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International Council for C.M. 1986 / H:60 the Exploration of the Sea Pelagic Fish Committee

FECUNDITY OF PERUVIAN ANCHOVY, ENGRAULIS RINGENS 1

Jürgen Alheit Alfred-Wegener-Institut for Polar and Marine Research Columbusstrasse 2850 Bremerhaven Germany (FRG) and Bertha Alegre Programa Cooperativo Peruano-Aleman de Investigaci6n Pesquera (PROCOPA). Instituto del Mar del Peru Apartado 22, Callao, Peru

ABSTRACT The Peruvian anchovy is aserial spawner releasing several batches of eggs per spawning season. Batch fecundity was estimated applying the "Hydrated Oocytes Method". With the large data sets avai lable the relationship between batch fecundity and female weight was determined for three different spawning peaks and two different populations. Relative fecundity, estimated for August/ (580 eggs/g female), October 1984 (604 eggs/g female) and August/September 1985 (556 eggs/g female), did not show interannual variation. A comparison of fecundity values from February and August/Sep­ • tember 1985 indicated seasonal variation. Although the stock size of the Peruvian anchovy increased considerably from 1981 to 1985, relative fecundity at peak spawning time was the same in both years and a compensatory mechanism between changes in fecundity and stock size was not observed. .

RESUME La fecondite de 1 lanchois du Perou a ete determine en 1981, 1984 et 1985 et sa variation interannuelle et saisonnere a ete etudie.

1 Contribution No. 28 of the Alfred-Wegener-Institut for Polar and Marine Research

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INTRODUCTION The spawning season of the Peruvian. anchovy, Engraulis r i ngen s, us Uall y 1 ast s ( f rom J u1y t 0 r~ arch wi t h t w0 s pawni n9 peaks, in.August(September and January(February~. '.

I The Peruvian anchovy iso a batch (serial) spawning clupeoid species releasing several batches of eggs per year (ALHEIT et al. 1984). The' number.of eggs spawned by a female in one single spawning event, the batch fecundity, can be determined by the recently developed'Hydrated Oocytes Method ' (HUNTER etal. 1985), which,'because,of.its rapidity,allows the collection 6flarge dati sets on fecundity in reasonable time. Considerable interannual (HUNTER et al. 1985) and intra­ seasonal (ALHEIT 1986a) variation in batch fecundity is reported for other batch spawning clupeoid fish species. As severalnew large data sets on batch fecundity of the Peruvian anchovy are now available, the seasonal, annual and regional variation in batch fecun'dity of this species is investigated~ •

r~ETHODS . \ Female anchovies were collecte~ along the Peruvian coast by ~ research vessel and commercial purse seiners in August/Sep­ tember 1981, October 1984, and August/September 1985. After they were caught, their body cavity (anus to pectoral fins) was immediately opened and they were preserved in a 4 % buffered formaldehyde solution (HUNTER 1985). In the laborato~y, females with hydrated oocytei 'in their ovaries ..weresepa~ated.and th~if weight (ovary-free) and that of their o v. ar i es de t e r mi ne d. Thr e e pieces 0 f ti s s ue 0 f ca" 50 mg wer e removed from different parts of their ovaries. The number of . hydrated oocytes, in each'of these three subsamples was counted. Hydrated oocytes can easily be separated from all other types of oocytes', as they are translucent, have a much larger size, and as their surface'is wrinkled due to formalin • preservation •.The total number of hydrated oocytes in the ovaries which corresponds exactly to theb~tch fecundity was calculated f6r each female bas~d on the aver'age numbe~ of hydrated oocytes per unit weight in the three'subsamples. The s aIn p1es' fra m t he c e n t r a1 a nd, n0 r t her n s t 0 ck 0 f t he Per uvian anchcivj were divided 'into two groups, a'central and a northern on e. Theb 0 r der 1 i ne be t wee n' t he setwog r 0 ups .was at 11 0 15 I (latitude) ..Batch fecundity was expressed as relative fecun- .dity (number of eggs spawned/ovary-free female weight) because' _Lt_i.s a more .convenie.nt 'fecundity term when compari ng 'fecun­ .dityar-different populations or species. The gonadosomatic index (GSI).was determined by dividing the ovary weight by the ovary-free femaleweigh~. .

