An investigation of the sources of variability in american lobster (Homarus americanus) eggs and larvae: Female size and reproductive status, and interannual and interpopulation comparisons

摘要

From 1997 to 2001, the effects of female size (cephalothorax length [CL]) and reproductive status on egg size (diameter, dry weight) and larva CL at hatching were investigated in two Homarus americanus populations in the Gulf of St. Lawrence (Iles-de-la-Madeleine, Anticosti) and one at Grand Manan (Bay of Fundy), Canada. The estimated size at 50% maturity was used to identify small (likely primiparous) females for each population. Multifactor, mixed-hierarchical ANOVA models were used to investigate the variability of eggs and stage I CL among years and populations. In all comparisons, the main source of variability in the egg and stage I larva size was females (within and among). Nevertheless, for the Iles-de-la-Madeleine population in each year except 2001, the mean stage I larva sizes from small (CL < 79 mm), probably primiparous females were significantly smaller (P < 0.0085) than the mean larva sizes from larger females. However, female CL per se explained very little of the variance in mean larval size at hatching (r(2) = 0.23, P < 0.05 and r(2) = 0.12, P = 0.22 in 2000 and 2001, respectively, when the entire size range of reproductive females was considered). Hatching larvae tend to be smaller in primiparous females or females maturing at a small size; however, over the entire size range of reproductive females, larval size at hatching is almost independent of female size (CL). It is as if, above a minimum viable size, there is a constant small range of egg/larval sizes produced in H. americanus. Conservation measures dealing with the imposition of a minimum legal size may be a means of increasing the number of females that will spawn at least once or twice within a population. However, the impacts of first-time spawning on quality of eggs and larvae need to be fully investigated to assess the response of the population's egg production and recruitment potential of this measure.