Does conspecific density influence the settlement of Caribbean spiny lobster Panulirus argus postlarvae?

Caribbean spiny lobster, Panulirus argus, are highly social and can detect and respond to the odour cues of conspecifics. We used a laboratory and a field experiment to test the hypothesis that lobster postlarvae can detect conspecific cues and use this information during settlement. First, using a Y-maze choice test, we found that more postlarvae oriented towards than away from conspecifics but these results were not statistically significant. Second, we manipulated the density of large benthic juvenile lobsters at eight locations in Florida Bay to test if the settlement of postlarvae or post-settlement survival was influenced by conspecific density. Microwire-tagged juveniles (controlled settlement) were added to all sites in equal density to estimate growth and rates of natural settlement. In subsequent months, density of these tagged juveniles did not vary between treatment and control sites; however, the density of untagged juveniles (natural settlement) was higher at treatment sites. Finally, multiple regression models of postlarval supply, macroalgal cover, shelter density, predator density, and large juvenile density on settlement cohorts found that the density of large juveniles at the time of settlement predicted the density of early juveniles 4 months later. Taken together, our laboratory and field results suggest that postlarval settlement may be influenced by the density of conspecifics.