EFFECTS OF STOCKINGDENSITYON PERFORMANCE, PRO XIMAT E COMPOSITIONAND PIGMENTAT IONOF CULTURED
ARCTICCHAR R(Sa tvet inusa/pinus)
by
A)Metusalach,B.Sc. Han.(Fishery)
/I.thesis submittedtothe School ofGraduate Studies in partialfulfilment
or
the requirementsfor the degree
o r
Master of ScienceDepartment of Biology MemorialUniversityof Newfoundland
September.1995
St.John's Newfoundland Canada
•••
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Canada
ABSTRACT
The effectsof stocking densityon pcrfonnance,proximatecompositionand pigmentationof culluredArcticcharr(Salvelinusa/pinus) were stud ied. Resultsindicated thatspecificgrowth rate (SGR),feed conversionratio(FeR),and protein efficiency ratio
(PER)offish were significantly (p<O,OS) influencedbystocking densities,butno significa nt (p>O.0 5)effects wereevident in the hepatosometicindex(HSI)offish.These performanceparametersoffishcorrelated inversely withstocking densityat 40,50 and
7S kg/m'(r
=
-0.9522forSOR,-0.9696 forFeR ,-0.9886for PER,and-0.9059 for HSI). AlthoughSOR.FeRand PER offish fromdifferent stocking densities varied sig nificantly (p<O.05),their finalweights didnot.Resultsalsoindicatedthatwhilethe moisturecontentdecreased.proteinand lipid content increased asfishgrew;themineralcontent remained relativelyunchanged over thisperiod. Analyses indicatedthat moisture.proteinand lipid contentvariedsignificantly (p<O.05) among densitygroups whileashcontent did not.Regression analysisshowed that moisture andash content were directlyrelatedtostocking density(r=0.9440and 0.9994.respectively). whereasprotein and lipid contentwerenot(r
=
-0.5394 and -0.7030,respecti vely).The total amino acid content of fish variedsignificantly (p<0.05) accordingto stocking densityandsampling dates.Asparticacid.glutamicacid.leucine and lysinewere themostabundantamino acidspresent, whereas hydroxyprolinewastheleast abundant.
Thefree aminoacid contentofthe fishalso variedsignificantly(p<O.05)andinversely with stockingdensity (r--0.9441)andsampling dales.The majorfreeaminoacidswere anserine,taurine.glycineandalanine.
lipidfattyacidcomposition ofcharrflesh wasrelativelyunchangedover the courseoftheexperiments.Amongdensitygroups. fattyaddcontentsof fish Ocshwere alsorelativelysimilar.Unsaturatedfatty acids were thedominantfatty acids.accounting for up to 75%ofthetotallipids. Saturatedand mauouusaturatedfauyacidscorrelated inverselywithstocking density(r=' -0.9914 and -0.9963,respectively),whereas polyunsaturated latty acids correlated directlywithstockingdensity(r=0.9984).
TheHunter L·.a'.h'valuesvariedsignificantly(p<O.05) among densitygroups.
Forbellyskin.these colourparametersdecreased with increasing stockingdensity.No correlationwas observedbetween thetotalcarotenoidcontentsoffishskinand these colourparameters.Onthe other hand.theHunterL'values offillets andhomogenized tissues wereinversely correlated withtheircarotenoid contents (r--0.9245 to -0.9844.
res pectively), whereas their HunterR'andb" values weredirectlycorrelatedwith total carotenoidcontents(r:0.9040to0.9824fora"valuesand 0.9527to 0.9924forb' values,respectively).
T'ic contentofcurotcnoldpigmentsinfleshandskinofchurrincreasedwith durationof feedingon pigmented diets. AfterII to 16weeksof feedingona canthaxcmhin-pigmcnted diet. fishfleshattainedtherequiredlevelof cerotenoids(3-4 mg/kgweitissue) consideredsuffic ient forproviding a satisfactorycolourimpression.
However , stocking densitydidnot correlate with fleshcarotenoidconcentration (r""
-O.6034) . Canthaxanthin.echinenonc,4'~hydroxyeehinenone, luteinand itsesters.
isocryptoxanrhin and p-carorene were identified in different organs of charr.
Canthaxanthinwasthemain carote noidinchart flesh. whereasa-carotene, luteinesters and 4'-hydroxycchinenonc. and cchin cnone were thedominantcarotcnoidsin .:harrskin.
gonadsand liver,respectively. Canthaxanthinwasnot detected inthe liver of fish.
Therefore,dietary carotenoidsmay be deposited indifferent organsas suchor may undergoreductive changes.
iii
ACKNOWLEDGEM ENTS
I wouldlike to expressmy sincereappreciation toDr.F. Shahidi and Dr.J.A.
Brown.my supervisors. fortheirinvaluableadviceandencouragementduringthe course of mystudiesatMemorialUniversityofNewfoundland. Ialsothank DO'.L.W.Crim, membe rof my supervisory committee.lorhisvaluable suggestionsrelatedto my experimentaldesign.I wouldalso liketo expressmysincere gratitude10the government ofIndonesia forprovidingmeIIscholarship.
Iwouldalso liketo extend my gratitude 10 CanadianCentre forFisheries Innovations (CCFI)for partialFinancialsupportandtoMr.Gary Wilton of Daniel's HarbourHatcheryforproviding fish rearingfacilitiesand assistance.Ialsothank Ms.S.
Banfield.Ms.P.Waddlcton and Mr.Sol.Hwang oftheamino acid facilities.Department of'Biochcmistry. MemorialUniversityof Ncwfcunulnnd. fortheirtechnica l assistancewith theamino acids analyses.Specialthanks arc extendedtoDr. JosephSynowieckl for his invaluabletechnical assista ncewithcarotenoidanalyses. Ialsowishtothank Udaye wanasunda ra forhisassistance for fattyacids analyses. My sincere thanks arcalso addressedtoall Dr.Shahidi"slab members torcreatinganencouragingenvironmentfor working.IalsoacknowledgeTitaMarlita.LiaJnmallah and Satria Bljeksana.Indonesian students01MemorialUniversityof Newfoundland.35wellasDr,AnnGregoryof Faculty of BusinessAdministration.MemorialUniver sity of'Ncwfoundlund.fortheir supportand encouragement. Ialsothankall myfriends andrelativesfor their encouragementduring
iv
the courseof thisstudy.
Finally,Iwouldlike toexpre ss mydeepest appreciation tomy wife,Dahniar Nur, and myson.Ilham Akbar Minanga as well asto myparents,brothers andsisters, fortheir invaluabl e sacrifice,encouragement and Prayers,without which this study couldnot have been done. Ipray that Allahrewardsthem with long-lifeandhappiness,Insha Allah.
TA BLE OF CONTENTS
ABSTRACT ...
ACKNOWLEDGEMENTS ..
TAB LEOF CONTENTS .
LIST OFTABLES LIST 01' FIGURES
ix
xi
LIST ()F APPENDIXES xiv
CI-IAPTE RI. INTRO DUCTION I.I Background 1.2 Objective ...
CI-IAPTER2.LITERATURE REVIEW
2.\ Performance 7
2.1.1Growth 7
2.1.2Feed conversio n ratio 9
2.1.3Protein efficiencyratio,.. 12
2.1.4Hcpatosomaticindex 13
2.2Stocking density 13
2.3 Proximate composition 17
2.:U Moisture 21
2.3.2 Protein 24
2.3.3Lipid .. 28
2.3.4Ash 35
2.4Total andfreeamino acids 36
2.4. 1Total amino acids 36
2.4.2Free amino acids 37
2.5Lipid fatlyacid compositions .
2.6Pigments .
2.6. 1Pigmentation offish
CHAPTER 3.MATERIALS AND METHODS .
3.1Fishand rearing conditions . 3.2Samplingoffish . 3.3Fish performance .
3.3.1Specificgrowth rate ..
3.3.2Foodconversion ratio. 3.3.3 Proteinefficiencyratio 3.3.4 Hcpatosomaticindex..
3.4Biochemical analysis .
3.4.1Moisturedetermination ..
3.4.2Crudeproteindetermination 3.4.3Total lipid determination . 3.4.4Ashdetermination. 3.5Total and free amino acids determination..
3.5.1Totalaminoacids."
3.5.2Free aminoacids 3.6Lipid fatty acid determination.
