age and growth of northeast atlantic mackerel … doccuments/2001/j/j4401.pdfon otolith size). the...

INTERNATIONAL COUNCIL FOR CM 2001/ J:44

THE EXPLORATION OF THE SEA Living Resources. Session J

AGE AND GROWTH OF NORTHEAST ATLANTIC MACKEREL

(SCOMBER SCOMBRUS) IN WATERS OF THE NORTH AND

NORTHWEST OF SPAIN (ICES DIVISIONS VIIIC AND IXA NORTH),

1990-2000 By

Begoña Villamor1, Pablo Abaunza1 and Celso Fariña2

1 Instituto Español de Oceanografía. P.O. 240. 39080 Santander. Spain 2 Instituto Español de Oceanografía. P.O. 130. 15080 A Coruña. Spain

e.mail:[email protected]; [email protected]; [email protected]

ABSTRACT

This paper analyses the growth of Northeast Atlantic mackerel (Scomber scombrus

Linnaeus, 1758) in waters of the North and Northwest of Spain (ICES Divisions VIIIc and

IXa North), in the period 1990-2000.

Age was determined by means of the interpretation and counting of growth rings on the

otoliths (sagitta) of 7732 individuals caught during the spawning season by the commercial

fleet and on fisheries research surveys.

Length distributions by age group were compared by applying non-parametric tests

(Kruskal-Wallis and Kolgomorov-Smirnov). Significant differences were found (p<0.05)

among the years analysed, with high variability to age 7.

mailto:[email protected]



The parameters of the von Bertalanffy growth curve were estimated for the whole period

studied (Linf= 44.3 cm, k= 0.228 years -1, t0= -2.70 years) and for each year. The results

obtained were compared with those of other mackerel growth studies in different areas of

the Northeast Atlantic.

INTRODUCTION

Northeast Atlantic mackerel (Scomber scombrus Linnaeus, 1758) is a highly abundant

pelagic species. It supports fisheries of great importance to several European countries, with

annual mean landings of 660,000 t from 1988-1999 (ICES, 2001).

For the purposes of assessment Northeast Atlantic mackerel was, until 1995, considered to

belong to three different stocks, the North Sea stock, the Western stock and the Southern

stock. As a result of tag-recovery surveys carried out in 1994 (Uriarte, 1995; Uriarte and

Lucio, 2001), the term Northeast Atlantic mackerel is now applied in the area which extends

from the south of the Iberian Peninsula (ICES Division IXa) to the north of Norway

(Division IIa), including the North Sea and Skagerrak (Division IIIa) (Fig. 1). It is now

considered to be a single stock divided into three components: the Western component,

made up of individuals that spawn in Western European waters (ICES Areas VI, VII and

VIIIabde), the Southern component, which includes individuals spawning in Southern

European waters (VIIIc and IXa) and the North Sea component, those whose spawning areas

are in the North Sea and Skagerrak (IIIa and IV) (ICES, 1996; 2000).

Mackerel is a migratory species. The pattern of migration in the Northeast Atlantic is well

documented by ichthyoplanktonic surveys (ICES, 1990; ICES, 1999b; Reid, 2001), spatial

and temporal distribution of the fishery (Walsh, 1994; Walsh and Martin, 1986; Lockwood,

1988; Villamor et al., 1994; 1997) and tag-recovery experiments (Walsh, 1981; Rankine and

Walsh, 1982; Bakken and Westgard, 1986; Iversen and Skagen, 1989; Uriarte, 1995; Uriarte

et al., 1999; Uriarte and Lucio, 2001). From these, it was determined that after spawning,

adults of the Southern and Western components migrate to the Norwegian Sea and North

Sea to feed during the second half of each year, returning to the spawning areas at the

beginning of the following year.

Several fleets and gears exploit the mackerel fishery in Southern European waters: handline,

purse seine, trawl and gillnet. This fishery is seasonal. In the first half of the year handline

targets mackerel and lands the bulk of catches from Division VIIIc, consisting of adult fish.

In the second half of the year, catches consist of juveniles coming mainly from Division IXa

(Villamor et al., 1997). Catches have increased in recent years, and in 1998 and 1999

reached a maximum of 44.000 t, 38.000 t of which were in Division VIIIc (ICES, 2001).

