Simulated Influences of Hatching-Date Dependent Survival on Year Class Composition and Abundance

摘要

Juvenile fish survival is often strongly density dependent and results in relatively consistent average recruitmentover a wide range of spawning stock biomasses. Hatching date-dependent mortality can limit contributions of individualhatching sub-cohorts (i.e., fish hatched in one period relative to another within the overall hatching distribution) tothe year class and influence the potential for compensatory survival. We used trophic-based ecosystem models to evaluateeffects of hatching date- dependent survival on the potential for compensation and regulation of year class strength andadult biomass by simulating variable early-life mortality. We built one model using data for north Florida lakes to representa contracted spawning distribution and one model for south Florida lakes to represent a protracted spawning distributionusing data for largemouth bass Micropterus salmoides with hatching-date dependent survival. Hatching datedependentsurvival strongly influenced contributions of individual hatching sub-cohorts to year classes (up to 70+%change in sub-cohort biomass), but total effects on year class strength and adult biomass were small (range -9% to +13%total biomass change). Total survival to age-1 was largely regulated by predation such that increases in individual subcohortsurvival did not result in large increases in total recruitment. Ecosystem models indicated that spawning distributionsaffected sub-cohort interactions to influence compensation and regulation, which had implications for understandingadult spawning periodicity and fisheries management.