39 43 53
59 59 60 60 60 60 ... 62 62 62 63 63 64 64 65 65 65 66
3.7Pigmentation 6K
3.7.1Colourmeasurements 68
3.7.2Pigment determination 68
3.1.2.1 Totalpigments. 68
a.Fleshpigments 68
b.Skin pigments 70
e.Gonadpigments 71
d. Liverpigments 71
3.7.2.2Individualpigments.. 72
3.8Statisticalanalys is . CHAPTER 4.RESULTS ANDDISCUSSION.
vii
73 74
4.1 Resu lts 74
4.1.1Fishperfo rmance 74
4.1.1.1Growth.. 74
4.1.1.2Feed conversionratio 77
4.J.J.3 Proteinefficiency ratio. 77
4.1.1.4Hcpatosomartcindex 79
4.1.2 .Proximate composition 79
4.1.2.1Moisture 79
4.1.2.2 Crudeprotein.. 80
4.1.2.3Totallipid, 83
4.1.2.4Ash 84
4. J.3 Totalund free amino acids 85
4.1.3.1Total amino acids 85
4.1.3.2Free aminoucids; 91
4.1.4Lipid laityacidcomposition ... 91
4.1.5Pigmentation. 100
4.1.5.1Colourparameters... 100
4.1.5.2Totalcarotenoi dpigments... 102 4,1.5.3Ind ividu al carotenoidpigm ents... 109
4.2Discussion, .. .. 118
4.2.1 Fishperformance IIS
4.2.2Prox imatecomposition. 122
4.2.3Total and free amino acids .... 125 4.2.4Lipidfatty acid com position 127
4.2.5Pigmenta tion ... 130
4.2.5.1Colourparameters ... 130 4.2.5.2Total carotenoidpigments 132 4.2.5.3Indi vid ual carotenoidpigme nts. 134 CHAPTER5.CONCLUSIONS AND RECOMMENDATIONS
5.1Conclusions.
5.2Recommendations .
REFERENCES .
140 140 14 5 ... 14 7
APPEN DIXES .. 19 1
LISTOFTABL ES
Tabl e1.Proximate composition(%)ofsomeselected finfish.. 26 Table2.Lipid compositionof various tcleostca nfish(mglgwetweight)... 30 Table3.Fatty acid com position(w/w %)oftotalmuscle phospholipids
ofsomespeciesofPacific (Japanese)salmon.. 40
Tab le 4. Carotenoid pigm entsinsome impo rtant seafood... 47 Table5.Caro tenoidcontentsofArcticchnrrfilletandskinduring a 15-
weekfeedingexperiment ,... ... 56 Table6.Deposition of pigment (mg/kgtissue) inrainbow trout.brook
trout.coho salmon,and Arctic charr Flesh fed differentsource
ofcarotcnoids , ,... 57
Tabl e 7.CompositionofArctic chartfeedusedduringtheexperime nts... 61 Table 8.Weight gain,SGR,FeR,PER,andHSIof Arcticcharrreared
at different stocking densitiesovera24-weck feedingperiod ... 75 Table 9. Pro ximate composition(%)of Flesh ofArcticcharr rearedat
di ffcrent stocking densities 81
Table10.Thc contentsof total aminoacids (mglgprotein) offlesh of Arctic charrrearedat different stockingdensities at the end
of the experiment s 86
Table II. Totalfreeamino acidcontents(llglg)of flesh of Arcticcharr reared at different stockingdensities at theendofthe expcri-
mcnts . 92
Table12.Totalfree amino acid contents(~glg)of feed andArctic charr
flesh prior to the experiments 93
Table13.Fattyacid composition(%)of totallipidof feed,fish prior
toand after24 weeks offeeding 95
ix
Table 14.The hunter L', a',b" values of Arctic eharr reared atdifferent stocking densitiesat the endofthe experiments 101 Table15. Totalcarotenoidcontents(mg/kg) of Ilcshand skinofArctic
charr fed on aeanthaxanthin-pigmentcd Iced.. 106 Table16.Co ncentrations (mg/k g)ofmajorcurotcnoids ofArcticcharr
feden a canthaxanthin -contatningfeedfor24weeks.... I10 Table17. Co mposition of carotenoidpigment sin Arctic charrre ed. 111 Table18.Pro portion(%)of individual carotcnoids presentin flesh.skin.
gonadsand liver of rearedArctic chnrr 117
LIST OF FIGURES
Fig.l,Absolutewe ight gain (g) ofArctic charr duringa24- week feedin gperiod. n=26-30 samplesper period. Ver-
ticalbars=sta ndard deviations 76
Fig. 2.Speci fic growth rate(A),feedconversionratio(fs), proteinefficien cy rat io
(n.
andhcpato somaticindex(0) of Arctic ch arr rearedat differentstock ingdens ities overa24·w eck feedingperiod.n= 26·30 forA,B,C anJ 10 determinati onsper periodfor D, respectiv el y. Vert icalbars=standa rddevia t ions 78
Fig.3.Moisture (A),crudeprotein(8),100ailipid(e).andas h (D) content sof Arcticcharrreared at differentstocking densitiesovera 24·wcckperiod. n
=
18for A andC.and 12 dete rminationsper period for BandD. respectively.Vertical bars>standard deviati ons 82
Fig.4.Thecontentsof lotal amino acids(mglgprotein)offle sh of Arctic chzrrprior tothe experiments.n'"3determinations . 87 Fig. 5.Thecontents oftotalamino acids(mg/gprotein) offle sh of
Arcticcharrreared at a densityof 40kg/m'attheendofthe
expe rtmerit s. n=3determinations .. 88
Fig.6.Thecontentsortotal amino acids(m3/gprotein) offlesh of Arcticeharr rearedatadensity of50kg/rn'attheendof the
experiments. n'"3determinations 89
Fig.7.Thecontents of Iota1 aminoacids(mglgprotein) offleshof Arctic charrrearedat adensityof 75kg/m ' at the end ofthc
experiments . n=3determination s 90
Fig.8.Totalfree am inoconte nts(~glgtissue)of fleshofArc tic charr fed on a camhax anthin-pigmcntcddietove r a24-week period .n'"4 determination sperperiod.Vert ica lbars=
stand ard deviations •.. . , , ,... 94
Fig. 9.Fatty acidcomposition(%)of tolallipids of feed and Arctic chartpriortotheexperiments.n'"3detenninations 97 Fig.10.Fatty acidcomposition(%)oftotallipidsofArcticcharr
reared at differentstocking densities at theendoftheexperi-
ments.n«3detenninations 98
Fig.II.HunterLO, aO,b"valuesof bellyskin of Arcticchert at dif- ferentcarotenoidconcentration.(A'"40kglml;B,.SO kg/m': C"7S kg/m';L'""-0-;a'--0-;b'..-6-). n'"
30~et.enninationsperperiod.Vertical bars standard
deviations 103
Fig,12.HunterL',a',b"valuesof filletof Arcticcharratdiffe- rentcarotenoidconcentration.(A...40kglmJ:B...SO kg/m';C=7SkglmJ:L'=-0-;a'..<)-:b'...~). n= 30~et.enninationsperperiod.Verticalbars""standard
deviations, ,... 104
Fig.13.HunterL'.a',b'valuesofhomogenized chart tissueat different carotenoidconcentration.(A'"40kglm';B""SO kgfml:C-7Skg/ml;L'--0-;a'--0-;b'=-6-). n=30 detenninationsper period.Verticalbars st ard ard devie-
tions lOS
Fig.14.Totalcarotenoidcontentof flesh(A)andskin(B)ofArctic chart fedonacanthaxamhin-supplemenreddietovera 24·
weekfeedingperiod.n
=
18and 6detenn inationsperperiod forAandB.respectively.Verticalbars...standarddeviations 107 Fig.IS. UVspectraof the non-carotenoid pigments fromArcticchartflesh 112
Fig.16.UVspectrainthevisiblerange for echinenone(I),canthaxan- thin(2) andlutein (3)from Arcticcharrflesh 113 Fig.17.UVspectra of echinenone(I) and 4'-hydroxyech inenone(2)
fromArcticchanflesh 114
Fig. 18.Thecontentsofechinenone(-0-l,4'-hydroxyechinenone(o/r), canthaxanthin(-0-),andIUI~in("'9")ofArctic chan fleshfed
xii
Fig.19.Possiblemetabolic pathwayor canthaxanthininArct iccharr
organs .
xiii
115
136
LIST OFAPPENDIC ES
Appe ll.l.The contentsof total aminoacids (mg.lgprotein) of flesh ofArctic chertrearedata densityof 40 kg/m' at different
sampling dates 19 1
Appell.2.Theconte n tsoftotalamin oacids (rosJgprotein)of flesh of Arcticcharrrear edata densityof 50 kg/m'at different
samplingdales. 192
Appe ll.3.The content s oftotalamin oacids (mglgprotein)of flesh ofArctic cbarrrea r edat a densityof75kg/m'at different
samplingdates . 193
Appe n.4. Total freeaminoacid con tents(~lglg)offleshofArctic charrrearedal adensityof'40kg/mlnt diffe rent sa mpling
dates 194
Appell .S,Tot al freeamino acidcon tents(~glg)offlesh ofArctic charr reared at adensityof50kg/m' at diff erent sa mpling
dates 19 5
Appe ll .6,Tot alfreeaminoacid con te ntshlglg)of flesh ofArctic ch a rr reared at a density of75 kg/m'at diffe rent samplin g
date s 19 6
Appen. Fatlyacidco mpositi onortotallipid ofArcticcharrreared nta densityof40kg/m'at different sampling dates.... 19 7 Appe n.8. Fattyacidcomposition of totallipidofArctic charrreared
at a densityof 50kg/m'ut dilli:rcntsamplingdates 198 Appcn. 9,Fatly acid composition ofto tallipidof Arctic cherrreared
atadensity of75kg/m'atdifferentsampling dates ..."... 19 9 Appcn. Iu.I-Iunter L"a", b' valuesofbellyskin of Arcticcharr reared
at different stockingdensitiesover a za-weckperiod 200 Appcn.fl.Hu nter I:,a",b"valuesof filletsofArctic charr reared
atdifferent stockingdensitiesovera 24·wcckperiod 20I
Appcn.12.HunterL',a",b"value s ofhomogenize dtissuesof Arctic eharrreared at differentstock ing dens itiesove ra24-weck
period , 202
CHAPTER I. INTRODUCTION
1.1 B~o:."kgrollnd
Unlikepure chemical compounds with definite andunchangeable co m positio n.themusculatur e ofafi sh enfo ldsa varietyof co nstantlychanging interactive systems.Thebalance between these systemscanvary wide lywithout causi ngth edeathofthe fishbut, aftercapturelindkill ing, thes efactorsinfluence theacceptabilityoffish meattorhumanfo o dand itssuitab ili tyfor processing (Love,1992).