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RESULTS Average rel~tive fecuridity of ~he entire centraland northe~n ,stock'of the Peruvian anchovy was estimated in August/Septem­ ber of 1981 and 1985 (Table 1). ,The results were very similar with 580 and 556 eggs/gfemale (ovary-free), respectively. When dividing the data into a cent~al and a northern compo­ nent, in 1981, the central populationhad,'a considerably higher fecundity, 637 eggs/gfemale, than the northern o~e; 502 e99s/9 femal e, as 'r e p0 r ted by ALHEl T eta1. (1 983 ). 1n 1985, there was no difference in fecundity between the two parts of the, stock (Table 1) .In order to investigate possible latitudinal differences in fecundity in more detai,l, relative fee und it Y \'I as c ale u1ated f 0 r .the di f f e ren t wei 9ht c 1ass e s 0 f the females. There'was a general trend of relative fecundity incr e asi n9 wi t hau9me nt in 9 si ze , ( Fi g. 1 an d 2). In 1981,. a th~ .---" large proportion (51 %) of the fecundity data of northern population were gained, from females of the four smal lest size groiJps, whereasit was only 6 %,inthecentral population. • Thus ,the different size composition of the' females in the two samples. from the central and th'e northern,stock explain's some of the differ~nce in t~e a~erage relative fecundity in 1981. However~ iri most weight classes fecundity was consider~bly , higher in the central part (Fig 1)~ Such a trend could riot be­ observed in 1985 ,(Fig. 2). , For the irivestigation of possible seasonal or interannual differences in fecundity~ four data sets were available for the northern pa~t of the Peruvian anchovy,stock (Table 1), .ranging betw~en 466 and 604 eggs/g female. The size ofthe October 1984 sample (11 females) was considered as too small to be used in a seasonal compa~ison. However, the value of 604 eggs/g female in October 1984 indicates that, there probably was no dramati'c change in fecundity at this time~ The data from August/September 1981, February 1985 and August/September

, , 1985 were grouped byweight (Fig. 3); In ,all these data sets it was obvious that the larger females had a higher relative fecundity. With exception of the weight group 30 .;. 32 g" the • fecundity was always highest in the August/September 1985 samples. In February 1985, the ~elative fecunditj was con'sis­ tently 10we~ than in August/September-1981 and' 1985 in all weightclasses. . A study of the seasonal and latitudinal variatio~ of the gonadosomatic index (6SI) showed that it.was highest in'1981, in the ,centra 1 part of the stock (Table2) .'The lower 6S1..in_, __ the northern part in 1981 might partly be attributed to size class differences. In 1985, the GSIs in,the central and in the 'northern part of the' stock, were nearly equal: 5.9 arid 5.6, respectively. The lowest GSI was recorded i~February 1985 with 3'.2, although,only,females )20 9 wer,e considered. This low,valuewas mainly due'to many small females having inactive ovaries. When considering only females >25 g, the GSI rose to 4.4. Obviously, the larger females were 'actively spawning in Feb~uary 1985, whereas a certain' proportion of the smaller on es did not. Due' to the size dependent spawning activity in February 1985, t~e comparison of the GSI does not indicate - 4 -

lower average relative fecundity in February 1985 coinciding with a smaller size of the ovaries. For this study, only ..females caught in the morning between 08.00 and 11.00 hours were used. At that time :of day, the weight increase caused by hydration of the ovaries is negligible. . The GSI of,females with'hydrated ovaries 'was calculated for the three different seasons (Table 3). To ensure that all the females considered here ,were in the same state of hydration, only females caught between 16.00: and 17.30hours .inAugust/ September and 19.00and 19.30 hours in February were used. In Februar} 1985, the GSI of the hydrated females was considerab­ ly lower .than in Augus't/September 1981 and 1985. Relative fecundity in February 1985 was also lower. Obviously, 'when the number of hydrated ooc~tes in the o~ary decreases, then the proportion of the weight of the.hydrated ovary to the fema1e weigh~ also decreases. ' , The relationship between batch fecundity (F) and ovary-free female weight (W) had the fol1owing form: • 1n F = 5.34 + 1.34' 1n W: r = .74 August/September 1981 n =. 249 (central)

