Studies on the sea cucumber fishery in the North Western coastal region of Sri Lanka.
D. C. T. DISSANAYAKE* AND M. J. S. WIJEYARATNE
Present study was carried out at the major landing sites at Kalpitiya and Mannar in the North Western coastal region of Sri Lanka from October 2002 to April 2003. A total of 16 sea cucumber species belong to the Order Aspidochirotida were identified. Of these, 12 species belonged to Family Holothuridae and four to Family Stichopodidae. Holothuria scabra and H. spinifera were found to be restricted to the Mannar area whilst H. fuscogilva, H. nobilis, Actinopyga echinites, Bohadschia argus, B. marmorata, unidentified Bohadschia sp, Thelenota ananas and T. anax were recorded only in the Kalpitiya area. H. atra, H. edulis, A. miliaris, A. mauritiania and Stichopus chloronotus were found in both areas but these species were not very frequent in catches. Sea cucumbers were harvested by fishers through diving and hand picking. Total catch and effort in the two areas showed marked differences. In Kalpitiya area B. marmorata was dominant in catches while in Mannar H. scabra was dominant. During the period of survey, the highest estimated catch was recorded in March 2003 in Kalpitiya area (22,692 Numbers) and January in Mannar area (16,269 Numbers). The fishing effort remained at a more or less steady level in Mannar area throughout the study period (7 – 9 boats day-1). However in Kalpitiya area, fishing effort varied considerably (7 – 13 boats day1) and the maximum and minimum fishing efforts were reported in March 2003 and October 2002 respectively. Nevertheless there was no significant difference between the mean number of boats engaged in this fishery in the two areas. Significantly high catches per diver per day was noted in Kalpitiya area (22.6 Numbers day-1) than in mannar (5.5 Numbers day-1) (p< 0.001). The estimated total number of sea cucumbers caught in Mannar and Kalpitiya area during the present study was 102,280. Of these 47,507 individuals were caught from Kalpitiya area and 54,773 were caught from Mannar area. Estimated values for asymptotic length (L∞) of A. echinites, A. miliaris, B. marmorata, unidentified Bohadschia. Sp. and H. scabra, were 32 cm, 41.5 cm, 56.3 cm, 41.5 cm, and 34.4 cm and the growth coefficients were 1.9 year-1, 2.3 year-1, 1.35 year-1, 1.8 year-1, 0.8 year-1 respectively. The highest mortality estimated for A. miliaris while the lowest was for H. scabra. It appears that size regulation is the most important measure for sustainable exploitation of existing sea cucumber stocks in the North western coastal region of Sri Lanka.