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

Abstract

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.

Keywords

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

Published in

ICES Journal of Marine Science
2009, volume: 66, number: 2, pages: 248-257
Publisher: OXFORD UNIV PRESS

SLU Authors

• Gårdmark, Anna

  • Swedish Board of Fisheries

• Bland, Barbara

  • Swedish Board of Fisheries

• Hjelm, Joakim

  • Swedish Board of Fisheries

UKÄ Subject classification

Evolutionary Biology
Ecology

Publication identifier

• DOI: https://doi.org/10.1093/icesjms/fsn199

Permanent link to this page (URI)

https://res.slu.se/id/publ/52322