Time to Metamorphosis of Blue Crab Callinectes Sapidus Megalopae: Effects of Benthic Macroalgae

There is growing evidence that postlarvae (megalopae) of the blue crab Callinectes sapidus can slow the progression through the molt cycle while in offshore nursery grounds, and delay metamorphosis until reinvasion of coastal habitat occurs. However, the cues that trigger metamorphosis of megalopae are not well known. This study tested the hypothesis that the time to metamorphosis (TTM) from the postlarval megalops stage to the first crab stage is shortened in the presence of 2 potential macroalgal settlement substrates, Ulva lactuca (Chlorophyta), and Gracilaria spp. (Rhodophyta). Megalopae and test water were collected from 3 locations (offshore, at a coastal inlet, and inside a coastal lagoon) and tested in a completely crossed factorial experiment with algal type and location as main effects. TTM was longest in offshore treatments (mean TTM 4.72 d) and similar in the inshore treatments (mean inlet TTM 2.73 d, lagoon TTM 2.51 d). TTM of offshore megalopae was reduced in the presence of Ulva lactuca, but macroalgae had little effect on the inshore treatment groups. The effect of algal cues may be masked once megalopae have initiated premolt prior to invading coastal lagoons

Fecundity of Blue Crab, Callinectes Sapidus, in Chesapeake Bay: Biological, Statistical and Management Considerations

Ovigerous blue crabs were collected from the mouth of Chesapeake Bay during the 1986 and 1987 spawning seasons. Mean carapace width was 14.7 cm; mean fecundity was 3.2×106 eggs. Fecundity was significantly related to carapace width, and did not vary significantly with developmental stage of the eggs. Mean fecundities were 2.6×106 eggs in 1986, and 4.0×106 eggs in 1987. An additive model with year and size effects described the observed fecundities reasonably well, was compact, and was easier to interpret than a multiplicative model. To fit a more general model without year effects, the authors took the mean of 1986 and 1987 results, and modeled fecundity as E=-2.25+0.38W, where E is predicted fecundity (106 eggs), and W is carapace width (cm)

Estimates of Spawning Stock Size of Blue Crab, Callinectes Sapidus, in Chesapeake Bay, 1986-1987

The 1986 spawning stock exhibited a single abundance peak, increasing from 1.0×105 individuals in early July to 9.3×106 in late July, maintaining high levels throughout the summer, and declining in the fall to 7.4×105 individuals. The 1987 spawning stock showed 2 peaks of abundance. The population reached the lesser peak, 1.0×106 individuals, in late July; the greater peak, 1.5×106, in late August. By late September, the population had declined to 6.5×105 individuals. The peak abundance of the 1987 female spawning stock was only 16% as great as the peak abundance in 1986; the 1987 spawning stock size in 1986. Variability of this magnitude calls for continued monitoring and watchful management, to prevent fishing pressure from exceeding the reproductive capacity of the stock