Fishing using mobile gears such as trawlnets has been identified as one of the major threats to the marine biodiversity and to the sustainability of marine fisheries. Studies on the fish fauna associated with bycatch of bottom trawlers of Kerala, on the southwest coast of India recorded 217 species classified under 21 orders, 90 families and 154 genera. Among the fish fauna in the trawl bycatch, 103 species (47%) belonged to the trophic level 3.5-3.99, 56 species (26%) to the trophic level 3.0- 3.49, 40 species (18%) to the trophic level 4.0-4.49, 13 species (6%) to the trophic level 2.5-2.99 and five species (2%) to the trophic level 2.0-2.49. The diversity indices recorded significantly higher values for the trophic level 3.5-3.99 and it was the lowest for the trophic level 2.0-2.49. In general, the dominant fraction of fish fauna (73%) of the trawl bycatch represented by 159 species was the mid level carnivores included in the trophic level 3.0-3.99. The diversity of fish fauna in the trawl bycatch differed significantly at different trophic levels; presence of large number of mid level carnivores in the trawl bycatch may indicate large scale removal of top level predators from the ecosystem. The length class distribution of fishes of the trawl bycatch at various trophic levels showed that fishes in the length group below 15cm were dominant in all the trophic levels. The mean trophic index of fish species in the trawl bycatch was estimated as 3.12. Reduction of fishing pressure and use of bycatch reduction devices are suggested for the sustainable management of trawl bycatch in the southwest coast of India.

Trophic level, Mean Trophic Index, trawling, bycatch, Kerala