1n F = 5.16 + 1.34 1n W: r = .90 August/September 1981 n = 191 (northern)

1n F = 3.88 + 1. 68 1n W r = .83 February 1985 n = 76 (northern)

1n F = 4.29 + 1.64 1n W r = .78 August/September 1985 n = 58 (central)

1n F = 5.39 + 1. 29 1n W. r = ~63 August/September 1985 n = 190 (northern) DISCUSSION • The advantages of the }'Hydrated Oocytes Method' for deter­ mination of batch fecundity are that it is much faster than traditiona1 methods and 'that' it has a high accuracy (HUNTER et al. 1985) Its disadvantage is that females with hydrated oocytes suitable for f~cundity estimates are encountered,only at certain times of the :day and that some effort i s required to find them as-theyare patchily distributed in the popula­ tion (ALHEIT et al. 1984). The method· has been successfully applied to a number of, other batch (serial) spawning fish species, such as riorthern anchovy, ·E. mordax, (HUNTER and G0LOB ERG 1980 ), Per uvian s ardi ne, Sard i n0 ps ~ 5 aga x, (L 0 et ale 1986), Chilean sardine, 1. sagax musica, '(RETAMALES and GONZALEZ 1983), North.Sea' sprat, Sprattus sprattus, (ALHEIT 1986a), Pacific mackerel',off Peru, Scomber japonicus peruanus, (PENA. e t . a1. 1 986), an d Per uvia n hake, r-1 er 1ucc i us ~ per ua­ ! nus, (ALHEIT 198Gb). ,Ii ,I - ' 5

