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Not to be eite,,! without prior referencv 0 lJw al (heu

International Cou. eil fOT theExploration of tlle Sea

CM 1997/U:ü2Reproducti ismrL n s 0

Marine Species, andContaminantRelated Issues (lJ)

OVARIES MATURATIO " ATCHEGGS FORMING, BAT HFECUNDr .AN!DISTRIBUTION DURING SEX CYCLE O:F BAL.Je SPRAT SPRArrU SPRATTUS

BALTICUS

by

•E.I. A1eksc va, M.M.Baranov~, } f.t'.Dmi 'eva, E.... y zantseva

Atlantic Scientific Research Institute ofMari e Fishe 'es and Oceanography (AtlMtNIRO), 5Dm.Donskoy Str., Kaliningmd, 236000 Rnssl"

ABSTRACT

The results of study of ovaries maturation, bateh ew onnation, diurnal pawrungrythrns, peculiarities of mature femaJes bathimetric distribution are prcsenlcd. The data on batehfccundity and its relation to females length (weigth) and spawning p~f·:}d stages are pre. ·ntrd.The requirement of further researehes aimed at estimation of intcrvals between eggs laying andproportion of females spawned per day and subsequent es imation of AAS production isdiscussed.

INlRODUCTION

The extend of Baliic sprat distribl:tir'} area stipulates ~ \"l.tidc aIlge 01' numcrousparameters ofits r~productive biology, such as spa rning period, sp•. ming dmac n, ~ggs siz\.:.

• fecl'ndity, ete. (Aps et al., 1994).

In the Southern Baltie Sea sprat spawning OCCUITCS from March to August. 'fhe hatehe~

number is from 4 (Skitskiy, 1968) to 8~10 (petrova, 1960; Polivalko, 1980; I It:indrich, 1925).Individual feeundity of fish of 10.0-13.7 cm in length iUllounts in averagl.: 12.5-27A thow. ~ggs

(petrova, 1960) and increases from 13.6 (in 2 youn[.~of~the-years) to 20.0 Ulous. eggs (in 6. young-of-the-years); a" ~rage number of eggs in the batch (batch lecundity) is from 1467 to

2S76 eggs respectively (Polivaiko, 1980). Batch fecundity incrcases wüh ü:males lengthincrease and during the spawning season. In Bomholm area the lancr vaJue amounls to 1986eggs in average or 122 eggs per 1 gof .tema es weight (Muller f:t w.; 1990).

We researched the 8prat reproductiVe biology primarily with thc pw'pose to obtain datarör spawning biomass estimation.

Attempts to estimate biomass of fishes with batch spawning (on the basis of ew andlarvaes production) in the Baltic Sea have been und~naken for several decaoes. However those

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works wen: unsuecessful. AB a rule, estimation was pcrfomlcd lJsing indices of totallccundity.lIowcvcr, rcliahlc assessment of individual fccllßdity in fishes with hateh (especiaUy, multi­bateh) spawning is diHicull (IIuntcr, Goldberg. 1980; Dc Martini, Fountai14 1981; Goldbcrg ct .al., 1984; Wolf, Smilh, 1985). . '

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Wc tLScd one 01' thc methods of assessmcnt of batch spa\\lling Hsltes biomass on tItebasis 01' eggs productiotl (AJekseev, Alekseeva, 1988 3,b,c, 1996; Alekseev et al, 1993). Taestimate the latter the sludy of vitcIlogenesis, specific features of ovaries mattrration and eggslaying ia' rcquircd as weil as hateh fecuIldity estimiltion, diurnal spawlling rythmics andasscssment orintervals between eggs batchcs (spa,\ning ü'e(luency) on tllC basis orthe latter.

J\·IATEIUAL.AND METHOnS

Material was colleetcd in 1992-1996 hy the personucJ of LahoratOlY of the Haltic Sea(AtJantNIRO). In March-June, Oetoher .md Dccemher random samplcs - of 50-70 iridividualswere laken and fixed in 10% [onualinc solution with 5% iey acetic aci.l addcd. Total nwnbcrof such sampIes was 73 (4174 individuals). In the laboratory <in tixcd individuals weremeasured to obtaul totaliengUt and lcngth to folk, bcsidcs tllC fi)llowing paramcters were •rneasureu: total weight,' guued weight, weight ofgonades, matwity stage. .