The assessmentof nutritiona lstatus of Ilshis importa n t in both culture lindinwildpopulations. Numerousmethodshavebeen described andthose wh ichdepen dupon the rela tionshipbetween bodyprotein,mo istureand lipi d appear10be stronglyindicativeof nutritional~1"'t1sof fish;themeasurementsto beperformed lire comparativelysimple(Shackley et al,1993).
The overall qualityoffishery productsas fooddepends onanumberof factors whichdeterm ine theiracceptanceby consumers,Amongthesearesafety, nutrition.flavour.texture.colour.uppcamnccandsuitabilityof the rawmaterial forprocessi ngandsubsequentstorage.TherelativeImportance ofa nyofthese characteristics dependson thespedfieproductand its intended usc (C onnell.
1990;Plgott andTucker.1990;Ha ard ,19923).
One of theadva nt ages ofseafoo dsistheirsup e rior nutritionalvalue comparedwithothercompeting protein foods. Fishis lo w incaloriesand fat, highin protein,lowin sodiumandverylow in cholesterol . In addition,fish and shellfish serve asanexcellentsou rce of'co-S fatty acids wh ich arethought to have importantihcrapeu ucand protective effec t sagains t heartdisease,diabetes,cancer andoth er major illnes se s. Consequent ly. theconsumer percep tionof high nutritional valueof sea foods is growing. Fish marke ters, therefore, now routinely uscnutritionaldatain theiradvertising and promotionalmaterials (Dere,1990).
Thesensory properti es of fish muscl e may change as theanimalage s .In thcwild.the diet offish maychangebecauseof feedavailability or dueto changesintheir habitat orabilit yto capture preyasthe ygrow. Thediet and otherfactorscan hnluenc c the freeamin oacid composition, mine ral andfatly acidprofileof fishflesh.Theseconstituen tsma y,in turn,Influe n cethe eating qualityandpost- harvestchangesof themeat(llaard, 19 9 2a).
Mumrmionof gonads andspawningoflish mayhavea profound influence onthequality ofIishfilletsasfood(Love,1988;Yamashitaend Kona g aya, 1991). Bilinskiefat(1984) found that during sexual maturation of Pacific salmon (Oncor hynchus kislilch) themoisture content of filletsincreased significa ntlywit ha conc u rren t decr easeintheirlipidand proteincontents.The
non-p rotein nitrogencontentremainedconstant, bunhc amount offreefattyacids increa sed significan tly.Papoutsegtouetat(1987)found thatbodylipidand proteincontentofrainbowtrou t(Onco r hynch u s mykiss) increas e d,their moisture conte ntdeclined,andtheir ashconte ntrema inedconstant withage. Fish.at higherstockdensitie salso hadhighermoisture andlow er fat contcnt.Fa ge rhm d cl (II(1981)fo und thatincrea sing thepopulat io n densityof cohosalmon raised inhatc herypondswas associatedwitha significantdecrease inweigh t,length, condit ionfac tor,andfeedco nversio nefficien cy;elevatedmoisturecontent; reduc edlipi dlindpro teincontentandincreas edmorta lity.
Colourofloadplnysanimportantroleinfheiracceptab ility. Inmany cases, thepriceor seafoods is directlyrela te d10theircolour. Salmo n,for exam p le.isol\enpriced accordingtothe intensityofitshue,therefore ,th e seafoodmar keting proceduresmustensurethatthecolourisma intainedboth in termsofqualityand quantity.Fish farmersmustprovide theright coloratio nfor theircultivatedfishinordertosatisfythecons umer'sexpectat io n.
Arcticchart(SaIl/cUI/USafpiJws;isclo s elyrelated to salmonand trout, Arctic chnrr is utilizedcom mercially inthe USSR and Northern Canada,
~..spcctu tlyinLabrador .Itis a highqualityfish,regardedbysomeexperts as superi ortoev en thebestsalmon (Da re, f990). Howeve r.the culture of this species isa relativelynew inCanadaascomparedtothat ofsalm onandrainbow
trout. Inthe Atlanticprovince s , total production of charrfor 19 92 wasaround 32tonnes(1993 AquacultureAssociationofCanadaBulletin, 93-2), most of whichwas inNewBrunswickandPrince Ed ward Island.InNewfou ndland.
thereisahat chery/growoutoperationin Da niel'sHarbour andagro w out facilityin Gra ndLake(Valleychartfarm),
Dueto highgrowth rates andtol erance ofhighdensities.there are high expectations fortheaq uacultureof Arc ticcharr(Jobling,1983; Wallaceetat, 1988;Bakerand Ayles,1990;Brownet ai,1991;Brownnat,1992). Johling (1983)foundthai unde rfanningconditions (intanks),the growthrates ofyoung chan wereamongstthehighestreportedlorsulmonldspecies.Arc ticcha rrhave become recognized as a food deli cacywithhigh consumer acceptabilityinNorth America(Iredale,1983).Inrecentyears therehasbeen increasedinte restin examin ingtheaquaculturepote ntialof Arcticcharr innortherntem perate areas.
Accord ingly,there hasbeenanincreas edinterestinthe cultureofArcticcherr inCanada(Paps t lind Hopky,1983),although thespeci es hasnot been widely cultured(Mac C rimmo n lind Gots,1980), Arc ticeharraresuccessfully grown inIceland andNorway.Productionis still relativelysmall,but the!ish has a highly- pricedgourmet market which encourages expansionof itsprodu ction (Dcre ,1990).
4
Arctic charr(Salllelim/s a/pinusL)is ngregariou s speciesinthe wild (Neekes ,1980). Itis themajor fish spec iesoftheCanad ian Arcticand it is an importantfoodsourcefor theind igenouspeople(Vurkowski,1986). Alth o ugh attempts to rear Arcticcharrinseacages underNor w egian fish farming co ndition shave not prove n promis ing( Gj e d rcmandGun n es,1978),the sp ecies appears suitable for prod uction by intensivecultu re (Papstanti Hopky,1983).
Wllndsvikaml Jobllng(1982)re ported thu tArcticcharr (sizerange 25-78g) reared at JjeC in freshwater had a specificgrowthra teof1.4% per day.
WallaceetIII(I 988)observedthatArctic chart frominitial weightof16 g/fish gr ewextre melywctluftc rbeing stocked at an initialdensityof 110 kg/ m'.
However.lillie attention has beenpaidtothequality ofthe edibleportion of Arcticcharr, Abett er understandingof qua li tychangesmay contributeto amore ctflclcnr utilization of Arcticchnrr resource. Thus,definingthepar a meters such as stockingdensityandtheireffectsonthebodycompositio n of Arcticcha rtis es sentialfor clearunderstandingof theeffects ordiettin{\'feedingrateonbody composition.
1.2 Objectives
Theobjectivesofthis studywere to examine theeffe ctof stoc k ingdens ity on thel1esh comp os itionand pigmen tation of Arcticcharr. Theinitialstock ing
densitieswerechosen withintheoptimal ra nges suggestedbyBakerand Ayles (1990). Some aspectsofArctic chartperformance.especia lly thegrowthrate, fe ed conversio n.proteinutilizationefficiency.andhcpatosomat icindex (HSI) werealsoexamined.
CHAPTER 2. LITERAT UREREVIEW
2.1 Fish perform ance 2.1.1 Growth
Different fish speciesmayvaryintheirpotentialgrowthret e.So me sp eciesnrccapableofgrowing fasterthantheothers.However.considerab le variatinn ingrowthalsoex istsamo ng ind iv iduals or groupswith inthesame sp ecies. The:stocking densityatwhichmaximumgrowt h(weightgain) is achieved islikelytobedependentupon anumber ofbioticanti abi o ticfact o rs suchasthe degreeofdomestica t ion. ab i lity of Fishto makebehaviou ral adjustment.physlologicalstatus,Iced availa bility,andwaterquality(Symons.
t968;Fende rsonandCar p enter, 1971jRcfst ieandKlttelsen,1976; Milcns k y, 1988;I'ostonmidWilliams,1988).
