INTERNATIONAL COUNCIL FORTHE EXPLORATION OF THE SEA

C.M. 19911G:54Demersal Fish Committee

A PRELIMINARY ANALYSIS OF SOME BIOLOGYCAL ASPECTS OF HAKE~ferIuccius rnerIuccius L. 1758) IN THE BAY OF BISCAY.

by

Imanol MARTIN

A.Z.T.I.-S.I.O.Txatarramendi irla, 48395 Sukarrieta, Bizkaia, BASQUE COUNTRY (SPAIN)

ABSTRACT

Some biological aspects of hake in the Bay of Biscay are analysed. incIuding weight­length relationships, maturity at length and time of reproduction. based on sampIes taken from1987 to 1990 from catches cf the Bay cf Biscay.

RESUME

Quelques aspects biologiques du merlu du Golfe du Gascogne sout analises, ycomprenent les relations poids-longitude, maturite sur longueur et temps de reproduction,base sur des echantillons de prises reaIises dans le Golfe de Gascogne de puis 1987 jusqu'a1990.

1. INTRODUCTION.

Hake is a very important species particularly for Spain and France. Estimated totalinternationallandings during 1989 were 79,000 tonnes (Anon 1990a) and the estimated valueof the landings cf only the Northern stock is about 385 million Ecus (Anon 1990a). Is is alsoone of the most important species for the Basque Country where totallandings were about15,000 tonnes in 1990.

AZTI-SIO started a program for routine sampling ofhake in 1987, in order to obtainsame general information on certain biological aspects of this species. This work is apreliminary analisis of some of the data collected.

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2. l\IATERIALS AND l\fETIIODS.

2.1. Sampling strategy.

Sampies of whole fish were bought at the fish market in two of the main ports of theBasque Country, Bermeo and Ondarroa. Sampies were bought as fresh fish and analysis werecarried out within the first few days after the sampies were bought. However, in some cases,due to logistic constraints, fish were frozen and kept at -180 C before they were thawed undercontrolled conditions and analysed.

•Experiments have been conducted in order to assess the effect of the freezing and

defreezing procedure on the different data collected and to correct for these effects. Thefactors estimated to correct the effect on length and on weight are (Lucio, pers. comm.):

Le = 1.006 Lo range = 19-60 cm number= 125 fish

We = 1.022 Wo range=40-1580 g number= 126 fish

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where,Le and \Ve are the estimated length and weigth of the fish before freezingLa and \Vo are the observed Iength and weight of the fish after the process of freezing and

defreezing. '

Sampies were collected each month from the landings of different fleets, but noattempt was made to sampie the fleets separately. From 1987 to 1990 the sampling has beenrestricted to catches coming from subarea VIII. Most of the sampies collected came fromcatches made in VIlla and VlIIb, although there has been some sampling made in the mostEasterly part of subarea VIIIc, that is, to the East of 30 \v.

From the sampies collected, a number of fish was analysed for each cm length class.Separate sampling of the different divisions of subarea VIII has been attempted.

From each fish analysed the following data were collected:

Total length (in mm)Total weight (in g)Gutted weight (in g)Sex (male, female, indeterminate)Weight of the gondads (in 0,1 g)Maturity stage ("de visu")Index of stornach fullness

Also, both sagital otoliths were removed for age determination studies.

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·,The maturity stages were assigned according to a basic key shown in Table 1.

However, in this paper the results have been analysed on the basis of a simplified key. Aprobable correspondance between these keys and the key proposed by Macer (1974) areshown in Table 1.

Data were stored in a MicroVax and programs were developed for the basic analysisof the data. .

3. RESULTS.

3.1. Weight-leneth relationships.

A preliminary analysis of different relationships was carried out using a GeneralLinear Models procedure of the statistical package SAS. The results for different relationshipsare described below. •

3.1.1. Totallength-totaI weight

The parameters of the weight-length relatioriships were estimated by fitting straightlines to the logarithm of the length and weight data collected throughout the whole period,this is from 1987 to 1990.

When the regression parameters were estimated for the whole set of data available,the values found were:

\V (g) = 0,2366 *10"'-5 * L(mm)A3.174 n= 9206 r2 = .99506

the standard error of the estimates were:

minimum length: 7,7 cmmaximum length: 103 cm

minimum weight: 2.5 gMaximum weight: 6.443 g

•y-axix intercept: 0.007796 (logarithmic scale)slope: 0.002331

In order to assess the effect of different factors on the slope and the y-axis intercept,a regression analysis was carried out using General Linear Models procedure of the packageSAS. The factors considered were sex, quarter, area (VIlla, VllIb, VllIc) and year. However,when the parameters where calculated taken this factors into account, the r2 was 0,99535.This was considered a small increment in the contribution to the variance explained by theregression, although some of the effects were statistically significant. Therefore, only theregression shown has been considered. Further analysis should be carried out before any ofthe factors taken into account here is included in the weight-length relationship.

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Previous authors provide estimates of the weight-length relationships of hake fordifferent areas of the sea, such as subarea VlIIc and IXa (Cardenas et al 1981), the West ofIreland (Farina et al 1985,1986) or the Bay of Biscay (Hake \VG 1973) althougth none ofthen provide confidence limits of the parameters estimated. In some cases (Cardenas et al1981) differences in the estimated parameters are reported, but, again no information on theconfidence intervals or the error associated to these estimates are provided.

3.1.2. Total weight-gutted weight.

A similar analysis to that carried out for the total weight-length relationship wasconducted for the total weight-gutted weight relationship. In this case, the variable totalweight was considered as a linear function of the gutted weight.

When the regression parameters were estimated for the whole set of data available,the values found were:

TOTAL \V (g) = 49.15 + 0,825 GUTTED \V(G)

n= 4313 r2 =.92543

the standard error of the estimates were:

y-axix intercept: 3.3slope: 0.0036

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Again in this relationship, a regression analysis was carried out usinga General LinearModels procedure of the package SAS. The factors analysed were the same as in the totalweight/total length relationship. \Vhen the regression parameters were estimated taken intoaccount these factors, the r2 obtained was 0.967. The increase in the percentage of thevariance explained by the regression when the factors are taken into accoun was consideredsmall, even though some factors had slopes or y-axis intercepts statistically different. Furtheranalysis shoul be conducted in this case again, before it is dear that the factors studied havea real effect in the population.

3.2. 1\'fnturity studies.

3.2.1. Variation with time. Time of reproduction.

In Figures 1 and 2 the percentage of fish spawning is shown for the different monthsseparately for males and females. Different size ranges are also separately represented.

