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Background: The fishes of the family Carangidae forms one of the largest families of bony fishes, representing about 140 species, widely distributed in all tropical and temperate marine waters of the world. In recent past, fishes of this family are exhibiting new geographical distribution which could be attributed to climatic variability. Methods: The specimens were collected from multiday trawl boats operated along Karnataka coast. Morphometric and meristic characteristics together with genetic analysis using DNA bar coding was used to validate the identity of the specimen. Spatial distribution map of the species in Indian Ocean was generated using the information from the present study and available literature. Result: The morphometric and meristic characteristics of the specimens of greater amberjack, Seriola dumerili collected during the study were comparable with the previous investigations. The phylogenetic tree constructed using sequences of COI (MW974826 and MW974827) of the Seriola species showed distinct clustering among species with significant bootstrap values confirming the identity to the extent of 99% with the sequences of Seriola dumerili deposited in NCBI GenBank. This study confirms the first distributional record of Seriola dumerili from the eastern Arabian Sea.

The relative abundance and biological characteristics of the spadenose shark Scoliodon laticaudus, from the south eastern Arabian Sea along Karnataka, India was studied. The average annual catch of the species during the period 2012–2017 was estimated at 112 t which formed about 13% of the total shark landing in the region. The species is landed mostly by trawl nets. Monthly abundance estimates showed that highest landing of the spadenose shark was observed in January. A total of 852 specimens were studied for biological characteristics. The length range of 19–63 cm was observed and length group of 45–55 cm formed the mainstay of the fishery. The length weight relationship for male and female and sexes pooled were 0.06588 L2.2386; 0.01118 L2.7497 and 0.01396 L2.6840 respectively. Analysis of covariance showed significant differences between the male and female ( p 0 . 05 ). In the present analysis, the regression co-efficient ( b value) for the species differs significantly from the value 3 indicating allometric growth. Lm50 for female and male were estimated as 32 and 33 cm. Chi-square-test on monthly sex ratio for the period showed that there was significant difference in sex ratio only in the months of January, October and November. S. laticaudus was found to be predominantly piscivorous in diet. The fishery is declining and efforts have to be taken for sustainable exploitation of resources.

Environmental parameters influence the productivity and abundance of fish in marine ecosystems. In this study, we attempted to analyse the relationship between environmental parameters and abundance of fish in trawling grounds in south-eastern Arabian Sea along the coast of Karnataka. Among the 85 species of finfishes and shellfishes caught in the trawling grounds, 41 finfish species, 24 crustaceans, 18 molluscs and two echinoderms were recorded. Seasonal differences were seen in biomass with the highest biomass during the post-monsoon period (October-January). Water temperature and nutrients were the key contributing factors of seasonal differences in the biotic communities studied. Season specific diagnostic species were identified using SIMPER analysis. Squilla which formed the major prey item of most of the demersal fishes dominated (>40%) coastal grounds throughout all seasons. This could be considered as a fishery indicator of the region. The dominance and abundance of copepods was found to be influenced by sea surface temperature (SST) and nutrients. The results of the study have implications on the fishery, knowledge on environmental factors influencing the abundance and importance of non-commercial species in sustaining the fishery in the region.