Sensitivity of potential recruitment to stock structure in the presence of temporally varying survival.

Abstract

In this paper we discuss the results-of a modelling study which quantifies differences in the number of potential recruits produced from a range of age-structured populations over a spawning season with temporally varying survival rates. We include investigations into the effects that variation in female condition and egg quality (as a function of female characteristics) may have on overall production. We also quantify the effects on production of potential recruits via changes in the overall duration of spawning seasons due to environmental influences. The population stock structure (the proportion of females in different age classes) has the most effect on overall potential recruitment. The effects of egg quality dramatically increases larger fish's output of viable offspring whilst decreasing that of smaller fish. Fish condition has a very large effect on potential recruitment, but the effects are felt by all age classes equally. The present model outputs dealing with the interactions of temporally varying survival vs. stock structure and condition suggest that the middle of the spawning period consistently produces the most potential recruits but that the relative production of recruits over the spawning season is heavily influenced by both condition and stock structure.