Phy siologicalstudies of growthinnnimalspredictthatgrowthrates sho uld dec rease withincrea singsize. Socialhncru c tionsarcknown10influencebo th gro wth nndsexualmaturatio ninu numberof aqu aticorganisms(Borowsky, 197 3.1978 ; Sohn, 1977;NelsonandHedgecock. 1983;Nelsonet af,1983;
Rn" Anan, 1983).Severalauthorsha vedcscrtbcdnnegative correlationbetwee n fish rearingdensity andgrowth(Kee nleyst d elindYamamoto,1962;Brown, 195 7;Fen dersonell/f.1968; Symo ns,1968;Refsnean d Kluelsen,1976;
Fagerlu ndet ai,19 81). However. whenArctic charrwere reared inlarge groupsthereWIlSoftena positive correlationbetween initialbody siz e and the grow t hrateof an individualfish(Jo b ling,198 5). Similarly, Wallaceet al (1988)observed thatgrowth ratein Arcticch arrwas positivelycorrela tedwith thestocking density. Likewise,Kjar ta nsson et01 (1988)foundtha t Atlantic salm o n(Sa/mosafar)did notexperience much chronic stress at either intermediateor highstockingdensitiesas com p ared toalowstockingdensity . Mazu ret al(1993)suggestedthat the si g nifica n t effectofrearin g density onmeanweig h toffishmayha vebeendue10energy allocationtowhat Schrec k (1982)termed"resistan ce and compen sat ionduringstress",l.e .•aneffectdueto increasedbehaviouralinterac t ions atIIhigher stocking densit y.Lower mean weightsmayalso hav e resultedfromdepressi on of feedingrates infishreare d et very high densitie s. Fenderson and Carpenter(197 1)found socia l intera c tion10bethe mainfactor that depressesfeeding ratesinsalmo n ids.
Wallaceelal(1988)observe dthat growth rateof Arcticcharrwas positiv ely correlatedwithstoc kingden sity.Arcticcharr(Saivelinusa/p illlls)of initial weight of 16ggrewextremel y well after beingsto c ked ataninitial densityof110 kg'm' ,
1..1.2 Feed ConversionRatio
[iced co nversio nratio (FCR) isdefined as the ratio ofthe weigh tof the feedconsumedtothatgained by thefish. FeRoftenservesasameasureof cfflclc ncyof thediet. TImmoresuita b lethediet for growth,thelessfeed is require dtilproduce aunitweight,i.c.• ulower FCR . One of theproblems regardin gtheFe Risthat, thedietend the weightgai nmaycomprise varied amountsofmo istureand fat. whichinturn. comp licatetheevalu ationof protein levelinthediets.
The partialeffi ciency offeedutilization lorgrowthdependsonmany fhetors;the com positio northediets lindits com patibilitywith therequire ments lorgrow this a majorfactor. Whcnthedietisdeficient inany oft he essential nutrients !tJrgrowth.such asUllessent ialaminoacid.rattyacid. vita m inor minera l.a large ramountofreedisrequ i re dtosupplythis deficie ntcleme ntand theeffic iencyof theteedutilizationdecreases. Also the fate offood inthebody is impo r tant. whetheritis convertedinto proteina ceous tissue oraccumula ted as lipid. Themaximum theoreticalefficie ncyorconversionof glucosetolatis about 70%ofthemetab olizable energy. Fortheconver sionof aminoacids to protein. ifaminoacidsUTepresentin therig ht pro portion. themaxi mum thcorctic ulcfflclcncy is about80%ofthe metabolizable energy. Howeve r.the actualefficiencies of utilization offoodlorgrow tharemuch lower(Hepjer,
1988).
Environmentalfactors suchastemperatu re alsoaffecttheFeR,since temperature affectsthe growt h of fish. Andrews andStickney(1972)have show n thatFeRofchannelcatfishdeclined withincreasi ngwater temperature overt1~;~angeof18 1030aC. This may bedueto the fact that while growth rate increaseswith theincrease intemperature.energy expenditure associated with maintenanceisrelativelylow at highertemperatures. Therefore,energyis allocatedmoreforgrowththanlormainte nance(Hepher,1988).
Thegradual incre aseinFeRwith increasingwe ight has been observedby manyresearchers(Par kerandLar kin, 1959;Davisand Warrell,1968; Brett andGroves,1979). Thismay also be associatedwith thedifferent ratesof increasein energyrequirementlo r maintenanceandgrow th with theincreasein weight. Whilemaintena ncemetabolism increases ata power of 0.8ofthe weight. growth rate.and thereforetheenergyrequ iredforit,increasesonlyby apower01'0.66of'thcbodywe ight. Thismeansthatthe ratio between these two function s changes infavo urof maintenance . which lead sto an increasein FCR (Hepher.1988). Yoshid a (1970a,b)triedtoformulatethe relationshipbetween we ight nnd FCRin theformofa regression,and sho wed thatthe regress ion coe fficientwasdirectlydependenton temperatu re; itwas higherat higher temperatures. butatlowtemperatu re,whengrowthis small, theeffect of body
10
weightwassmall. De SilvallD dBalhnntln (1974)observed that at 14°C.the FeRdrasticallydecreased with increasing weight. however,at6SCno such trendwas observed.They alsoreportedthat the meanfeed conversionof young herring (ell/pea harengu s}fed at1.3%ofits bodyweight/day washigher than that or lishfed tosatiation.
Thelowerconversion rate in lishduringwinter monthswasprobablydue toreducedenergy requirements.caused bylower water temperatures(Smith, 1989).Ithasbeen shown thatfeed intake insockeye salmondeclinewith decreasingwater tc mpcrnturc. and thaiit declined ata lasterrate thandidthe decreaseinenergy requirement (Brett(1ttl,1969). Since the energyfor growth as well,ISotherfactors intheenergybudget of animalsmustbefoundin the difference betweenmaintenance energy requirementsandthe feed energy consumed.thedifferencein therates of declineof thesetwoparameterswould likely result inreducedgrowth (Mazuretat,1993). Accordingto Hepher (1988). the usc orFe Rfor comparingthe performanceof dietsof different compositionisevenmore complicatedthan its use lor evaluatingthe performance of'the sumc diet underdifferentconditions. Moreover.there is no common denominatorforcomparingdietsofdifferent composition.since theycandiffer invarious nutrients(energy,protein, vitamins. minerals)whichhave,sometimes, very littlein common.andwhichbecome important at differentlevelsor
stockingdensity. However.sincethemain purpose ofthefish fanner isto evaluate the economic efficiency ofthe feed.FCR canbe expressed interms of cost, wherethe costof eachfeedismultipliedbythe FCR. Thisexpresses the cost offeedrequired by fishto gainoneunit of weight.
2.1.3Protein Efficiency Ratio
Proteinefficiency ratio(PER)isdefined astheratio oftheweight gain of fishtothe amount of proteinconsumed. PERisprobablythe most widelyused methodforevaluating proteinqualityin fish,Thisratio correctstheerrordue tovaria bility of themoisturecontentsinthediets. However,this proposition also hassome drawbacks:(1)Itevaluatesthe proteinin thediet ratherthanthe diet itself Thehigher the PER.the moreefficientthe dietary protein,but not necessaril ythe levelof proteinin the diet. (2) Similarto FCR.PER docs not consider differences in thc compositionor theweightgainedand the accumulationof lipids.Therefore.PER mayincreaseasfeeding levelincreases, (3)Itisassumed that allproteinin thediet isutilizedfor the synthesis of new tissues.whereasinfact, part ofitisutilizedfor maintenance (Hepher,1988); the latterdrawbac kmaybecorrectedbyaddingtheweightgainof fish fedon experimentaldiets withthe body weightlosswhcn thefisharcfedona protein- freediet (Nose,1971).
12
For maintenance level.fis h requireproteinfor replacement ofdegenerati ve tissuesand proteinaceousproductssuch as intestinal epithelial cells,enzymes and hormones.which arcvitalfor proper function of the body.and arerecycled very quickly.The requirementof proteinforthesynthesis of new tissuesis obvio us, sinceproteinsmakeup45 to 75% of thetissue.on a dryweight basis. The capacityorthe fishto synthes ize proteinsdenovofromcarbonskeletons is lim ited:therefore.most of the protein must besuppliedthro ugh the diet (Hepner,1988).
2.1.4 Hcpnto somnti c Inde x
Thehcpnrosornarlcindex (I-lSI).theweightratio of liver to the who lefish ,isone of theparametersused toevaluatethe nutritionalstatus of fish.Hcpatosomatic indexisquireusefullo r expressing thenutritionalstatus offish,especiallythose whichstore much oftheir energyintheliver(Love.1992). Therefore.much info rmation may be extracted fromprimarydata.especiallywhen studying nutritiona lstatus
or
lean fish.2.2Stockin g density
Stockingdensitymay be expressed eitherasbiomass(i.e.•in kg/ml)oras thenumber offlsh per unitvolumeof water(or bottomarea of culturemedia).
However,tokcep densitieswithindesired biomasslimitsthe numberof fish withinrearing units are regularlyreduced asfish grow[Kineald el al.1976;
Refstle, 1977; westers and Pratt 1977; Soderberg and Krise 1986;
Kjartansson et aI, 1988).
