Variability in Reproductive Potential among Exploited Stocks of Tanner Crab (Chionoecetes bairdi) in Southeastern Alaska

Variability in Reproductive Potential among Exploited Stocks of Tanner Crab (Chionoecetes bairdi) in Southeastern Alaska

J. Webb and J. Bednarski

Variability in Reproductive Potential among Exploited Stocks of Tanner Crab (Chionoecetes bairdi) in Southeastern AlaskaThis is part of Biology and Management of Exploited Crab Populations under Climate Change
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Description

For many exploited crab stocks, management has been challenged by uncertainty in estimation of abundance, effective spawning biomass, and stock-recruit relationships. Crab fishery management strategies strive to optimize trade-offs between yield and variability in yield by harvesting males only above a minimum size limit, typically set at one molt larger than size of 50% male maturity. However, there is limited understanding of the implications of this harvest strategy for mating frequency and female reproductive potential (e.g., sperm limitation). To evaluate reproductive potential of female Tanner crab (Chionoecetes bairdi), we characterized egg viability, spermathecal load, and sperm cell counts in six spatially discrete locations in southeastern Alaska. All females carried viable egg clutches with low incidence of nonviable eggs. Mean spermathecal load was significantly lower in primiparous compared to multiparous females in four of five locations compared, but sperm cell counts were similar between primiparous and multiparous females in all locations. Mean sperm cell counts were significantly higher when fresh ejaculate was present versus when it was absent for both primiparous (454% higher) and multiparous females (320% higher). The proportion of primiparous and multiparous females with fresh ejaculate was correlated with mean sperm cell counts by location and may be a useful index of variability in female sperm cell counts among stocks. Evidence of sperm limitation was not observed in this study, but mean sperm cell counts of primiparous females by location were negatively correlated with exploitation rate index suggesting that male-only harvest may decrease levels of stored sperm available for fertilization of a subsequent clutch.

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