Nocturnally active western rock lobsters Panulirus cygnus forage close to shallow coastal reefs

Abstract

The western rock lobster Panulirus cygnus is an abundant consumer along the lower west coast of Australia, sheltering in reef during the day and foraging in surrounding habitat at night. We used acoustic telemetry to determine the distances from high-relief reef where nocturnally active P. cygnus forage at 3 sites representing 3 common shallow-water habitats: meadows of the seagrasses Amphibolis spp. and Posidonia sinuosa and macroalga-dominated pavement. We focussed on among-site variation in core and total nocturnal activity area, distance of foraging from high-relief reef and total distance between position estimates. We found that P. cygnus moved over an extensive area at all sites and that 90% of lobster activity occurred within 60 m of the nearest high-relief reef at all 3 sites regardless of habitat type. Foraging activity by P. cygnus is therefore likely to be greatest within this zone around coastal reefs. Core (50% utilisation distribution (UD)) and total (95% UD) nocturnal activity areas did not differ significantly between sites and averaged 2556 ± 482 m 2 and 10 437 ± 2221 m 2 , respectively. Total distance between position estimates and average distance from reef did not differ between sites either.