The biology and artisanal fishery of lobsters of American Samoa

Coutures, Emmanuel

A study of the lobster population in American Samoa was undertaken between October 2002 and 2003. Panulirus penicillatus is the main species speared by night near the outer slope by free divers while diving for finfish. Total landings expanded from market survey were estimated to be 576 kg (1271 1b) of spiny lobsters sold per year (without taking subsistence and recreational catches into account). Sex ratio was in favor of males. This difference in sex ratio could be due to the fishing technique which not includes the highest part of the reef edge and the beginning of the reef flat. This could also explain why commercial catches rarely include slipper lobsters (Parribacus caledonicus and some P. antarcticus) whereas they are relatively abundant in the field. With the aid of data from market surveys undertaken in 1999 (i.e. before the ban of scuba fishing), we established that free diving was the most efficient technique. Comparison between markets surveys done in 1999 and 2002-2003, showed an increasing of Catch Per Unit Effort in terms of weight but not in number of lobsters caught, and a decrease in the mean length. Size at sexual maturity, i.e. size when 50% of females are ovigerous, was estimated to be around 7 cm CL (2.76 in) for Panulirus penicillatus whereas the smallest berried females measured 5.25 cm CL (2.07 in). Relationship between fecundity (number of eggs) and carapace length (CL) is provided. Although it was unlawful since 1995 to catch berried females and spiny lobsters smaller than 7.94 cm (3 1/8 in) of CL, they are often found in the markets. Values from market survey were used to estimate the total mortality. The discontinuation of the field survey following accident did not allow estimation of local growth parameters and natural mortality which were taken from literature. Results of fishing mortality and Yield per Recruit (YPR) were in accordance with other lobster fisheries in the Pacific. YPR would slightly increase if length at recruitment was at the legal minimum size. The main recommendation provided is the ban of spearfishing for the commercial fishery. This regulation will allow fishermen to i) verify if lobsters are berried or undersized without injuring them, ii) to catch more slipper lobsters which are easily marketable, and iii) to sell high quality product in markets.