Tu assess malluily stage, a scalc eJahorated specially for tltat species (AIekseev,AJckseeva, 1996) was used, which unlikc thc 3vailahlc scale (De Sylva, 1973), fetlecteu batcht}l)C of spawning. Bridly that scak is as fol1ows: . .

SI. II. Non-nuturt:. OVariC8 are small, tubular, slcndcr, colOtules8, grcrish. Oocylcs areimlsihlc "llh UtC nakcd cyc, diameter be)ow 0.2 111m.

SI. IU. l\lalurily.

lIla. 0\"U11.:8 are not llrgc. Small non-transparent whitish oocilcs are(ÜSlillguished \\;th the nakcd cyc.

lIIh. O\!arit.:s an.: largc, e1a.slic. Numcrouä uocytes uf v.tdous diameters Jrom 0.2to O.·t mm an: apparenl.

SI. IV. l\bIUfC. Övarics OCCUPY entire free spacc 01' the hody, ydlow. Oocytcs diameter •is up 10 0.7 nun. .

St.lV-V (VI-lV-V). Prl.:spawning.Transparcnl ouertes ofO.7-1.2 nuu in diamcter Me

"isually dctcr.lcd tluuugh a streiched l:11\'dope uf ovancs. No l:ggs aa: availahh.: in lhe ovarieseavily.

SI. V (VI-V). Sp"'wning. Süght pressure u)lon a ie.nalc bdly cxtrudcs eggs from thegenitale opening.

Si. VI·IV. Mature partially spawned. Ovaries as al stage IV, hm"ic\'er, smallcr, rcdish orbrownish

SI. VI. Spawned. Ovaries are snull, brown-redish..Ovariau cavity wiUt huge frcc spacc.. Si. VI-lI. Postspawning. Ovaries are small, ovalial cavily dcclcases, no uocytes an:

distil1guishcd witll thc naked eye.

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Description of variations, occurredin the process of ovaries ffi.lturation· and spawning,was obtained on the basis of hysto!ogical prep1fations analysis (40 ovanes) <and yotk oo..ylcssizc< composition (18 ovanes). Hystological prccessing was made using standard mcthow. Toprovide dehydration the mixturc of methyl and ethyl alcohuls was 'used (Roskin. Lcvinson,1957). Prcparations \vere coloured withferroU:1 hemalo>.yline by. Gaidcnga4l's metIloJ andpolychrom:.tica!Jy by Mallory's method (Romeis, 19~4). To describe oocytes size compcsition,an ooc}1es larger t11an 0.2 nun (in sa.'1lpls weig11ted 0.03-0.06 g) wcre measurcd from ovanes cfprespawning and spawning flShes. . .

;'Absolute indi~dual fecundity" was estimated in 25 ftshes; "nd batch fecundity - in 492fishes.· .' '.. . . .' .

To estima.\: absolute bateh. fecundity (ADF) all hydrated oocytes (in. sampls wdghlcd .~.3-0.5 g) were counted in ovaries ofstages IV-V anJ VI-IV-V (not ~l stages V andVI-V). .

Relative hatch fecundily (RBF) and gonadosomatic indices (GSI) ~erecalculated bascdon females \Vcight WUlout intcstines. During th ~ rcsults processing. average values of ADF,RBF, GSI, 1Cmalcs weight and standard deviations (Kirpichnikov, 1979) were estimatcd by

. 'length groups and montllS of each ycar. .

Percent ratio 01' oocyles nwnber in a batch and total nwnber 01' yolk oocytcs in ovanesat spawning bcginning was assumed to be a batcheness cocfficient.

Dwing thc data analysis, felUates wcre classilled according to reproductive cycle asfollows:immalure (11, VI. VI-lI), matwing (IIl), mat:'re (IV, VI-IV), spawning (stages IV-V,VI-lV-y, V, VI-V). .

Because 01' the <tata lack during se,:eral months of one yeM, the reproducti",c cycl~ \vas. reconstmctcd on the basis ofjoint material fcr 1992-1995 (Getober and Decembcr of 1993).

