Sperm and Eggs: Connecting Sex-Selective Harvest to Stock Productivity in Crustacean Fisheries

Many crab fisheries are managed using size- and sex-selective (e.g., large-male only) harvest rules.  A challenge of this management approach is that removing large males may disrupt mating biology and adversely affect reproduction.  Additionally, assessments of the fished (male) component of the stock as an index of stock productivity may provide a biased view relative to a more biologically plausible index such as female egg production.  Using eastern Bering Sea snow crab (Chionoecetes opilio) as an example, we will illustrate an approach and provide insights from a long-term research project that directly monitors female mating success and reproductive output at the population scale.  Female sperm reserves are low for this stock relative to other populations, vary regionally across the distribution, and vary with reproductive history (between primipara and young multipara).  Fecundity is highly variable and strongly influenced by female body size, age relative to the molt-to-maturity, and mating success. Clutch fullness index, a visual method used to index differences in female egg clutch size during surveys, is a robust predictor of variability in fecundity. Using female egg production as an index of reproductive potential provides alternative perspectives from male-based indices on recruitment and possible density-independent drivers of recruitment variability.