Due to its economic importance, the biology of the Northeast Atlantic mackerel is well

studied. Studies of growth are many: the growth of North Sea and Skagerrak mackerel was

studied by Aker (1961), Castelló and Hamre (1969), Kändler (1957), Nedelec (1960),

Postuma (1972) and Skagen (1989), that of Western mackerel by Bolster (1974), Corten and

Van de Kamp (1978), Eltink and Gerritsen (1982), Kästner (1977), Lockwood and Johnson

(1976), Molloy (1964), Skagen (1989) and Steven (1952), and that of the South by Cort

(1982), Cort et al. (1986), De la Hoz and Villegas (1987), Gordo et al. (1982), Gordo and

Martins (1984), Lucio (1997) and Martins (1998). Nevertheless, none of the above carried

out a comparative analysis of growth taking the year factor into account.

The aim of this paper is to examine the growth pattern of Southern component mackerel and

its interannual variability taking into account a wider geographical area and a greater

number of years than the studies previously cited for this component. The growth

parameters obtained are compared with those referred to for other areas of the Northeast

Atlantic.

MATERIAL AND METHODS

Sampling and ageing

During the period 1990 to 2000 biological sampling was carried out on 7732 mackerel

individuals obtained from commercial catches and annual acoustic and bottom trawl surveys

in the N and NW of Spain (Divisions VIIIc and IXa North). Due to the seasonality of the

fishery, samplings were mainly performed in the first half of each year. Most mackerel

samples were analysed fresh.

Fish were measured (total length to the lower cm), weighed (wet weight, g), and their sex

was determined by macroscopic examination of the gonads. Sagitta otolith pairs were

removed for age assignation.

Age was determined by the interpretation and counting of growth rings on otoliths (sagittae).

For the preparation and examination of otoliths, the procedures and criteria described in

Anon. (1987) and ICES (1995) were followed. Whole otoliths were mounted on a blackened

background, covered with resin (Eukit), and illuminated by reflected light. A binocular

microscope was used to observe the banding pattern (20x or 40x magnifications, depending

on otolith size).

The following were assumed in determining age: 1) the date of birth was considered to be 1

January, and 2) each year a translucent and an opaque growth band are deposited on the

otolith. The translucent rings were counted, preferably the anterior part (rostrum) and

posterior part (post-rostrum) of the otolith. When different ages were recorded in the two

areas of the otolith, the greater age was considered, since this is more consistent with the

history of the fish (Anon., 1987; ICES, 1995).

Data analysis

With the results of otolith readings, an annual length-age key was elaborated (ALK, 1990-

2000) and a synoptic ALK for the period studied. Ages up to 14 years were considered, and

those which were greater were accumulated in one group (15+). To estimate the annual

growth rate and explore differences in the growth pattern between males and females in the

period of study, mean weight, mean length and standard deviation were calculated by age

class for each year and sexes combined, and the mean length by age class and sex for the

whole period.

Length distributions at age were compared between years by using non-parametric tests of

Kruskal-Wallis and Kolmogorov-Smirnov, and between sexes and the whole period by

using Kolmogorov-Smirnov test, since conditions for ANOVA were not fulfilled. The

analysis of length distributions at age is one of the best methods to compare growth studies

(Zivkov et al., 1999). In these studies it is common to find the application of non-parametric

tests (Overholthz, 1989; Landa and Piñeiro, 2000). For the comparison between years, firstly

the Kruskall-Wallis test was applied to the length distributions by age groups for all years.

When significant differences were found in certain age groups, the Kolmogorov-Smirnov

test was applied by pairs of years to find the years in which the differences were found

(Sprent, 1993; Heath, 1995).

The mean lengths by age class were fitted to the von Bertalanffy equation, Lt = L∞ [1-exp(-

k(t-t0))], for the estimate of the growth curves. Von Bertalanffy growth curve parameters

were determined by Marquardt non-linear iterative least-squares regression analysis using

SPSS 9.0. Growth parameters were calculated for sexes combined and each year 1990-2000,

and for individual sexes and set period. Index of length growth performance φ’ was

calculated by the equation φ’ = 2 log Linf + log k (Munro and Pauly, 1983) to compare

growth among years and between sexes. To compare growth among areas, the index φ’ was

estimated from growth parameters reported by other authors.

