The behavior of juvenile Caribbean spiny lobster in Florida Bay: Seasonality, ontogeny and sociality

We conducted laboratory experiments and field manipulations to evaluate the extent to which ontogenetic and certain environmental conditions interact to alter the behavior of juvenile Caribbean spiny lobsters following settlement. In addition we evaluated whether particular behavioral changes could increase a juvenile's chance of survival. We tested the effects of time of day, season, developmental stage and the presence of conspecifics on the activity state and sheltering behavior of lobsters. We also estimated relative predation rates by tethering lobsters under five types of shelter during summer and late fall. Algal phase lobsters (8-12 mm carapace length) were more active at night and foraged more and walked less in summer than in the late fall. Post-algal phase lobsters (24-28 mm CL) were more active when in the presence of conspecifics. Predation rates in all seasons were highest for lobsters without cover and lowest while in algal cover. The proportion of algal juveniles found walking during their active period changed with the seasons and significantly fewer individuals foraged in late fall than in summer. Variation in the behavior of post-algal lobsters may reflect the niche shift from full-time algal dwelling to diurnal crevice sheltering yet the difference in predation risk between algal sheltering and crevice sheltering is not sufficient to explain the size at which this transition should occur. Shifting from algae to crevices could potentially produce a population bottleneck for lobsters in areas devoid of appropriate structure. This may be especially important for evaluating the impact of recent widespread shelter loss by sponge die-off in the Florida Bay lobster nursery, Florida Bay is the largest and most important nursery of the Caribbean spiny lobster, Panulirus argus, in U.S. waters (Davis and Dodrill, 1989). A mixture of algal dominated limestone hardbottom and extensive seagrass beds provides habitat for juveniles from settlement until sub-adult phase (18-24 months) (Marx and Herrnkind, 1985a; Herrnkind and Butler, 1986; Forcucci et aI., 1994). Surviving lobsters migrate from the nursery to make up the Keys lobster fishery; one-third of the catch occurs within the bay (J. H. Hunt, Florida Department of Environmental Protection, personal communication). Understanding the role of recruitment including the impact of post-settlement mortality is essential for management of this valuable marine resource (Butler and Herrnkind, 1992). In this study we analyze ontogenetic and seasonal changes in behavior and habitat use and evaluate them in light of their potential survival value. The Caribbean spiny lobster has a complex life cycle in which different ontogenetic phases occupy three ecologically distinct habitats (see reviews in Kanciruk, 1980; Phillips and Sastry, 1980; Herrnkind et al., 1994). Clear, leaf-like phyllosoma larvae enter the plankton upon hatching and spend approximately 9 months presumably moving with the oceanic currents around the Caribbean although the pathways are unknown. Planktonic larvae metamorphose into benthic lobsters by a two-step (two molt) process that occurs while moving inshore toward shallow bays and lagoons. Last stage phyllosoma larvae molt into clear, streamlined pueruli or postlarvae (Lewis et al., 1952). Non-feeding pueruli (Sweat, 1968; Lyons, 1980; Wolfe and Felgenhauer, 1991) swim onshore during evening flood tides at new moon (Lewis et al., 1952; Calinski and Lyons, 1983). Pueruli gain pigmentation then molt into benthic algal phase juveniles shortly after settling