Management Implications of Trends in the Population Dynamics of the Caribbean Spiny Lobseter, Panulirus argus, at Looe Key National Marine Sanctuary

Hunt, John; Matthews, Thomas; Forcucci, David; Hedin, Brenda; Bertelsen, Rodney

A two-year study designed to delineate trends in abundance and population dynamics of the spiny lobster, Panulirus argus, in Looe Key National Marine Sanctuary was conducted from April 1987 to April 1989. The goal was to evaluate existing management strategies, primarily the effectiveness of the non-consumptive core area, in providing protection for shiny lobsters. Abundance fluctuated within each year but did not increase in any zone over the course of the study. Mean density on the Fore Reef was 64.9 lobsters/ha, less than half that recorded in the lobster sanctuary at Fort Jefferson National Monument, Dry Tortugas. During the open fishing season, abundance decreased in three of six zones and lobster size declined throughout the Sanctuary. The largest lobsters were found on the Fore Reef. There, sex ratio was heavily skewed toward females and nearly 100% were carrying external eggs or ripe ovaries. Multiple spawning was commonplace. In contrast, on the adjacent Reef Flat, lobster size was reduced, males were more abundant, and reproductive ability was reduced. Residency was greatest within the Core Area. Core Area lobsters foraged nocturnally in the rubble and mixed rubble-grass habitats on and surrounding the Reef Flat. Core Area lobsters were captured by fishermen in those regions. We conclude that the existing Core Area does not offer much protection to spiny lobsters. We recommend that its size be increased to include the entire foraging range and habitat of Reef Flat and Fore Reef lobsters plus a reasonable surrounding buffer.