Larrañeta, M.G. (Manuel Gómez)

Paz, X. (Xabier)

English

Repositorio Institucional Digital del IEO

NOT TO BE CITED WITHOUT PRIOR REFERENCE TO THE AUTHOR(S)  Northwest Atlantic Fisheries Organization Serial No. N1653   NAFO SCR Doc.69/72            SCIENTIFIC COUNCIL MEETING - SEPTEMBER 1989  Cod in Div. 3N0I Year-Class Variations and the Abundance of Other Commercial Fish by 7. Paz and M. G. Larrifieta Institute de Investigations Marinas, Eduardo Cabello 6 36208 Vigo, Spain INTRODUCTION Physical-environmental factors govern the fluctuations of ecosystems, especially the long term changes, but how these fluctuations effect the species is not clear yet. It can be expected that the immediate factors in the dynamics of a species are essentially biological ones through the feeding process, and that physical factors are remote causes of these relation-ships. Perhaps multispecific models have the defect of limiting themselves to trophic relationships, ignoring the fact that these depend, at least in the long term, on physical environ-mental factors. SPECIAL SESSION ON CHANGES IN  FISH In this paper we explore the possible biological relation-ships of cod (Gadus morhua ) with other fish of commercial impor-tance, with no other reason for selection than to have a major amount of available data. To be exact, cod year class variations are compared with variations of yellowtail flounder (Limanda fermiginea ) and American plaice ( llippoglossoides platessoides) spawning biomasses, mackerel ( Scomber scombrus ) age 1+ group abundances, and redfish ( Sebastes sp.) densities. Adults of these species are not considered to be predators of eggs and larvae of cod, though they can be of their young. The biomasses of adult fishes of these species are considered as an index of their egg and larval abundances. There will be competition and predator-prey relationships between the 0-age groups and young individuals of cod and these species. The sign of correlations will indicate the nature of these relationships. The possibility of trophic relationships between 0-age groups and juveniles belonging to cod and other species is explored relating every cod year-class size to the biomass of the other species, from one to three years before (negative lag) or after (positive lag) the year of the cod year class. Finally, the cod year class is also related to the cod spawning biomass - 2 which gave rise to it, and to the cod spawning biomass lagged from one to three years before or after. The cod year-class size is measured at time of recruitment according to VPA; in the usual practice at three years old (N 3 ). MATERIAL AND METHODS 'The cod recruitment (N 3 ) and spawning biomass (B 64. ) data have taken from Baird and Bishop (1988). The yellowtail flounder spawning biomass data from Brodie and Walls (1987), getting .higher correlation coefficients using table 23 than using table 24 of the authors. The American plaice spawning biomasses (B 114. ) have been taken from Brodie (1988). The redfish abundances have been taken from Power and Atkinson (1987), using figure 3 of the authors on catch rates in NAFO Div. 3LN during 1959-1986, the values used being the mean abundances calculated from three consecutive years. Finally, the mackerel biomasses (B 14. ) have been taken from Anon. (1986), referred to the Labrador-North Carolina area. All these data are shown in tables 1-5. When a 0-lag is used, the year class of recruitment is related to the spawning biomass of the species in the same year as the cod year class, that is to say, three years before recruitment (N 3 ). RESULTS Correlations between cod recruitment and cod spawning ' biomasses are shown in table 6; no coefficient appears to be significant, the only exception a slight significance for 0-lag. Correlation coefficients between cod year-class size and redfish abundance are shown in table 7, none of them being significant. Also, no correlation coefficients between cod recruitment and yellowtail flounder spawning biomass .