Sex Ratios and Average Sperm per Female Blue Crab Callinectes sapidus in Six Tributaries of Chesapeake Bay

Abstract

Sperm limitation has been a concern for several crustacean species around the world. It may be of particular concern for blue crabs Callinectes sapidus in Chesapeake Bay due to the species’ reproductive biology and the sex-specific fishery regulations in place. Our objectives were to characterize the differences in sperm counts in mated females from six tributaries of the Chesapeake Bay and to determine whether sperm quantity was affected by the ratio of males to females in each system. Mature females were sampled 1–4 times in each tributary on a biweekly schedule from September to November 2011. We quantified sperm storage for each crab by microscopic examination and compared the sperm counts of females among river systems with the adult male : female sex ratios using ANOVA and linear regression. Total sperm quantity per female varied 16-fold (0.9–13.0 × 10⁸) among tributaries. The sex ratio was also variable among tributaries. Total sperm quantity per female was not significantly related to sex ratio, tributary, or month but was negatively related to the development stage of the spermathecae. Estimated sperm : egg ratios varied from 153:1 to 2:1 but were always higher than 1:1. Our results suggest that sperm quantities are not affected by male : female sex ratios and that sperm limitation caused by low sex ratios is likely not a concern in tributaries similar to those in our study.

Received April 3, 2015; accepted June 24, 2016

Acknowledgments

This research was partially supported by a grant from the Maryland Department of Natural Resources. We also thank the Maryland Department of Natural Resources, Virginia Institute of Marine Science, Potomac River Fisheries Commission, and local watermen for their data and sample collection. Lastly, we thank the Fish and Invertebrate Laboratory of the Smithsonian Environmental Research Center for their insight and training in processing our crabs; J. Humphrey for help processing crabs; and L. Harris, the associate editor, and two anonymous reviewers for providing helpful comments on a previous draft of the manuscript. This is contribution 5208 of the University of Maryland Center for Environmental Science.