The size ranges shown were selected in order to show the portion of the populationfully mature and the portion comprised by mature individuals together with individuals thatwere spawning for th~ first year. The "fully mature" portion was regarded as the fish biggerthan 45 cm for males and those bigger than 60 cm for females. The other size range analysed

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was 30 to 45 cm in males and 45 to 60 cm in females. These ranges were se1ected accordingto the results of the analysis of 1ength at first maturity (see be1ow).

The different size ranges within each sex were studied in order to evaluate whetherthere was any difference in the time of reproducion related to size.

According to Figures 1 and 2,. reproduction in the Bay of Biscay takes placethroughtout the whole year in both males and females. The main period ranges fromDecember to June in males bigger than 45 cm and from January to Ju1y in females biggerthan 60 cm. In some cases the level of sampling is small and does not al10w a precisedefinition of the main period of reproduction on the basis of only these data.

In smaller sizes, the main period of reproduction seems to range from December toMarch in males between 30 and 45 cm, although a relatively big percentage is also seen inJune. In females between 45 and 60 cm the main period seems to take place between Januaryor February and May. Only 8 females of this size have been sampled in January, andtherefore the percentage estimated should be interpreted with care.

On the other hand, in this smal1er range of sizes, the effect of the inmature smal1individuals growing into this range as time advances might interfere in the results.

3.2.2. Variation with length. Length at first maturity.

In this work an approach similar to that used by \Velch and Foucher (1988) has beenfollowed to estimate length at first reproduction, in that the parameters of a logistic curvehave been estimated by fitting the curve to the absolute numbers oberved mature andinmature. The form of the 10gistic curve chosen has been:

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1P(1) = ------------------------------

1- LSO-ln(9) (-------------)

1+ e L75-L25

(1)

wherePO) is the proportion of mature fish at 1ength 1LSO is the length at first maturity (at which P(l)=0.5)L75-L25 is the range of length between the lengths at which P(l)=0.75 and P(l)=0.25

This particular form of the logistic curve has been chosen because it is the· formcurrently used by the leES Working Group of Fisheries Units in Subareas VII and VIII(Anon, 1990b).

In this work, the function to be minimized has not been the one used by \Velsh andFoucher, but the parameter A of Schnute and Fournier (1980):

A =2 L1=1

m=2

Lm=l

. fobs(l,m)fobs{1,m) In (-------------)

fexp(l,m)

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(2)

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·wherefobs(1,I) are the observed absolute frequencies of individuals inmature and fobs (1,2) theobserved matures at length 1.fexp(1, 1) are the expected number inmature_and fexp(1,2) the expected mature at that length.The expected number of matures are obtairied by multiplying the number of fish analysed ateach length by the value of PO) calculated for the particular length from (1). The expectedinmatures are the numbers analysed minus the expected matures.

The minimization of A also leads to maximum likelihood estimates of the parameters,and has some advantages over the pure Maximum Likelyhood discussed by MacDonald andPitcher (1979) and Schnute and Fournier (1980).

\Vith this method, the binomial nature of the distribution of the probability of findinga mature fish at a given length interval has been taken into account as suggested by \Velshand Foucher (1988).

The absolute frequencies used to estimate the parameters were the number ofindividuals mature and inmature observed in the sampIes from January to May (see belowdiscussion on the evolution of the Gonosomatic Index). The estimates obtained for LSO andL75-L25, both for the whole area sampled and for each Division studied are shown in Table2.

As previous authors have found, males mature at a smaller length than females. Thevalues found in this work were 37,7 cm for males and 50,5 for females.

If a different range of months were selected to estimate the parameters, the estimatesobtained would be different. This can be seen in Table 3, where the estimates derived foreach quarter of the year are shown.

Three features appear in these estimates: first, males mature at a smaller length thanfemales, second the estimates obtained are smaller for the first two quarters of the year, andthird, the parameters L75-L25 are not very different between sexes or quarters.

The differences between quarters are likely due to the effect of the growth of inmatureor maturing fish during the year, and this might lead to different estimates if data fromdifferent time periods are used, particularly if the time periods are very different and short.For example, if data from surveys are used, they may reflect the situation in one month, andnot the average situation throughout the main period of reproduction. Therefore, in order toobtain a standard figure, only the months of bigger reproduction have been used.

Length at first maturity of hake has been studied by several authors, (see Table 4 and5). Most of these works (if not all) estimated length at first maturity by analyzing thepercentages of individuals mature at each length interval, maybe in some cases, by fitting alogistic curve to the percentages observed.

This procedure has some disadvantages discussed by Welsh and Foucher (1988): thelargest residuals are usually those with small sampIe sizes, the sign (direction) of the residualsis also important, and finally, Welsh and Foucher found that in some cases the residuals are

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not normally distributed. They propose a maximum Likelyhood method to estimate theparameters on the basis of the analysis of the observed absolute frequencies.

The method used in this work has been applied not only to the data collected here, butalso to data from previous works when numbers of fish observed at each length, rather thanthe percentages, were available. When the absolute numbers found were not available, theestimate obtained by the particular author has been used. The estimated LSO, and whenavailable the estimated L75-L25 found for different authors are shown in Tables 4 and 5.

As a general feature, and as Hickling pointed out as early as in 1930, the length atfirst maturation varies with the Ioeation of the samples. Hickling observed that this wasrelated to Latitude, the further North the sampling was eonducted, the bigger was LSO. Anexception to this are the estimates from the Norwegian Deep and the Skagerrak , andHickling attributed this to a different stock of hake.

Another feature of the results is that the estimates of L75-L25 do not seem to showany particular trend. They seem to vary in relation to the level of sampling.

•3.3. Gonosomatic index (GSD.

The gonosomatic index was calculated here as:

Gonad weightGSI = --------------- .* lQA 4

Total weight

3.3.1. Variation with time. Time of reproduction.

Monthly GSI values were calculated for different size ranges in order to assess theimportance of each time of the year for reproduction. The ranges of size chosen were three Afor each sex, and were chosen according to the parameters LSO and L75-L25 derived for hake ,.,of the Bay of Biscay in previous sections:

- A first range whieh would represent the inmature part of the population. It rangedfrom 20 to 35 cm in males and from 20 to 45 cm in females.

- A second one which would be intermediate and would inc1ude a mixture ofimmature, maturing and probably already mature fish. It ranged from 35 to 45 cm in malesand from 45 to 60 cm in females.

- Finally, the third range would inc1ude mostly fish already adult. It comprised fishbigger than 45 cm for males and fish bigger than 60 cm for females.