To study diurnal rythmic of matwation and spawning (he relation bet\vcen GSI andooc)1es diameters dwing hydration was analYfcd as weil as variationsof OSI and hydratedoocytes diameters 101' 24-how'S in 330 females at rnaturity stages IV-V, Vt-lV-V. The 24-hourperiod was divided into 4-hoUf intervals as fot'()ws: '1). 00 - 04; 2). 04 - 08; 3). 08 - 12;4). 12 - 16; 5). 16 - 20; 6). 20 - 24.

RESULTS

Vitel~ogenesls and formation of blltches

. ' Duriitg tru~hop..4imatic growth (viteHogenesis) of sprat .the follo~ing' phascs .are. specitied: . phase of..vacuoli:wtiott .. atid ... inhiat yolk accwnulalion,.. phas9 . of ..in"~ive .

trophoplasinatic growUl, ~hase of l}ocyie filliilg with yolk. bUring ril~tilia(joHyolk gninules joint .and hydration Oocure.

Dwing presl,<!wniügaJiJ ni~~t part df spawriliig perlod oocyies oralt \iicii~genesis'plwc from its start (ahout 0.2 huri ill dJariieter) to finish Me fotJnd in sprai ovaries. TIms,ovanes maturation (iCCWTCS as a' conlmuous Process in coltlpliancc: with classification· byGotting (1961). .

In ovaries al IV maturity Btage uocytes gent:rat!on linishing vitcllogencsis (Hg. Ia) i.sidcntificd acconling to cens size.\Vhen o\':u1CS transfer info' stJgc IV-V oocytes of tlHltgeneration nwluralc amI forni a hateh. At that time ooc}1cs finishing tlll; phase of intensivetrophoplasmatic growth ümn the next gencratio~ whieh is compalihlc with eggs batehaccording to eclls mmlher (Fig. Ib). Relative number of oocytes in tlw first balches (coeflicientof batclmcss) amounts to 6-10% of a11 oocytes in trophoplasmatic growth. Low coeflicicnts ofhatchncss c\idence probahility of spawning 10 and mor~ eggs hatches. Allcr 5pawning of eachcggs batch sprat ovaries transfer to st.1Ce VI-IV. wllere the older oocytes completc vittelogcnesisand their size is up to 0.6-0.7 mrn (in hysto!ogicaJ preparations). Since those oocyt~s should'piUlS only shorr-timc nwturation penod to fomt an eggs bateh, it may be misurilt:d tlwt intervalshetwccn batehes spawncd by sprat Me short, :lnd soon aflt:r spawning of nexr halch ovaricstransfer to stage VI-IV-V and VI-V (Fig. lc-e)~ In thc proccss of sp3wning relative numbcr cfoocytes in the hatehes [onncd (from all yolk ones availahle in an ovary) incn:.a.ses to 15% andmore. while the batch ahsolute valuc r~'CaIs no significant variations. Thercfore. prcspawningfund ofyolk ooc}1es (expcndablc [und) gradually deereases. (Fig.l1). . '

Before the last batch spawning the major part of residuJl expcndahlc fund i<: reprcsent!;uby oocytcs ar initial St.1gCS of vitellogcnesis (Fig. 19). In ovanes studie<! (stage VI) tO!21. •resorption of those ooc)1es was observed. l1H:refore it may be assumed that not aB oocytes cftrophoplasmatic growtlt m<lrurate and are spawncd.

Feculldlt)'

For most fishcs total oocytes of trophoplasmatic growth pedoll a\'~::Jble in ovaried atIV maturity stagc' are assumcd to be an individual nbso!utc fCClmdily.· It is tme for alt fishspccies with a single spawning, as welt as for n11 specks \Virh hatch spawning, when ovariesmaluration is of iutcmlittcnt paUem. Sprat has ooc}1CS in OVatics durind cntirc spawning period,whieh start \itcllogencsis. Prohahty. ooc}1cs transler from protopl3smatic to trophoplasmaticgrmvlh oceur~s in the proeess of spa,'lnillg. In this casc actual ab~':'lutc .individual fccundity(All') ntay hc lIigh-=r than thc number ofyolk oocytcs in ovanes at IV (VI-V) stage of maturity.Sißllilkant 1111mher t)f ooeylcs ~H' initi.:ll .pltascs of \oltdlogcncsis n:vcr reach malurity andhecolllc n:sOl hcd \,. hen spawning pt,;riud is finishe<!. TIH.:n.:forc, accufat~ cstimatiun of AIFvalue rcmaills prohlematic. We prefcr tn use a leim "cxpc.:ndahle Hmd" instead of AIF.