RESULTS

The Northeast Atlantic mackerel otolith sagittae has a pattern of wide opaque bands

alternating with thin translucent bands, and the first opaque bands are notably wider. In

total, 7732 whole otoliths were examined (3596 males, 3850 females and 286

undetermined). Fish ranged in size from 20 to 48 cm, and the oldest fish aged were 18 years.

Mean length by age group in each year (1990-2000) estimated from data pooled (Table 1)

indicated that the growth rate was high in the first two years of the life of the fish before

slowing down in the third. From the fourth year of age a significant inhibition in growth was

observed. There were slight differences in the mean length and mean weight by age class

among years, although no trends were observed throughout the period studied (Table1, Fig.

2).

Length distributions by age group presented interannual variability (Kruskal-Wallis,

p<0.001 in age groups 1 to 7; p<0.01 in age groups 8 to 10. Kolgomorov-Smirnov between

pairs of years, p<0.05 in 33% of cases up to age 7, p<0.05 in 5 % of cases in ages 8 to 10,

Table 2).

Mean length by age group from data pooled for the years 1990-2000 differed slightly

between the sexes (Table 3). Females were greater than males (except in the 15+ group)

with differences ranging from 0.1-1.2 cm. There were significant differences between sexes

in some length distributions at age (Kolgomorov-Smirnov, p<0.05, ages 4 to 7, 9 and 11,

Table 2).

The von Bertalanffy equations fitted well to the data observed (R2≥0.97 in all cases, Table 4,

Figure 3). The growth parameters of the von Bertalanffy model estimated for the sexes

combined and the whole period were Linf = 44.3 cm, k = 0.228 year –1 y t0 = -2.70 year. L∞

(44.3) was slightly higher than the mean length of the oldest individuals (15+ group = 43.8

cm). In the time series, the lowest values of Linf (43.1 cm) and the highest of k (0.277 year-

1) came in 1999, and the highest Linf (46.0 cm) in 1991, corresponding to a relatively low

value of k (0.164).

The parameters estimated for the data set for 1990-2000 were Linf = 44.0 cm, k = 0.226

year –1 and t0 = -2.78 year for males and Linf = 44.4 cm, k = 0.232 year –1 and t0 = -2.63 year

for females (Table 4). The respective growth curves are shown in Figure 4.

The index φ’ for sexes combined ranged from 2.42 to 2.71 during 1990-2000. The index

was very similar between males and females (2.63 and 2.65 respectively) (Figure 5).

DISCUSSION

The first studies of Northeast Atlantic mackerel age determination were controversial for

ages over 5 years. Steven (1952) stated that 25% of age readings using otoliths

corresponding to fish of more than 6 years were not reliable. For Postuma (1972) age

determination in fish of up to 5 years was reliable, while in older fish it was not. For Hamre

(1978) age determination was only reliable up to 7 years. Later, with the aim of unifying

mackerel age determination criteria several international otolith exchanges and workshops

were held (Dawson, 1986; Anon., 1987; Villamor and Meixide, 1995), but the difficulties in

defining the growth pattern of older fish were not solved. In 1995 (ICES, 1995) growth to

age 8 was validated for the first time, reading otoliths of fish of known age obtained from

Norwegian tag-recovery experiments. In this workshop the oldest ages could not be

validated by this method and the modal age of the ages assigned was assumed to be the

actual age. One of the recommendations suggested was that for the assessment of the

Northeast Atlantic mackerel stock the matrix of catches should range up to age 11 with a

12+ group. The validation of the methods used to determine age are of great relevance

(Beamish and McFarlane, 1983) as the use of incorrect growth rates can lead to large errors

in the estimates of stock production (Ricker, 1989). In this paper the age determination

criteria established by ICES (1995) were followed and ages of up to 18 years were assigned

(considering the 15+ group) with the aim of determining the growth parameters.