Rearingdensity is oneof themost importantfactors influencing controlled fishcultivation (Papout soglouet aI,1987;Refstieand Kittelsen,1976).This has been described foralmostallcultured fish species.and forall types of productionsystems(Haskell,1955;Kilambietai, 1977;Refstie,1977; Carr and Aldrich,1982). Inoptimisingproduction, a number offactors related to stocking density must be considered.Ofthese.thephysicochemical conditionof water. theproductionsystem.the type andsizeof rearing tanks,thewater exchangerate,thesizeof fishand qualityofthe ration have been particularly emphasized (Tnebiatowski et at,1981).
Rearingconditions suchas rearing density canhave a significanteffect, at the productionlevel,on parametersoi economicimportancetofishfarmers.
In intensive aquaculture.the density at whichalish speciescan bestocked is an importantfa ctor in determinationofproduction costs in relationtocapital investment. Thehigher thestocking density,the lower willbethe production cost of fish.providedthat satisfactorysurvivalandgrowthnrc maintained (Wallac eet 01,1988). Earlier investigationshaveshown that growthofeultured
14
fishis influencedby stocking density(Keenleysidc and Yamamoto.1962;
Refstl e and Klttelsen,1976; Refstle, 1977;Trzebiat owskiet ai,1981;
Picker ingandStewar t. 1984).As mighlbe expected,optimalstockingdensities vary from speciesto species.Age and/nrsizewithinaspecies, and exogenous factors.suchastemperatureand feedingrate.canalso influence the stocking densitieswhichgiveoptimalproductio nresults. Insalmonidculture,there is a remarkab leuniformity oftechnology,at least withregardtohatcheryrearing, however.lillieattentionhasbeen paid to possibleinterspeci ficdifferencesin husbandry requirements (Wallace ettil,1988).
Many authorshavestudied theeffectof densityof fishon behaviour.
growth. aggress ion.andmigrationinrivers andlakes(Fenderson
a
ai,1968;Keenleysideand Yamamoto,1962;Fenderson and Carpenter.1971;Symons.
1970,1971).However.allthese studies have used lowdensities and theresults cannothedirectlyrelatedto crowded rearingtanksand ponds.Other researchers have deult withdensityand carrying capacitiesinponds.tanks. andcages (Swingle ,1951;Andrews1:1til.1971;Hackney,1974 ;Brownet
at,
1992)which usedwarmwaterspecieswhe refoodandwaterturnoverwere limiting factors.
Conflncrncrnofsalmonids attheunnaturally highstocking densities employed incommercial rearingunitsmayhavedirect effectson bothbehavioral
and physiological variables (Pickeri ngandStewart, 1984; Sh reckel01.1985;
Laidley andLeathertand 1988; VijayanandLearberland,1990). Pat inoet 01(1986) reported thatstockingdensityclearly affectedthe physiologicalstatus of coho salmon(Oncorhynchus kisutch}, Analternativeapproachmaybe adopted.in thatthenumberof Iishper unitvolume ofwater iskept constnnt throughoutthe experiment. Consequently,stocking:density in termsof biomass increases with time as the fishgrows. Thisapproach is adoptedbecauseregular removalofindividualscoulddisturb thesocial relationshipswithin thetreatment group (Laidleyand Leath erlan d,1988;Baar d vikand Jobling,1990).
An increase in populationdensity generally resulted in increased aggressionamongsalmon as a resultof territorial defense and competition for evallablefood(Kcenleysideand Yam am oto,1962;Fend ersonandCarpenter, 1971). Inculture facilities,the stresson fishmay be increasedby a concomitant deteriorationofwater quality,dueto decreasedoxygenand increasedammonia contents(Wede meyeretal, 1976). A moderatedegree of crowding over extendedperiodsinducesa generalstate ofstressinsalmonids,which manifests itselfin reducedgrowth rate (Kawa na be,1969; Rcfstie and Klttelsen,1976;
LIandBrocksen,1977;Refstle,1977), reedconsumption(Fende rso nand Carpenter,1971).feedutilization,bodylipid content(Liand Brockscn, 1977) andphysiologicalchangesassociated with thegeneraladaptation syndrome
10
(Sclye, 1950)such as interrena l hypertr oph yand increasedplasmacortisol,blood glucose.and liver glycogen concentrations(Wedemeyeret ai,1970;Noakes and Lea th e rfa nd d,1977;EjikeandSch reck;1980).
Crowdingstresshasadverseconsequencesonthe healthofhatcheryfish (Schreck,1981 ).Aninverserelationsh ipbetweenrearingdensityand plasma cortisolin rainbowtrout(Oncorhy nch us mykiss) hasbeenreported(Leathe rfan d andClio,1985).However.the relative importance of[hisfactor as amediator or thedeleterious actionof high rearing density on coho salmon (Fuge rl u ndet (II,1983; Schrecket(II,1985 ) isunclear. ldcntilieation ofmajor factorsby which rearingdensity affectstheeatin g qualityof fishisdesirabl e since it may be usedtoimpro vepresenthatcherypractices.
2.3Prexlmntecomposition
Thecontentor moisture.protein.lipid andash (proximate composition) isroutinelymeasured forexper imental Ilshat theend of feeding trials.
Knowle dge01"the proximate compositionof fish and factors affectingit allows assessment of !ishhealth.dete rmi nationor cfflclcncy oftransferof nutrients fromfeedto fish .lind predictionof carcasscomposition(Sheare r , 1994).
Thenutritive andcommercial value01" various fishdepends on flesh structureandother ediblepartsand their proportionin the lotal massof the
specimen, In addition,the chemical compositionofthemeat. gonad, liver and factors related tofishingand handlin gprocedures areimportant factorsaffecting the commercialvalueoffish.The mainchemicalcomponentsof fishmeat are moisture,protein and lipid. Toge ther.theyconstitute up toabout 98% of the totalmassof theflesh. These componentshavethe largestimpact onthe nutritive value.thefunctional properties.thesensory qua lity,and the storage sta bilityof themeat.The other constituents.namelycarbohydrates.vitaminsand minerals.althoughminorinquantity.playasignificantrole in the biochemical processes occurringinthepost-mortemtissue. Theseminor constituentsarc also corcsponslblcforthesensory properties.nutritive value.andwholesomenessof theproduct(Sikorski, 1990a).
Physiological conditionoffishhasbeen definedasthegross nutritional state(Low',1970)andthe levelofreserve nutrients.particularly fat.presentin thebody(Gcrshanovichet ot,1984).Consequently.chemicalcompositionof anindivid ualfish carcass shouldcharacterizeitsphysiological conditionand.in general. itshealth, Furthermore. this physiologicalstatusdetermines the individual' s abilityto competesuccessfully (c.g.through optimalforag ingand reproduction). sustaingrowth.maintai n andrepair tissues,andcope withstresses inducedbyenvironmentalchanges. ..uriutionsinbodycompositiongenerally reflect storage ordepletionof energyreserves(Brownand Murphy.1991).
18
Quantitativeanalysisof primarybody constituents ofnumerousmarine and fresh-waterfish specieshasbeen reported (Ja q uet , 1961). Generally.whole- bodycom pos ition offishis70-80%moistu re.12-26%protein.2-12%lipid. and 1· 2%ash:however.extremevaluesofthesecomponentsmay falloutsi de these ranges(wear her leyand Gill.1987). Severalstudieshave shownsign ificant chan ges inwhole-bodycomposition orspecificorgansor muscletissuesdueto age.diet.feedingfrequency.migration. ration.season.sex.starv ationand tem peratur e(Chang and Idler.1960; UreUelnl,1969;Groves, 1970; Sav itz , 1971;Nllml,1972;Ellio t.1976;Cr mg,1977; Gray tonan dBeamish.1977;
Millikin.1982 ;Weatherl ey and Gill.1983 ).
Avallublc evidenceindicatesthattheproteincontentofsalmonidsis determine dso lelyhylish size(isendogenou slycontrolled);lipidlevel isaffected by both endogenous and exogenousfacto rs: ash content ishomoesta tically controlled.and thewhole bod ymoistureisinverselyrelatedtobody lipid.
Shearer (1994)divided theeffectsof endogenous factorson proxi mate compositi on:ISgivenbelow.
I. Where nutritionis adequate.therelative sizesofthetissuesand organsare dependentonthesize andIUccyclestag e of the fish.
2. Protein.aminoacidsundashlevels arclife-cycle andsize-dependen t.
3.Dietary energyintake inexcess
or
the maintenance requirementresult'!inlipid storage.
4. Lipidand moisturecontents areinverselyrelated.
In culturedfish,whole bodyproteinand ash aresize-dependentandlipids increasewithincreasing fishsizebut areaffectedbylife-cycle stage and energy intake.Furthermore,themoisture and lipid levelsare inversely related. When experimentaltreatmentscreatesize differencesbetweentreatments,differences inproximatecompositionmaybedueto endogenous factors,such assize.life- cyclestage, and exogenous factors(treatments).or both.Itis thereforenecessary toremovetheendogenous effectsbeforetreatmenteffectcanbe examined (Sh ear e r, 1994).