EXP'C1Hhihlc fund value (in !\'larch) (lf fcmaJcs 10-13 cm in lcnglli and 5-llg in guHed •wcight amounted to 10.3-26.6 lhuus. ew, in average 2.0-2.& UlOllS. cggs per 19 of gutte<!wdghl.

Ah:iOlutu batch fccwullty (ABF) incn:ascs With !ehgth and wcight illl.:rcasc. Iri the mostreprcscntativc material (April ] ()93, laIe Ivlay - earIy lune 1992 .anJ i995) individlt\l AUFvalucs of fcmates of 10.0-13.5 cm Jtl 1cngth werc .Withirl thc raJigc früin 1.0 tu :i.b tJlOUS. cggs.An indh.idual tishes of more thart 1.icni iri bngHi AßF appr<jachcd 3.(j UlOUS. eggs. Averagebateh fcewu!ity hy lengUt l)'OUpS are showii Hi Table i. .

In late !\'fay - eariy lune 1992; 1994, 1995 no ltinerences 'in Idative baleh lecundity(RBF) \vere observcd in tishes of.varioilil ienntli WilltUl prevailing Icngth groUl)s (11.5-13.0em). In largcr fishes thc trend of RUF decreasc was ohserveu. which was c\idcIlt only in largo·sampIes (Hg. 2,3).

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From April to JUll:: for two 'years (1992 .1m! 199·1) a slight increasc of average RBF inlishes 01' sirnilar It:ngtlt (Table 1) and average RBF for a sampIe as a wItale. In 1992 average·s.1mple value of RBF amountcd to 117.9±7.7 in April and 156.3±3.3 eggs/g in ~fay·lune; in1994 these valucs wl.:re 122.5±9.4 and 1·12A±5A ewig, r~~pcctively. In April 1993 itamounted to 13~).8±8.0, in M. j-June 1995 - 151.5±3.3 eggs.g. Partially that increase may becallSed by decrcase 01' average wdght 01' simil'lr lengLt-t 1ishes in the SP:l\VI~ng pcriod (Tabl~l).

HowC\·.::r, that prohh:rn requires further research.

Hcproductlvc cycle

11. 1\.Jarch matUJlng fcmalcs (st. !II) with 'lVcragc GSI 3..t 1 predominated in calches..Gonades at stage 11 with average GSI 1.89 were observed in 20% of [emales. Part of femalelJ(17%) had already transferred to st.'\ge IV wilh average CiSI 6.6 (Fig. 6, Table 2).

In April, when vitcUogenesis was ~pproachirg to the entl, proportion. of maturing fIshcsin catchcs uccreased anu mature (bcluding tllose spavroed part of b t ..hes) and bpawningimli"idtuls prcdominated in catchcs. Most females in spawning phase of reproductive cyclewere reprcscntcd by individunh Witll ovane" at VI-IV maturity stages.. Proportion of

.. prespawnillf! and spawning individuals (IV-Vs V, VI-lV-V, vI-V sL1ges) arnounted to about

.400/0.Averag:; GSI o[ malure femaks with ovanes at IV SLlg~ .of maturit:v approrhes

maximwn (8.85) typical for stage lV in April.· Average GSI of mature partüllly spawnedfcmales (VI-IV st41gcs) wc.:rc lower - 7.36-7...J3 Cl'ahll.l 2). In pn.:sp.\wning aud spawrung l~ma.lcs

significant seattering of inilividu:l1 OSI valucs W&1S obscrvcd in April - June (S.O-33.), whileaverage OSI artlmmted to 14.7-17.6.

In April first spawncd fcmalcs wcre obscrvcd in catches, hawcvcr, in proportionexceedeu no 2.5C}o (in June). Awragc GSI 01' spawncd flshes amoun1c<! to 3.6-4.7. Afterresorbtion of non-spawncd eggs, residual yolk oocytcs and recovclY processes. sprat ovariestransfer into stage II, \vhilc GSI dccrcascs anel apPlOach(;!t minimum, typical for stage II.

In Gelober the bulk or fernaIes had !mmaturc ovaries at stage ll. Average iength of thesefcmales was 10.7 cm, average GSI "- 1,45. Larger 1effisl1t:s 01' 11.7 cm in length (average GSI =1.48) wen: i·cft.'1TCd to maluring ones (stage llla) ll.ccording to visual indications.