During the period of study (1990-2000) a significant interannual variability was detected

between the length distributions by age group, although when viewed graphically the

differences are not very appreciable. The length distribution of an age class is partly

determined by the temporal difference (during the spawning season) of the moment when

the larvae hatch, food availability, environmental conditions, etc. All these factors may

give rise to different growth rates (Wooton, 1990). In the area of study, primary production

is, to a great extent, determined by upwelling processes (Blanton et al., 1984; Lavin et al.,

1998) which may have a great influence on juvenile growth (Cushing, 1995). During their

migration, adults are subject to highly variable environmental conditions, which influence

their growth and spawning potential (Lam, 1983; Weatherley and Gill, 1989).

Due to the variability in the length range by age group among years, mean length was

estimated in order to calculate the growth parameters of the set of all years, to obtain an

indicator of the mean growth of mackerel in the area. The indices φ’ estimated for each year

are fairly similar, those of 1991 and 1992 being the lowest and having the greatest

confidence interval. The calculation of growth parameters was performed without age group

1 in 1992 and with a reduced number of individuals in 1991, which is probably the cause of

these differences.

Despite numerous references to Northeast Atlantic mackerel growth, few indicate

differential growth between males and females. Eltink (1987) found differences in length

and mean weight of males and spawning females but attributed them to temporal differences

in maturity. In the present paper the growth rate of females was significantly greater than

that of males from age 4, and no significant differences were found up to age 3. For certain

geographical areas included in our study area, different growth between males and females

has already been indicated (De la Hoz and Villegas, 1987; Lucio 1997). Differences in

growth between sexes have also been cited in Northwest Atlantic mackerel (Neja,1990).

The mackerel growth curves of the southern area estimated by other authors show quite a lot

of similarity (Table 5, Fig. 6). The greatest lengths at age were estimated by Gordo et al.,

(1984). This is probably due to differences in age interpretation with respect to other authors

(Table 5).

Unlike other authors who studied the Southern mackerel component, the growth curve

calculated in this paper was based on data with a greater coverage of the area of distribution

of this component and over a longer period of years. If we compare the curve we obtained

with those cited for the Western and Northern components (Table 5, Fig. 7), noteworthy

differences appear with that estimated by Kästner (1977) in waters of the West of Scotland

(Division VIa).

In general, from age 6 mackerel growth is observed to be faster in the southern area. Kästner

(1977) described two groups of mackerel in the West of Scotland based on growth rates,

one group of rapid growth and another of slow growth. Corten and Van de Kamp (1978)

also described differences in the growth pattern in the Celtic Sea, indicating that western

mackerel from the British Isles did not constitute a homogeneous stock.

The rapid growth group follows the pattern of growth described for mackerel in the North

Sea (Nedelec, 1960; Aker, 1961) and the slow growth group follows that proposed by

Steven (1952), Nedeler (1960), Molloy (1964), and Lockwood and Johnson (1976) in the

Celtic Sea, Northwest of Ireland and the English Channel. Nevertheless, Eltink and

Gerritsen (1982) and Eltink (1987) discard the hypothesis that there are two sub-populations

in the Western area and postulate an alternative explanation, that the growth differences are

due to gradual spatial temporal changes in the length at age during migration. The largest

fish of a certain age reach spawning areas earlier and also leave for feeding areas earlier than

smaller ones, which leads to successive changes in length and weight at age. Eltink and

Gerritsen (1982) calculated a growth curve for mackerel of the Western area in Divisions

VIa and VIIbj, which was intermediate between the two groups described by Kästner

(1977). For this reason they considered that it represented mackerel growth in the Western

area. Skagen (1989) estimated a growth curve using a modified von Bertalanffy equation.

Using data of Norwegian catches, he concluded that mackerel caught in the North Sea are

generally larger than those of the Western area. The values of the index φ’ referred to for the

different areas also show considerable similarity, with the exception of the slow growth

observed by Kästner (Fig. 8).