The values obtained for males and females are shown in Figure 3. The level ofsampling ofbigger males in January was very small, this leads to a large confidence interval

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which is not shown completely in order to show the other months. A similar effect is seenin several months of females (February in females from 45 to 60 cm and December infemales bigger" than 60 cm).

Tbe main period of reproduction seems to range from January-February to July,according to the maximum values of the GSI observed. The lowest values are found inSeptember-Detober. The bigger values found in males between 30 and 45 cm seem to rangefrom February to June.

In females, the main period of reproduetion seems to be from January to April insmaller females, although important values of GSI are also found during May. Tbe minimumvalues are found in summer and autumn. Iri females bigger than 60 cm, the biggest valuesare [ound between January and July. As pointed out above, the value found in December hasa very large confidence interval. The differences between the lowest and the highest valuesare mueh bigger than those [ound in males.

A different set of data was also analysed. An estimate of the GSI of the landings ofthe port of Ondarroa, was obtained by dividing the weight of the roe landed by a boat by thelandings of hake of the boat, this was done for a number of boats eaeh month and an averageof all boats used was calculated. In order to make sure that the roe really belonged to hakeand not to any other species, only landings from long liners whose cateh was mostly hakewere used. Also, in order to make sure that the weight landed of inmature fish did notinterfere with the analysis, only landings of big h3.ke were taken into account. The sizecategories used were those bigger than "karioka". These categories comprise almostexcIusively hake bigger than 50 cm. This size corresponds mostly to mature females as canbe seen in the sex ratio of the landings of hake (see below). The estimates obtained by thismethod correspond to a Gonosomatic index refered to gutted weight since long liner land theircatch of hake as gutted fish.

The monthly variation of this GSI is shown in Figure 4.The values obtained are relatively elose to those obtained from our biological samples, thismeans that the estimates probably reflect quite accurately the (gutted) GSI of mature females.Also, the pattern of the variation throughout the year is very similar to what has been foundin the biological sampIes.

Therefore, is is thought that the monthly variation of the GSI obtained from thelandings data as described here reflecs reasonably accurately the (gutted) GSI of maturefemales. Furthermore, since the "sampling level" is much bigger in the GSI derived from thelandings (the tonnes of hake considered range from 5 to 68), this estimate might reflect witha better precision the (gutted) GSI of mature females than the estimate derived from thebiologica1 sarripling.

Tbe process of reproduction seems to be continuous in female hake in the Bay ofBiscay without drastic change, and therefore it seems difficult to define limits to the begginingor end of the 'main period.

If limits should be dcfined, on the basis of Figure 4 the main period of n:productionof female hake in the Bay of Biscay seems t~ range from Deceinber to May, or even to July.

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Tbe biggest reproduetive effort seems to take place in the first quarter of the year (winter inthe Bay of Biscay), and the smallest effort from August to November.

Several authors report than hake spawning takes plaee throughout the whole year ormost part of it in different areas like the Mediterrenean eoast in front of Castellon in Spain(Larrafieta, 1970), in subarea IXa (Anon, 1986) or in subarea VII (Hiekling; 1930)

Tbe timing of the peak of spawning varies in different areas. It is eloser to wintermonths in the South, and takes plaee eloser to spring or summer months the further Norththe area iso Larrafieta (1970) reports peak spawning in Caste1l6n from January to April;simiIarly, in subarea IX, Portuguese data from surveys and monthly sampling of landings(Anon, . 1986) indicate that peak spawning of hake takes plaee in February and March,although Monteiro and Lima Dias (1965) suggest that in the Portuguese fishing groundsbetween 38° N and 39° 31 'N spawning takes plaee more frequently during spring andsummer, on the basis of the percentage of females newly spent found by quarter in thesampling of the landings. Perez and Pereiro (1981) found that in ICES Divisions VlIIe andIXa the main spawning period for female hake took place between January and May, and formales between Oetober and May. In subarea VII peak spawning takes plaee from March toJuly (parina and Fernandez, 1986). Hickling (1930) reports maximum reproduction fromApril to July in his study of hake to the West of Ireland and Britain. He also reports that thereproductive period seems to be longer in males than in females.

3.3.2. Variation with Jength.

The average of the value of the GSI was obtained for all individuals iri 5 em intervalsby quarters in order to study the size at first maturation from a different approach to whatwas done before.

These results aie shown in Figure 5 for both males and females.

In males, GSI starts to inerease between 30 and 35 em during the first quarter. Tbisshows the size range in which some individuals start maturation. GSI tends to inerease withsize. A smooth inerease in the values is seen from 35 em onwards. This was also found by aHickling (1930). .,

In males between 35 and 55 em, GSI of the first and second quarter are very similar,and so are those of the third and fourth quarter. The values for the first and second quarterare bigger than those of the second half of the year. Tbis indicates again a more importantreproductive period in the Bay of Biscay during the first half of the year, as has beenmentioned above. In males bigger than 55 em this effect is not clearly seen, it might be dueto a smaller sampling level.

In females, the first values of increasing GSI are found between 45 and 50 em. Tbemain period of reproduetion takes plaee, as in males, during the first half of the year. Thefirst quarter gives consistently higher values of GSI than the second one in alllengths, oncea eertain length has been reaehed. Tbis was not seen in males, although variations in the GSIin males are always smaller than in females. The values of the GSI in the third and fourth

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quarters are very similar, and smaller than those for the other quarters.. .

As opposed to males, in females it is not dear that the GSI inereases with length.During the first and second quarters, and onee a eertain size (around 60 em) is reached thevalues do not seem to increase with size. J"his effect was already pointed out by Hiekling(1930).

However, during the third and fourth quarters there seems to be an increase in the GSIwith length which could be due to a bigger proportion of females spawning in the third andfourth quarters, as length increases.

3.3.3 Differences in GSI for different maturity stages.

In Figure 6, GSI for different maturity stages has been plotted for eaeh quarter forboth males and females. As a eomparison three portions of the poputlation have beeneonsidered:

- Inmatures: males smaller than 30 em and females smaller than 45 em.- Matures resting from reproduetion: males bigger than 45 em and females bigger than

60 em- Matures reproducing: males bigger than 45 em and females bigger than 60 em.

The GSI is eonsistently bigger in individuals reproducing than in individuals resting.Also GSI of resting individuals does not seem to change through the year in eithe~ males orfemales. Finally, GSI of reproducing individuals deereases from the first quarter to the fourthquarter.

3.4. Hepatosomatic Index ffiSD

The Hepatosomatic index was ealeulated as folIows:

\Veight of the liverHSI = --------------------- * 10"'4

Total weight

3.4.1. Variation with Iength.

The results for the average values over 5 em length groups are seen in Figure 7.

