Species composition and conservation status of shark from fishery landings and fish markets in Sri Lanka revealed by DNA barcoding

Abstract

Sharks are considered to be top predators in marine ecosystems. Due to the high market value of shark fins, fishing pressure on these top predators has increased significantly and they are currently considered to be a threatened marine vertebrate group. Sri Lanka is an island nation with 21 major fish harbours in operation and one of the top 20 shark fishing countries. With an increasing local and global demand for shark meat and fins, the species consumed by Sri Lankans as well as species composition of the landing are in question because the identification of processed shark is difficult (e.g. fish filet) and there is a lack of species-specific landing data. In the present study, we applied a DNA barcoding approach to identify species composition of the shark catch in Sri Lanka. Shark tissue samples were collected in 2018 and 2019 from 10 fishing harbours and fish markets around Sri Lanka. In total, 330 out of 353 tissue samples were successfully barcoded and the results revealed 17 shark species corresponding to five families including Alopias superciliosus, Carcharhinus amblyrhynchoides, C. falciformis, C. leucas, C. limbatus, C. longimanus, C. melanopterus, C. sorrah, Chiloscyllium griseum, Hemipristis elongate, Loxodon macrorhinus, Paragaleus randalli, Prionace glauca, Rhizoprionodon oligolinx, R. acutus, Sphyrna lewini and Galeocerdo cuvier. Among them, C. falciformis (silky shark) is the most dominant (39.4 %). Variation in fishing area and fishing gear used could be the main determinants of species composition across localities. The results showed 62 % of shark species identified in this study are threatened globally based on IUCN categories. Surprisingly, two banned species, A. superciliosus and C. longimanus, were found with low abundance. The results of this study provide crucial information for improving the Sri Lankan shark management plan in the future. In addition, we suggest a regular assessment of shark landing species composition be implemented to monitor the efficiency of current management.