Fish growth is characterised by its variability and the same species can show different

growth patterns. The factors causing this variability are many and may be exogenic (i.e.

environmental, density-dependent) or endogenic (i.e. genetic), (Wooton, 1990). Parrish et

al., (1985) analysed the variability of anchovy growth, attributing the causes to the variation

in spawning periods, the composition at age, migration of specific lengths or a combination

of these factors. The growth of Northeast Atlantic mackerel may be influenced by this kind

of factor. The spawning season occurs earlier in the south of Europe than in the north

(Iversen, 1981; Lockwood et al., 1981; Jorge et al., 1982; Solá et al., 1990; 1994). Dawson

(1991), referring to the spawning season, found that the radius of the first otolith ring was

greater in mackerel from the south of the Bay of Biscay. The catch composition at age also

varies in the different areas of the Northeast Atlantic (ICES, 1996, 1997, 1998, 1999a, 2000,

2001). As previously stated, Eltink (1982, 1987) related differences in growth with gradual

changes in length at age in time and space during migration by Northeast Atantic mackerel

in European waters.

Another cause of variability in mackerel growth may be the effect of population density, as

found by Mackay (1973), Overholtz (1989) and Neja (1995) in the Northwest Atlantic,

above all in the youngest ages. In the Northeast Atlantic, Agnalt (1989) also found a

negative correlation between mean fish length at 1 and 2 years of age and North Sea

mackerel stock biomass in the 1970’s. Northeast Atlantic mackerel has not shown great

variations in annual classes in the last fifteen years (ICES, 2001) and these effects are more

difficult to investigate.

The whole of these factors makes the pattern of Northeast Atlantic mackerel growth variable

in time and space. Therefore, the use of length distributions for age assignation is

questionable (Skagen, 1989) and it would be appropriate to make more effort in age

determination through the analysis of hard structures such as otoliths.

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Table 1: Mean length at age (TL, cm) and standard deviation (SD) determined from mackerel otolith readings (n: number of samples,

sexes combined) from ICES Divisions VIIIc and IXa, sampled from 1990 to 2000.

Age TL SD n TL SD n TL SD n TL SD n TL SD n TL SD n1 25.2 1.50 73 25.5 1.41 7 25.1 1.18 43 25.4 0.98 44 26.1 1.40 312 29.2 1.88 46 30.3 0.83 13 31.9 0.98 7 30.3 2.99 9 28.8 1.57 49 30.8 1.79 443 33.1 1.89 47 32.2 1.11 46 33.3 1.77 94 34.1 1.29 11 32.2 2.03 55 33.6 1.40 764 34.9 1.59 62 34.6 1.68 55 34.5 1.57 83 35.6 1.44 113 36.3 2.19 75 35.6 1.67 495 36.6 1.94 86 35.4 1.28 42 36.2 1.59 87 36.5 1.68 61 37.3 1.87 148 36.8 1.74 286 38.0 1.76 99 37.4 1.94 24 37.5 1.59 40 37.6 1.65 81 38.5 1.69 110 38.0 2.32 407 40.2 1.42 23 38.6 1.36 8 38.3 1.54 22 39.2 1.80 46 39.4 1.74 83 39.3 1.76 368 40.5 1.93 57 38.8 1.49 8 39.2 1.99 22 39.8 2.05 22 40.1 1.46 39 40.1 1.83 439 41.2 1.65 55 39.6 1.96 9 39.7 1.72 9 41.4 1.32 23 40.7 1.48 30 40.5 2.22 1610 41.0 1.59 17 41.5 1.60 8 40.1 1.14 5 40.4 2.08 18 40.9 1.86 16 41.9 1.58 1711 41.9 2.07 5 42.5 2.00 3 40.4 1.83 9 41.3 1.19 12 42.3 2.12 12 41.4 2.25 1812 42.2 1.89 7 44.5 1.41 2 42.1 1.82 5 43.5 1.51 8 42.9 1.14 5 43.1 2.01 1013 46.5 1.41 2 0 40.0 0.71 2 43.3 1.09 13 41.8 1.53 3 44.1 1.52 514 42.5 1 43.5 1.41 2 0 43.4 1.64 8 43.0 1.76 6 44.0 1.64 6

15+ 45.5 1 43.5 1 45.8 2.52 3 43.8 1.97 12 44.5 1 43.9 1.99 7Total 581 228 388 480 676 426

