Batch fecundity, the number of eggs released per spawning event,
was determined for the first time in pilchard Sardina pilchardus
(Walb.) off the Atlantic coast of the Iberian Peninsula.
The mean relative fecundity (number of hydrated oocytes per gram
of female weight was 416 (standard deviation = 112.9).
Different regression models with Portuguese and Spanish data of
batch fecundity by weight are presented. A linear model weighted
least squares regression is established. The weighted regression
presents a homogeneous distribution of the variance, small mean
square error of the regression and highest R-squared, according
whit this expression:
F = -1260.8 + 444.43 W
Linear regression of batch fecundity by age for Portugal data is:
F = 30811.11 + 3711.88 

Figueiredo, I. (Ivone)

Pérez-Contreras, M.N. (María Nélida)

Santos, A.M.

English

Pérez-Contreras, María Nélida

Figueiredo, Ivone

Digital.CSIC

Batch fecundity of Sardina pilchardus off the Iberian Peninsula

Repositorio Institucional Digital del IEO

\International Council forthe Exploration of the SeaC. M. 1989/H: 17Pelagic Fish Comrnittee••BATCH FECUNDITY OF, Sardina pilchardus OFF THE IBERIANPENINSULAbyPerez M. N.,* Figueiredo 1.,** andSantos A. M.*** Instituto Espanol de OceanograflaCentro Costero de VigoApdo. 1552 36280-Vigo, SPAIN** Instituto Nacional de Investiga~aodas PescasAv. Brasilia 1400, Lisboa, PORTUGALABSTRACTBatch fecundity, the number of eggs released per spawning event,was determined for the first time in pilchard Sardina pilchardus(Walb.) off the Atlantic coast of the Iberian Peninsula.The mean relative fecundity (number of hydrated oocytes per gramof female weight was 416 (standard deviation = 112.9).Different regression models with Portuguese and Spanish data ofbatch fecundity by weight are presented. A linear model weightedleast squares regression is established. The weighted regressionpresents a homogeneous distribution of the variance, small meansquare error of the regression and highest R-squared, accordingwhit this expression:F = -1260.8 + 444.43 WLinear regression of batch fecundity by age for Portugal data is:F = 30811.11 + 3711.88 A••INTRODUCTIONSardina pilchardus is aserial spawner, (spawns several batchesof eggs each year), (Blaxter and Hunter,1982)During 1988, Portugal, and Spain applied the "Egg ProductionMethod 11 " (EPM), (Parker; 1985) to estimate spawning biomass ofthis species off the Atlantic coast of the Iberian Peninsula.'Theapplication of this method requires an estimate ofbatchfecundity, which'was made'by theapplication of,the "HydratedOocytes Method" (Hunter and 'Goldberg 1980), a technique based onFulton (1898), who discoveredthat all oocytes which are to bereleased in the next spawning'batch increase their size byhydration process.With these data we were also able to compare the fecundityparameters of pilchard in Portugal,and Spain watersMETHons AND MATERIAL.. .Sardines were collected along theAtlantic Iberian coast byPortuguese and Spanish research vessels on a joint cruise held inMarch/April -1988. A total of 126 sardines 'wi th ovar ies in thehydra ted condi tion were collected during the, EPM cruise' ( 37Portugal and 89 Spain). ..' . ,.,. 'After they were caught, their body cavity (anus to pectoral fins)was immediately opened and sex was determined. The ovary~freefemales (Spain) 'and gutted females (Portugal) were frozenimmediately. From all pilchard, the' ovaries were excised andpreserved. The fixative used on their preservation was different:Spai~ preserved the ovaries iria 4% buffered formaldehydesolution (Hunter 1985) and Portugal in Bodian's AAF (LILLIE andFULLMER,' 1976) modified, according to the following formula:-,Alcohol 50%Formalin 40%- Glacial acetic acid65 ml32 ml13 mlIn the laboratory, females with hydrated oocytes in theirovarieswere used to determined'batch fecundity.Sinc~ fecundity estimates should be gi~en in terms of liveovary-free weight, correction coefficients were determined. InSpain those were based on epi-pelagictrawl samples collected,during the cruis~. In Portugal, those were based on samplescollected by the commercial fleet. 'Sardine total and ovary.