Distribution, Relative Abundance, and Reproductive Output of Spawning Female Blue Crab (\u3ci\u3eCallinectes sapidus\u3c/i\u3e) In Offshore Waters of the Gulf of Mexico

Effective assessment and management of migratory species require an understanding of stock boundaries and habitat use during critical life history periods. The blue crab (Callinectes sapidus) is considered a primarily estuarine species and has traditionally been assessed and man-aged on a state basis, relying on abundance estimates derived from estuarine sampling. Females undertake a sea-ward spawning migration, and recent evidence indicates that coastal and offshore waters may provide important spawning habitat. We investigated occurrence and reproductive output of spawning blue crab in offshore waters of the northwestern Gulf of Mexico, and results indicate that these waters may be an important spawning area for this species. Densities of blue crab were low offshore compared with those in estuaries, but given the large extent of available offshore habitat, the total abundance of adult females is likely similar in offshore and estuarine waters. Analyses of the reproductive output of females collected offshore indicate that they continue to spawn after leaving the estuaries. Fecundity and measures of egg quality were assessed and were similar to previous estimates for estuarine regions. Future management and assessment efforts should account for this previously understudied portion of the blue crab spawning stock

Large-Scale Movements of Postcopulatory Female Blue Crabs \u3ci\u3eCallinectes sapidus\u3c/i\u3e in Tidal and Nontidal Estuaries of North Caroline

For migratory species, understanding the timing, direction, and mechanism of migration is critical for successful fisheries management. We investigated migratory movements of postcopulatory female blue crabs Callinectes sapidus in three estuaries with different tidal regimes in North Carolina using a mark–recapture study. All crabs tagged were within about 2 weeks of the terminal molt to maturity (mating generally takes place immediately after the molt). In general, distances traveled (mean ± SE = 6.8 ± 0.6 km) and net movement rates (0.5 ± 0.05 km/d) were quite low compared to those in previous studies of mature (but not necessarily recently molted) female crabs, suggesting that rapid seaward migration does not take place until several weeks after mating, presumably upon production of a clutch of eggs. Although most crabs moved short distances (85% moved \u3c 15 km), movement was generally oriented seaward, indicating that some down‐estuary movement occurs prior to oviposition, especially in crabs mating in low‐salinity estuaries that would be unsuitable for embryonic and larval development. Crabs moving seaward in the weeks between molting/mating and first oviposition were likely walking rather than swimming and taking advantage of seaward currents, as indicated by the low movement rates and similarities among the three areas