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

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