.• In Decernber relative number of fernllies at stage II sharply decrcased ?'1d maturingfem.lIes became prcdominating ones. Aver'Jc GSI offcmales at stage m inccased to '1.77.

In March GSI of females ilt stage TI, which may becomc mature dwing tlu: nextspawning season, has incrcased to 1.39. In April most 01' these females transt'en'eu to maturingcatcgo.y, which resultcd in dccrcLlSC of St.lgC n proportion 10 «baut 2-5% during April-lune. InJU!lC the group of, fishes with irnmaturc got1adcs was reprcsented by juvenile Md spawnedfishes.

Peculillritil''' 01' f('Ill.lles spllUal distrHmtlon duriutf n spawning pt'riod . In Aprilonly maturing and mature fc.;males were CIlUght nt the depths of 28-60 m and no spawninp,fenUlles were found, whilc at the dept1ts of 75-105 m spawr...ng fcmaks proportion in variouscatches amo\h\ted tu 34-16%. Mature end partinlly spAwncd fcmales· (lV, VI-IV) wereobsetvcd at thc depth abovc 60m. 11 eviJcnccs a bathYlllctrie. illrrercntiation of fctnalcs duringspaMlittg phase ofreproductive cyetc. Prob:1blY presp3wnittg fetrtafes (IV-V, Vt-IV-V) migrateto the larger deptlts dunng a Hext eggs bateh Hpening. ' .

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, . In the laIe May - early Jt:ne no such distinct diffcn.11tiation was ObSCIVcd and spawning .fcmaJes were found in catcltes from 48-107 m, though maximum proportion of thc !aUer wasstill observcdat large dcpths. Catchcs \,,.it.h spa\'ming fcmalcs proportion up to 80% cvidenceformation 01'·short-time specitic spawning aggregations and batllymctric segregation ofspawning and fecding fc:hes dwing intervals bctwcen batchspawning.

Diurnal rythmlcs or nlllturntfon and spnwnfng.-In the process of hydration, resultedin incrcase of ooC)1cs sizc in a batch (up to 1.5-1,7 mm), GSlincrcasc also, approaching 30­33% in somefishes. Durine 1111' pd"iod from tilill- \pdl to ct1rly June averaee di:uncters ofhydrated ooc)'tcs \\lthin alt diurnal intervals [rom the third to thc six~ amoWllc.:d to i.32-1.37mnl. Average aSI values, typical for stages IV-V, VI-IV-V (at the level of 17.2-18.2), alsowere observcd during all intervals considercd (Fig. -1,5). It may bc cxplaincd by tlIc lack ofapparcnt diumal rytlImics of lllaturatior. and sp.:wning charactcIistic 01' many lish' spccicsresearched (Alekscev, AJekseeva, 19883, Alckscev cl al., 1993). ßcsidcs, it is probable thJ!oOC}1es maturalion process in sprat lasls more than 2-t hours, anJ WWll31 I)'thmics, if availablein individual fishes, will not observe<l at thc gTOUp level. 1'0 study this problem and :md toasscss sprat fcmalcs spamling frequcncy, 2.J-hour st.'\tion should bc cMricJ out during thc mass •spawning wilh trawJings .d all dcpths, espccially wherc the maximum relative number ofprespawning and spa\'ming femalcs are [ound during a survey.

CONCLUSION

,1. Ovarics maturation in ßaltic sprat. occurres as a continuous type. Vitellogcnesis is anintennillent - asynchronous. Dy the moment of cggs batch ScpJr:ltion a gc lcration of OOC)1CSfmishing vitcllogencsis has already forme<! in ovarics. 1'he spawning is a multi-batch ODe. 'Thebatches nwnber may bc more than 10.·' .

2. ExpendabJe flmd of oocytes ("absolute indivi~ual fecundity") in ovaries 01' females of10-13 ,CM in lcngth and 5-1 Ig in wcif,ht aIlIOWlls to 10.3-26.6 tllOUS. eggs or 2-2.8 tllOUS. eggs

, per Ig of femalcs wcight. Absolute batch fecundity is from 1 to 2 thons. cggs, and in individualflShes of more than 14 cm in length - up to 3 Lio~. eggs.

