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Sperm acquisition and storage dynamics facilitate sperm limitation in the selectively harvested blue crab, Callinectes sapidus

Matthew B. Ogburn*, Kimberly D. Richie, Morgan A. Jones, Anson H. Hines

*Corresponding author:

ABSTRACT: Selective harvest of male blue crabs Callinectes sapidus can reduce the operational sex ratio and alter male mating history and behaviors, reducing the quantity of sperm females acquire during mating. Females mate shortly after molting to maturity, storing sperm at least two years, and fertilize multiple broods of eggs. We combined field surveys, a mark-recapture experiment, and modeling in the most extensive study of sperm storage and use after mating in blue crabs evaluating: 1) spatiotemporal patterns in sperm quantity acquired during mating, 2) the pattern and rate of decline of sperm during storage, 3) the quantity of sperm used for fertilization, and 4) the potential for sperm limitation. We also explored the spatial extent of spawning in Chesapeake Bay in comparison to the spawning sanctuary. Female crabs acquired up to 3x109 sperm, but sperm stores declined by 90–95% in the first 1–2 months after mating. Sperm quantity differences between first and second year spawners indicated use of 4 sperm egg-1 during fertilization. Approximately 15% of spawning females were in their second spawning season, and remaining sperm stores were indicative of sperm limitation resulting in a 5–10% decrease in reproductive output of the spawning stock. The current spawning sanctuary encompassed 98% of ovigerous females and 100% of females with evidence of prior spawning. Although many females do not experience sperm limitation prior to harvest or natural mortality, reductions in the reproductive output of second-year spawners likely limits population resilience to inter-annual variation in spawning stock biomass.