Spawning in the nick of time? Effect of adult demographics on spawning behaviour and recruitment in Chesapeake Bay striped bass

Abstract

Striped bass (Morone saxatilis) is an iteroparous anadromous species that spawns dispersive offspring into freshwater habitats and exhibits a high fecundity and high embryo and larval mortality rates. Field studies indicate that temperature differentially affects spawning behaviour and larval survival, and periods of high egg production are often mis-timed for optimal larval survival. I hypothesize that age structure of females may be an important determinant in reducing variability in recruitment through its influence on spawning behaviour. Age diversity of Chesapeake Bay female striped bass is indexed according to expectations of age-specific reproductive values in an unexploited population. The age diversity index was positively correlated to spawning dispersion (egg presence ratio) and 0+ juvenile abundance during the recent period of population recovery (1985-1995). Diversity in age structure and spawning behaviour may contribute to a storage effect, because in most years minority behaviours would result in sustained recruitment. A diverse age structure may thus contribute to an accumulation of spawning stock biomass and increase the future likelihood of dominant year classes. (C) 2000 International Council for the Exploration of the Sea.