-freewet weights were determined'few hours after fishing, and after 24hours, it was frozen. Data of live and frozen fish weights:werefitted into a regression model which was later used to convertfrozen wet weight into live weight.The relation between female body weight without ovary and female••weight with ovary (excluding those with hydrated or immatureovaries) was established using a linear regression model. Thisregression was used to convert ovary-free weight to total bodyweight, for Portuguese data.The 'ovaries of all hydrated'females were preserved. After 1 montheach preserved gonad was blotted to remove the excess of fixativeand weight. The correction factor is the value of the slope of a'regression model used to convert fixed weight to live weight whenthe intercept is assumed to be'zero.Three pieces of ovarian tissue were taken fromeach ovaries, inorder to prevent biases on the estimates of batch fecundity dueto a differential distribution of the hydrated oocytes within theovary.Each subsampIe was weighted and hydrated oocytes were countedunder a stereomicroscope. All the ovaries were investigatedhistologically for the presence of post ovulatory follicles.Their presence is an indication that spawning has already beeninitiated, and consequently those ovaries can not be used ·forfecundities estimations,since some hydrated oocytes have beenalready released.Batch fecundity was estimated based on the average of the threesubsampIes and determined as a function of female ovary-freeweight. Ovary-free wet weights were used since females withhydrated oocytes, temporarily weight more than the average female(HUNTER et al., 1985).Sampling hydrated females was very difficult at the southernregion off Portugal. Biological information and lengthdistribution of sardines along the coast, showed that sardines inhigher length classes were concentrated in the south., ~Linear iegressions of batch fecundity on' ovary-free fish weightfrom both countries were compared. If little difference was foundbetween these two regressions,data of both countries werecombined to increase sample size. Different models were fitted tothe batch fecundity and ovary-free fish weight data and the modelwith smal'l mean square errors and highest R2 "(from linearregression) was chosen as the final model.The number of eggs per batch and age were also used in differentregressions, with only Portuguese data.Relative fecundity (number of eggs spawned/ovary-free femaleweight) was also estimated for both regions and resultscompared.•e.RESULTSHydrated oocytes preserved in different fixatives, presentdistinct characteristics. Table I contains abrief description ofthe morphology of hydrated oocytes preserved in formalin and inBodian's AAF modified.The values of weights and of relative fecundity obtained byPortugal and Spain were expressed in terms of ovary-free wetweight. Table 11 summarizes the correction factors obtained.Table 111 presents the va lues of means, standard deviations ofweights and relative fecundities determinated for each country.No significant difference was found in the ovary-free fishweights and the relative fecundities between two countries.Setting a linear regression model to the existing data sets onfecundity of sardines, showed that variance ofbatch were nothomogeneous distributed, increasing with females weight.In order to express the relation of female batch fecundity tofemale weight in terms of a linear model, a weighted leastsquares regression was used. The unweighted regression wasdivided into smaller sections in which variance was ·homogeneouslydistributed and total variance was calculated based on thefemales number in its section. The inverse of total variance asthe weighting factor to the estimate the new regression model,(Draper and Smith, 1971, in Hunter et al 1985).According to this proceeding a minimal variance and unbiasedestimate of the regression coefficients can be obtained (Hunteret al 1985).Four models were chosen to fit the.data. Two were linear and twowere nonlinear. The mean square errors and R2. from four modelswere·computed. The weighted linear model had small mean squareerror and the highest R2. Therefore it was ·chosen as thefinalmodel (Table IV). Fig 1. shows the .weighted least squaresregression model and linear model. .The relationship of batch fecundity and age of female fish inPortugal waters was also investigated. The linear regressionindicated that the variance around the linear was homogeneous.However the nonlinear regression fit the data better than thelinear regression. It was also observed that the batch fecundityand fish weight relationship was more pronounced than the batchfecundity and age relationship. Table V. Show thevalue of batchfecundity to age data for Portugal.The mean relative fecundity (number of hydrated oocytes per gramof female weight was 416 (standard deviation = l12.9)...