Increasing temperatures counteract the evolutionary consequences of fishing in model of Northeast Arctic Cod (Gadus morhua)

Abstract

Fisheries and climate warming are two stressors known to induce evolutionary changes in fish life histories. While their independent effects have been well documented, their interactive effects are less charted, although likely important for sustainable fisheries management and conservation strategies. We investigated the evolutionary responses of the Northeast Arctic cod stock (Gadus morhua) to warming temperatures and fishing pressure using a mechanistic modeling approach. Our individual-based simulation model incorporates explicit energy and oxygen budgets, and a simplified genetics framework to capture the complex interactions among traits governing energy acquisition/allocation and maturation schedules. Our results provide a theoretical basis for positive consequences for this particular cod stock in a warming climate. Warmer temperatures increased the aerobic scope, which reduced natural mortality. We found that if food availability and temperature are not linked, a warming climate leads to larger population sizes. By selecting for maturation at larger sizes, adaptation to warming climate at least partially counteracts the evolutionary consequences of fishing, namely smaller body sizes and earlier maturation. Our findings emphasize the benefits of adaptive management approaches, considering fish as evolving organisms and integrating ocean warming into fisheries management strategies.

Keywords: Climate; Eco-evolutionary dynamics; Fishing pressure; IBM modelling.

Figure 1

Conceptual overview of critical processes. Solid arrows indicate direct influence, and dashed arrows indicate the energy flow. The shaded ’%’ area represents the proportion of energy dedicated to somatic vs. gonadal growth. Figure is modified from Jessen et al., with mortality relations modified from Holt and Jørgensen.

Figure 2

Stabilized populations compared to ICES data (squares). (A) Average length-at-age ±SD, compared to ICES averages from 2014 to 2021. (B) Average proportion-mature-at-age of the last 200 years of model runtime, compared to ICES averages from 2014 to 2021 (black squares) and 1946 (hollow squares).

Figure 3

Temperature time-series used throughout the model runs ±SD based on data given by IPCC scenarios.

Figure 4

Resulting average genetic appetite and PMRN intercept ±SD at the end of the model’s runtime. Dashed lines visualise the effect of fishing pressure within warming scenarios.

Figure 5

Resulting growth curves at the end of the models simulation time of 2000 years, showing average length-at-age ±SD.

Figure 6

Average age/length at maturation ±SD at the end of the model’s runtime. Dashed lines visualise the effect of fishing pressure within warming scenarios.

Figure 7

Average number of individuals and total population biomass at the end of the model’s runtime. Dashed lines visualise the effect of fishing pressure within warming scenarios.