Lowpressur

e fis h washin g syste m



# Figur e 3 Sectiona

l View o f A Band Scree

n Fitted wit

h Fis h Bucket

sP.3 3

SPRA Y TRANSVERS E TROUG H

CHANNE L T

O ^TRAS H PIT S

(FRO M DRG . SPG/F 2 105 ) O F DRU M SC R 

# Figure 4 Sectiona

l View o f a Dru m Scree nP.3 4



## Figur e 5 Surviva l of Nort h America n Fis h Specie s Followin g Impingemen t (Afte r Burton , 1976 )

10 0

C O 8 0 > 

## c/ ) ^ 6 0 C D > 

## .S3 E 

# o 4 0

2 0 \

\ •X

- \ \ \ 

### J T ~--

h~ 4- - L . 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 10 0 

## Hours afte rImpingemen t Trinecte s maculatu s -Syngnathu s fuscu s Leiostomu s xanthuru s Ancho a mitchill i

### Fis h Retur n System s

Figur e 6 Summar y o f Post-Impingemen t Surviva l Rat e Finding s i n Hudso n

Rive r Studie s (afte r Muessi g e t al. , 1988 )

Percen t o f Fis h Aliv e "96 h post-Impingemen t Famil y Commo n Nam e <10 % 10-50 % 51-80 % >80 % Soleidae Sole s ' r. ' * JJJ.t Sf $<• £ * rn.

~' l" \ Cr

.*' 

### Gasterostidae Stickleback s JfffJ 

### Gadidae Cod , et c - < it&jg&y Syngnathidae Pipefishe s Percichthyidae Stripe d bas s Osmeridae Smelt s 4 "%\ ^ fSU $1. g£r 

### Anguillidae Eel s %»* 

### Clupeidae Herring s Engraulidae Anchovie s WWSWffifffWWfJWvi

Note : shade d area s represen t th e surviva l clas s int o whic h th e majorit yo f observation !



### FAWLE Y aquati c researc h laboratorie s Lt d

### Ban d scree n Backwas h troug h Fish/tras h separatin g pit .

Distanc e a » heigh t abov e dec k o f backwas h trough , sufficien t t o provid e adequat e fal l t o fish/tras h separatin g pit . C.W . discharg e sea l pi t M i l



## Figur e 7 General Arrangemen to f Fis h Retur n Syste mP.3 7



## Pla n vie w 

# r . Fro m ban d p^ screen s

Fro m ban d screen s



# Figure 8 A Simpl e Fish/Tras h Separation Pit

# FIGUR E 9 Chlorin e Toxicit y t o Marin e Fis h i n relatio n t o dos e an d tim e i n CW discharge s (Dose/tim e fo r 50 % mortality ) Legen d 1 . Atherinida e 2 . Anguill a anguill a 16 C 3 . Anguill a anguill a 23 C 4 . Sole a sole a 12-14 C 5 . Pleuronecte s platess a 16-17 C 6 . Gasterostida e 7 . Percichthyida e 8 . Clupeida e 9 . Salmonida e 

## Exposure Tim e (hours ) 10 0 

### 5 0 2 0 1 0 Reference s 2 & 3 : Emberto n & Turnpenny , 198 1 4&5 : Alderson , 197 4 2 Others : Mattic e & Zttel , 197 6 

### 1 

### 0. 5 0. 2 

### 0. 1 Dose-tim e are a fo rCW discharg e 

### S 0.0 1 0.0 2 0.0 5 0. 1 0. 2 0. 5 

### 1 2 5 

## Chlorin e Concentratio n (mg/ L TRO) 1 0 (Test temperatur e shown , wher e available )

# FIGUR E 1 0 Seasona l Fis h Catc h o n Fawle y Powe rStatio n

Screen s i n Relatio n t o Wate rTemperatur e 

# i

Numbe ro f Fis h pe rMont h Temperatur e C 200,00 0 150,00 0 100,00 0 50,00 0 0 c d