••CONCLUSIONSLinear model is usually preferable than other models because itsregression coefficients have a simple biological meaning andbecause for the egg production estimation the fecundity oflargest and smallest fish are not as critical as for the fish inthe middle range, which is well explained by the simple ·linearmodel, (Hunter et al, 1985) •If we compare the data of relati~e fecundity with thevalue ofvarious clupeiform fish, listed by Alheit, 1988, we can see thanthe pilchard produce more eggs per gram body weight per batchthan all clupeidae, in spite of the weight range of pilchard issmaller than ot~er sardines species. 'ACKNOWLEDGEMENTSWe thank to the Joint USA-Spain Committee for Scientific andTechnological Cooperation, and Junta Nacional de Investiga~äoCientifica e Tecno16gica de Portugal, for supporting the lbericSARP projected. Our special thank to Nancy Lo, whose scientificassessment has been fundamental in our work. .REFERENCESALHElT, J.1988. Comparative Spawning Biology of Anchovies,Sardines and Sprats. Early Life History Symposium lCES C.M. 1988Paper N 16.BLAXTER, J. H. 5., and J. R. HUNTER, 1982. The Biology of theClupeoid Fishes. Advances in Marine Biology. Vol.'20.FULTON, T. W. 1898. On the growth and maturation of the ovarianeggs of the teleostean fishes. Annu. Rep. Fish. Board Scotl.16:88-124.HUNTER, J. R., and S. R. GOLDBERG, 1980. Spawning incidence andbatch fecundity in northern anchovy, Engrau1is mordax. Fish.Bull. u.s. 77:641-652.•HUNTER, J. R., 1985. ~reservation of the norther anehovy informaldehyde solution. In R. Lasker (editor). An Egg ProdutionMethod for Estimatting Spawning Biomass of Pelagie Fish:Applieation to the Northern Anehovy, Engraulis mordax. p. 63-65.U.S. Dep Commer., NOAA Teeh. Rep. NMFS 36: 99p.HUNTER, J.R., N. LO & R. LEONG, 1985. Bateh Feeundity in MultipleSpawning Fishes. In R. Lasker (editor). An Egg Produetion Methodfor Estimating Spawning Biomass of Pelagie Fish: Applieation tothe Northern Anehovy, Engraulis mordax. p. 67-77. U.S. Dep.Commer., NOAA Teeh. Rep. NMFS 36: 99p.LILLIE, R. D. and H. M. FULLMER, 1976. Histopathologie Teehnieand Praetieal Histoehemistry (4th edition). MeGraw-Hill, Ine.,New York, 942.PARKER, K. 1985. Biomass Model for the Egg Produetion Method. InR. Lasker (editor).An Egg Produetion Method for EstimatingSpawning Biomass of Pelagie Fish: Applieation to the NorthernAnehovy, Engraulis mordax. p. 5-6. U.S. Dep. Commer., NOAA Teeh.Rep. NMFS 36: 99p.TABLE IEffeets of two different fixatives on hydrated ooeytes•PRESERVATIVESOLUTION4% bufferedformaldehydeBodian's AAFmodifiedMORPHOLOGICAL CHARACTERISTICS OF THE HYDRATEDOOCYTES- large sizewrinkled appearanee (yolked but nonhydratedooeytes usually retain their smooth eontour)- translueenee (nonhydrated ooeytes arerelatively opaque)- large size- unwrinkled eontour- translueenee appearanee similar to unfertil-ized planktonie eggs- yolk granules visibleTABLE 11Corrections factors determined by each country (fW - frozenweight, gW - gutted weight and fWov - fixed weight ovary)COUNTRYC 0 R R E C T IONCOEFFICIENTSfrozen/wet weightbodysgutted/total weightfixed/wet weightovarySPAIN1. 0559 * fW0.991 * fWovTABLE 111PORTUGAL1. 044 * fW- 0.568 + 1.127 * gW0.852 * fWovMean weight and relative fecundity (no. eggs per gram female)of sardine: standard deviations in brackets. N is.. number of samples.. COUNTRYPORTUGALSPAINTOTALMEAN WEIGHT(g)23.04 N = 37( 7 .5)66.90 N = 89(17.9)54.00 N = 126(25.3)RELATIVE FECUNDITY382.50(88.6)429.41(118.7)416.34(112.9)••TABLE IVModels used to express the relation of fernale batch fecundity (Y)and fernale ovary-free weight (X)MODEL a b MSE R2(se) (se) 10- 6Y = a + bX -2304.51 471.28 50.1 0.74e (1485.9) (24.91)Y = a + bX -1260.80 444.43 50.7 0.82(weighted) (650.9) (18.5)Y = a * Xb 252.48 1.12 50.0 0.74(85.6) (0.77)Y=e(a+bX) 8.9614 0.0185 58.4 0.70(0.0914) (0.0012)TABLE VModel used to express the relation of fernale batch fecundity (Y)tt and fernale age (X)MODEL a b MSE R2(se) (se) 10- 6Y = a + bX 3081.11 3711. 88 4.7 0.64(806.85) (470.089)Y = a * xb 6696.24 0.68884 4.2 0.68(392.818) (0.0742)Y = e(a+bX) 8.66856 0.25835 6.2 0.52(0.8061) (0.0343)"•70D60 DfjD D50 D'"' DDD Dt') D D( 400 D Dm~ lb'J D..III D h.!l &' JjJE 30 cfl D D D D:I D 0 % DcD f9Jru D61 tF D20 OöI1JD010 D DD00 20 40 60 80 100 120female welghtsD DATA + UNEAR <> WEIGHTEDF.l. Weighted least squares regresion model andlinear model.

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Batch fecundity of Sardina pilchardus off the Iberian Peninsula

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