Age TL SD n TL SD n TL SD n TL SD n TL SD n TL SD n1 24.5 1.31 57 24.3 1.36 300 25.4 1.18 170 23.4 1.03 75 24.4 1.53 290 24.6 1.47 10902 32.2 1.37 6 28.7 1.57 160 29.8 1.00 141 30.0 1.10 53 29.0 2.22 75 29.5 1.74 6033 33.2 1.26 58 32.9 2.34 46 32.3 1.57 167 32.2 1.41 46 32.4 1.63 289 32.7 1.71 9354 35.2 1.56 129 35.0 1.62 254 34.7 2.05 82 34.7 1.81 132 35.2 1.92 127 35.1 1.78 11615 37.2 1.86 39 36.9 1.61 168 36.8 1.64 155 37.3 1.98 68 36.4 2.12 232 36.7 1.86 11146 39.2 2.06 22 38.1 1.78 55 37.7 1.55 128 38.1 1.63 101 38.5 1.63 103 38.0 1.75 8037 39.7 1.84 61 39.7 1.54 69 38.5 1.73 62 38.7 1.51 65 39.1 1.36 141 39.2 1.66 6168 40.5 1.87 35 40.1 1.63 71 40.3 1.42 36 39.7 1.99 25 39.7 1.38 66 40.0 1.74 4249 41.1 1.83 41 41.2 1.40 75 40.2 1.73 41 41.1 2.01 19 39.5 2.03 18 40.8 1.74 33610 41.9 2.52 20 42.0 1.50 55 41.3 1.75 38 41.8 1.29 26 41.8 2.11 17 41.5 1.80 23711 41.9 2.06 17 42.8 2.02 33 41.6 1.68 17 42.3 1.35 18 41.9 1.50 11 42.0 1.91 15512 42.9 2.55 10 43.5 1.64 33 41.9 1.70 20 41.8 1.36 12 42.3 1.23 10 42.7 1.80 12213 45.5 0.00 2 43.6 1.55 8 43.2 1.15 3 43.6 1.07 7 41.7 1.30 5 43.3 1.69 5014 43.0 0.71 2 44.3 1.10 5 43.5 2.00 3 41.5 1 42.3 0.84 5 43.3 1.48 39

15+ 44.5 1.41 5 44.7 1.55 10 43.0 2.12 2 43.2 1.15 3 44.5 2.83 2 44.2 1.78 47Total 504 1342 1065 651 1391 7732

1994 19951990 1991 1992 1993

2000 Total 1990-20001996 1997 1998 1999

.

Table 2: Comparisons of length distributions by age group of mackerel, 1990-2000. (K-

W:Kruskal-Wallis test; K-S: Kolmogorov-Smirnov test;(p<0.05*;p<0.01**

;p<0.001***; ns: not significant)

Table 3: Mean length at age (TL, cm) and standard deviation (SD) for male and female

determined from mackerel otolith readings (n: number of samples) from ICES

Divisions VIIIc and IXa, sampled during 1990-2000.

Age TL SD n TL SD n1 24.6 1.47 487 24.7 1.48 4912 29.4 1.79 255 29.7 1.64 2983 32.6 1.68 462 32.7 1.71 4304 35.0 1.74 619 35.3 1.81 5235 36.5 1.87 549 37.0 1.84 5546 37.8 1.73 354 38.3 1.75 4367 39.0 1.72 275 39.3 1.60 3368 39.8 1.79 197 40.2 1.76 2239 40.5 1.66 141 41.2 1.72 18910 41.3 1.95 93 41.7 1.70 13811 41.4 1.94 72 42.5 1.72 7712 42.4 1.54 41 43.0 1.83 7613 42.4 1.30 21 43.6 1.69 3114 43.3 1.47 17 43.4 1.55 20

15+ 44.3 2.03 13 44.2 1.63 28Total 34.7 5.34 3596 35.4 5.61 3850

Male Female

Table 4: Von Bertalanffy growth parameters of mackerel (Linf, k, and t0) and their standard

error (SE), calculated for sexes combined from data of annual mean lengths at age and

pooled data 1990-2000, and for each sex from pooled data (R2: correlation coefficient,

n: number of samples).