In both males and females, the values show a slight inerease until 40 or 45 em, butthen they remain relatively constant over length. On the other hand, there seems to be noeonsistent differenee beween the different quarters. In partieular, the dear differenees seenin the GSI are not found in the HSI.

3.4.2. Differences in HSI for different maturity stages.

In Figure 8, the values of the HSI for different sizes and reproduetive stages of hake

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are shown calculated on the basis of the same criteria as Figure 6 of the OSI.

The values of the HSI seem to increase with size and seem to be bigger in reproducingindividuals than in individuals resting, although the latter differences are not significative. Onthe basis ofthe data available in this work ifcan be said that there is no significant differencebetween the HSI in reproducing and in resting individuals. Also, there are no apparentdifferences between different quarters.

Therefore, there seems to be no apparent relation between weight of the liver andreproduction. This is against what Hickling found in his work (1930).

3.5. Canditian factar (CF).

The condition factor in this work was calculated as follows:

Total weightCF = -------------- * 10"5

Total lengthA 3

3.5.1. Variation with length.

The results of the values calculated as averages of 5 cm length classes are shown inFigure 9.

The CF shows a slight increase with length until about 30 or 35 cm in males and 35or 40 cm in females. At bigger lengths there seems to be no clear change, except perhaps asmall decrease in the values.

3.5.2. Differences in the CF for different maturity stages.

In Figure 10, the values of the CF for different sizes and reproductive stages of hakeare shown calculated on the basis of the same criteria as Figure 6 of the OSI.

There seems to be no difference in the condition factor of hake between reproducingfish and resting fish. Also, no clear change is seen when different quarters are compared.There are no big differences between males and females

This constant CF throught time of the year has been found by Perez & Pereiro, 1985in Divisions VIIIc and IXa, even though they were working with the gutted weigth data.

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3.6. Sex ratio.

Tbe sex ratio found throughout the whole period of sampling can be seen in Figure11. Tbe number of fish sampled to obtained these values is shown in Table 6.

Tbe main features shown in this figure are also found when the data are analysed foreach year, because of this, the figures obtained for each year are have not been inc1uded.

Sex-ratio is dose to 0,5 in the smaller hake, until 30 or 40 cm. From this size malesare more abundant than females until SOor 55 cm, and from this size onwards females aremore abundant. It is very unlikely to find males bigger than 60 cm in the Bay of Biscay.

Tbe reduction in the percentage of females in intermediate sizes and the increase intheir percentage in larger sizes has been observed in other areas by previous authors. Farifiaand Fernandez found this in sampies of landings from the \Vest of Ireland (1986). Similarresults have been found during English research surveys (Anon, 1987). Spanish sampling ofthe landings from the Southern Stock of hake in 1981 also found this pattern (Anon, 1982).Portuguese survey data from area IXa in several years from 1981 to 1986 (Anon, 1982; Anon1983; Anon, 1986; Anon, 1987; Anon, 1988) fount this as weIl.

The pattern observed is usually a decrease in the percentage of females from 30 to 40­50 cm, an increase in the percentage of females from 50 cm and from 60 cm onwards thepercentage of females is usually almost 100. In some cases, the perceritage of females isc10se to 50% in intermediate lengths, as in French data from sampling of the landings fromsubarea VII of semi-industrial trawlers of Concarneau in 1985 (Anon, 1987), or data fromPortuguese surveys in subarea IXa in June 1981 (Anon, 1982).

A difference in growth between both sexes could explain this sex-ratio. If males growat a smaller rate, particularly after the start of reproduction, which takes place between 30and 35 cm, the combined effects of a lower growth and a similar mortality rate at lengthwould lead to a bigger percentage of males in intermediate lengths and a bigger percentageof females at bigger lengths.

ACKNO\VLEDGEl\fENTS

I wish to thank J. Alvarez, 1. Artetxe and A. zamakona who did the biological analysis ofthe fish; P. Lucio defined the maturity stages and supervised many of the biological analysisand specially the assignation of the maturity stages; C. Idokilis and M. Sevillano developedthe data base and the programs to do a first proccessing of the data. Special thanks are givento Dr R. Cook and Dr J. OUason for supervising the analysis of the results.

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4. BIBLIOGRAPHY.

ANON. 1982. Report ofthe Working Group-on assessmentofhake stocks. ICES, Doc. C.M.1982/Asess:14

ANON. 1983. Report ofthe Working Group on assessment ofhake stocks. ICES, Doc. C.M.19831Asess:20

ANON. 1986. Report ofthe \Vorking Group on assessment ofhake stocks. ICES, Doc, C.M.19861Assess: 1.

ANON. 1987. Report ofthe Working Group on the assessment ofthe stocks ofhake. ICES,Doc. C.M.19871Assess: 1

ANON. 1988. Report of the Working Group on the assessment of the stocks of hake. ICES,Doc. C.M.1988/Assess:2

ANON 1990a. Report of the Hake \Vorking Group. ICES CM 1990)/Assess:22

ANON 1990b. Report of the \Vorking Group on Fisheries Units of Subareas VlIb-k and VIII.ICES CMI Assess:23

CARDENAS, E. and FERNANDEZ, A. 1981. Length/girth and length/weight relationshipsof hake in Divisions VlIIc + IXa. ICES, Doc. C.M. 19811G:31.

FARINA, A.C. and FERNANDEZ, A. 1985. Length/weight and length/girth relationshipsof \Vest Ireland hake. ICES, Doc. C.M. 1985/G:27.

FARINA, A.C. and FERNANDEZ, A. 1986. Datos biol6gicos de la merluza deI Oeste delrlanda. lnf. Tee. lnst. Esp. Oceanogr. N 47 1986.

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HICKLING C.F. 1930. The natural history of the hake. Part TII. Seasonal changes in thecondition of the hake. Fishery lnvestigations of the Ministry of Agriculture and Fisheries. •Series H. Vol XII. No 1.

LARRANETA M.G. 1970. Sobre la alimentaci6n, la madurez sexual y la talIa de primeracaptura de Merluccius merluccius (L.). lnv. Pesq. 34(2):267-280.

MACER C.T. 1974.- The reproductive biology of the horse mackerel Trachurus trachurus(L.) in the North Sea and English Channel. J.Fish.Bio1.6,415-438.

MACDONALD P.D.M. and PITCHER T.J. 1979. Age-groups from size-frequency data: aversatile and efficient method of analyzing distribution mixtures.J.Fish.Res.Board Can.36:987-1001.

MERIEL-BUSSY M. 1966. La maturite sexuelle du merlu dans le golfe de Gascogne. ICES,Doc. C.M. 1966/G: 16.