(table 8) appear significant, except with a +3 years lag. On the contrary, correlations between cod recruitment and mackerel abundance (table 9) are negative and slightly significant, and with American plaice biomass are positive and strongly significant (table 10) with 0. +1, +2 and +3 years lags. DISCUSSION The relationship between cod recruitment and its spawning biomass (table 6) corresponds to the complex problem of the stock-recruitment question, which is not the object of this study. Simply, these correlations are made to follow the same method as in the case of the other species abundances. Never-theless, the absence of negative correlations with negative lags (cod spawning biomass before the year class) indicates that cannibalism does not determine year class size. There is no significant relationship between redfish and yellowtail flounder abundances, on the one hand, and cod year class size on the other. On the contrary, a negative correlation appears with mackerel suggesting that this species is a cod predator. These correlations extend also to +1 and +2 year lags, but predation by mackerel on 1 and 2-age groups of cod seems anadmissible because of the excessive size of the prey. It is more reasonable to think that mackerel abundance will remain similar during the following two years to that of the 0-lag year, giving an unreal biological relationship. According to Koslov at al. (1978), several authors have noted the influence of mackerel abundance on Gadidae and herring. recruitment in areas from Georges Bank .to the Gulf of Saint Lawrence, which has been attributed to predation by mackerel. In contrast"one of us (BSez and Larrafieta, 1987) has found that silver hake year class sizes on the Scotian Shelf are positively correlated with mackerel biomasses, suggesting • predation on mackerel 0-age group by silver hake 0-age group. The most spectacular results (table 10) are obtained with the American plaice. The positive and high correlations suggest 'a great predation of 0-group cod on American plaice spawning products and resulting 0-group fish, which occurs throughout the cod pre-recruitment period. Significant correlations with -1 and -2 lags may be because of American plaice spawning biomasses will have a previous similar abundance to that corres-ponding the year with lag 0 year. 	In a previous paper (Larrafieta, 1986) it was shown that variations of cod Div. 3NO and American plaice year class sizes were inversely related; which is coherent with the present results. In fact, if 0-group cod prey actively on 0-group American plaice, or both are strenuous competitors, they would mutually exclude the simultaneous production of the highest year classes possible for each species. In the literature we find data that•permit us to accept that the American plaice can be an important prey of cod during the 0-age group and pre-recruitment stages. For example, Marak (1960) studied the feeding habits of haddock and cod postlarvae (19-23 mm) on Georges Bank and found that 33% of the stomach content were fish eggs. Palsson (1983), in Iceland waters - in October and November - cited the predation of cod on American plaice. The stomach content weigth in cod ranging from 15 to 19 cm was formed by 16% of American plaice, and 9% in those of 25-29 cm. Daan (1973) cites the Pleuronectidae (85% timanda /imanda) as food of cod 10-19 cm long in the North Sea. Hawkins (1985) also quotes the Tleuronectidae, without being more speci-fic, as food of young cod (13-43 cm). These studies support the idea of strong predation by cod on the 0-group American plaice and also an active predation on juveniles of this species. The data available on cod and American plaice distribution in Div. 3N0 favour this idea. The northern and southeastern -slopes of •the Grand Bank support the largest American plaice concentration in the Northwest Atlantic (Pitt,1966). According to Wells et al. (1988), cod