In spiny lobster, Panulirus argus (Latreile), fisheries in Cuba, Mexico and the Bahamas, artificial shelters (casitas) are successfully used as fishing gears. However, the mechanisms underlying the operation of these artificial shelters and their long-term effects on the resource and benthic communities are unclear. Lowered predation-induced mortality due to casitas has led to the proposal that they be placed in benthic habitats with adequate food, but where natural shelter is lacking. In this study, firstly the availability of natural habitat types was measured and secondly, habitat features which could influence the occupancy of artificial shelters by lobsters were evaluated. Casitas were placed in benthic habitats differing in the relative availability of seagrass and hard bottom. Spiny lobsters and faunal assemblages were monitored from December 1993 to July 1994 at six stations, two for each benthic habitat type. The study area was a typical spiny-lobster nursery area, with bottom cover dominated by seagrass and macroalgae (79.7%); while hard bottom, including patch reef, amounted to only 0.2%. Hence, a population bottleneck probably occurred, negatively affecting postalgal juveniles and subadult lobsters. The results suggest that seagrass availability was the key factor determining casitas' occupancy by lobsters. The lowest occupancy was found where seagrass was scarce and hard bottom was available. Given seagrass availability, casitas harbored a similar number of lobsters irrespective of the hard bottom availability; allowing to infer that artificial shelters provided critical habitats (refugees) for postalgal and subadult lobsters. The mean size of lobsters did not vary among stations, and commercial-sized lobsters were scarce. An index of predator presence showed a significant variation among stations and with time, with higher values from April to June. Sea temperature was positively correlated with lobster abundance and predator index; the latter two variables were not correlated. These study results support the use of casitas for the enhancement of preadult lobster populations.
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