= 3 C c d (dat a fro m Turnpenny , 1983 )

— Nomina l Chlorinatio n Period : Contain s 13 % o f Fis h Catc h

% Vuary



## n 

## oarch 

### 5April %

^JuneJulygust

< 

# Mont h C D

. Q 

### E O D Q . C D tt C

D X J O +- 1 o O C

D 

### n E C D > O 

## z C

D 

### n E C D O C D D 

### 2 0 1 5 1 0

- 5 0P.4 0

Al. l A l INTRODUCTIO N A fiv e mont

h stud y wa s undertake n at

Fawle y Powe r

Station , Hampshire , to investigate an dclassif y th e types o f injurie s sustaine dby several specie s o f fis h commonl y occurrin g o n th e screens . Thi s stud y wa s carrie dou t

i n 198 7 bu t

ha s no t bee n reporte dpreviously . A 2 DESCRIPTIO N O F TH E FAWLE Y POWE RSTATIO N Th e 200 0 MW e oil-fire dpowe r statio n a t

Fawle y i s situate da

t th e south-western extremit y o f Southampto n Water . It use s amaximu mo f

63m 3 s" ' of coolin g wate r

take n fro ma900 mlon g dredge dchanne l connecte dt o th e mai n body o f

Southampto n Wate r

(Figur e Al) . Th e coolin g wate r

i s screene dbefore enterin g th e condense r system , b y coars e vertical bar s t o preven t th e entry o f larg e objects , an dthen by fin e rotatin g dru mscreen s with a9.5m msqirare mes h (Plate s 1 an d2) . A s th e scree n rotates , fish , wee dan ddebri s ar e caugh t o n stee l ledge s (Plat e 3 ) an dar e liftedou t o f th e water . Wate r jet s (Plat e 4) was h th e scree n an dth e debri s fall s abou t l mint o atransvers e meta l troug h (Plat e 5) . Th e was h water

carrie s th e debri s to th e en do f th e troug h t o adro p o f

50c mint o aconcret e channe l (Plate s 6 an d 7) , a t the en do f

whic h i t fall s afurther

80c mint o astee l baske t 1.5 m(Plate 8 an d9) . Thes e basket s ar e emptie dperiodically , typicall y onc e ever y eigh t hours , an ddebri s remove dt o alandfil l site . A 3 METHOD S A s maximu mnumber s o f fis h ar e caugh t

o n th e intake screen s at o r jus t before lo w wate r

(Turnpenn y an d Utting , 1981 ) sample s wer e take n durin g thi s period . A Nedo n ® collectin g baske t wa s place di n t o th e concret e channe l jus t before th e tras h basket . Thi s enable d th e fish t o b e coUectedeasU y .an d ensure dth e sampl e wa s fresh . Th e entir e flo w wen t throug h th e b.asket . Whe n th e retaine dmateria l impede dth e flo w o f wate r th e baske t

w.a s remove dan dth e fis h extracted . Th e material wa s returne dt o th e laborator y i n water , wher e specimen s o f b.ass , Dicentrarchus labrax (L ) (Plate 10) , herring , Clupea harengus (L ) (Plat e 11) , poUock , PoUachiu s poUachiu s (L ) (Plate 12) , pout , Trisopterus luscus (L ) (Plate 13) , san dsmel t Atherina presbyter

(Plat e 14) , sprat , Sprattus sprattus, an dwhiting , Merlangius merlangus (L ) (Plat e 15) , wer e remove dfo r examination . Thes e ar e amongs t

th e commones t

specie s recorde dat

Fawle y (Holmes , 1975) . Eac h fish wa s identified , measure di n standar dlengt h (SL ) aad

examine dfo r

damage . Afte

r preliminiar

y examinatio n th e foUowin

g categorie s wer e used , b.ase do n categorie s recogni.se d b y DadsweU , Rulif-so n an d Dabo m(1986) , i n studie s o f fis h passag e throug h hydro-electri c turbines : Scal e los s - determine da s th e percentag e o f scale s missin g fro mth e lef t body sid e o f

th e fis h an d assesse dvisuaUy . I t

wa s als o assesse dseparatel y fo r th e five area s show n i n Figure A2 . Fi n damag e i haemorrhag e - th e presenc e o f bloo di n th e fin membrane ; i i spli t

