Abundance and distribution of commercial sea cucumber species in the coastal waters of Sri Lanka

Abstract

The sea cucumber stocks off the east and northwest coasts of Sri Lanka were estimated by surveying 1307 km2 and 1779 km2 by an underwater visual census (UVC) in June and October 2008 respectively. The presence of twenty-five sea cucumber species belonging to seven genera; Actinopyga, Bohadschia, Holothuria, Pearsonothuria, Stichopus, Thelenota and Acaudina was identified in five hundred sampling sites randomly selected in each area. The overall average density (± SD) of sea cucumbers was higher in the northwest (350 ± 648 ind ha-1 ) than in the east (90 ± 130 ind ha-1 ) and low-value species were predominant in both survey areas (79 ± 125 ind ha-1 in the east, 244 ± 488 in the northwest) when compared with medium (10 ± 34 ind ha-1 , 105 ± 175 ind ha-1 , respectively) and high-value category ( ). The estimated total biomass in the northwest (13 024 t) was roughly four times greater than the east (3027 t). Holothuria edulis was the most abundant species in numbers while Holothuria atra had the highest stock biomass in both areas. Sea cucumber densities were significantly different among the habitat (p < 0.001) in the northwest while other commercial groups were dominant in 20–30 m depth range in both areas. Temporal banning of the fishery for high and medium-value species would be a better management option to avoid further stock depletion.