Regional variation in fish species on the continental shelf of Sri Lanka

Abstract

Sri Lankan marine fishery resources were not assessed and updated for the last four decades. A comprehensive survey was performed by R.V. Dr. Fridtjof Nansen, starting from June 24 to July 16, 2018. Variations of fish density and diversity on the continental shelf of Sri Lanka were determined by region (East and West) and depth (20–50 m and 50–100 m) using 65 trawl samples collected. Associations between ichthyofauna, ecological parameters, and hydrographic variables (temperature, salinity, and oxygen) were determined. There were 620 species from 137 different families observed during the survey, with family Myctophidae being the most dominant with the highest number of individuals caught from all station (24.61% out of the total number of individuals) while the most represented families by density (t/NM2) were Carangidae (8.01%). A total of 440 species were found in the East region compared to 385 species in the West region; the density of fish was 1.3 times higher in the East region (9.00 ± 1.08 t/NM2) compared to the West region (6.85 ± 1.40 t/NM2). Similarly, the East region was 1.3 higher in the Shannon Wiener’s Diversity Index (SWDI) than the West region. Shallow-water (20–50 m) area has been reported as more diverse and denser than deep-water (50–100 m). Canonical correlation analysis showed a positive association of fish density with oxygen and a negative with temperature and salinity. This study would be an invaluable baseline for monitoring future changes and preparing recommendations and management action plans.