- th e break

o f th e fin membrane ; ii i shor

t - th e absenc e o f

aU o r part o f th e fin. The.s e wer e recorde da s zero , light , moderat e o r severe , dependin g o n th e degre e o f damage .P.4 1

A1. 2 Ey e damag e i 're d eye ' - th e presenc e o f haemorrhagin g withi n th e eye ; i i 'po p eye ' - bulgin g o f th e eye . Th e damag e wa s recorde do n arecor dshee t (Plat e 12) . A 4 RESULT S Scal e Los s A U th e specie s showe dscal e los s to varyin g degree s a s show n i n Tabl e Al . Th e clupei dspecies , herrin g .an d sprat wer e mor e susceptibl e to los s o f scale s tha n th e othe r

.species studied . San dsmelt wa s th e specie s o f

whic h fewes t individual s she dscales . Fo r a U th e species , are a5 (th e regio n containin g th e lateral line ) showe dth e greates t degre e of

loss , althoug h th e othe r area s ha dsignificant

los s (Tabl e A 2 an dFigur e A2) . Ey e Damag e Herrin g an dsan dsmelt

wer e th e tw o specie s mos t susceptibl e t o ey e haemorrhag e (Plat e 16) . Bass , whitin g an dpou t wer e th e leas t

affecte d(Tabl e A3) . Bulgin g eye s wer e no t

commo n .amongs t

th e fish studied , (Plate 17 , Tabl e A4) . Pout , poUoc

k an dbas s a

U suffere dsome fin haemorrhage , wit h th e greates t

damag e bein g in pout . Th e caudal an dpectoral fins wer e mos t vulnerabl e i n pou t

an dpoUock , .an

d th e pectoral .an

d pelvi c fins i n bass . Whitin g onl y suffere dhaemorrhag e i n th e caudal an dpectoral fins, whil e .ssm d smel t an dherrin g ha dUttl

e haemorrhagin g an dsprat wer e no t affecte dat

aU , (Tabl e A 6 an dFigur e A 4 - Plat e 18) . Th e spUtting o f

th e fin membran e i s th e major sympto mo f

damag e to th e fins . Al l th e specie s ha dasignificant incidenc e o f

sph t fin s (Plat e 18) , .althoug

h pout , poUoc

k an dwhitin g ha dalittl e .damage t o th e pectoral , pelvi c an d.ana l fins (Tabl e A 7 an dFigur e A5) . A sma U percentag e o f

bass , herring , pou t

an dsan dsmel t

suffere dlos s o f

a U o r par t o f any o f thei r fins, (Tabl e A8 , Plate 10) . A 5 DISCUSSIO N Scal e Los s Scal e los s occur s naturaU y i n fish a s aresul t

o f abrasio n o f

th e bod y .surface againr

f th e substratu man dsoh d objects . On e consequenc e i s th e destructio n o f th e integrit

y o f th e epithehu mcausin g disruptio n o f essentia l osmoti c differentiatio n betwee n fis h bod y fluid s an dthei r

environment . However , provide dth e are aaffected i s no t krge , scale s rapidl y regenerate . Fo r ex.ampl e u p t o 73 % (Tesch , 1956 ) o f th e .scale s o f

brow n trou t (Salmo trutta) ma

y b e replacemen t

scales . Kosteck

i an dKynard(1982 ) foun dtha t scal e los s wa s asignificant facto r i n laten t mortahty o f

salmo n smolt s an dclupeid s du e to ionic/osmoti c imbalance . Scale s ca n b e los t b y mechanical abrasio n i n an y part o f th e impingemen t

process , althoug h th e majo r caus e o f scal e los s wi

U b e contac t

wit h th e dru mscreens . Are a5 , containin g th e lateral line , i s mor e susceptibl e t o abrasion , probabl y du e t o th e overa U shap e o f

th e fish an dth e lateral lin e are aprotruding . San dsmel t

hav e apelagi c habi t

simila r to herrin g an d.sprat ; however , they d o mov e inshor e int o shaUo wP.4 2

