Reproductive cycle and maternal effects on offspring size and number in the neogastropod Buccinum undatum (L.)

Abstract.

This paper examines relationships between maternal phenotype and offspring phenotype in the commercially exploited marine neogastropod Buccinum undatum (L.). The study also aimed to estimate the effects of female size on subsequent recruitment, and to determine the reproductive cycle of B. undatum in Swedish waters. The evaluation of gonad development in field-sampled animals from August 1998 to February 2000 revealed a definite annual reproductive cycle with a single major egg-laying period in the autumn. In addition, adult whelks of varying sizes from two locations and in two consecutive years were kept in aquaria to study the influence of female size on fecundity. Twenty-seven females deposited eggs in the laboratory. Offspring quality, measured as egg and hatchling size, was independent of female size, although larger females produced more eggs and hatchlings than smaller females, and thus probably account for a disproportionately large share of potential recruitment; the relative fecundity (number of eggs or hatchlings per gram of body weight) was constant with female size. I found no evidence for a longer time interval between successive egg-layings in larger females, i.e. mature females of all sizes probably spawn equally often. The present results therefore indicate that spawning-stock biomass is probably a better measure of spawning-stock size than the number of mature individuals in the population. Effects of an individual female's characteristics on stock productivity have largely been overlooked by fishery managers but could help to explain the weakness often found in stock–recruitment relationships.