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MONTEIRO R. and LIMA DIAS M. 1965. On some aspects of the ovary development inthe hake (Merluecius merluecius L.) of the Portuguese eoast. lCES, Doc. C.M.1965/G:37.

PEREZ N. and PERElRO F.J. 1981. First data on sexual maturation and sex-ratio of hake(Merluecius merluccius L.) from lCES -Divisions VIIIc and IXa. lCES, Doc. C.M.1981/G:37.

PEREZ N. and PERElRO F.J. 1985. Aspectos de la reprodueei6n de la merluza (Merlucciusmerluccius L.) de la plataforma gallega y canta'brica. Bol. Inst. Esp. Oceanog. 2(3):39-47.

SCHNUTE 1. and FOURNIER D. 1980. A new approach to length-frequency analysis:growth structure. Can.J.Fish.AquaLScLVo137(9):1337-1351.

WELCH D.W. and FOUCHER R.P. 1988. A maximum likelihood methodology forestimating length-at-maturity with application to Pacific eod (Gadus macrocephalus)population dynamies. Can.J.Fish.Aquat.Sci., Vol45:333-343 .

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a) Basic key used b) Simplified key c) Key of Macer

1. Juvenile (Vi rgi n) I Virgin 1. Vi rgi n

2. Very earl y begi nni n9 of maturetion HBegi nni ng of 1- 3. Developing virginmaturation 2. Resti ng (mature fish)

3. In maturation3'. Agai ni n maturetion

3. Developing (early)111 Active 4. Developing Oster) •4. Presps'w'ni ng 4'. Re pes ted pres pa'w' ni ng

S. RipeS. Spa'w' ni ng

6. Runni ng6'.Partly spent

7. Partl y spent

6. full spent IV ful1 spent 8. Spent

7. Resti n9 V Resti ng 9. Recove ri og

•Table 1. Correspondance between a) the basic maturity stages keyas used for the biological analysis of hake, b) the simplifiedmaturity stages key used in this paper, and c) the maturitystages key of Macer (1974).

Table ~ Paran~ters cf length at first laturity in hake of the Far of FiscayIL50 and Li5) estimated for all Divisions co:bined and fcr each Division. The datauS2d refer to sa;pling carried out fro! January to roay lainly frol 1988 tc 1990.The value of the para:eter Afeund at the jinimuQ is also indicated.

I'l ALE S

Division Per iod L50 Li5-L50 NUiber Range Value cf A

VIII., Vmb~

ViiIc lEast)Januar] te May, 19a8tc 1990

37,7 1129 20-62 35,02

•VI I10

vIIlc

Division

vIiI;, VIIlb,VIIlc (East)

VlII;

ViIIb

vIiIc

Jan-May, 1988-1990

Jan-May, 1988-1990

Jan-~ay, 1968-1990

F E 1'1 ALE S

Period

January tc May, 1988tc 1990

Jan-Ma;, 1988-1990

Jan-~ay, 1988-1990

Jan-May, 1988-1990

34,9

38,4

38,5

L50

51,3

51,5

4,5

11 ,b7

L75-L50

7

6

231 20-62

643 20-62

254 20-55

Nu.ber Range

1013 20-75

263 20-75

545 20-73

205 20-75

18,82

11,67

Value of A

26,46

24,07

L50 Li5-LSO NUIDer Range Value cf H

• Division

VIIi 2, VIllb,VIIi.: lEast)

SEX ES C0 HBIN ED

o '.l, enDu

January to May, 1988to 1990

41,4 S,l 2142 20-75 130,84

~able 3 . Preli~inary estimates of the paraNeters of length at first ;aturity in hakeof the Bay Qf Biscay ILSO and L75i e5ti~ated for each quarter for all Divisions co;bined.used refe~ to sa;pling carried eut froD January to ~ay lainly frei 1988 to 1990.Tne estimates obtained when the per iod considered ranges fro; January to Hay are also included.

~ ALE 5

Per iod

Quarter 1

Quarter 2

Quarter 3

Quart~i 4

Per iod

Quarter 2

Quarter 3

Quarter 4

Yem, ef da ta

1987 to 1990

Ide!l

lees

Iae~

Ide!S

f E 11 ALE 5

Years cf data

19Bi to 1990

lae;

ldem

laell

l50 L75-L50 HUlber Range Valu!! of A

37,i 4~8 1129 20-62 ~S .,~

.j ~ t~~

')"~,~ 700 20-61 45,6,,/

39,2 5 608 2Q-62 32

45 7,0 743 20-b2 47 •41,6 7,2 1049 20-62 ~': 1

",Il..,&

l50 L75-L50 NUl:lber Range Valu!! of H

50,5 7 1013 20-75 130,94

48,2 6,4 486 20-62 33,S

<:':1 ' b,2 691 20-70 29,5w .... ,~

~o <: 10,4 674 20-69 <:' "~'pJ ..:0,1

r' '" 6,4 1023 20-68 26,3.JO!,' •

• rable~. Pira~eters of ler.~th at first laturity in hake of several areas as reported by several authcrs.When the authcrs ineluded the .etual numbers observed, esticates of LSO and L25 have been obtainedby the method used in this paoer. In these eases, the value of the paraleter Afound at the linilul is also indieated.

11 ALE S=========

Area Refere~ee Data Period L50 L75-L50 Nu;ber Range Value of A-------------------------------------------------------------------------------------------------------------------------Mediterrane.n Larraneta 1970 Harket s.aoling

•

IXa

IXa

\lIIIe-IXaVlIie- IXaVIIIe-IX.VIIIe- IXa

Anon 1982Aocn 1983Anen 1986Ide.llAnen 1988

AnOll 1986IdBIee~

1de;Ide5

rerez 1981Anen 1982Pere!! 1955Anen 1986

Portuguase surveyIae;Iael!Idealoe;

Spanish eilt ..Ide;ide'llId;:~

Ide!!

