Population Dynamics Reflect an Interaction of Life Histories, Fishing, and Temperature Variability: Evidence Drawn from Atlantic Cod

Different species or con-specific populations display variable life histories and/or population dynamics in response to fisheries exploitation. Such variability may reflect that 1) other factors confound fishing effects on fish life histories, and/or 2) life history variation mediates differential population responses to fishing. We evaluated these hypotheses based on seventeen Atlantic cod Gadus morhua populations. Different cod populations express a wide range of life history variation, and are influenced by variable temperatures and fishing intensities. Our analysis indicated that fishing mortality covaried with temperatures (r = 0.58), and that temperature had a strong effect on inter-population life history variation; after accounting for temperature, fishing effects on life history variation were not significant. However, differential inter-population dynamics (indexed by lifetime spawning biomass; LSB) was attributed more to different fishing mortalities than different temperatures. Furthermore, two populations (Irish Sea and 3NO) demonstrated life history variation-mediated fishing mortality effects on LSB.