Present status of threatened and conserved species entanglement in multiday tuna fishery in Sri Lanka
Sri Lanka is one of the oldest and most important tuna producing island nations in the Indian Ocean. Multiday fishing crafts in Sri Lanka are mainly operated targeting tuna and tuna like species and this is a multi-gear, multi-species fishery. Certain threatened and conserved species are protected in Sri Lanka by the existing law notably oceanic white tip shark, three species of thresher sharks, whale shark, marine mammals and turtles. It has been reported that accidental catching of above species to fishing gears frequently operate in tuna fishery such as gillnets, longline and ring net. The present study was undertaken with the aim of studying the present status of threatened and conserved species recorded in tuna fishery for improving the conservation and management of them. Log book data of Sri Lanka tuna fishery operated during 2016 to 2018 with multiday fishing vessels in EEZ of Sri Lanka and high seas were used for this audit. A total of 4014 recodes of incidental catches of threatened and conserved species were reported of which 73.1% were caught to gillnets16.0% were caught to longline and 10.9% were caught to ring nets. However, for all gear, the live release rate of incidental catch was around 90% and zero mortality was recorded for ring nets. When comparing three consecutive years, entangling of conserved shark species especially thresher sharks to fishing gear was considerably higher in 2018 and probably this may be due to the enhancement of thresher population after imposing a total ban on thresher sharks in 2012. Moreover, total turtle entanglement in all the gears was 3351 of which gillnet was the highest (80.6%). However, around 87% of sea turtles were released in live. Furthermore, Green turtle was the utmost among turtle by-catch recodes. A total of 672 and 945 Green turtles were recorded in 2017 and 2018 respectively. Among them, 89.5 % was reported in gillnets followed by longline (8.2 %). Occasional dolphin catches were also recorded mostly for gill nets. The results revealed that gill net is responsible for catching protected species than other gears. Further, the records indicate that a slight increasing trend in the total entanglement with the highest number of
2327 reported in 2018. However, 88% of them were released in live. The slight increase of recorded catch of threatened and conserved species could be mainly attributed to the improved logbook fisheries data collection system in Sri Lanka.