Limnol. Oceanogr., 44(3), 1999, 494–501

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 newand 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. 1985; Shulman 1985; Olson and McPherson 1987; Young and Chia 1987; Morgan 1992; Eggleston and Armstrong 1995) and zooplankton (Lebour 1922, 1923; Glynn 1973; Huntley and Hobson 1978; Seben and Koehl 1984). In response to predation pressure, aquatic prey have evolved a number of morphologies and behaviors to avoid detection, capture, and contact with predators (see reviews by Sih 1987; Morgan 1995). Cryptic coloration, for example, is an important morphological trait that may reduce the detection of prey by predators. In pelagic environments, trans1 Present address: South Florida Research Center, Everglades National Park, 40001 State Road 9336, Homestead, Florida 33034.