Exogenous factors,bothenvironmentaland dietary, have been reported to affect theproximatecompositionofcultured fish.These include temperature, salinity,exercise.hurespccifie differences.interspecific differences,diet,timeand frequency of feeding.among others. Shea rer (1994) drewthe followin g conclusionsfromthe effectsofexugcncusfactorsontheproximate composition of eulturcd tlsh.
I.The proximate compositionof salmonldsisdetermined byendogenou sand exogenousfactorsthat operate simultaneously.
2.The primarydeterminantsofproximate composition ingrowing fisharesize, life-cyclestage andenergyintake.
20
3. Foraparticular species. at agiven weight and life stage,organand tissue, weight. wholebodyprotein.amino acid andashcontents are controlledwithin narrowlimits.
4.The amo untof wholebodylipidisdependentondietaryenergyinputandthe metabolic energy demandsofthefish.
5. Wholebody moisture is inverselyrelatedto whole bodylipid and decreases orincreasesaslipid is stored orutilized.
Nu merous authorshave reported marked variabilityof proximate compositionwithin11speciesdue toage. sex.season.diet.and combination of thesefactors. Fat appearstohemostaffectedbecause ofenergydemand s assochucdwithoverw interingstarvationinjuvenile and maturefishandeventual gonad maturationinsexually matureIlsh,Proteinandash nrelessdynamic as comparedtofat(Bro wnand Murphy,1991 ).
2.3.1Moisture
'111emoisturecontentoffishis usuallyexpressedona wet-weightbasi s.
i.c.themussorwmcrinunitmassoffish. The moisturecontent offish isusually dete rminedby ove n drying al100 to120"Clor16to18hours.The loss of mass is equivalent10themassofw ater intheoriginalsample(Doc and Olley,1990).
Musclesofmarinefish contain from about60to 80%moisture.depending on the species andthe nutritionalstatusof the animal.Starvation.whichis common in many fishspecies duringspawning.depletes the energyreserves of thetissuesand consequently increases the water contentofthe flesh.In muscles andother tissues.waterplaystheimportant part ofa solventfor a host of organic and inorganicsolutes.providestheenvironmentforbiochemicalreactioninthe cel ls.is anactive partnerin manyreactions. andhas a largeimpacton the conformationand reactivity orproteins.The hydration ofproteinsisresponsible lor the rheologicalpropertiesand juicinessof muscle foods (Sikor ski.1990a).
The amountof wateraffects boththe qualityandprocessingoffish(Kent, 1985).Moisturenormallyrepresent about80%(w/w)in lowfat speciesandis less in species whichstore lhtin theirmuscles. The lipid andwaterconte nts normally add up to nbout80%ofthe weightofthe muscle(Pigott and Tucker.
1990;Haard,1992a). A numberoffactors mayinfl uence the moisturecontent or muscle tissues. In particular.thenutritionalstatusand sexualmaturityor fish canluwe u marked effect onthe moisturecontentortheflesh (Connell. 1990 : Heard, 1992a). Depletionof' nutrients during sexual muturation or starvat ion mayincrease the moisturecontent of lean muscle. The moisturecontent or muscle of culturedfish isless than that ofthewild fish(Saek iand Kumagai, 1984) which may reflecttheir better nutritionalstatus.Ithas beensuggested that
22
themoisture content ofraw flesh isan important quality indicator for determiningthe acceptability orsalmonlor cunningduring sexualmaturation (Bilinskll!lot,1984).
The state of water inthefishllesh depend s uponvarious interactionsof waterstructures with differentsolutes and especiallywith proteins.The hydrophilic aminoacid residuesparticipateinll-boading withwater molecules.
whilethc hydrophobic groups in proteins and lipidsact as structure makers.i.e.•
they induce "round the mselveslayers ofhighlyordered waterclathretcs.Thus.
infishmeal.nnlya part oruquccus mediumcanbe regarded asintercellular water:the restisinvolvedinwater-protein-lipid-solute interactions(Sikorski, 1990:1).
Moisture conte nt is clearly II goo d parameter lor identifying undernourishedfishand ithas been long recognized thatbodymoisture varies inversely with la tcontent(Jacquot. 1961.Gardi nerandGeddes.1980).Water moves intotheextracellularspaceusfatandcarbohydrate nrcutilized and muscle proteins arc ca tabolized (Shac kleyetat.1993).In chronically-starvedflsh.body lilt.umlhuer.body proteindecreases(love.1980).Thesenrcreplacedbywater and theproportion of bodymoisture increases .
2.3.2 Protein
Protein is one of the most important nutrients obtainable from consumptionofmuscl efoodsand fish (Nettleton, 1990;Gorga and Ronstvetlt, 1988).The crude protein contentoffish muscle normallyrangesfrom II to 24%(SikorskiaaI,1990b);however. inextreme cases, maybeless than6%
orgreaterthan25% of thetissue weight(l taard,1992; Pigott and Tucker.
1990) depen ding on the speciesofanimal. nutritional condition,and the typeof muscle (Sikors kiet aI,1990b), The total content andnutritio nal quality of protein ofmeat fromfarmedandwild tlsh appearto be similar (Nettleton, 1990).In I\yu(Ptecogtossusaitlvelis),theprotein contentof muscledecreased slightlyfrom summer toautumnwith110appreciabledifferencebet weencultured ami wildfish(Hiran o etftf,1980). Theaminoacidscore loressential amino acidswas similarforwild(89) andcultured (83)bastardhalibut (fara/ichlhys oiivaceusi(Sate1'1ul,1986) andcohosalmon(0.kisutchi(Hata erat;1988), Snekilind Kumaga i(1982)reportedthat theprotein contentinpuffermuscle didnut change duringthe growth ofbothwild and cultured fish .
Theaminoacidcomposition oftotalmuscleproteins.i.c. of the whole sk innedfillets.of variousfishspecies donot differmuehfrom one another.The nutritive value of fish proteins whichconstitute65 to 75% of thetotal body weight nn adryweig htbasis (Wilson,1989),is very highbecause oftheir
24
favourableessenti alaminoacid pa ttern.Thein vivodigest ibilit yoftheproteins ofraw flshmeat is intherangeor9U-98% (Sikorskier ai,1990a).
l'infisharc a goodso urce ofprotcin(11.40-2 1.90%) and arcrelativelylow (O,Sg-IO.24%)inIatconten t (Tab leI). Thepercentageofash (toralmtncrals) inthe lishranged from0.80104.66%. whilethemoistu re rangedfro m70.16to 81.50D/.,.Intables offoodcomposition . the contentofprotei nusuall y refersto thecrudeprotein(%Kj cl d ahl nitrogenx6.25). Thisrep resentsproteins and othernitrogenouscompoundssuch as nucleicacids.nuclcotldcs.trim e thylam ine (TMAland itsoxide (TMAO).free amino acidsand urea,among others (Sikorskiet(/1,1990b). Basedon Ihesolubilityin salt solutionsofincreasin g concentration.proteins may he classified into three distinctgroups:the componentsofthesarcoplas micfraction whichperfor mbiochem icaltasksin the cel l(Ig-20%) :themyofib ri llurproteins ofthe contract ivesyste m(65-8 0%);and the protein or the connective tissues.responsiblemainly for the integrityof the muscles(3-5'VD)(Hnll andAhm~ld.1992ll;Sikorskiet al. h90b).The relative ernoumsIll'different gro ups
or
proteins in lish depend upon the sexual dcvctoprncr ulinddepletion ofth ebodyproteinoffish and mayfluctuateinthe annual cycleby ale wpercen t (Siko rs kil!tot,1990b).Theterm sarcoplas micproteinsusuallyre fers totheprotein s or the surceplnstu. thecompo nentofthe extracellula rfluid,andtheproteinscontained
Table I.Proximatecomposition('Yo)orsome selected finfishfillets.
'
Species Moisture Protein Lipid Ash
Anchovy" 81.50 11.40 6.10 0.80
Barracuda" 79.50 18.6 0.98 1.01
Bluefish' 70.16 19.56 2.00 1.12
Croaker" 79.37 18.i3 1.90 1.08
Flounder" 77.00 21.23 1.19 1.23
Giantperch" 78.20 16.00 0.70 1.70
Greasy grouper" n.70 19.20 0.58 1.29
Macke rel" 80.00 16.10 1.80 1.60
Mackerel" 74. 90 21.90 1.49 2.95
Mullet'" 79.10 15.30 2.20 1.10
Muller" 74.23 17.6 1 2.96 4.66
Pinkperch" 79.50 15.30 1.30 1.50
Redsnuppc.... 78.69 19.30 1.10 1.36
Snrdjnc" 77.60 17.10 1.20 1.60
SeaBass" 79.80 18.46 2.08 1.09
SellTrout (Gray)" 76.98 18.62 3.41 1.13
Spot" 70.23 19.70 10.24 1.20
Yellowtail' 75.0 5 20.3 2.95 1.49
'Source:"Anthonyet al.1983;"ChandrashekarandDeosthalc,1993; <Maraisand Erasmus. 1977; 'IEI_Faer etal.1992.
