A practical field technique for the assessment of spiny lobster resources of tropical islands

The population density of post-recruit spiny lobsters Panulirus argus in the reef-system of Bermuda during May through October was studied using a combined transect and capture-recapture approach in the northeastern reef-system. Population density was greatest near the reef-crest (6.0 +/- 2.0 post-recruits ha(-1); 95% confidence limits) and second greatest on the reef-front terrace (4.1 +/- 1.4 post-recruits ha(-1)). The density of undersized P. argus lobsters on the outermost slopes and terraces of the Platform edge to the south of the island in September was estimated at approximately 97 lobsters ha(-1), indicating that aggregation of young post-recruit lobsters in deep water to the south of the island occurs at the dose of the breeding season. The standing stock of P. argus post-recruits on the Bermuda island shelf was estimated at 1.3 X 10(5) lobsters from the combined transect and capture-recapture technique, and the mean density at 2.9 post-recruits ha (-1). An estimate of the annual fishing mortality coefficient (F) in the 1986/1987 season (0.42) was derived from the total biomass estimate. The technique has potential for assessment of standing stock biomass in the spiny lobster fisheries of island nations. The ratio of the catchability coefficient (q) to the effective area fished (E) was approximately the same (0.059 and 0.058), with baited Antillean arrowhead traps, for trappable P. al-gus and Panulirus guttatus lobsters of different size composition in the northeastern reefs at Bermuda. An average estimate of the parameter q/E for P. guttatus was used to derive a first approximation of the population density of sublegal P. argus (from the catchability coefficient, q) on the outer shelf edge associated with the South Shore. The mean sampling-area and sampling-radius of baited Antiilean arrowhead traps at Bermuda were estimated to be approximately 0.36 ha and 34 m.