Habitat Thresholds and Bottlenecks in Production of the Spiny Lobster (Panulirus Marginatus) in the Northwestern Hawaiian Islands

Variations in landings from the lobster fishery among banks of the northwestern Hawaiian Archipelago were compared with bank topography and benthic habitat characteristics. Summit depth, harvest area, amount of shallow habitat, and latitude were considered in relation to pre-exploitation research catch rates and 6 years of commercial fishery landings. A threshold between lobster production and the depth of bank summit was observed; banks with summits deeper than 30 m yielded few lobsters. The effect of benthic habitat relief was then examined for three selected, bathymetrically similar banks, two commercially productive and one unproductive. Percent cover of habitat variables with characteristic relief such as sand, algae, and coral outcrops were measured on each of the banks during 70 scuba dives. Juvenile lobster stages were found significantly associated with habitat scale. The nonlinear relationship indicated both high and low extremes in relief yield poor catch per unit of effort (CPUE). Only the variable intermediate relief (5–30 cm) was associated with high sublegal lobster CPUE. The two productive banks had much more benthic relief at this scale than did the unproductive, suggesting that the abundance of intermediate relief habitat represents a bottleneck to adult lobster production.