Casitas are artificial structures used widely in the Caribbean to facilitate the harvest of spiny lobsters by divers. Casitas are often used by many non-target species, and therefore have the potential to increase local species diversity and mitigate the loss of natural habitats. Their ecological impact, however, is largely unknown. We examined the distribution of benthic habitat and the abundance and diversity of fish and motile invertebrates at casitas (artificial structures), coral heads (natural habitat with vertical structure >15 cm high), and low-relief hardbottom (natural habitat with vertical structure <15 cm high). Casitas and coral heads exhibited similar habitat features and fish and invertebrate species assemblages. Low-relief hardbottom sites had significantly less abundant and diverse fish and invertebrate species assemblages than at either structure. The only significant difference observed between casitas and coral heads was the abundance of lobsters. Lobsters were found in significantly greater numbers at casitas than at either coral heads or on low-relief hardbottom. Determining how an increased concentration of lobsters at casitas affects the local ecology is complex, but our data suggest that the presence of lobsters in such large aggregations at casitas did not alter the surrounding flora and fauna. In regions with limited shelter, species composition and ecological function at casitas are similar to those at coral heads. This study shows that casitas may be efficient dual-purpose devices; that is, they function not only as lobster fishing gear, but also as the ecological equivalent of coral heads in shelter-limited habitat.

The sublethal effects of fisheries (e.g. reduced nutritional condition or injuries) on the target species population are poorly understood, yet have the potential to reduce fishery efficiency and sustainability. The Caribbean spiny lobster Panulirus argus trap fishery in Florida (USA) uses live, sublegal-size lobsters as bait to lure other lobsters into the ~462000 traps employed by the fishery. Long-term confinement of lobsters used as live bait causes stress, leading to the degradation of their nutritional condition or mortality; however, cumulative effects of confinement on nutritional condition throughout the fishing season and the effect on the population were unknown. We sampled sublegal- and legal-size lobsters hand-caught from a fished area (potentially affected by traps) and caught in commercial lobster traps in the fished area to determine how lobster health varies throughout the year and whether the intense recreational and commercial fisheries exhibit sublethal effects on lobster health. We compared the health of lobsters monthly for 1 yr using 2 nutritional indices (hepatopancreas dry weight and blood serum protein), and by the presence of external injuries and shell disease. Lobster blood serum protein and dry weight index varied throughout the year, peaking in late summer to early fall, dropping sharply during the winter, and rising again through the spring, likely in response to seasonal changes in environmental factors, such as water temperature. Both legal and sublegal lobsters within actively fished traps showed lower nutritional condition than lobsters from the surrounding population throughout the fishing season, suggesting that few lobsters escape traps.