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Forskningsartikel2009Vetenskapligt granskadÖppen tillgång

Two- and three-dimensional maturation reaction norms for the eastern Baltic cod, Gadus morhua

Vainikka, Anssi; Gårdmark, Anna; Bland, Barbara; Hjelm, Joakim


Industrial fisheries have caused decreases in the size and age at maturation in several stocks of cod (Gadus morhua). Although earlier maturation can be a phenotypic response to improved growth conditions, estimation of probabilistic maturation reaction norms (PMRNs) can remove most impacts of growth and demography from maturation schedules and has often revealed a residual, potentially genetic, trend. In this study, size- and condition-based PMRNs were estimated for eastern Baltic cod cohorts from 1987 to 2003. The PMRNs suggested that both length and condition at 50% probability of maturing (Lp(50) and Cp-50) had decreased by 15-20%, more notably in females. Simultaneously with changes in maturation schedules, the length-at-age of mature fish decreased for most combinations of age and sex. Decrease in growth may be partly explained by advanced maturation, but temporal fluctuations in PMRNs suggest also a residual environmental impact on both growth and maturation. The results may indicate a genetic change in the eastern Baltic cod stock, adding pressure to reduce fishing mortality on it.


fisheries selection; fishing-induced evolution; growth; maturation schedule; PMRN

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ICES Journal of Marine Science
2009, Volym: 66, nummer: 2, sidor: 248-257

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