ALHEIT et a1. (1983) observed latitudinal variation 'in batch fecundity of the Peruvian anchovy studying a data set tram 19.8 1 ' an deo nc 1ud e d t hat an c h0 v' i e s 0 f. hi 9her' 1at i tudes 10 i 9ht have a higherbatch fecundity.' The same findings .were reported for the northern anchovy (LAROCHE and RICHARDSON 1980). A new data set. ga i ne d i n 1985 d i d 'n 0 t s upp'or t t he hy pot hes isof latitudinal variation in batch fecundity of Peruvian anchovy. Dividing the data into female weight classes revea1ed that some of the 1~titudina1 variati6n observed'in'1981 was due to relative fecundity being dependent on.femäle weight, however, most of 'the variationcannot be exp1ained in this way." For the sprat, Spratt~s'sprattus, f~om Kiel Bay, it has been. c1ear1y shown that the batch fecundity of aserial 'spawner can va r y co ns i der ab 1y dur i n9 t he s pawri i n9 se as' 0 n, e. g. i t ca n' double within a few 'weeks (HEIDRICH 1925, ALHEIT 1986a). As the 1981 data on the northern population of Peruvian anchovy wer e co 11ec ted, .0 n ave r 'a 9e' , t w0 we e ks 1ater t ha n t h0 s' e fr 0 10 thecentra1' population, the observed differences; presumed to • be regional, cou1d very we1l be due to intraseasona1 variation in' batch fecundi ty., ," ,, . In view of the highinterannual variat~on of relative' fecun­ dity reported by HUNTER et a1. (1985) forthe northern anchovy and considering the potentia11y high intraseasonal .variation in batch fecundity of 'serial spawning c1upeoids (ALHEIT 1986a), the simi1a~ity of thefecundity va1ues of the Peruvian anchovy gained in 'August/September 1981, 'October. 1984 and August/September,1985 seems somewhat surprising •. On1y ~he low va1ues from'Februar~ 1985 indicate a seasona1 ~ariation in batch fecundity. An interesting,outcome of the ana1ysis ..of t,he data from February 1985 is that mainly the larger'females were spawning whereas the smaller~ones'had inactive ovaries. February is near the end of the Peruvian anchovy's protracted spawning s e aso n' and t he s malle r f e 10 ale s', had pro bab 1y a1re ady ce as'e d spawning~ . • , In August/September 1981; 'the spawning"biomass of the centra1 and northern stock of the Peruvian 'anchovy, was estimated at 1.2 ,million tons (SANTANDER et al. 1984); In August/September 1985, the spawning biomass of the sam~ stock was 'estima~ed at ,several million tons, a multiple' of thebiomass from 1981. Still, the average relative fecundity,'stayed about the same (Table 1). There is no indication of a,compensatory mechanism between fecundity and stock size, such as fecundity decreasing .with augmenting stock size, as reported e.g. for the Sout~ African pi 1cha~d (SHELTOtl and ARMSTRONG 1983). In any' case,· as batch fecunditycanv'~ry considerably 'during the spawning .. season (HEIDRICH 1925, ALHEIT 1986a) and as' annual fecundity is a function of both. average batch fecundity,and number of spawnings per year, a proof' of such a compensatory mechanism f 0 r bat c h s pawner s , s uc h ast he an c ho vY wo U 1 d re q u i r. e, _a._ very.. high sampling effort over the entire spawning season. , ----. :I , , 6.- , , I, i I I' ~ LITERATURE CITED I , I ALHEITiJ.1986a.Reproductiv·e biology of sprat, Sprattus j I sbrattus.ICES C.M. 1986/H:58, 16 pp. .. I ALHEIT,J.1986b.A new method for determining batch fecundity of I hake (Gen~s: Merluccius). ICES C;M. 1986/G:62; 9 pp. I ALHEIT,J.,V.H.ALARCON and B.MACEWICZ.1984.Spawning fiequency I I arid sex. ratio in the Peruvian anchovy, Engraulis ringens. I Calif. Coop. Oceanic;Fish. Invest. Rep., 24: 43-52. AL HEl T,J• ; B• ALE GRE', V•H"AL ACR0 N an d B• MAC EWI CZ• 198 3 • Bat eh f e c und i t Y a nd s p a w'n i n 9 f r e q ue n c y 0 f v a riousanc h 0 vy (Genus: Engraulis) :populations from upwelling'areas and their use for: spawning biomass estimates. FAO Fish. Rep., . 291: 977-985.' . ,. .' HElD RICH, H• 19 25 • Uberdi e Fo'r t pfl an zun9 von C1upe asprat t us i n der Kieler .Bucht. Wisse Meeresunters., Neue Folge, Abt. Kiel, 20: 1-47'.,.' '. . HUNTER,J.R~985.Preservation of northern anchovy in formalde- . hYde sol ut ion. In:. An e 99 produc t i 0 ri met h0d fo restimatin9 • spawningbiomm ofpelagic fish: application to the northern ,anchovy, Engraulis mordax (Ed. R.LASKER). NOAA Technical'Report NMFS, 36: 63-65 HUNTER,J.R. arid S.R. GOLDBERG.1980.Spawning incidence and batch fecuncli ty in II10rthern anchovy, Engraul i s mordax. Fish. Bull., U.S., 77: 641-652. HUNTER,J.R. ,N.C.H~LO arid. R.LEONG.1985.Batch. fecundity in . multiple spawning fishes. In: An egg 'production method for estimating,.spawning .. biomass of pelagic fish: applicat'iön to the riorthern anchovY,·Engr'aulis· mordax {Ed •.R.LASKER).·, ...... ' NOAA Technical Report NMFS, 36:67-77. .'.. ". "" LAROCHE,J.L. and S.LRICHARDSON:T980.Reproduction of no'rthern . anchovy; Eng~aulis 'mordax~ off Oregon and Washington. Fish. Bull., U.S., 78: 603-618. . . LO,N.C.H., J.ALHEIT and~.ALEGRE.1986.Fecundidadparcial de la sardina peruana .(Sardino'ps sagax) •. Bol. Inst. Mar Peru, . Callao, 10:.45-60.· : ,- ,'. . PENA, N• , J • ALHEl T an d M. E ~ NA KAM A• 1986 •Fe c uncl i d ad parc i al de 1a I caballa del Peru (Scomber japonicus peruanus). Bol. Inst •.• ' I MarPeru, Callao, 10: 91-104. J RETAMALES,R. 'and L.GONZALEZ.1983.Fecundidad de sardina , t (Sardino~s m~sica)~ I espano)a,. sagax Corporaci6n de I . Fomentode la' Produccion,AP 84-5, Inst. Fom. Pesq. .! . Chile: 30 pp. ,,',' . I SANTANDER,H.,J.ALHEIT.:and. P.E.SMITH.1984.Estimacic5n de la I biornasa de la poblacion desovante de anchoveta peruana, / I, En' 9 rau 1 i s r i n gen s " . p0 r ' a pli c a c i 6n . de 1 " Met 0da.' de Produccion de Huevos". Bol. Inst. Mar Peru, Callao, 8: 209-250. ":' .' - ~HELTON,P.A. a~d M.J.ARMSTRONG.1983~Va~iations in 'th~ parent stockand recruitment of pilchard and anchovy populations in, t h e sou t her n Ben 9 u' e 1 a s y 5 t Ei m. .FA 0 Fis h. Re p ., 291: 1113-1132. ;, ". .-