3. At the spawning peak the relative batch fecundity of ftshes within prcdomina!cdlcngth groups (11.5-13.0 em) (Ire a1 a simiL'U" level, howcver, from April to Junc average RDF ain ftshes of similar length (and for :s sampIe in general) increases. .,

4. ,Formation ofshort-time -spccific spawning aggregations and balhymctricdifferentiation by physiologicaI co~dition is char41ctcristic to sprat.

5. To revcaJ diurnall)1hmics of spawning anc! fcmales proportion spawning during 24­how'S, it is ncccssary to cany out 24-hour stations wllter a specia!ly ucvc]opp"d programme.. .

6. Average vaIues of relative batch fccundity obtaincd in ftshes of prevailing leng!..'"lgroups, may be uscd 10 cstimate eggs production of sprat. . .

'ACKNO~DGEMENTS

.' We are gratef1!l to F.E.A!ekseev for Ws cammcnts and valuable advices dwing aur workwith alte manuscript. . ' . .... ' . '. .

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REFERENCES

. t\lelsecv F.E., Alcksceva E.I. 1988a. Methodical reconunenlUtions tor eggs productionasscssmcnt in lishcs with a b61teh spawning. Kaliningrad, AtlantNIRO, 24 p. (InRussian). .

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Alckseev F.E., .\lcksceva E.i. 1988b. Mcthodical instructions Ln sarnpling and assc'ssment of 'spccific cggs production. Katiningrad, AtJantNLO, 11p. (In Russi. I).

•Ald..secv F.E., Aleksceva E.I. 1988c. Assessment ofspecific eggs production in P...uvian horsemackcrd l'rahurus symmetriclls murphyi Nichols. Methods and Results. All- ,Union' .Confcrcnce on Fish Early OntJlogenesis. Mwmansk, p.12-14. (In R~jan)., , '

Alekscev F.E:, Al~k~~eva' E.I. 1996. Idcntification of gonades maturity stages and sttidy of ." .rcproductive cycles, fccWldity, eggs production i.Jld rate ofmaturatio'n in marine,

conuncrcial fi"hes (Mcthodical Ivtanual). Kaliningrad,AtlanttvlRO, 7S p. (lri Rus~ian)..

Alcksecv F.E., Aleksccva E.I., Ry~ants~va E.I.• Lobov S.N.. 1993. Con )..rative study ~f'ews prodllciion in three <\btindant ho.ose mackercl species of Trachurus. Ecology andresourccs 01' conunercijJ fishcs in the Ea.···cm Atlantic Ocean. Collected Papers', . ,"Tn·dy AtlantNIRO", Kaliningrad. p.71-88. (In Russian).,

. Aps P.A., S!m;tsov F.G., Grauman G.n., Starodub M.L., Kondratie_a.N.M. 1994. Spral. ~ea

IIydromctcorolopy ..nd IIydrochcmistry, ,,'al rn. Baltic Sea, Iss. 2: llydrochemicalConditions and Oceanological Principles ofDiological ProuuCti\1ty Formation,St.Petersburg, p 60-81. (In Russian). '

De Martini E.E., FOWltam RK. 19&1. Ovarian cyclin~ frcqucncy and batch fecundity in thequcnnfish, Seriphus politus' attributes representative of scriaJ 'spa\\ning tishes. Fish. .Bul1., Vol. 79, N.3, p. 547-560. '

Oe Sylva S.S. 1971. Aspccts oftlle rcproductive biotogy ofthe sprat, Sprattus spraltus, ininshore waters 01' the west coast of Scotland. J.Fish.Diol., Vol. 5. p.689-705.

Goldberg S.R., Alarcon V.H., ,\!heit J. 19~4. Poswvu1~tol)' [ollicle histo!ogy ofthe Pacific'• sarCine, Sardinops sagax, from Peru. Fish.BuU., Vol. 82, N.2, p.443-445.

Götting K.J. 1961. Beitr~e 7ur Kenntnis des C.unillagcn der Fortplartzung undFruchtbarkeitsbestinunung bei mari"en Teleostecm. Wiss.Meeresunt.. IIelgoland, V.S•.N.t, S. 1-41.' ' . ,

. IIeindrich H. 19:t5. Über die Fortpflanzung von Ciupea - sprattus in der Kieler Bucht: wissenschaft. Mceresuntersuch. Abt., Kiel, NF.XX.H;1.' ' .'