26
in the sm allpart iclesof thesarco plasm. The trulyintracellularsolublefraction mnkcs 1111to90-95% of the total proteins ofthe extract obtain e d by homogen izingthemuscl etissuewith wa teror solutionsof neutralsaltsofionic strength below 0. 15. Thesarcoplasmic proteins arc alsosolu ble in more concentratedsaltsolutio ns. Gen erally.the sarco p lasmic fractionmakesupto about 30%or thetotal amount ofproteinsinfishmuscles.The con te ntof sarcoplasmic proteinsishigher in pelagicthan in demersalfish muscles (Sikorski el(fl.I99I1b).
Themyotibrillarpro teinscunbeextractedformthecom minuted fishmeal withne utr alsaltsolutionsof'tonicstrengthabove0.15.usuall yrangingform 0.30 tol.n. Thefractionof themyoflbrtltnr proteins.whichcanbeprecipitatedby te nfolddilutionof'rhc centri fugedsupernatant with distilledwater.makesup 40·
60'Yo,ofthetotalamountofNx6.25offishme at.Themyolibrillarproteins participat ein thepost-mo rt emstiffcningof thetissue s (rigo urmort is ). Chan ges intheseproteinslaterlead to nrc resolutionnfstitTncss.wh iledur inglong -term frozen stora getheymaycausetou ghening of thcmeal.Themyolibrillarproteins arcalso responsiblefor the water holdingcapacity offish.forthecharacteristic texture ofFishproducts.aswellasforthefunctionalpropertiesoffish minces and homcgenctcs. especiallytheirgel-forming ability. The residue after extraction
or
sarc oplusmlcand myofibrillarproteins.isknown asstromaand iscomposedofthe main con nec tivetissueproteins namelycol lagenan delastinof reticulin.and ordenatured aggregatedmyolibrilla rand possiblysarcoplasmic pr o teins. whichmight havelostthe ircharacteristicsolubility.111Cstromawh ich is insolub le indilute solutionsofhydrochloric acid or sodium hydrox ide constituteabout3% of the totalmuscleproteinsof telcostsand upto10% of clusmcbranchs(Sikors kiet al.1990b).
The technologicalvalueof fish l1eshdependsmainlyonitsproteins. The functionalproperti esattributed to protein s offishfleshcomprise hydrati on, which is reflectedinsolubility,dispcrsibllity,waterretention. swellin g,lindgel- forming ability.aswellasInteractionwith lipids.i.c.emulsifying capacity and emulsionstability. Thes e properties depend on the composition and co n formn tionof'prctclns. Theycha nge during storageandprocessingofthe fish (Sikorski et(,f.1990b).
2.3 .3Lipid
Fis h displayu partic ularlydiverseanatomicalpatternof lipid storage.In clasmobrnnchs.lipidmayco mprise90%or the weight cf'thc liver.Mueh of the lipid issqualeneordiacylglyccrylet her.both ofwhi c hhavelo wer de ns itiesthan teia cylglyc crols.contributing10the buoyancyof thesesw imbladderlcssfish (Mallns und we k elt,1970 ). Different tclcostsdeposit fatin a varietyof
28
locations.including liver,muscle.andbonemarrow(Phlege ret
at,
1976).The primary fatstorage typeinhigherbony(teleost)fishistriacylgly cerol(TO), however t-u-alkyldiacylglyccryl ethers (longchainhydrocarbons linkedto glycerolby<IIIether bond plus two fallyacidslinked byesterbonds)havebeen reportedincertain tissuesofsomespecies. Themajor stora gesitesorlipidsin fish arc mesentericrat. muscle lind liver.Compositionaldataof variousorgans inscvcruttclcostcauspeci esarcshowninTable2.The skel etal musclesofcod conurlnliulclipid.hutco nsid crublc amo untso r
fatlirestoredintheirliver (Shcrtda n,1988). Whetherthelivernrthe muscleserves asthepredomin ant site varieswiththespeciesof!ish. Ingeneral. theliverserves asthemain storagedepotforlipidinsluggish bnuomdwellingfish.whereasth eskeletal muscle serves this function in moreuctlvc species(RobinsonamiMead,1973).Thelnucr~t,\tcmenlcorrespondswiththefindings ofShe ri dan(198B) who observedthairainbowtrouthave suhstnntla! amorous oflipidstored intheir skeletalm uscles.
Marinelipidsarccomposedof'phosph ottpkls. sterols.triacylglyccrols.wax est ers.minor quantities of their metabolicproducts.aswellas smallamountsof unusuallipids. such asdlacylgtyccrylethers(DAGE) . gtycolip tds.sulpholipids, andhydroc arbons(Sikorskietnl,t990a). Phosph olipidsand sterolsoccurin small. butrelativelyconstantamountsor0.610 1.2%basedonthewetweig h t
Table2.Lipidcomposition(mglgwetweight ) indifferen torga nsof so mefish spec ies.
Fishorgan Lipidclass
PYA Cit WE TOl;.a l Tr ou t . salmogai rdnerii(Juvenil e, FWparr )
MF 6.2 529.0 - 527
DM 26. 0 113. 0 5.5 137
LM 20.a 46 . 0 3.0 62
L 22.0 17.0 1.2 O.Ofi 0.12 1.23 46
S 7.5 11.0 2. 3 1.5 1. 6 1.2 25
Tr ou t, sallRO ga f r dn erff(Ju v e n i le: FW&11I01 1;.)
MF S.B 53 5.0 540
DM 39 .0 10. 0 0.2 47
LM 21.0 10.0 0.2 27
L 25.0 5.0 0.6 0.03 ocoa 0.10 30
S 5.2 7. 0 1.1 0. 5 0.26 0.66 14
Trout, Salmogafrdn e rf1 (Adu lt : FWre siden l;.)
MF 10 . 0 34.0 s.» 2.0 sa
OM 4.a 16. a 2.0 l.5 23
L~ 9.6 2. 9 6.2 4. 4 3.1 26
Sal mon,a. kisutch (Juvenile,f'Wpa r r)
MF 19.0 590.0 17.0 625
OM 37.0 53.0 1..1.0 107
L 19.5 22.0 13 . 0 5. 0 t r t r 60
sal mon, o.kisutch (J uvenile,FW smelt)
MF 17.0 52 5.0 18.0 580
OM 27.a 41. 0 9.0 62
L 12. 0 10 . 0 7. 5 3.0 tl: t r 41
Whi t efi s h, Co r e gonu s albl11a (Adult) MF 10. 0 <----·· · - - - -··20.0···--- -- ····-- :> 30 Ro e 22.5 62. 1 1.4 .02 <---1.1'· - -:> 98
Til a p ia,Oreo c:h rCJtr!lsmossamblcl1S
LM 3.3 1.7" 17.8 66.5
L 31. 6 15.6" 47.6 164.4
Gi ll 3.8 3.5" 8.5 76.9
Brain 80.4 25.S' 35.0 21 2.3
Bogue , Boopsbo op s
LM 5. 3 12.1 0.3 tr 1.7. 7
L 2B. 2 48.1 0.9 tr 77.8
He a d 12.0 14 4.0 2.0 t r 158
Skin 8.0 169. 3 1.0 t r 178
'Includes serum:'Datafor all neutrallipidscombined :'Data forCEand WE fractio nscomb ined;dData forWE lindalcohols;'Dntafor totalCH~includesboth ellandellesters:'Includesunidentifiedcom ponents andhydroc arbons:PL- phospho lipid.TG-lriacylglycero l. Cll-ch olcsterot,FFA·freefattyacid.CE- cholcsterylester.WE-waxester.Ml-mcscnrericfat, DM-dark muscle,Ljvt-light muscle.Lllver. Secrurn,Pw-frcshwatcr. rr-rrac c. -,data notavai lable."Adapted fromPhlcgcrcol01(1976).
30
oftis sues. Theyplayanimportant structural role in biomembmnesand participateinbasiccellularfunctions,The remaininglipids arcessentiallyenergy storesmill nrc importa ntlorbu o yancy.
Thereservelipids arcusedinvariouspartsofthebod ywhenneeded during starvation.overwinterin g.1;Isimovem ents, reproduction, and growth . Durin g gcnudmaturation,lipids an: trans ported fromthe liver an dmuscleslothe gonads .Alterspawni n g,theIish resumesintens ive feeding and the lipidcontent intheI1csh an dliverincreases . whileit decrease sinthe gonads (Sikorsk ietat, 1990b )ifgon adsnrcre sorbed. Otherw ise.eggs/sperm arclost.
Sincereportsrelatedtothehea lth-promoting effectsofseafoodwere published. considcmbl caucntio uhasbeen focusedon thenutritionalvalueof fisheryproduct s(Kayama.1986;Nettle ton.1985.1987;Pigottand Tuc ker.
