Effects of fishing on growth traits: a simulation analysis

Fishing tends to be size selective, targeting larger individuals so that spawning stock shifts toward smaller, slower-growing individuals; if somatic growth is genetically based, this shift may select differentially for smaller size-at-age individuals. The evolution of life history traits can affect potential yields and fishery sustainability, and should be considered by fishery managers, although few do. Some guidance in this regard is provided through an individual-based model of a population with overlapping generations and continuous reproduction. The model simulates size-selective fishing to generate and quantify growth selection differentials. Various common life history and fishery characteristics are considered: variability in growth, correlations between growth parameters, maturity rate, natural mortality rate, spawning season duration, selectivity curve slope, fishing mortality rate, maximum size limit, age at 50% selectivity, and fishing season duration. Each of these traits affected the magnitude of the selection differentials. The most vulnerable stocks tend to have short spawning or fishing seasons. For most of these characteristics, selection differentials under realistic fishing mortality rates can be considerable.