May life history traits be used as indices of population viability?

Abstract

Concern has been raised that the widely used spawning stock biomass might not be a sensitive index of the reproductive potential of fish populations. On the other hand, there is increasing evidence that fishing affects life history traits of fish. Fish compensate for fishing mortality by faster growth, earlier maturity and increased fecundity. Because life history traits are affected by fishing and are also critical in determining the population growth rate, they may be used as indices of population viability. In this paper, the traits that meet both criteria are investigated among age-at-maturity, fecundity and growth. In the framework of matrix population models, the life table response experiments (LTRE) method is used to quantify the effects of fishing on demographic parameters, and the contributions of these effects to the population growth rate. This approach is used for comparing parameters and population growth rates of flatfish populations between periods with different fishing pressure. It is found that age-at-maturity, the proportion of repeat spawners in the spawning stock and some proxy for lifetime fecundity may be used as indices of population viability.