Ontogenetic habitat shifts affect performance of artificial shelters for Caribbean spiny lobsters

Abstract

Early benthic juveniles (EBJ) of Caribbean spiny lobster Panulirus argus dwell solitarily in vegetated habitats but eventually shift to dwelling gregariously in crevice shelters ('crevices'). This habitat shift may depend on the interplay between the refuge value of the local vegetation (which increases with complexity) and that of available crevices (which increases with the potential they offer for gregariousness). We examined how these factors influenced density enhancement of lobsters with large artificial shelters ('casitas', 1.1m2 in refuge area) in a coastal reef lagoon. We deployed 10 casitas at each of five 1 ha sites, 3 located in the mid-lagoon zone (ML) and 2 in the back-reef lagoon zone (BRL). These zones differed in vegetation complexity and abundance of algal-dwelling EBJ (greater in the ML), and abundance of crevices (greater in the BRL). Over 4 yr (22 surveys), abundance of large juveniles (>20 mm carapace length, CL) was initially higher in casitas in the BRL but tended to converge over time between lagoon zones, whereas EBJ (≤20 mm CL) were consistently more abundant in casitas in the BRL. Even when controlling for a potentially stronger conspecific chemical attraction exerted by greater aggregations of large juveniles in BRL casitas, significantly more EBJ shifted to casitas in the BRL than in the ML. Thus, lobster density enhancement with casitas was more immediate in the BRL, where the local vegetation ceased to protect lobsters sooner, but increased over time in the more lushly vegetated ML as gradually more lobsters shifted to, and persisted in, casitas. © Inter-Research 2009.