and American plaice have similar distributions on the Grand Bank, though cod does not tolerate temperatures less than -1QC as well. Yellowtail flounder is distributed •in shallower zones and warmer waters, with tempera-tures always above 19C. On the south of the Grand Bank a sepa-ration between American plaice pre-recruits and adults is not observed -(Walsh, 1982; Walsh and Brodie, 1988) as it is in Europe, because the oceanographic conditions tend to retain the spawning products near the spawning area (Nevisky, 1973). The metamorphosed juvenile individuals ( >20 mm) occupy the same areas as the spawning adults. American plaice larvae concentrate almost exclusively on the Southeast Grand Bank, in waters colder than 1QC. One other distinguishing characteristic of yellowtail flounder larvae is that they are distributed in waters warmer than 1QC. According to Kenneth at al. (1988) American plaice appear not to migrate vertically during either the larval or pelagic juvenile phase, and were always collected below the pycnocline with an average depth of about 30 in. The poor disper-sion of American plaice could make it more vulnerable. These considerations suggest two conclusions: a) It is not possible to obtain cod and American plaice year classes of the highest level simultaneously. b) The presence of an abundant American plaice spawning biomass promates high cod recruitment. ACKNOWLEDGEMENT We are indepted to Dr. T. Wyatt for critically reviewing this manuscript. REFERENCES Anon. 1986. Status of the fishery resources off the North- eastern United States for 1986. NOAA Tech. Mem. MNFS/NEC 43. 130 p. Baez, M. and M.G. Larrafieta. 1987. Fishery ecology of silver hake in Divisions 4VWX. NAFO SCR Doc., No.11, Ser. No.1280, 19 p. Baird, J.W. and C.A. Bishop. 1988. Assessment of the cod stock in NAFO Div. 3N0. NAFO SCR Doc., No. 19, Ser. No. N1455, 47 p. Brodie, W. B. 1988. An assessment of the American plaice stock in Division 3LNO.. NAFO SCR Doc., No. 37, Ser. No. N1477, 51 p. Brodie, W. B. and S. J. Walsh. 1987. An assessment of the yellowtail flounder stock in Div. 3LNO. NAFO SCR Doc., No. 44, Ser. No. N1331, 24 p. Daan, N. 1973. A quantitative analysis of the food intake of North Sea cod, Gadus morhua. Netherlands J. Sea Res., 6(4): 479-517. Hawkins, A. D., N. M. Soofiani and G. W. Smith. 1985. Growth and feeding of juvenile cod. J. Cons. int. Explor. Mer. 42(1): 11-32. Kenneth, T. F., J. E. Carscaden and W. C. Legget. 1988. Compa-rative analysis of factors underlying of capelin and flatfish larvae on the southern Grand Banks. ICES, Early life history Symposium, Paper No. 107, 11 p. + 10 fig. Koslow, J. A., K. R. Thompson and W. Silvert. 1987. Recruitment to Northwest Atlantic cod (Cadus morhua ) and haddock (Melanogrammus aeglefinus) stocks: influence of stock size and climate. Can. J. Fish. Aquat. Sci., 44: 26 - 39. Larrafieta, M. G. 1986. Dynamics of yellowtail flounder and American Plaice populations in the Grand Banks. NAFO Sci. Coun. Studies, 10: 35- 45. Nevinsky, M. M. and V. P. Serebryakov. 1973. American plaice, Hippoglossoides plateasoides plateasoides Fabr., spawning in the Northwest Atlantic area. IMF Res. Bull., 10: 23-36. Pfilsson, 0. K. 1983. The feeding habits of demersal fish species in Icelandic waters. Rit Fiskideildar , vol. VII (1): 60 p. Pitt, T. R. 1966. Sexual maturity and spawning of the . American plaice, Hippogiossoides platessoides (Fabricius), from New- foundland and Gran Bank areas. J. Fish. Res. Board. Can., 23: 651-672. Power, D. and D. B. Atkinson. 1987. Redfish in NAFO Divisions 3LN. NAFO SCR Doc., No. 58, Ser. No. N1347, 18 p. Walsh, S. J. 1982. Distribution and abundance of pre-recruit and commercial-sized American plaice on the Grand Bank. J. Northw. Atl. Fish. Sci., 3(2): 149 - 157, Walsh, S. J. and W. B. Brodie. 19 6 8. American plaice distribu-tion on the Nose and Tail of the Grand Bank. NAFO SCR Doc., No. 28, Ser. No. N1464, 12 p. Wells, R., W. B. Brodie, C. A. Bishop and J. W. Baird. 