A1. 3 watert o breed , wher e they ar e likely t o suffe r abrasion . Thi s ma

y b e th e reaso n fo r

th e tougher

coatin g o f

scale s foun di n thi s species . Ey e Damag e Ther e appear s to b e n o recor do f natura l occurrenc e o f

ey e damag e suc h as see n a t th e powe r

statio n intake . However , ther e hav e bee n observation s o f bulgin g eye s i n traw l sample s an dbulgin g an dhaemorrhage d eye s at turbin e site s (Crame r

an dOUgher , 1964) . Althoug h i t wa s though t

previousl y tha

t thes e wer e symptom s o f pressur e damage , recen t

experiment s carrie dou t

at Fawle y o n awid e rang e o f fis h specie s involvin g controUe d pressur e change s hav e show n tha t ey e damag e fro mthi s caus e i s rare . I t seem s likely tha

t mos t damag e foun d i s cause dby abrasio n an dcontac t wit h soh dobjects . Th e consequence s of

ey e damag e hav e no t

bee n investigate dbu t

i t ma y b e surmise dtha

t ey e damag e wi

U impai r th e foo dsearchin g abUit

y o f fish an dth e risk

o f predation , owin g t o th e inabilit y to detec t

predators . Ther e i s som e evidenc e tha t mino r cornea l abrasion s i n fis h wil l hea l (Ubel s an dEdelhauser , 1982-83) . Fi n Damag e Fi n damag e occur s naturaU y in fish, cause db y fin-ro t o r attac k by othe r fish (Abbo t

an dDiU , 1985 ; Abbot , Dunbrac k an dOrr , 1985) . Th e immediate consequence s wi U includ e impairmen t

o f mobihty an dstabilit

y . Onc e the fin s ar e damaged , th e fis h ar e mor e susceptibl e to dise^ e an dfung.a l attac k leadin g to fin-rot.

REFERENCE S Abbot t J C & DU

I L M (1985) . Pattern s o f aggressiv e attac k

i n juvenil e steelhea dtrou t (Salmo gairdneri). Can. J . Fis h Aquat . Sci. , 4 2 (11) , 1703-1706 . Abbott J C ; Dunbrac k

RL & Or r

C D (1985) . Th e interactio n o f siz e an dexperienc e i n dominanc e relationship s o f

juvenil e steelheadtrou t

(Salmo gairdneri). Behaviour , 9 2 (3-4) , 241-253 . Cramer F K & OUghe

r RC (1964) . Passin g fish throug h hydrauU c turbines . Trans . Am . Fish . Soc. , 9 3 p p 243-259 . Dadswe U M J , Rulifso n RA & Daborn G R(1986) . Potential Impac t o f Large-scal e Tidal Powe r Development s i n th e Uppe r Ba y o f Fund y o n Fisherie s Resource s o f th e Northwes t

Atlanti c Fisheries , Vol . II , No . 4 , p p 26-35 . Have n K F & Gin n T C (1977) . A mathematical mode l o f th e interaction s o f

an aquati c ecosyste m.an d a thernra l powe r statio n coolin g system , p p 321-34 2 In: Jen.se n L D , Ed. , Fourth Nation ^ Worksho p o n Entrainmen t

an dImpingement. , Ecolocigical Analyst s Inc. , MelviUe , NY . Holme s RH A (1975) . Fis h an dWee do n Fawle y Generatin g Statio n Screens . CER L No . RD/L/N129/75 . Kosteck i P & KynardB (1982) . Potential effect s o f scal e los s o n mortaUt

y o f Atlanti c Salmo n smolt s an d juveml e clupeids , hr. Knap p W E , Kynar dB (Eds ) Potential effect s o f Kaplan , Ossberge r

an dBulb Turbine s o n Anadromou s Fishe s o f th e Northe^ t

Unite dState s (U S Fis h & WUdlif e Service , Newto n Corner , Massachusets . Tesc h F W , (1956) . Ube r Unterschied e i n de r

