Long-term interplay between harvest regimes and biophysical conditions may lead to persistent changes in age at sexual maturity of Northeast Arctic cod ( Gadus morhua )

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Rørvik, Carl Jakob, Bogstad, Bjarte, Ottersen, Geir, Kjesbu, Olav Sigurd
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2022
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Arctic; Arctic cod; Gadus morhua; Northeast Arctic cod
• Online Access: http://dx.doi.org/10.1139/cjfas-2021-0068; https://cdnsciencepub.com/doi/full-xml/10.1139/cjfas-2021-0068; https://cdnsciencepub.com/doi/pdf/10.1139/cjfas-2021-0068

This investigation commenced by constructing principal maturation schedule equations as a function of fishing mortality (F), key biophysical factors and a term attributed to fisheries-induced adaptive change (FIAC). Following the onset of industrial trawl fishery on the model stock, Northeast Arctic cod (NEAC; Gadus morhua) (1934–2020), F on immature age group 5–8 years (F5-8) increased and mean age at 50% maturity (A50) decreased from ≈10 years in the late 1940s to ≈7 years today. Large annual fluctuations in total stock biomass (TSB), sea temperature (KolaT) and F5-8 were used to better understand A50 responses. In the model, the annual accumulation of F5-8 drives FIAC. The model includes the option that NEAC may sustain F5-8 up to a certain level (F_bal) before FIAC becomes statistically evident, with F_bal falling between 0.00 and 0.40 for A50. This dynamic range in F_bal indicates a sophisticated, underlying adaptive response. Independent of F_bal, our analysis clarifies that FIAC is necessary to explain the observed changes in A50.