1988. Distribution and abundance of three fish species on the Grand Bank in relation to depth and temperature of the water. NAFO SCR Doc., No. 94, Ser. No. N1546, 26 p. Table 1.- Cod Div.3110: recruitment (N3) and spawning biomass 	(36 + ).From Baird and Bishop 	(1938): Year class Recruits Biomass (10 3 ) (tons) 1956 53690 1957 53183 - 1958 82103 - 1959 107740 89675 1960 78245 73485 1961 112308 90569 1962 162565 81108 1963 210010. '88649 1964 183244 113136 1965 100519 120736 1966 127670 104829 1967 80340 93442 1968 34402 82672 1969 62130 80264 1970 35153 81224 1971 37006 88151 1972 23398 76144 1973 27996 76244 1974 46587 53972 1975 45802 19545 1976 21151 12711 1977 25669 17604 1.972 36031 21234 1979 23395 22761 1920 36816 62439 1981 58513 93261 1902 46439 112095 1933 9585 126E151 1924 23574 127189 1925 - 140613 1986 - 156649 Table 2.- Yellowtail flounder Div.3LN0: spawning stock biomass (86.1.). Front tables 23 and 24 of Drddie and Walls (1987). year t. 23 (tons) t. 24 (tons)    1968 25926 25926 1969 40372 40372 1970 50199 50199 1971 48747 48747 1972 33846 33846 1973 24049 24049 1974 21034 21034 1975 18159 18159 1976 19152 19152 1977 18809 18809 1978 21776 21776 1979 17413 17412 1980 26322 26322 1981 20350 20337 1982 16838 16642 1983 30565 28894 1984 53811 47448 1985  63087 50550 1986 39536 23722 Table 3.- Redfish Div. 3LN: average catch rate of three years. From figure 3 of Power and Atkinson 	(1987). flidle year Catch rate 1960 1.15 1961 1.21 1962 1.28 1963 1.25 1964 1.04 1965 	, 1.11 1966 1.08 1967 1.06 1968 0.89 1969 0.90 1970 1.01 1971 1.04 1972 1.06 1973 1.15 1974 1.18 1975 1.13 1976 1.02 1077 0.92 1978 0.9:1 1979 1.11 1900 1.25 1901 1.33 1982 1.33 1983 1.25 8- Table 	Mackerel Labrador-North Carolina: population biomass (Bl + ). From figure 19.1, Anon. (1986).. Year 13101113ss 0906 tons) 1963 275 1964 311 1965 323 1966 371 1967 623 1968 1198 1969 1533 1970 1856 1971 1868 1972 1653 1973 1389 1974 1126 1975 970 1976 719 1977 491 1978 467 1979 503 1980 467 1981 479 1982 599 1983 695 1984 1078 Table 5.7 American plaice.Div. 3LNO: spawning stock biomass ( 0111). From Brodie (1932). Year 	Biomass (tons) 1965 138197 • 	1966 158756 1967 157325 1963 138337 1969 120238 . 	1970 94378 1971 31403 1972 62129 1973 52619 1974 50889 1975 45906 1976 39864 1977 45515 1972 48818 1979 60346 1930 67125 1981 53978 1922 46852 1983 42294 1534 46090 1925 56357 1986 43333 Table 6.- Correlation between cod years class size and cod spawning stock biomass. (N3) Lag -3 -1 0 1 2 3 n 23 24 25 26 27 28 29 r = 0.300 0.320 0.324 0.342 0.331 0.277 0.168 P = 0.166 0.123 0.115 0.087 0.092 0.15G 0.387 Table 7.- Correlations between cod and redfish catch rates. year class sizes (N3) Lag -3 -2 -1 0 1 2 n = 22 23 24 24 24 24 24 r = 0.305 0.225 0.317 0.176 -0.001 -0.198 -0.303 p = 0.169 0.190 0.132 0.409 0.995 0.358 0.152 Table 8.- Correlations between cod year class sizes (N3) and yellowtail flounder spawning stock biomass (136 + )• Lag 	-3 	-2 	0 	1 	2 	3 F =1 	n= 	14 	15 	16 	17 	18 	19 	19 r= 0.016 -0.037 -0.011 -0.065 0.006 0.278 0.599 p= 0.950 0.899 0.967 0.808 	0.982 	0.254 	0.006 Table 9.- Correlations between cod year - class sizes (N3) and mackerel stock biomass. Lag 	-3 	-2 	-1 	0 	1 	2 	3 n = 	19. 	20 	21 	22 	22 	22 	22 r = -0.435 -0.47E-0.458 -0.438 -0.393 -0.266 -0.087 p = 0.062 0.033 0.036 0.041 0.070 0.235 0.705 Table 10.- Correlations between cod year class size (N3) and A. plaice s)3awning stock biomass. Lag 	-3 	-2 	-1 	0 	1 	2 	3 n = 	17 	10 	15 	26 	21 	22 	22 r = 0.394 	0.644 0.745 	0.857 	0.021 0.858 0.940 p = 0.119 0.003 <0.001 <0.001 <0.001 <0.001 <0.001 

Cod in Div. 3NO: Year-Class Variations and the Abundance of Other Commercial Fish

Paz, Xabier

Larrañeta, Manuel Gómez

Digital.CSIC

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/635/1/scr-89-072.pdf

Cod in Div. 3NO: Year-Class Variations and the Abundance of Other Commercial Fish

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