Linf SE K SE t0 SE R2 n

1990 45.4 1.129 0.204 0.035 -3.09 0.741 0.97 581

1991 46.0 1.213 0.164 0.025 -4.20 0.757 0.98 228

1992 45.2 1.601 0.130 0.028 -7.38 1.505 0.99 388

1993 44.0 0.693 0.227 0.029 -2.96 0.542 0.98 480

1994 43.7 0.510 0.250 0.024 -2.45 0.378 0.99 676

1995 44.9 0.635 0.198 0.021 -3.64 0.498 0.99 426

1996 44.5 0.830 0.239 0.036 -2.68 0.620 0.97 504

1997 45.2 0.376 0.220 0.013 -2.62 0.233 1.00 1342

1998 44.0 0.384 0.217 0.014 -3.07 0.291 0.99 1065

1999 43.1 0.474 0.277 0.026 -1.98 0.333 0.98 651

2000 43.4 0.530 0.250 0.025 -2.38 0.384 0.98 1391

1990-2000 44.3 0.334 0.228 0.013 -2.70 0.233 1.00 7732*

Male 44.0 0.437 0.226 0.017 -2.78 0.313 0.99 3596

Female 44.4 0.299 0.232 0.012 -2.63 0.208 1.00 3850

* indeterminate included

Table 5: Von Bertalanffy growth parameters, index φ’ and expected length at age of the mackerel from different Eastern Atlantic areas

(ICES Divisions).

Period of studiesICES Area (months) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+ Linf K t0

(1) Division VIa 1973-1976 23.3 25.1 26.5 27.6 28.6 29.3 29.9 30.4 30.7 31.0 32.27 0.221 -4.767 2.36(IV-VI)

(2) Division VIa 1973-1976 30.5 32.7 34.5 35.8 36.8 37.5 38.1 38.5 38.9 39.1 39.96 0.272 -4.293 2.64(VII-VIII)

(3) Divisions VIa, 1981 25.1 28.5 31.1 33.1 34.7 35.9 36.8 37.5 38.0 38.5 39.90 0.259 -2.840 2.62 VIIb - VIIj (III-VII)

(4) North Sea and 1960-1985 23.1 29.0 32.2 34.0 35.3 36.3 37.1 37.8 38.5 39.2 39.9 40.6 41.3 42.0 0.750 -0.600 - Western Area

(5) Division IXa 1981 21.1 26.5 30.6 33.8 36.2 38.1 39.5 40.5 41.3 42.0 42.4 43.94 0.272 -2.404 2.72 (Portugal coast)

(6) Division IXa 1981-1983 23.8 28.7 32.4 35.2 37.3 39.0 40.3 41.2 42.0 42.5 43.0 43.3 43.5 43.7 43.9 44.0 44.36 0.268 -2.874 2.72 (Portugal coast)

(7) Division VIIIc 1982-1983 23.7 28.1 31.5 34.1 36.2 37.7 38.9 39.9 40.6 41.2 41.6 41.9 42.2 42.4 42.5 43.07 0.258 -2.095 2.68 (Cantabrian Sea) (II-VI)

(8) Division VIIIc 1985-1986 25.1 28.6 31.5 33.8 35.8 37.3 38.6 39.7 40.6 41.3 44.50 0.199 -3.180 2.60 (Asturian coast)

(9) Divisions VIIIabc 1987-1993 25.0 28.7 31.8 34.3 36.4 38.1 39.5 40.6 41.5 42.3 42.9 43.5 43.9 44.2 44.5 45.88 0.196 -3.026 2.62 (Basque Country) (II-V)

(10) Division IXa 1990-1996 21.4 26.0 29.7 32.7 35.0 36.9 38.4 39.6 40.6 41.3 41.9 42.4 42.8 43.1 43.3 43.5 44.30 0.227 -2.900 2.65 (Portugal coast)

(11) Divisions VIIIc-IXa North 1990-2000 25.2 29.1 32.2 34.7 36.6 38.2 39.4 40.4 41.2 41.8 42.3 42.7 43.0 43.3 43.5 44.28 0.228 -2.700 2.65 (Spanish coast) (I-VI)

Age (years) ParametersΦ

(1) (2) Kästner, 1977 (5) Gordo et al., 1982 (8) De la Hoz and Villegas, 1987 (11) Present work

(3) Eltink and Gerritsen, 1982 (6) Gordo and Martins, 1984 (9) Lucio, 1997

(4) Skagen, 1989 (7) Cort et al., 1986 (10) Martins, 1998

VaIIa

Vb

IVa

IVb

IVc

VIb VIa

XIIVIIc

VIIkVIIg

VIIhVIIe

VIIIdVIIIe

X

IXb IXa

VIIIa

VIIIb

VIId

VIIaVIIb

IIIa

VIIj

VIIIc

IXaNorth

60º N

55º N

50º N

45º N

40º N

STUDY AREA

Figure 1: Location of the study area and ICES Areas .

