Résumé
Age and size at maturation has declined for several fish stocks the last decades. Knowing that these traits may evolve rapidly in response to the selection pressures exerted by human fisheries, we explore reproduction and maturation changes for the Northeast Arctic stock of Atlantic cod Gadus morhua. We use a mechanistic and physiologically realistic model where energy allocation between growth and reproduction depends on three individual states: age (in months thus including seasonality), length, and stored energy. Food intake varies stochastically. Under the historic fishing regime that targeted mainly mature cod, maturation was late (10.2 years, 117 cm, and 20.8 kg). Recent trawling has increased juvenile and immature mortality, and we find that the evolutionary endpoint under todays fishing regime implies much earlier maturation at a smaller size (4.9 years, 51 cm, and 1.6 kg). Among the consequences of earlier maturation is a decrease in the stocks per-biomass potential for egg production. As a result, fisheries-induced life history evolution will systematically reduce the slope of SSB-egg-production diagrams with time. If todays fishing continued, the predicted evolutionary endpoint will produce only 60% of the eggs for the same biomass when compared with the historic population.