HWlter J.R.,' Goldoerg ~.R. 1980. Spawnlng meidense and batch fec~mlity in N~I1heinancho\oy, Engraulis mo~dax. Fish.null., Vot 77, N. 3. p.641-652.

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Kirpichnikov V.S. 1979. Genetic r.rinciples offuh selection. L.. 391p. (In RUssian).··

MlUlerA., Muhsin K., Köster F.1988. Ovarian maturation and batchfecundityin Baltic sPrat ." fr~m the Domholm Dasin.. ICES, C.M.J:30.··

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Pctwva E.G. 1960. On fecundity and maturation ofBaltic sprat. Fisheries Researehes in thcBalticSea. Collecled Papers. VNIRO. M., p.99-108. (In Russian).

Potivaiko A.G. 1980. Some data on maturation, spawning and fecwulily ofspral. FishereiForshwlg. Jg. 18, A.2, S. 69-72.

Romeis B. 1954. 1\1icroscopic Researches. M., 718p. (In Russiall).

Roskin 0.1., IA:vinson L.B. 1957. Microscopic researches. M., 467p. (In Russian).

Skitskiy V. A. '1968. Peculiarities ofotoliths maluration in relation tu batch sllawnillg oi" HalticSpral. Trudy KTIRPiKH, Iss. 20, p.ll-IS. (In Russiall).

WolfP.) Smith P.E. 1985. An inverse cgg production method for detennining the relativemagnitude or Pacitic sardine spawning biomass off Califomia.Calif.~~oop.Fish.Ocean.lnvest.Repts" Vol. 26, p.130-138.

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Average absolute {ABF) and relative (R8F) batch fecundity and average gutted weight CvVg) of sprat females~~~g~~. . '.

Table 1

Year Index n 100 ...1M.. 11.0 11 5 12,0 .12,5 130 I 135 140 14 5 150 155 fMc::m±mABF.lnd 1149,0 948,0 1366,0 1638,0 878,0 1486,1 !

April 1992 RBF t indfg 149,0 101,5 125,5 149,0 75,0 117,7 117,9±7,7Wg,g 7,7 9,3 10,9 11,0 11,7 12,6

n 14 1 2 2 1 1 7ABF,ind 1572,0 1514,8 1721,8 1667,1 1840,1 1945,8 1895,9 2570,2 2031,7

May- Yune . RSF, indlg 210,0 167,0 181,2 153,6 155,7 150,4 135,2 170,7 . 128,0 156,3±3,31992 W9,9 7,5 . 8,8 9,5 10,9 12,0 13,0 14,1 15,2 15,9

n 213 1 6 25 48 53 43 21 13 3ABF, ind 1034,8 995,0 1474,0 1162,5 1600,6 1933,3 2055,8

ApriJ1993 . RBF, ind/g 139,0 140,0 120,5 134,7 9.5,8 134,0 130,0 151,2 .130,8±8,OW9,9 t 5,5 7,4 8.4 11,1 10,5 12,0 14,7 .. 13,8

n 32 1 4 4 3 4 8 3 5ABF., ind 598,0 592,2 1178,0 1096,0 1364,0 1713,0

April 1994 . RBFtind/g 94,0 87,6 134,8 117,5 145,0 149,0 122,5±9,4

. Wg,g 6,4 6,6 8,8 9,3 9,4 11,5n 15 1 4 5 2 1 2

ABF,ind 1233,0 1056,5 1178,4 1476,0 1631,1 1411,7 2051,3 1732,0 1985;0May- Yune ;RBF, ind/g 173,5 123,8 146,9 144,8 139,1 149,0 139,0 108,0 . 126,0 142A±5,4

1994 Wg,g . 7:;' 8,6 8,4 10,2 11,7 . 12,4 14,8 16,0 15,1n 58 2 6 14 21 7 3 ·3 . 1 1 .-ABF, ind 1770,0 1353,3 1368,6 1484,9 1530,5 1669,4 1578,6 1670,1 2939,0 3020,0 .

May - Yune RBF, indlg 242,0 173,4 160,8 155,7 144,9 144,3 130,9 119,1 169,0 154,0 151,5i3,11995 W9,9 I .

