Enhancement of juvenile Caribbean spiny lobsters: an evaluation of changes in multiple response variables with the addition of large artificial shelters

Abstract

Shortage of natural crevice shelters may produce population bottlenecks in juvenile Caribbean spiny lobsters (Panulirus argus), a socially gregarious species. We conducted a field experiment to test enhancement of a local population of juvenile P. argus with the addition of artificial shelters ("casitas") that mimic large crevices (1.1 m(2) in surface area and 3.8 cm in height). Changes in density and biomass of juvenile lobsters 15-50 mm carapace length (CL) were assessed with a multiple before-after control-impact (MBACI) analysis. Separate analyses were also conducted on small (15-35 mm CL) and large (35.1-50 mm CL) juveniles to assess size-related effects. First, we carried out 13 lobster surveys on nine fixed 1-ha sites over a shallow reef lagoon ("before" period). Then, we deployed ten casitas in each of five sites and left four sites as controls, and conducted 22 further surveys ("after" period). Deployment of casitas resulted in a sixfold increase in juvenile density (76% contributed by small and 24% by large juveniles) and a sevenfold increase in biomass (40 and 60%, respectively). Capture-recapture results revealed that enhancement was achieved not by promoting individual growth but by increasing survival, persistence, and foraging ranges of small and large juveniles. Casitas both mitigated shortage of natural shelter and increased sociality, allowing for cohabitation of smaller, more vulnerable juveniles with larger conspecifics that have greater defensive abilities. Casitas may help enhance local populations of juvenile P. argus in Caribbean seagrass habitats, typically poor in natural crevice shelters. The use of MBACI and the simultaneous assessment of multiple interrelated response variables may be a powerful analytical approach to test shelter limitation in other species and to examine the function of structural habitat in other systems.

Influence of local habitat features on disease avoidance by Caribbean spiny lobsters in a casita-enhanced bay

“…Field experiments have shown that casitas do not merely concentrate the existing lobster biomass but actually increase lobster biomass by enhancing survival of the full size range of lobsters that co-occupy casitas (Eggleston et al 1990, Eggleston & Lipcius 1992, Mintz et al 1994, Briones-Fourzán & LozanoÁlvarez 2001, Briones-Fourzán et al 2007). However, as PaV1 can be transmitted by contact, we began an investigation into the dynamics of the PaV1 disease in the population of Panulirus argus from Bahía de la Ascensión.…”

Variability in clinical prevalence of PaV1 in Caribbean spiny lobsters occupying commercial casitas over a large bay in Mexico

“…Gregariousness increases survival of P. argus because shelter-sharing lobsters use their long and spiny antennae in concert to fend off approaching predators , and lobsters seeking shelter reduce their time of exposure by following chemical cues released from sheltered conspecifics (Ratchford & Eggleston 1998, Nevitt et al 2000. Thus, by promoting gregariousness and hence survival, casitas increase local density and biomass of P. argus lobsters (Briones-Fourzán & Lozano-Álvarez 2001, Briones-Fourzán et al 2007). …”

Spatiotemporal bioeconomic performance of artificial shelters in a small-scale, rights-based managed Caribbean spiny lobster (<em>Panulirus argus</em>) fishery

“…Artificial shelters for spiny lobsters mimic their natural dens and have been designed specifically to aggregate individuals for fishing purposes, to increase lobster population productivity, and in some cases to mitigate population loss arising from lack of shelter (Herrnkind and Cobb 2007). The complex issue of whether artificial shelters only aggregate lobsters already present in the ecosystem or actually increase production of lobster biomass has been studied by various authors (Sosa-Cordero et al 1998, Briones-Fourzán et al 2007). The three main ways in which artificial shelters increase production of lobster biomass involve enhancement of lobster survival by (i) alleviating demographic bottlenecks by mitigating limited crevices and shelter availability; (ii) allowing wider access to food resources; and (iii) providing anti-predator group defence to lobsters of all sizes.…”

“…The three main ways in which artificial shelters increase production of lobster biomass involve enhancement of lobster survival by (i) alleviating demographic bottlenecks by mitigating limited crevices and shelter availability; (ii) allowing wider access to food resources; and (iii) providing anti-predator group defence to lobsters of all sizes. Briones-Fourzán et al (2007) have shown that artificial shelters can enhance local populations of juvenile P. argus in Caribbean seagrass habitats, which are typically poor in natural crevice shelters.…”

“…The hypothesized functional benefits of den sharing include the dilution effect or group defence against predators (Eggleston and Lipcius 1992, Mintz et al 1994, Butler et al 1999), the guide effect, which reduces predation risk during the search for shelter (Childress and Herrnkind 2001), and cohabitation of smaller more vulnerable juveniles with larger conspecifics that have greater defensive abilities (Sosa-Cordero et al 1998, Briones-Fourzán et al 2007.…”