Abstract

A benthic megafaunal study off Concepción Bay, central Chile (36°32'S, 73°W), provided abundance and bathymetric distribution data of the newly recruited squat lobster Pleuroncodes monodon (Decapoda, Galatheidae). The megafauna was surveyed 8 times between July 1991 and April 1992, with an Agassiz trawl at depths of 40, 64, and 96 m along a transect across the continental shelf. Recruits of P. monodon (carapace length (CL) 3-10 mm) were first sampled in all depth strata in early March, and then in April. April density (1 ind/m2) and mean size (6.1 mm CL) were significantly higher than March density (0.07 ind/m2) and mean size (5.3 mm CL). Depth did not affect abundance and its significant effect on mean size was conditional on month effect. We interpret these results as evidence that the main pulse of recruitment occurred simultaneously across the continental shelf transect in April, and that larvae settling in April have a larger size than larvae settling in March. Recruitment appears to be associated with late summer development of the giant sulfur bacteria Thioploca spp., suggesting an ecological relationship. Moreover, the observed recruitment occurred in late summer to early fall when the oceanographic regime in the area shifts to a postupwelling regime.