1990; Gordonnnd Ratliff. 1992). Comparisonor thenutritionalvalueof funnedandwildIlshha shccnmonitore dhyexaminingtheirlipids(Net t leton, 199/1,191J2). Wild fis htendto containu higherpercen tagc
o r
longcha in(llo}HIllyacidsthan farmedfish(VlietandKa lan.19 90:Nett leton, 19 90)alt h ough thenbs olurcamou ntofHlt t}'acids is often stmller(H aard, 1992a). Diet influences ihcamountofn ntririon ullyimporrnru OJ·3 lattyacidsinthemuscleof limned lish(L ovell.19 88;Ne tt leton, 1990). However.thefinallim yacid composition of culturedflshcan beadjust ed through dietarychangesever afour- to.~Lx-wccks period pr io r10 harv est(Nettleton.1990).
Due tothereported benefits of e-J polyunsat urated fauyacid s(PUFA)in red ucingtheriskof coronaryheart disease s(Brad low, 198 6; Kinsella, 1987), lipidsinfishmuscles havereceivedmuchinterest asa sou rce ofunsa turatedfat in the human diet (Barlow an d Stansby,1982; Kinsella,19 87). As a consequence.thenutritional quality ofaqua cuftured produc tsisapo ssible factor indetermin ingtheconsumerecccpta nceoftheseprodueu(Erickson,1993).The nutritionalbenefitsofconsuming 0)-)rallyacidshas clearlyincreasedthe markctabllityof salmon(Carroll.1986;HeraldandKinsellll,1986;Kinsella, 19 86;Lands,1986;Hea rnef nl,1987;Stansby,19 90;Holu b, 1992 ;Nettleton, 19 9 2).How ever.SOO1Cconc ernhasbee n ex p ressedasmostculturedfish spe cies havehighe rlevelsofro-6fattyaci ds. lower levelsof00-3fattyacids, and thus low erro-3/00·6ratioscomparedtothe wi ldstocks(Ackmanand Takeuchi, 19 8 6 ; Chanmugamttat.1986;Suzukietai,19 8 6).Itshould benotedthai somefishsuchesfarmed catfish arenaturall yrichinoHifallyacids.andla ck EPAandDHA.while salmonidsarc naturallyrichin(1)-)fatty acidsevenwhcn CI8: 200-6issup plicd (Polv iand Ackman, 1992).
Polyunsaturatedfattyacidsinflsh ussu cspred ominan tty belongtolhc00-3 series(Cowey lindSargent,1977) . rallyacidsofthe (1)-3seriesareessen t ial for fish. Some species havethe ability10conve rtlinolen icacid (CI8:3w· 3) rapi dly tolongerchain PUFAs(C22 :Sro-3.C22:6w -J) that havefullessent ial fatt y acid activity. Otherspecieslack thisability and the co-JPUFAmust be
)2
su p p lied in theirdiet for maximalgrowthan dfreed om from pathogen s.
Thelong-te rmconsumptionof PUFAsofthe(0-)classbyhum ansIcads todecreasedincidenceofcoronaryarterialdise ases,andalleviationofsympto ms of breast cancer. rheumatoidarthritis. multiple sclero sis, and psoriasis (Goodelgh r,tlat,1982;Kinsella .1988). Theirmodeofactionistwofold.
First.theyin hibitproductionofthc biorcgulatory z-scrtcseicosa noidfamilyfrom (1)-6 PUPAs: seco n d. theyproducethebloe c tlvc3-serics clcosnnoidsfromth e precursorclcosnpcn taonolcacid(EPA.C20:5w- ) )(Dye rberg,1986;Fisc her and We ber.1983),Asa resultofjoint roles of00-)andw-6PUFAsineicosanoid production.theratioisusuallycalculatedulcngwith thele velof EPAwhen nutr-itionalevaluatio nof lipids ismudc.
Alpresent.withtheexceptionof'thcadditionofcarorencidstoth edietfor flesh cukirntinn. littleaucrnpt hasbeen madetomodify carca ss comp ositionto meetthe cons umerpreferencefora spe cific characteri sticinculturedsalmon ids [Shearer, 19 9 4).Numerousreportsindicatethatcarc ass lipidisdirectlyrelate d 10 dietary ene rgy intake.andthntthe profileofstore d lipidreflectsthatof the diet(Sargen ttI/II.1989). Giventhe growin g awarene ss of the importanceof ro-) and ro-6 fattyacids in h u man diet.it is onlyamatt erof timebeforedemand forco- J enhanced culturedsalmonincreases(Austrcngand Krogd ahl,198 7 ).
Thefatty aci dcomp osition of theFishalso appearstoaffect itsorganoleptic properties, Studiesof Spine lli(1979)on rainbow troutand Burne(1989)on
catfishindic ate thatfishcontaining long-chain(18 ormore carbon atoms)PUFAs show less desirableflavour andtexturelinerfrozenstorage when comparedto fishcontaini ngsho rt-chain(12· 14carbonatoms) saturated fattyacids.
How ever. when discu ssingthebenefi cial effectoffishlipids,it mustbe rememberedthatthe propo rtionsofthevariousPU FAs in fishmuscle s are not cons tant. Wenrcagaindealing withadynami c sys tem. The lipid compositio n of fishfoodintake hasprobablythemostimport ant influ enceon thelipid compositionofitstis sues(Lovern,1935;Hall,t9(2).WorthingtonandLo v e ll (1973 ) reportedthat thelipid composition of the foodaccounted lor93%ofthe veri..mccinthefatty acidcom position ofcha nnel ca tlish{lctalumspuncta/us);
the geneticundotherfactors accountedlorthe rest.
Thelipidsintheedible partoflishare importanttothefoodscientistsin thre erespects . Firstly.any oilydeposits noticeablyInfluencethe sensa tion orthe cook ed fleshinthemouthof theconsumer. Second ly,fish lipids, asisnow wide lyrecognized.posses benefic ia lhealtheffects. Thirdly.fleshlipids contributetotheflavouror thefish. Altho ughlipidsthemselveshave3slight taste.theirpropensityto devel opanoff-flavourthrough oxidat ioninthefrozen stateis ofgreaterimportanc e(Love .1992).
34
2.3.4 Ash
The mineral components arc conta ined in pod asmac roand microclcmcnts.Thc macroclemcnlsarcpresent inquantitiesofseveral hundreds ofm i lligmms(M..'T100gramswetwe ig ht Themlcroelcmentsare presentinthe 111::-11in quantitiesnotIilr~rthanthatof iron.i.e. from below0.\10afew lens ofmicrograms pergram. Thecomponentsofbothgroupsarcimpo rtantin huma n nutrition.Someofthemarchighlydesirablein largequantit ies.while olhers arereq uired insmallamou n tssince theymaybe toxic inhigher cmcc nnurtons.Nutr itional req uirementsforhumansdependupon the biological suuc ofthe organismundefficiency
or
unlizatlonoftheclementsof the diet (Sikorskiet(II,1990b).IIItclco sts. litewater environmentmay contribute significantly 10 the mineral requirements
o r
boththeadult and young lish. Minerals maybe absorb edand becomea pan ofthetiss ues.ortheymay serve important functions inosmoregulation. Hayesetnl (19 4 6)foundthatcalciumand sodiumwere absorbed Irom.amiphosphorus anti potassiumwerelostto,the environ mcnlby eggs ofAtlanticsalmon(Sa/lIlosatan. Theamou ntofion move ment is undoubt edlyintlucnc cdbyioniccon centratio ninthe water. Qua n titative measur ementor
neteffectsindicatesthat thewater mediummaycontribute signifl c nnt amountsofcalcium.sodiu m.potassiumand iron (Zeitou net at, (916).Morinefoodsserveasnrichsourceof'min erals,astheircontentin the raw flesh ranges fro m0.6 to1.5%ofwet tiss ueweig h t(Sikorskiet al,I990a).Fish muscle nonnally contai nspracticallyallthe mineralelements occurrin ginthe waterhabitat. Minerals arcim portant constituent s offishflesh becauseorihcir nutritiv evalue.safety considera tions.and their contribution to taste.The ash content inthe muscle of culturedand wildfishisoftensim ilar (Saeki and Knmagnl, 1982;Dateand Yamamoto,1988;Morishitaetat,1988; Jahnke eI01, 1988).Ho wever.KlInisakiI!f(II(1986) reportedthat wildhorsemackerel (lroc tumeiap o nicus),andbastard halibut(Paralichthysolivaceus)(Saf e eI01.
1986)tendtohav esligh tlyhigh er ash contents than theirculturedcount e rparts.
Dateand Yamamcro(1988)suggested thatconsiderable seasona lvariatio nsmay existinthe content ofspecific mineralssuchas Ca.Na.and Kin muscl es of culturedyellowtail(Sertotaqutnouemdiatotmuscle .
2,4Tutafaed free amino lIehls 2,4.1Totalam inoacids
The actua laminoacidcompositio nof!ishmuscleisroughl y thesame as thatin terrestri al anim a ls.althoughtheproportion s of dillcrent protein types vary, reflectingthe env ironmen tinwhic htheseanimalslive(Ha lland Ahmad.
199211).Theam inoacid compo sition is importan tin two respects:nutrit ionand flavour(Uall and Ahmad,1992b). The compositionoftotalami noacidseffects
36