Haufigkei t

de s Auftrerten s vo n regenerierte n Schuppe s be i de r BachfereU e (Salmo trutta fario L. ) unte r verschiedene n unweltverhaltaissen . Biol .P.4 3

A1. 4 Travad e F (1981) . Survi e de s Organisme s Entraine s su r le s FUtre s Rotatif

s d e laCentral e d

u Blayais . Electricit e d e France , HE/31-82.04 , ARD- E 3 A 08 . Turnpenn y A W H & Uttin g N J (1981) . Tida l factor s i n fish impingement , CER L No . RD/L/2109N81 . Turnpenn y AW H (1983) . Swimmin g performanc e o f juvenU e sprat , (Sprattus sprattus L) , an dherring , (Clupea harengus L ) a

t different .salinities . J . Fis h Biol. , 2 3 p p 321-325 . Ubel s J L & EdeUiause

r H F (1982) . Healin g o f cornea l epitheh d wound s i n marin e .an d freshwater

fish. Curr.Ey e Res . 2(9 ) 613-620 .P.4 4



### APPENDI X Investigation s o

f Fis h Damag e Symptom s o n Fawle y Power Statio n Screen s

CONTENT S A l A2 A3 A 4 A 5 Introductio n Descriptio n o f

th e Method s Result s Discussio n Reference s Table s Figure s Plate s Fawle y powe r statio n coolin g wate r

intak e syste m

1 - 8 1 - 5 1 - 1 9P.4 5

Tabl e A 1

Bas s Herrin g Polloc k Pou t San d Smel t Spra t Whitin g Averag e Percentag e o f Fis h wit h Scal e Los s (% )

35. 2 80. 3 5 2 58. 8 14. 5 91. 3 41. 4 Numbe ro f Fis h Examine d 1 8 10 0 1 2 10 0 6 7 2 7 9

Tabl e A 2

Bas s Herrin g Polloc k Pou t San d Smel t Spra t Whitin a Percentag e o f Fis h wit h Scal e Los s Area s o f Scal e Los s 1 2 3 5 5 8 9 6 7 6 6 7 9 2 4 4 2 7

8 6 6 7 7 3 1 0 9 6 5 5 3 3

8 9 4 2 6 2 2 5 10 0 4 4 4

4 4 9 0 5 0 6 7 2 0 10 0 5 5 5

8 8 10 0 6 7 9 4 7 1 10 0 7 7 Numbe ro f Fis h

Examine d 1 8 10 0 1 2 10 0 6 7 2 7 9

Tabl e A 3

Bas s Herrin g Polloc k Pou t San d Smel t Spra t Whitin a Percentag e o f Fis h wit h Red-Ey e Numbt t o f Red-Ey e 0 10 0 4 0 6 7 8 4 5 3 7 2 8 9 1

3 3 1 7 1 1 3 8 1 2 1 1 2

2 7 1 6 5 9 1 6 0 Nu m .be ro f Fis h

Examine d 1 8 10 0 1 2 10 0 6 7 2 7 9

FAWLE Y aquati c researc h laboratorie s Lt dP.4 6

Tabl e A 4

Bas s Herrin g Polloc k Pou t San d smel l Spra t Whitin q Percentag e o f Rs h wit h Bulging-Ey e Numbe ro f Bulging-Ey e 0 10 0 9 3 8 3 8 7 9 3 9 6 10 0 1

