No abstract

Like many marine species with meroplanktonic larvae, the Caribbean spiny lobster (Panulirus argus) has a postlarval stage that moves from the oceanic plankton to inshore nurseries only under specific environmental conditions (i.e., at night, in the surface water layer, on the flood tide, and during new moon), presumably to avoid predation or to enhance onshore transport. Using field and mesocosm experiments, we compared predation on planktonic postlarvae swimming at night near the surface and bottom over coastal habitats along typical offshore-inshore transport paths and determined whether predation rates differed between lunar periods (new moon vs. full moon) and with prey density (i.e., predator encounter rates). We also measured predation on transparent (newly settled) and pigmented (nearing metamorphosis) postlarvae sheltering in coral reef, seagrass, and macroalgal habitats during the day.We measured predation on postlarvae swimming near the surface and bottom along typical offshore-inshore transport paths (i.e., coral reefs, coastal lagoon, and bay) by tethering postlarvae to floats that drifted on the nightly flood tide during new moon. To test the hypothesis that new-moon transport of postlarvae may have evolved as a means to avoid higher predation under the bright full moon, we repeated the pelagic tethering experiments at the reef and in the bay during full moon. Mortality was highest over coral reefs regardless of lunar phase, but it was lower nearshore, especially in the bay near the surface and during new moon. Predation on benthic, recently settled transparent postlarvae and pigmented postlarvae (nearing metamorphosis) was also higher when tethered on the reef as opposed to vegetated habitats in the lagoon and bay. In experimental mesocosms, planktivorous fish were equally efficient at consuming postlarvae under new-and full-moon conditions when postlarval density was high, as it is in the constricted water column over the reefs. However, when postlarvae were less dense, mortality was significantly lower during new moon. Collectively, these results indicate that several behavioral traits exhibited by postlarval spiny lobsters, including inshore migration during the darkest lunar phase, use of surface waters, and settlement in vegetated habitats, reduce their risk of predation, particularly in the shallow bay. No single behavioral strategy is universally advantageous across all coastal habitats, but combined, they are an effective means to reduce predation across heterogeneous environments that postlarvae must transit during recruitment.Many marine organisms have complex life cycles, with pelagic larval stages that function in dispersal, colonization, and gene flow but that generally experience high mortality (Thorson 1950;Scheltema 1971). In both pelagic and benthic environments, predation can reduce the abundance and affect the spatial distribution of larvae (Cowden et al. 1984;Rumrill et al.

Abstract. The use of mangrove prop roots and associated coralline habitats by Caribbean spiny lobsters was investigated near two types of mangrove islands in Belize. Spiny lobsters sheltered among mangrove prop roots, in undercut peat banks and under corals near islands, and they ranged in size from newly recruited juveniles to subadults. Lobsters prefened to shelter under large stony corals, but their use of mangrove prop roots nd undercut peat banks increased when the density of corals was low. Den residence time and distance moved within a site were similar at islands isolated by deep water channels and islands separated by shallow seagrass beds, but as a consequence of high immigration rates, population sizes were highest near shallow islands. Predation on newly settled juveniles was greater in seagrass and coral crevices than in mangrove prop roots, whereas the survival of largerjuveniles was higher in mangroves and coral patch reefs than in seagrass. These results suggest that mangrove habitats may function as a nursery for juvenile spiny lobsters but that the use of this habitat depends on shelter characteristics and the isolation of islands.

Understanding how populations of target species interact with their habitats is necessary for developing an effective conservation strategy. During its complex life history, the Caribbean spiny lobster (  Panulirus argus) uses a variety of benthic marine habitats, but how habitat characteristics affect their dispersal is unclear. To assess how habitat insularity affects the benthic dispersal of spiny lobsters, I compared lobster abundance, size class structure, and migration among insular mangrove and coral reef habitats that were surrounded by bare rubble fields or by seagrass meadows. Lobsters were significantly more abundant on mangrove and coral islands surrounded by seagrass. The size‐class distributions of lobsters in these habitats had higher proportions of juveniles, whereas islands surrounded by sand and rubble had skewed distributions dominated by adult lobsters. Seagrass is known to serve as settlement habitat for larval recruits and is likely associated with the higher abundances of lobsters found in seagrass‐isolated habitats. Immigration and emigration rates were three to four times higher on seagrass‐isolated islands than on rubble‐isolated islands, reflected in the significantly greater number of juveniles moving into and from seagrass‐isolated islands. Rubble fields appeared to function as a barrier to benthic dispersal for all lobsters except adults. Vegetated substrates may function as movement corridors for juvenile lobsters and may facilitate dispersal to areas containing new resources. The effects of insularity on a population may be lessened by the nature of the surrounding habitats if those habitats have important functional roles as larval settlement areas, foraging grounds, or movement corridors. Protection of insular habitats like coral reefs may be ineffective if related habitats like seagrass meadows are left unprotected. Conservation strategies for mobile benthic species need to incorporate the protection of areas with heterogenous habitats that are important to meet the changing habitat requirements in complex life cycles.

No abstract