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Table 1. Relative fecundity (nr. eggs/g female) of Peruvian anchovy.

Month Year Relative S • 0 • n Population Fecundity

580 +139 437 northern + central Aug/Sep 1981 637 +134 254 central 502 +103 183 northern

• Oct 1984 604 +137 11 northern Feb 1985 466 +128 76 northern

556 +134 251 northern + central Aug/Sep 1985 568 +153 58 central 553 +128 191 northern • Table 2. Gonadosomatic Index (GSI) of non-hydrated females of Peruvian anchovy.

Month Year GSI S .0. n Population

+2.2 central Aug/Sep 1981 6.5 96 4.1 +2.0 109 northern

3.2 +1.9 90 northern, females > 20 9 Feb 1985 4.4 +1.5 49 northern, females > 25 9

5.9 +1.9 234 central Aug/Sep 1985 5.6 +1.9 211 northern

• Table 3. Gonadosomatic Index (GSI) of hydrated females of Peruvian anchovy.

Month Year GSI s.o. n Population

Aug/Sep 1981 14.2 +3.3 82 northern + central Feb 1985 7.4 +1.6 77 northern Aug/Sep 1985 11.9 +2.6 56 northern + central ­ "

800- m CENTRAL r:: 700- 0 NORTHERN ~ r:-: ~ .-:- : r:-:" r-:: : :::~ ~ ~ 600- " jj :' : t- :' W r.-: :: I- ::t- ....J TI :: ~:t- :: ~~~

FEMALE WEIGHT CLASSES ( 9 ) .

Fig, 1. Relative fecundity of Peruvian anchovy in August/ September 1981. , 0

,- 800 "7- ": b:;] ," CENTRAL ," ': ," )- 0 NORTHERN r.: 700 := ," :: ""= :: " " :: " ~:"- " ,.... " 600)- r-~ :: ': ': :- "7- ~ , UJ ':" :: : .' --I ~ :' ;:1- ," ~ I- « ""'10:' · .'.: j :E 500 r- - n ::" UJ H u. " ..... · H .':' -:- .: ~ .' .' :: :: :: i '. :: Cl .: .':' - [.001- U"l ~~ ,, .:H H :: ~! :' H .' e:> .' .' " :: e:> .' :: " :: .'.: UJ . j~ .'.: 1- :. ."" '. ci 300 :. .: ~! '. z :'.' H .: " " H '. .' " .: :: " ,- .' " 200 H.' :: I1 H :: .' " :: H " :: ~ " .' : .:" ~ ~ 100- J 7 S 7 5 2 ;: ,. : 2. " rI •.":: 2• a :. Z7 ,. 7 2 • :: ':; ::" ~ : .' :;; " ,"" ;~ : :. :; :: ': · Hi . U. 16 18 20 22 2[, 26 28 30 32 3L.

FEMALE WEIGHT CLASSES(g)

Fig. 2. Relative fecundity of Peruvian anchovy in August/ September 1985 I

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AUG /SEP 1981 FES 1985 AUG/SEP 1985 600-

soo- r:" c.: '. ~ 400 , :: « " ~ w LL 300- ::" " ii Cl " " ::" " - 200- " ~j :g " <..9 " "'. W '. " ci " z 00 23 44

I 14 16 18 20 22 24 26 28 30 32 34 36 FEMALE WEIGHT CLASSES (g )

Fig. 3. Relative fecundity of northern subpopulation • of Peruviatt1nchovy. ~ , " -.. j