0 5 1 7 9 5 4 0 2

0 2 0 4 2 0 0 Numbe ro f Rs h

Examine d 1 8 10 0 1 2 10 0 6 7 2 7 9

Tabl e A 5

Bas s Herrin g Polloc k Pou t San d smel t Spra t Whitin g Percentag e o f Rs h wit h so m for m o f Fi n Damag e (% ) 94. 4 8 9 8 3 8 7 98. 5 10 0 10 0 Numbe ro f Fis h Examine d 1 8 10 0 1 2 10 0 6 7 2 7 9

Tabl e A 6

Bas s Herrin g Polloc k Pou t San d smel t Spra t Whitin g Percentag e o f Fis h wit h Haemorrhage d Fin s (% )

Dorsa l Cauda l Pectora l Pelvi c Ana l 6 0 8 9 0 0 0 1 1

1 3 3 6 9 1 0 3 3 2 8

4 3 3 4 5 1 1 1 2 8

0 1 7

. 9 0 0 0 6

1 8 2 0 0 0 0 Mumbe ro f Rs i Examine d 1 8 10 0 1 2 10 0 6 7 2 7 9

FAWLE Y aquati c reserac h laboratorie s Lt dP.4 7

Tabl e A 7 Specie s Bas s Herrin g Polloc k Pou t San d smel l Spra t Whitin g Percentag e o f Fis h wit h Spli t Fin s

Dorsa l 3 9 6 4 5 0 3 9 4 9 8 8 6 7 Cauda l 6 7

5 1 5 0 4 7 7 5 7 2 7 8 Pectora l

3 3 5 6 8 1 8 7 5 6 4 0 Pelvi c 2 8

6 0 8 6 4 7 6 1 1 [Ana l 3 3

6 5 8 8 4 6 8 0 1 2 Numbe ro f Fis h Examine d

1 8 10 0 1 2 10 0 6 7 2 7 9

Tabl e A 8 Specie s Bas s Herrin g Polloc k San d smel l Spra t Whitin g Percentag e o f fis h wit h Sortene d Rn s

Dorsa l 0 5 0 3 0 0 Cauda l 0

1 0 6 0 0 Pectora l 0

0 0 4 0 0 Pelvi c 6

0 0 2 0 0 Ana l 1 2

0 0 0 0 0 Numbe ro f Fis h Examine d 1 8 10 0 1 2 6 7 2 7 9

FAWLE Y aquati c researc h laboratorie s Lt dP.4 8

•V:? ] SAL T MARS H

"(O O Ic V SUB STATIO N

POWE R STATIO N 

### 2 3 LAN D

CHIMNE Y



## . A COASTGUAR D TOWE R

FIG . 1 MA P O F FAWLE Y POWE R STATIO N INTAK E ARE AP.4 9



## Pou t

\

Fig . 2 . , Pout , Trxsopteru s luscus , showin g th e 5 are a s assesse d fo r scal e loss ,P.5 0

Percen t 10 0

5 0

O . Herrin g

Jn, . li n l l ,II...IIII, „ i n m

4 Polloc k

Percen t .San d smel t

Spra t

lo o Whiting

, *'l'^r | . t ^.»,•,•,•,•.•r•^•. .,*,.,•.•,•.•,• • ! , K , 4 l 4 , 4 , 4W.|.;,;4;>K>x , ,v,;. v s ' Wfiia^- M

I I.' , f .f4'*!4.'4V . 4 4 i.C| . Fig . 3 Amalgamate d histogram s fo r th e percentag e o f fis h wit h scal e loss ,

showing are a 1 (heav ystippling) , are a 2 (diagona l shading),are a 3 (horizonta l shading) , are a 4 (ligh t stippling ) an d are a 5 (vertica l shading) .P.5 1

