Dynamics of a protected Western Mediterranean population of the European spiny lobster Palinurus elephas (Fabricius, 1787) assessed by trap surveys

Abstract

A protected population of the spiny lobster, Palinurus elephas, was studied eight years after establishment of the Columbretes Islands Marine Reserve (western Mediterranean). Experimental trap fishing in the reserve and at two unprotected sites revealed that cessation of fishing in the reserve is probably responsible for high catch rates observed there and that the annual fishing closure is effective in rebuilding populations in exploited areas. In the reserve, variations in abundance, sex ratio, and size of lobsters were conspicuous. Catch rates were always higher in deep (50–80 m) than in shallow areas (20–50 m). Bathymetric differences in abundance were smallest in early summer, possibly because of seasonal onshore movements associated with reproduction. Females were always more abundant than males and less variable in number and size. Ancillary data suggest that reproductive and moulting behaviour, particularly of males, influences population estimates of P. elephas from trap surveys. Presence of subadults in deeper waters of the reserve suggests that 2- to 3-year-old juveniles undergo ontogenetic migration from the shallow settlement habitats (<20 m) to deeper habitats (>50 m). The results highlight the effectiveness of fishing restrictions in rebuilding P. elephas populations and suggest that the lobster population in the reserve is not closed.