Market saio+surveySoanish dahHarket sacp+surveySpanish data

./Iareh and June 1980 1981April/Harch 1980 to 1983June 1983June 1964Feb-~arch 87

Quarters 1,2,3 1981QuartErs 1,2 1982Quarters 1!2! 1983Quarters 1,2 1984Quarters 1,2 1985

All Quarters 1911ay 1980­All Quarters 1980-1961Ail quarters 1980-1982Quarters 2,3,4 1980

24!3

3332

31,.j28,627,5

3736,532!5

3732

3939

35-3939,5

2252199

1::,',-"'I

428207162li6176

1539 "I: 'I:t.ro..;

1865 25-651230

VIiIVIII

Present ~ork ~arket sa~oles

Heriel-B. 1966 French surveysJan to /'layHpril,llay

198i-mo1965,1966

3i,7 4,8 1129 20-62 35!0236-37 lesti;ated fro~ the figure previded by the öuth~r)

Vli+IJIIIaVii +ViIla

Anon 1986Anon 1990

English surveysIde~

F E MAL E S;============

Mareh!üec1983-19861987-1989

33,433,15

11 !20,37

854 12-85 34!1

Mediterrane.n Larraneta 1970 Harket sa~oling

l1arket sa;o+survey All Quarters 19Hay 1980­Spanish sarket sa~p.All Quarters 1980-1981Harket sa!!lo+surveys All quarters 1980Soaoisn data Quarters 2,3,4 1980

BaIXaIXalIaIXaIXa

IXa

•IXaII~.

HaIXa

VIIIe-ihVIIIe- IXaVIlie-BaVIIIc- IXa

l1~nteiro 1965Anon 1982"ncn 1983A;oc,n 1936lee!Anc.n 1958

Aoen 1986idE.llIde;IduIde;

Perez 1931Aocn 1962Fenz 1985Ancn 1986

Market sa;:llingPcrtu2uese surveyide;;Ide;Ide!Port. Survt~arket

Spanish dataldelllCEILIde!Ioel

Quarters 2!3 1959/larch and June 1980 1931April/March 1980 to 1983June 1983June 1984Surv 1986 aod Feb-l1ar 19

Quarters 1,2!3 1981Quarters 1,2 1982Quarters 1,2, 1983Quarters 1,2 1984Quarters 1,2 1985

32,2

57,7 B,4 2023 4Cl-56 l1S,Si4949

55,5 45358 27151 874

49,5 28547 19046 14145 32047 263

56 922 25-755658 C7:l E5-751J ........

SB 832

ViiiVIiI

rresant werk Market sa;piesHeriel-B. 1966 Frenen surveys

Jan to l1ayApril,May

19Bi-19901965,1966

50,5 7 1013 20-75 43,354-Si lesti;ated freI the figure prcvided by tre iuthor)

Vil+VIIIaVIi+VI!Ia

Ancn 1985Anon 1990

Eng.surveysEng.suneys

5 E X E S

l1arch,Dec

C 0 11 BIN E D

1983-19861987-1989

i81 12-85 19,65

===:===:::====:==============!Xa Anon 1987 Portuguese surveys 1982-1984 39ViIi Present work !'Iarket HiP!es hn tt' May 196i-1QQO 41,4 6,1 2142 20-iS 130,8:'VII 'VIIia Ancn 1986 Eng li sn surveys 1983-1986 43,3 12,5 1635 12-85 35,96VII +VII! a Anon 1990 Idel! Hatcn.D~c 1987-1989 39,98 13.6

lable 51. Para~eters of length at first aaturity in hake of several areas calculated on the basis of the dataprcvided by Hickling 119301. lhe ~ethod proposed in this paper has been used to obtain the esti;ates.

MAL E S

Area Fishing gnund Per iod L50 L75-L50 Nu;ber Range Value cf A

Vll Salley Head, Saiway August 1928 28,5 4,4 1136 15-49 31,66

Bay and BuH

F E 11 ALE S

Aiea Fishing grcund Per iod L50 L75-L50 Nusber Range lJalüe cf A

Viii westward February 1926 78,9 b,B 321 50-89 4,8

loe!l\ Apr-May 1928 75,7 b 315 50-94 4,i

Iae; August 1928 72,1 1,2 67 50-94 0,01

Bull March 1926 79,5 7,6 443 50-94 3,6 •Ioem Apri I 1926 80 8 351 50-94 3,9

Ide. !lay-June 1926 80,5 6,4 630 50-94 6

Idee June 1926 81 5 648 50-94 1,3

Ide'l July 1926 81,5 7,2 562 50-94 " .,.... 1

Ioem August 1"'" 70,5 5,4 193 50-84 4,3'1;:0

IdeS! October 1926 85 7 381 5(H4 2,7

!dem Nov-Dec 1925 85 4,4 263 50-94 L L1J!:'"

VIa Tory lsiand April 1927 82,2 6,4 135 50-94 ! ~ 1

IdeUl Septe~ber 1927 79,9 " L 144 50-94 4~3... ,''''''

St Kilda January 1926 81,2 7,2 362 50-94 ö~c

Jde!! May 1926 83,2 4,6 20E 60-9~ l! ~

Idem Septe!lber 1927 80,2 7,8 124 50-89 ~ ':':"'~w""

Ide& October 1928 75,1 b 362 50-94 4,9

Butt of le\>lis !larch 1927 81 4,8 "0" 50-94 ~eie: ...

IVa Horwegian deep June 1nS 71,4 3,8 438 50-94 :: .1... ~ .

IlIa Skagerrak June 1923 70,7 4,6 305 50-94 17,6

Taole 6.. Nu~bE!r of fish sa~pled from 1987 to 1990 to E!stimate thesex-ratio !:hcwn in Figure 11.

Length NUlliber Length NUlLber Length NUlLbe

20 337 40 '168 60 6121 311 41 165 61 4622 :I~~ 42 116 62 i6Lwl

23 ~~:I 43 126 63 45''1~

:I' 285 44 110 64 63... '+ -25 304 45 113 65 5026 291 46 107 6b 56:I~ 299 4- 110 67 32... 1 !

28 :I'~ 48 100 68 29.. '+ö

29 214 4~ 85 69 25.1

30 242 50 '1' 70 15IV

31 ~~~ 51 i1 71 3ce"32 200 ~~ 64 i2 1-..!~

~':I 172 <:':1 ~~ 73 4~ ... ..." I,;

34 151 ~, SB 74 5,J'+• 35 172 55 71+ 75 23l It.9 <:' 59... "'J

37 180 57 7938 182 ~~ 70":ö

39 18i) 59 62

January July

Pereenlaoe

'jll,= LJ~

I 11 la IV V

~aturity etages

tr.Aatuf"ity Ilegea ~ .S-60 cm (7.)_ . 60 cm (96)

B .S-60 cm (8) _. 60 em (.6)

August

"r"·~ ·60 I

60 i

:~~I 11 111 IV V

Malll'"ity stagea

U--.-.J11 111 IV V

Malurity Itaoei

Perc~ntaoe

February

lOOl80

60

.0

20

o

~ .S-60 cm (2) _ • 60 cm (0) ~ .5-80 em (19) _ • 60 em (6)

March September

100 Percentagoe

80 ~60- ~

~.0 ~201 ~0'-------'=---=:------.1

11 111 IV VMaturity stages

~ <S-60 em (68) _ • 60 em (S6)

100 Percentaoe

111 L d_-,,-__.J~=-.__11 In IV V

Jrw4alurity ataQe.s

~ .S-60 cm (.2)_ • 60 em (.3) •April Oetober

t oo;ercenI3,..oec:.... _

80: J j-~~~ II ~

20~' -"f'''-'.~ ~ _o 11 111 IV V

Maturity staoee

I. ~I,-"",,~--...~=-.11 111 IV V

Maturity staoel

~ 45-60 cm (14) _ l SO cm (51) ~ .S-60 em (70) _ • 60 em (15)

May November

PercentaQe

11 111 IVMatIXity stage.

