Evaluation of the fisheries and resource of sea cucumbers in the coastal waters of Trincomalee district, Eastern Sri Lanka

Though sea cucumber is one of the key export-oriented fishery resources in Sri Lanka, there is some evidence for the population depletion of most of the sea cucumber species in the shallow coastal waters. The present study was aimed to study the status of the sea cucumber fishery in the Irrakkakandi coastal area, eastern Sri Lanka, and carry out a stock assessment on the critical sea cucumber species presently harvested in this area. In order to achieve the objectives, logbook records based survey was conducted to cover the fishing season in 2019, from late February to the end of September. The harvest was collected by skin diving from shallow nearshore waters and Scuba diving from distal coastal waters about 5 km away from the shore. Thelenota anax was the dominant species in the catch from both fishing grounds, with a relative abundance of 86.82% in shallow waters and 91.30% in distal waters. The average Catch Per Unit Effort (CPUE) during the fishing season in 2019 for SCUBA diving and skin diving was 50±8.59 individuals /boat/day and 8±1.12 individuals /diver/day, respectively. The dominant stock of the T. anax in the distal fishing ground was assessed using the depletion method. The initial stock size of T. anax at the onset of the fishing season was estimated at 112,067 individuals, and about 25% of the initial stock had been fished by the end of the fishing season in 2019. The estimated catchability coefficient (q) was 0.00046. The study revealed that the stock of T. anax along with other recorded threatened species in the Irrakkakandi coastal waters might be led towards extinction if the fishery prevails without proper management.