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 km 2 and 1779 km 2 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 highvalue category (<2 ind ha −1 ). 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) and depth categories. The highest density was reported in rocky habitat associated with seagrass and / or macroalgae. The density of low-value species was significantly high in 1-10 m depth category (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.

Sea cucumbers in the Seychelles: effects of marine protected areas on high‐value species

“…Habitat can also affect the distribution of marine fauna and should be incorporated in assessments of MPA influence, particularly when there are no temporal data (Russ et al, 2005). Many shallow water, tropical holothurians have distinct habitat associations (Dissanayake and Stefansson, 2010;Bellchambers et al, 2011). Consequently, benthic composition within each count area was estimated by eye and expressed as percentage cover.…”

The effect of random and density‐dependent variation in sampling efficiency on variance of abundance estimates from fishery surveys

“…Other examples are numerous (e.g. Dressel, ; Dissanayake & Stefansson, ) as using CV estimates from observations to assess quality of surveys appears to be a standard among survey scientists. Unfortunately, these assessments are usually performed without regard for accuracy or precision of AIV estimates.…”

“…Coefficients of variation derived from AIV are often used to compare the reliability of AI estimates derived from surveys using different tools or sampling designs (Pennington & Volstad, 1991). For example, Lingen et al (1998) Dressel, 2005;Dissanayake & Stefansson, 2010) as using CV estimates from observations to assess quality of surveys appears to be a standard among survey scientists. Unfortunately, these assessments are usually performed without regard for accuracy or precision of AIV estimates.…”

Sea cucumber fishing pattern and the socio-economic characteristics of fisher communities in Sri Lanka

“…However, fishing activities did not sustain for a long period in the south and east coasts due to over-harvesting of sea cucumber resources. Currently, the sea cucumber fishing is confined to the north-west, north and north-east coasts of Sri Lanka (Dissanayake and Stefansson, 2010;Kumara et al, 2013). Although many sea cucumber species are commercially exploited in the coastal waters of Sri Lanka, there is no tradition of consuming them locally Stefansson, 2010, 2012).…”