Habitat use and population biology of Bahamian spiny lobster

The spiny lobster Panulirus argus is extremely important both for basic scientific research (Davis, 1980) and the seafood industry. Despite the economic significance of Bahamian lobsters, their ecology has been the subject of limited study. Investigators have recorded fishery information (Smith, 1948, 1951), mass migration (Herrnkind and Kanciruk, 1978; Kanciruk and Hermkind, 1978; Hcrmkind, 1980), autumnal reproduction (Kanciruk and Herrnkind, 1976), commercial size composition (Simpson, 1976), life history and ecology of juveniles, and experimental fishing techniques (Waugh and Waugh, 1977; Waugh, 1980). (...) We report here on a 10-month (Sept, 1979-June, 1980) study of Panulirus argus in the region of Lee Stocking Island, north of Great Exuma Island. Size distribution, habitat, reproduction, and molting cycles are emphasized.https://scholarworks.wm.edu/vimsbooks/1141/thumbnail.jp

Population dynamics and habitat partitioning by size, sex, and molt stage of blue crabs Callinectes sapidus in a subestuary of central Chesapeake Bay

Abundances, size-frequency distributions, sexual composition and molt-stage composition of blue crabs Callinectes sapjdus were measured during 1983 to 1985 in the Rhode River, a subestuary of central Chesapeake Bay, USA. Crabs at the mouth and head of the river basin were sampled with monthly triplicate otter trawls. Crabs in the principal tidal creek of the river were sampled 3 d a week with a fish weir, which caught crabs moving upstream and downstream separately. Crabs exhibited consistent, marked seasonal cycles in abundance as well as considerable annual variation in July peak abundances. New recruits entered the subestuary in late fall and spring and grew rapidly to 70 to 100+ mm in their first summer; by the second year they reached mature sizes of 120 to 170 mm. Sixty % of crabs in the river basin were males; and after maturation and copulation in late summer to early fall, mature females left the subestuary. Crabs partitoned habitats within the Rhode fiver subestuary by size, sex, and molt stage. Polymodal size structures were similar throughout the river basin, but increased percentages of males were found at the head of the river. Predominantly (90 %) medium-sized (80 to 120 mm) males utilized the tidal creek as a molting habitat. Most crabs moving upstream were in premolt, whereas most crabs moving downstream were significantly larger and in postrnolt, so that about 70 % of crabs in the creek were near ecdysis. Males and females exhibited significantly lower, but still appreciable (about 25 Oh) rnolting activit; Lhrsughout tie river basin. These data provide one of the best documented cases of habitat partitioning by size, sex and molt stage in crustaceans

Efficacy of blue crab spawning sanctuaries in Chesapeake Bay

Sanctuaries can potentially protect a significant fraction of the spawning stock, and thereby sustain heavily exploited populations. Despite the worldwide use of marine and estuarine spawning sanctuaries, the effectiveness of such sanctuaries remains untested. We therefore attempted to quantify the effectiveness of the spawning sanctuaries for adult female blue crabs (Callinectes sapidus) in Chesapeake Bay. We used baywide winter dredge survey data to estimate the potential spawning stock prior to the major exploitation period, and summer trawl survey data to estimate spawning stock abundance within the Lower Bay Spawning Sanctuary and adjacent Bayside Eastern Shore Sanctuary during the reproductive period. Hence, we were able to approximate the percentage of the potential spawning stock that was protected by both sanctuaries after exploitation. On average, approximately 16% of the potential spawning stock survived to reach the Lower Bay Spawning Sanctuary and Bayside Eastern Shore Sanctuary. Even under a best-case scenario (i.e., crab residence time of 2 weeks), the sanctuaries only protected an estimated 22% of the potential spawning stock, which is well below the percentage recommended by recent stock assessments for sustainable exploitation (28%). In the worst case, a mere 11% of the potential spawning stock survived to reach the spawning sanctuaries. Hence, we recommend a substantial expansion of the spawning sanctuaries, as well as the complementary protection of other life stages in critical habitats, such as nursery grounds and dispersal corridors. Furthermore, traditional fisheries management measures (e.g., effort control) should be used in concert with sanctuaries to thwart impediments to effective implementation of the sanctuaries, such as redirected fishing effort.https://scholarworks.wm.edu/vimsbooks/1084/thumbnail.jp