Differential population response to fishing mortality: A case study based on fifteen Atlantic cod populations

Commercial fisheries operation can affect fish populations through altering life history traits and interacting with other factors (e.g., climate variability). Although such fishing-induced effects may lead to population extinction, population dynamics can vary dramatically among exploited species and con-specific populations. We hypothesized that intra-specific life history variation may lead to differential population responses to fishing. We evaluated this hypothesis based on life history data and abundance estimates of fifteen Atlantic cod Gadus morhua populations. These cod populations express different life history traits, and are exposed to differential levels of exploitation over time. We estimated fractions of unfished lifetime spawning biomass (FLSB) per yearclass for each population, and evaluated spatial correlations between FLSB and life history metrics, including fishing mortality rates (F) for mature fish, growth (based on mean weight at age 4), age at 50% maturity, number of age classes, and population density. Our results revealed that FLSBs ranged from 0.03 to 0.45, and were negatively correlated with F. The effects of life history variation on population response might not be significant or be compromised by other concurrent effects (e.g., changes in community structure). Nonetheless, at a relatively high F FLSB responses varied between the fast- vs. slow-life history populations.