Research Document - 2011/079
Lobster Size at Maturity Estimates in Eastern Cape Breton, Nova Scotia
By A. Reeves, J. Choi, and J. Tremblay
Abstract
This study describes spatio-temporal variability in female size at maturity for three areas in eastern Cape Breton, Nova Scotia, Canada. Cement gland staging techniques were used to assess sexual maturity and were confirmed as required by ovary examination. Sampling took place from April to November (2005-2008). Generalized Linear Models (GLMs) were constructed to explore the relationship between maturity and carapace length using a binomial distribution for the dependant variable with a log odds (logit) link. Preliminary regressions of individual samples suggested that the estimates of size at maturity (SOM50) were variable across the three sites, variable across years from 2005 to 2007, and variable across weeks with years. Further investigation using two separate models, one incorporating terms for annual and seasonal components, and another incorporating spatial and seasonal components verified that size at maturity was annually, spatially and seasonally variable. These models indicated reduced size at maturity for the most northern site and the most recent year (2007), while indicating an increased size at maturity as the sampling season progressed. The results suggest that monitoring size at maturity over time may represent a valuable non-fishery based indicator of stock status and health. Furthermore, the need for standardized, replicated seasonal sampling over the period prior to extrusion and hatching is clearly necessary for accurate estimates of SOM50.
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