Bycatch and discards of scorpaenoid and dactylopterid fishes from deep-sea shrimp trawlers operating in the southeastern Arabian Sea: Diversity, trophic levels, ecological guilds and towards management priorities

Abstract

The shrimp trawl fishery has raised significant concerns both regionally and globally due to high levels of bycatch and its substantial contribution to the total global discards. This study aimed to investigate the temporal patterns, species diversity, trophic levels, and feeding guilds of scorpaenoid and dactylopterid fish caught as bycatch from trawlers targeting deep-sea shrimp off Kollam in the southeastern Arabian Sea. A total of 31 species of both scorpaenoids and dactylopterids were collected fortnightly from Sakthikulangara Harbour, Kollam, India, between January and December 2022. The results revealed that the bycatch included 27 species from the suborder Scorpaenoidei, spanning 8 families, and 4 species from the order Dactylopteriformes, all belonging to a single family Dactylopteridae. Biodiversity indices indicated the highest species diversity (H’ = 4.18) in November 2022, the species richness index (d = 3.243) peaked in February 2022, and the dominance index (lambda' = 0.3248) was highest in August 2022. Majority of the species belongs to top-level predators (83.3 %), followed by carnivores (16.7 %), respectively. The feeding guild analysis indicated that 35.5 % are high-level carnivore followed by invertebrate feeding, crustacean feeding, midlevel carnivores, carnivores, piscivore feeding and zoobenthic feeding (19.4, 12.9, 12.9, 9.7, 6.5 and 3.2 %), respectively. Fishes caught as bycatch belongs to ‘least concern’ (67.7 %), not evaluated (25.8 %) and data deficient (6.5 %) as per the IUCN conservation status. Survey conducted across various stakeholders associated with the trawl fishery indicated significant differences in priorities warrant participatory approach to minimize conflicts among various stakeholders. Present study provides valuable insight and benchmark information on various aspects on the deep-sea shrimp fishery in the southeastern Arabian Sea for the sustainable exploitation and effective management of these vulnerable fishery resources.