Effects of temperature on life history set the sensitivity to fishing in Atlantic cod Gadus morhua

Abstract

Concern over sustainable fisheries resources has motivated investigations of possible synergistic effects of climate variability and fishing on marine populations. While many studies suggest that fishing increases population sensitivity to climate forcing, the effects of climate variability on the population response to fishing is relatively understudied. To fill this knowledge gap, we conducted a synthesis based on 20 Atlantic cod populations (11 in the Northeast and 9 in the Northwest Atlantic). These cod populations display considerable life-history variation and are exposed to different temperature regimes and differential harvest pressure throughout their broad geographical range. We hypothesized that the differences in life histories that result from the different temperature regimes determine the sensitivity of cod populations to fishing. Spatial correlations between life-history traits (growth, maturation, and natural mortality) and water temperatures confirmed that warmer temperatures lead to faster individual growth, earlier maturation, and higher natural mortality. Analysis of a population model revealed how temperature influences on life histories lead to differential population responses to fishing. We represented such population responses to fishing using a proxy for lifetime reproduction (fraction of unfished lifetime spawning biomass, FLSB). This index revealed that — all else being equal — populations in warmer regions in the Northeast Atlantic Ocean can sustain higher fishing rates than those in the cooler Northwest. Life history-mediated temperature effects on population dynamics provide a novel perspective on synergistic relationships between climate and fisheries. Understanding population life-history variation will enhance the capabilities for forecasting future fisheries production under climate change.