Assessing the ichthyofaunal diversity and trophic level from trawl bycatch of Chennai Fishing Harbour, Southeast Coast of India

Abstract

The present study aimed to document the temporal diversity and trophic level of ichthyofauna from the Chennai Fishing Harbour, Southeast coast of India. The trawl bycatch consists of 45,527 ichthyofauna individuals collected fortnightly during the period June 2018 to April 2019. The recorded ichthyofaunal diversity includes 156 species belonging to 2 classes, 14 orders, 66 families, and 119 genera. The order Perciformes dominantes with 74 species (47%) followed by Scorpaeniformes (12%; 19 species) and Tetraodontiformes (11%; 18 species). Temporal diversity analysis revealed that the maximum species diversity was observed during the North-east monsoon (123 species) while the minimum was observed during the post-monsoon (107 species) period. Numerically dominant bycatch species were found to be Leiognathus equulus (6%), Equulites lineolatus (5%), Gazza achlamys (5%), Karalla dussumieri, (4%) Otolithes ruber (3%) and Nibea maculata (2%). Biodiversity analysis revealed that the Shannon–Wiener​ species diversity index ranged from 5.37 (South-west monsoon) to 5.53 (North-east monsoon) whereas the species evenness was observed from 0.77 (South-west monsoon) to 0.81 (Post-monsoon). The habitat-wise diversity analysis revealed that demersal species group was dominant (72 species; 46%) followed by reef-associated (70 species; 45%), benthopelagic (8 species; 5%), pelagic (5 species; 3%) and bathy-demersal (1 species; 1%). The results of the trophic level shows that the bycatch fish species was dominated by top-level carnivores (49%) followed by mid-level carnivores (26%), apex predator (19%), primary carnivores (5%) and herbivores or planktivores (1%). The IUCN categories of bycatch species are mostly classified as Not Evaluated, Least Concern, Data Deficient and Vulnerable viz., 58%, 36%, 5% and 1% respectively. The present study also gives information on juvenile fish that are encountered in trawl bycatch along the Chennai coast. The outcome of the study gives baseline information on the bycatch diversity which paves the way for the sustainable exploitation and also the management of exploited fisheries resources in this region.