Percen t ^Q O

5 0 Dorsa l Cauda l Pectora l Pelvi c Ana l

piiLimiiiiiiiipiiii l

pi n

Percen t IO O

5 0

0 t — Bas s

Herrin g

Polloc k

Pou t

San d smel t

Spra t

Whitin g

Pig . 'i '< TVmalgarnated histogram s fo r th e percentag e o f haemorrhage d fins ,

showin g dorsa l fi n (vertica l shading) , cauda l fi n (ligh t stippling) , pectora l fi n (horizonta l shading) , pelvi c fi n (diagona l shading) , an d ana l fi n (heav ystippling) .Percen t 10 0 Dorsa l Cauda l Pectora l Pelvi c P.5 2

Ana l Bas s 5 0

„ ! j ",'„in!hi i 'I , "|| , , 1 ' l i ' I ' I 

# mm 

# U ! 

# i li'VWi'iy

fwVJ J'" 1 

### I'l l

10 0 5 0 

# ^M , 

# rann I P1 1 ,ni i 1 1 h . J L 1 

# 11,1; "i, ' 'i 1 , ' h i i , i ii' l |': i < i n i , "11 1 n, i , ii"' ' Percen t Herrin g

Polloc k

SSSSSS^SSSSSSSMS a Pou t

San d smel t

Spra t

Whiting 

### ^^^^^^PgJP^^J ^ Fig . 5 Amalgamate d histogram s fo r th e percentag e o f spli t fin s showin g dorsa l fi n (vertica l shading) , cauda l fi n (light stippling) , pectora l fi n (horizonta l shading) , pelvi c fi n (diagona l shading ) an d ana l fi n (heav ystippling) .P.5 3

Plat e 1 . Fawle yPowe r Statio n dru mscreens .P.5 4

Plat e 2 . Dru

mscreen mes h ( ^ metr e rul e fo r scale) .P.5 5

Plat e 3 . D.ru

mscree n stee l ledges .P.5 6

Plat e I4 . Hig h pressur e je t wash .P.5 7



### •afe^iaj*. . vi >

Plat e 5 - Transvers e meta l troug h ( ^ metr e rul e fo r scale) .P.5 8

Plat e 6 . Dro p fro mth e meta l troug h int o th e concret e channel .P.5 9

Plat e 7 . Concret e channe l (- J metr e rul e fo r scale )P.6 0

Plat e 8 . Meta l baske t ( J metr e rul e fo r scale) .P.6 1

Plat e 9 . Raise d meta l basket .

### Bas s P.6 2



### miiflrHi!! ! Ih l 100'rfm.'n o 12

0 

### III I 0

Plat e 10 . Bass , Dicentrarchu s labrax .



### Herrin g

5I 0 6I 0 7l O 8l O 9l O T



# b ioo . Plat e 11 . Herring , Clupe a harengus ,P.6 3

Plat e 12 . Pollock , Pollachiu s pollachius , o n a recor d sheet .

Pou t

]|]!![l!llll!|ini|llll|lill|iiiniHUiHiiiiii|ii|i||H ^ ido-J m ii o d o i • w o IT O 26 0 Plat e 13 « Pout , Trisopteru s luscus .P.6 4



### Sandsmel t 

# m

K>'**lf 0 12 0 13 0 14 0 15 0 16 0 170 18 0

' ^ % • . 1

Plat e 1^ . San d smelt , Atherin a boyeri .

Plat e 15 . Whiting , Merlangiu s merlangus .P.6 5

Plat e 16 . Aspecime n o f herring , Clupe a harengus . showin g 're d eye 1 .

Plat e 17 . Aspecime n o f pout , Trisopteru s luscus . showin g 'pop eye' .

### Pou t P.66 _

• *

Plat e 18 . Aspecime n o f pout , Trisopteru s luscus . showin g haemorrhag e an d

splittin g o f th e cauda l fin .



# y V2m m 

# l b 2 0 3 0 4 0

Plat e 19 . Aspecime n o f whiting , Merlangiu s merlangus , showin g splittin g

o f th e cauda l fin .