7,3 7~ . S,6~j

10,5 11,ß 12.0 14;1 17.4 19,1

I"

160 .1 9 34 32 23 8 8 1 .

1rn .

labte 2

. Gonado - somatic indeces of sprat fernales at various maturity stages by months .

Stage Monthsmarch april may yune . october december

11 1,89±O,89 (80) 1,63±O,18 (15) 1,86±O.11 (42) 1,38±O,22 (6) 1,45±O,02 (147)

111 3,41±O,09 (141) 4,55±O,17 (117) 4,87±O,16 (152) 7,76±0,42 (8) 1,48±O,04 (6) 1,7t±O,09 (26)

IV 6,60±O,50 (18) 8,85±O,30 (16) 8,85±O,60 (23)

VI-IV 6,58±O,14 (122) 7,36±O,10 (445) 7,43±O,19) (139)IV-V,VI-N-V 17.50±O,25 (390) 17,56±O,46 (99)

VI 3,60±0,36 (13) 4,70±O,70 (7)

forsampl 3,00 5,56 10,49 11,10 1,45 1,77

% ~~t: a10- ~5 . ~o -.--. I I i I I i~') , i , i

Maturity stages

IV

i i, 'i

IV-V%2C~ . b1510 . .

05~~ :~.--,--T--r-,--,.----r-~~-r-r__.__,.1"""""ir·

% 20C: C15 .' . VI-lV-V10 . -,

. g~:~e~·~~.~e·

VI-V

~~''''''''''VI-IV

j I i I I I 1

:> . CDci ci

~ ro m 0 ~ N ~.~ ~ wÖ ci ci ~ r ~ ~ r r ~

D!amoter. mm

. Flg. 1. Length distribution' of yolk oocit~s in oval ;es of mature (a. g)and prespawning (b - t) apret femsles; b - beforc the first batch of .

.spawning; c - e - partlally spawned In tho spawning beggining; f ­partially spawned at the end of sj:>awning;'9 - finishing spawnlng. ;

.'

3500

3000

2500

tfl2000V){)')(1)

u:1500Cl<

1000

500

360

300 -

<:>

o~......

o lO 0 ~N N ri ('f)oq- ,- ,- .....

Length, cm

b

""'o ~iC-,<"'>

250.Q't6t"1') 200ö)(I)

1.1.." '1~O -00 ....n:;

100

60

<:>

o~N

t.O o~ l..'10- . T"" ...-

...- ..... 'l-

o t..'i')N N,- ,,-

L~.mgth, cm

10tri~

. .Fig. 3. Absolute AßF (::!) and relative RBF (b) batch fecI.lnd1tyof sprat by lehgth groupE In Ml1Y ~ '{uno 1995 (legonds' aB inFig.2).

rI

I

•

1,7

1,6

1,5

E 14E 'tB 1,;i1)

. E 1,2CilCi 1,1

1,0

0,90,8 4----..-------.,---------;,-----...,.--

3

Interval

5

I

I.

Fig. 4. Diametem of hydrotated oocytes in sprat in •vsrious time of d~y {legend as in Fig. 2}. .

•

..., .

•

%::iI25

1J ~- 20-1 pw lr

~ 'liI15

I.. 10 J !5 -

o -1-'l 4 G 6..

lntervß!

•Fig. 5. Gonedo - ~Qm~iic Indsr. of spr~t prsspawningfema!ss in \'eriol.!~ tim!) cf dßY.(legend os in Fig. 2).

r--

,#

•

•

2

4

10

8

Fig. 6. Ratio of juvenile (a), riponing (b) ,md mature spawning(c) females of sprot nnd average; OSl (cl) by months

1:Jj- 0I

.r::. ~ C) >.. ot.. .... L- i- ...';:: (t) (') ") C) .8~ 0- ro c:: ""';; :::s .0 ~ .0E :::i

-s

\1.'1 ro ~~\ öl E 0 E E

E :s "0es 1} CI) 8a 0 >0 Cl)

91 &: "0!oli

Month

% 100

90 -

80 .

70

CIJc>

600)~1i)>...a 60c:0:e8- 400...

Q.

30

20

~-b -Q-C -d

(doUoo Une - 0 ~I'~od ':r,.-ith 110 cIf1.ta avaUnbls)