~ .S-60 em (271- • 60 cm (3.)

11 IR IVMah..lly Itaoel

Percentaoe

'~~i20,

o

~ .S-60 em (6') _ • 60 em(nS)

June Deeember

l"·"·~1 ~I11 ~II --IV---V--

Mahxity atagel

Percentaoe

'~~ ~ I~~, I ~ ~_

11 111 IV VMalurity ItaQes

~ .S-60 em (3') _ '60 cm (30)

~ 'S-60 em (22) _ • 60 em (2)

Figure 1. Monthly frequencies (in %) of maturity stages of hakefernales in the Bay of Biscay from 1987 to 1990. Two size rangeshave been considered, from 45 to 60 Gm and bigger than 60 cm. Inbrackets, the nurober of fish analysed by month. (I:Virgin orjuvenile, 11: Beginning of maturation (very early), 111: Advancedmaturation, spa~ning and partly spent, IV: Full spent. V:resting) .

January

'~jl"«""· I20_~ I I0, " 11I ~~IV-:-----:':V-

Malurity slaget

§ 30'(5 cm (63) _. 45 cm (5)

July

100 Percen lage

111. L ~I _1 " 11I ~---:'IV---:-:V--'

MatU"ity .taO~1

~ 30-45 cm(218)_ '(5 cm(116)

February August

100 Percentaoe

111.. L .1I 11 11I ~----:l:-:V---V:-:--~

~aturity .lage.

~ 30-.(5 cm (""). '.S c:m (18)

Percentage

m 30-(5 cm(1601_ • 4S cm (42)

'jt 11 Jo I " m '---IV---V-

Maturily .laoe.

~ ~~ ~

11 111M aturity slaOes

•Mareh

100 Poreonl.ge806040

2~ ~IV V

September

11 11I IVMaturity slages

V

~ 30,(5 cm(138)_ • (5 cm (69) ~ 30-45 cm(160)_ • (5 cm (521

April Oetober

~ 30'(5 cm (31) _ • (S cm (16)

V11 11I IVMaturily stagee

Percentage:100,-----------•• -------,

80'

60 l(Of,20f~

o!~I

Percentaoe

~ 30-45 cm(lS51_ • (5 cm (73)

November

'1/1; I_~ •I '" -~IV---V--

Maturity .tages

~ 30-(5 cm (811 _ • 4S cm(112)

May

1:~r·nl.ge I:~1I I ~o I---==II---""'m ~.....JIV---V--.J

Maturity It8get

•June Deeember

V

d~]11I IV

Maturily ttagee

Percenlage

ai 30,(5 cm(t541_ • 4S cm(120)~ 30-(5 cm(1831_ '45 cm (39)

Figure 2. Monthly frequencies (in %) of maturity stages of hakemales in the Bay of Biscay from 1987 to 1990. Two size rangeshave been considered. trom 30 to 45 cm and bigger than 45 cm. Inbrackets, the number cf fish analysed by month. (I: Virgin orjuvenile. 11: Beginning of maturation (very early). 111: Advancedmaturation. spawning and partly spent. IV: Full spent, V:resting) .

MONTHLY GSI

Males between 30 and 45 cm Females between 45 and 60 cm

•121110986 7

MONTHS121110

il '"U .lL.- U

4 5 6 7 a 9

MONTHS32

O'5f

GSf

0.4

0.3 r-

Ii

0.2,.II

0.1 rI ,..,-

o .....~------=--------=------_---.:

Males bigger than 45 cm Females bigger than 60 cm

GSI0.81

Iil

0.7,I1

11O,6r- n 'I

1-:'""'""" 1l :10,5 ~ J LJ II !!

I n U0.4\ u i,n ;i

U'I

0,3 ~, ,.,

I ni1 :-

0.2 !- .., , . ;,

I U!.J :!

0.1 r- J iiI I1

0'2 3 4 5 6 7 8 9 10 11 12

MONTHS e9 10 11 12

..,

O~------'------------_--.J234 5 678

MONTHS

0.51-.:....I • II 't

0,4 r : i

I :!! : i

0.31- 'i

iI

0,21- :.

; ;;I !\

GSI

O. 1 ~ :

Figure 3. Monthly variations in the Gonosomatic index (referedto total weight) of male and female hake in the Bay of Biscay.Data from 1987 to 1990. Two size ranges have been considered foreach sex: in males one from 30 to 45 cm and the other one biggerthan 45 cm, in females one from 45 to 60 cm and the other onebigger than 60 cm. For each month, the mean value and the 95%confidence limits are shown.

,..------------------ -- ~~

GONOSO.MATIC INDEXDERIVED FROM LANDINGS DATA

IGS

1768

0,7 1I 5

0,6 r- 13

0,5

0,4

0,3•

1 2 3 4 5 6 7

MONTH8 9 10 11 12

• Figure 4. Monthly variations in a Gonosomatic index (refered togutted weight) derived from landings data (see text) of longliners fishing in the Bay of Biscay during 1990. The numher oftonnes of hake added up each month is indicaterd above eachcolumn.

MALESIGS

0,25

0,2

0,15

0,1

0,05

o~~~20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-60 60-65 65-70

SIZE RANGES (cm)

_ QUARTER 1 ~ QUARTER 2 0 QUARTER 3 _ QUARTER 4 •FEMALES

IGS0,7 1

0,6 l0,5 I

;a>

J~

I;1l-

" "<-~

~

0,1 ~

O -="'" -=" WZI:J1tl .?Oll hnl l"l::.___.--.,a-...o<"--I I I • I I

20-2525-3030-3535-4040-4545-5050-5555-6060-65 65-70 70-75 75-80

0,4

0,3

0,2

SIZE RANGES (cm)

_ QUARTER 1 ~ QUARTER 2 0 QUARTER 3 _ QUARTER 4

Figure 5. Quarterly values of the Gonosomatic index in males andfemales of hake in the Bay of Biscay for each 5 cm lengthinterval. Data from 1987 to 1990.