400

450

500

550

600

650

700

750

800

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Years

Mea

n w

eigh

t (g)

8 9 10 11 12 13 14 15+

10

110

210

310

410

510

610

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Years

Mea

n w

eigh

t (g)

1 2 3 4 5 6 7

Figure 2: Mean weight at age (g) of mackerel from ICES Divisions VIIIc and IXa, 1990-2000.

Upper figure, ages 1 to 7 and lower figure, ages 8 to 15+.

0

5

10

15

20

25

30

35

40

45

50

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age (years)

Tota

l Len

gth

(cm

)

Observed Mean Length Growth curve

Figure 3: Von Bertalanffy growth curve fitted to mean length at age data for sexes combined and

the whole period 1990-2000, and observed mean length at age (+/- SD).

0

5

10

15

20

25

30

35

40

45

50

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age (years)

Tota

l Len

gth

(cm

)

Female Male

Figure 4: Von Bertalanffy growth curve fitted to mean length at age data for males and females

and the whole period 1990-2000.

1.80

2.00

2.20

2.40

2.60

2.80

3.00

3.20

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Gro

wth

Per

form

ance

Inde

x

1.80

2.00

2.20

2.40

2.60

2.80

3.00

3.20

Male Female

Gro

wth

Per

form

ance

Inde

x

Figure 5: Values of Growth Performance Index (φ’) and confidence intervals. Upper graph

shows annual values (1990-2000) for sexes combined and lower graph shows values for males

and females for the whole period.

0

10

20

30

40

50

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+

Age (years)

Tota

l Len

gth

(cm

)

1 2 3 4 5 6 7

Southern Area

Figure 6: Theoretical growth rate of the southern component of Northeast Atlantic mackerel,

according to the von Bertalanffy equation calculated by different authors: 1. Gordo et al.

1982 (Division IXa, Portuguese waters); 2. Gordo et al., 1984 (Division IXa, Portuguese

waters); 3. Cort et al., 1986 (Division VIIIc, Cantabrian Sea); 4. De la Hoz et al., 1987

(Division VIIIc, coast of Asturias); 5. Lucio, 1997 (Divisions VIIIbc, Basque country

coast); 6. Martins, 1998 (Division IXa, Portuguese waters); 7. Present work (Division

VIIIc and IXa north).

0

10

20

30

40

50

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+

Age (years)

Tota

l Len

gth

(cm

)

1 2 3 4 5

Southern, Western and North Sea Area

Figure 7: Theoretical growth rate of Northeast Atlantic mackerel in different areas, according to

the von Bertalanffy equation calculated by different authors: 1. Southern Area (Division

VIIIc and IXa north) (present work); 2. Western Area (Division VIa) (Kästner, 1977); 3.

Western Area (Division VIa) (Kästner, 1977); 4. Western Area (Division VIIb and VIIj)

(Eltink & Gerritsen, 1982); 5. Northern and Western Area (Skagen, 1989).

1.80

2.00

2.20

2.40

2.60

2.80

3.00

3.20

(1) VIa

(2) VIa

(3) VIa,

VIIbj

(5) IX

a

(6) IX

a

(7) VIIIc

(8) VIIIc

(9) VIIIa

bc

(10) IX

a

(11) V

IIIc- IX

aN

Gro

wth

Per

form

ance

Inde

x

ICES Areas

Figure 8: Values of Index φ’ in different areas of the Northeast Atlantic. See Table 5 for

corresponding Divisions and authors.

age and growth of northeast atlantic mackerel … doccuments/2001/j/j4401.pdfon otolith size). the...

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