Reproductive potential of individual male blue crabs, Callinectes sapidus, in a fished population: depletion and recovery of sperm number and seminal fluid

We evaluated the depletion and recovery rates of sperm number and vas deferens weight following mating for male Callinectes sapidus both below (< 127 mm carapace width) and well above (> 140 mm) the fishery size limit for hard crabs in Chesapeake Bay (127 mm). Large males had low sperm count and vas deferens weight immediately after mating and required approximately 9-20 days to fully recover. After mating, small males had significant reduction in sperm number despite no significant change in vas deferens weight. Furthermore, small males with completely recovered seminal stores had significantly lower vas deferens weight than fully recovered large males but did not differ significantly from large males in number of sperm. The changes in vas deferens weight and sperm count following experimental mating suggest that large males delivered 21 times as much seminal fluid and 2.25 times as much sperm as small males. Field collections in a subestuary of Chesapeake Bay revealed that the majority (50-90%) of males had extremely low vas deferens weight relative to males with fully recovered sperm volume. Since the fishery targets males primarily, reducing both the number and average size of males in the population, many females may be mated with small or recently mated males that transfer less seminal material.