GONOSOMATIC INDEX.. Males of different sizeand reproductive stage

GSI0,6

0,5 ~---"'--,.._._-,." _. . ." ., ,- _.....•-..__....._.-. -,,-_..- -_. -_. - ,,_.' -' . ..-

0,4

0,3

0,2 ~ _.- nu-

-8- n

f"U

0,1 M ........... :::

n -a- ,...,LT -w-

0A B C A B C A B C A B C

• GONOSOMATIC INDEXFemales of different sizeand reproductive stage

GSI

0,6/ n1f

O'5~0,4 -- n

1f %0,3,

-B-I0,2r

B.. tr0,1 L _. _...'.. ....., trU

• 0A B C A B C A B C A B C

Figure 6. Quarterly values of the Gonosomatic index of males andfemales of different size and reproductive stage in hake of theBay of Biscay. Data from 1987 to 1990. -Mean values and the 95%confidence intervals are shown.

Males:

A: Fish smaller than JO cmB: Fish bigger than 45 cm in maturity stages II, IV and VC: Fish bigger than 45 cm reproducing (Maturity stage III)

Females:

A Fish smaller than 45 cmB Fish bigger than 60 cm in maturity stages II, IV and VC Fish bigger than 60 cm reproducing (Maturity stage III)

HEPATOSOMATIC INDEXMALES

HSI0.6 ~--------------------------------,

0.5

0.4

•

"10.2 - -n

20-2525-3030-3535-4040-4545-5050-5555-6060-65 65-7070-7575-8080-8585-90

LENGTH (ern)

.. Quarter 1 lliJ Quarter 2 c=: Quarter 3 ~ Quarter 4

HEPATOSOMATIC INDEXFEMALES

HSI0.6 ~------------------------------

•

0.5

0.4 J

0.3

I-~ ~ ~

i~

~ { I~ -n :

t~ ~

~

~1i1

- ~ -- ~;

- I~ - ;

I~ I~

• - ~ ..-I~ ~- ~, , , I I I I

20-2525-3030-3535-4040-4545-5050-5555-6060-65 65-70 70-75 75-8080-8585-90

LENGTH (cm)

- Quarter 1 ~ Quarter 2 CJ Quarter 3 _ Quarter 4

Figure 7. Quarterly values of the Hepatosomatic index in malesand females of hake in the Bay of Biscay for each 5 cm lengthinterval. Data from 1987 to 1990.

• HEPATOSOMATIC INDEXMales of different sizeand reproductive stage

HS!0,5....----...,------------------------,

0,4 ,....._-

Jl. 11o 3 ~ U ---------------U·--·1}, -- ------8--0__..-8-__--= .-o-__-B-_

0,2 ~ _--- - ---.--lf--..... tr- '--:e:-'---

0,1 _. '-' -- - ---- --..---..- ------.-------..---.-.

08 CA 8 C A 8 C A 8 C A

• HEPATOSOMATIC INDEXFemales of different sizeand reproductive stage

HSI0,5

0,4 ] --~-B- ~:l-y n

nLJ

-8-trl0,3

1fn ..0-

.~U u

0,2

0, 1 ~ -...... ---..-.-.----.---.-- - _ -_ -- - .

A 8 C A 8 C A 8 C A 8 C

Figure 8. Quarterly values of the Hepatosomatic index of malesand females of different size and reproductive stage in hake ofthe Bay of Biscay. Data from 1987 to 1990. Mean values and the95% confidence intervals are shown.

Males:

A: Fish smaller than 30 cmB: Fish bigger than 45 cm in maturity stages II, IV and VC: Fish bigger than 45 cm reproducing (Maturity stage III)

Females:

A Fish sma11er than 45 cmB Fish bigger than 60 cm in maturity stages II, Iv and VC Fish bigger than 60 cm reproducing (Maturity stage III)

0,8 -,------------------- --,

0,' 1.0,5 - ,......e-.-~""'--- I L

20-2525-3030-3535-4040-4545-5050-5555-6060-65 65-70 70-75 75-8080-8585-90

0,8

0,7

0,6

0,5

0,7

CONDITION FACTORMALES

CF

- I

~I"i'l

~l~

'" ~

~

,

~,i'il

~ I H~

,

11II I I I r I I I I I

20-2525-3030-3535-4040-4545-5050-5555-6060-65 65-70 70-75 75-80 80-85 85-90

LENGTH (ern)

_ Quarter 1 ~ Quarter 2 0 Quarter 3 _ Quarter 4

CONDITION FACTORFEMALES

CF

n

LENGTH (ern)

- Quarter 1 ~ Quarter 2 0 Quarter 3 _ Quarter 4

Figure 9. Quarterly values of the Condition Factor in males andfema1es of hake in the Bay of Biscay for each 5 cm 1engthinterval. Data from 1987 to 1990.

•

•

.. CONDITION FACTORMales of different sizeand reproductive stage

CF0,8

0,7 .~ r

%] un ..., n-er U ...n..

n

1Tu

U-D-

u

0,6

IIIIII

.lJ.... \

U I;

• 0,5 A B C A B CA B C A B c

CONDITION FACTORFemales of different size

and reproductive stage

CF0,8

0,7 '-

-S-

0,61- .

A B

·ntr..D.­u

-D--Pr u

-a- u

nlf

Figure 10. Quarterly values of the Hepatosomatic index of malesand females of different size and reproductive stage in hake ofthe Bay of Biscay. Data from 1987 to 1990. Mean values and the95% confidence intervals are shown.

Males:

lI.:- rish smaller :..h.. i1 JO cmB: Fish bigger than 45 cm in maturity stages II, IV and VC: Fish bigger than 45 cm reproducing (Maturity stage III)

Females:

A Fish smaller than 45 cmB Fish bigger than 60 cm in maturity stages II, IV and VC Fish bigger than 60 cm reproducing (Maturity stage III)

SEX RATIO OF HAKE1990

Probability of females1,----------------------------.-.....-.Y"W1

0,8 - ...---.....-.---

0,6

0,4I

II

0,2

0 1<JlJ..JLIIUUl.A.Il..a..AUI.JUl.JLLIlJUI.JUl.JLLIlJI.........'I,LJl.A.AJIIII...............~................LA.A..&J

20 2224 262830 32 34 363840 42 44 46 48 50 52 54 56 68 80 82 8~ 88 68 70 72 H

LENGTH (ern)

Figure 11. Sex ratio of hake in the Bay of Biscay as derivedfrom the data co11ected fram 1987 ta 1990.

..

•