How oceanography influences Fishery Biology?- A Case of distribution differences incarnivorous and planktivorous fishes along theCoastal Waters of Eastern Arabian Sea In: ICAR Sponsored Winter School on Recent Advances in Fishery Biology Techniques for Biodiversity Evaluation and Conservation, 1-21 December 2018, Kochi.

Understanding the link between physical oceanographic events and seasonality in catch composition is a critical component in the accurate assessment of climate change impacts in context of fisheries. This remains elusive owing to the lack of synoptic-level datasets on the relevant oceanographic variables. The advent of satellite remote sensing that can measure oceanographic variables at high spatial and temporal resolution has helped to address this challenge. Prior studies have communicated the puzzling dominance of carnivores (fish groups) in North East Arabian Sea (NEAS) whereas planktivores appear to thrive in South East Arabian Sea (SEAS). The study attempts to address this conundrum by taking cues from the influence of oceanographic forcing upon seasonal trends in catch composition using remotely-sensed oceanographic variables and mean standardized catch. The anoxic conditions associated with intense seasonal upwelling in SEAS waters leads to the reduction in the vertical extent of demersal carnivore habitats. The demersal habitats in NEAS waters have a higher likelihood of entraining oxygen rich (>0.5 ml/L) water column when compared with its southern counterpart especially from August to November. Moreover, NEAS waters cater to the nutritional requirements of juvenile demersal carnivore population as it supports primary production both during summer and winter monsoon months. The perpetual presence of chlorophyll biomass allows for the persistence of a prey base that maximizes the likelihood of demersal adult population being well-fed. The poleward directed West India Coastal Current facilitates the passive drift of juveniles towards productive and oxygen rich habitats in NEAS waters. For demersal/pelagic carnivores that undergo recruitment over a long span of time (> 6 months), NEAS waters provide the best spawning ground capable of meeting their long-term nutritional demands. Pelagic planktivores thrive in SEAS, where seasonal upwelling supported primary production remains the norm, owing to their relatively short recruitment span (< 4 months). Unlike SEAS, NEAS waters are found to provide suitable environment geared towards the successful larval recruitment, sustenance and survival of the demersal carnivore group. This could act as a forcing function in driving the annual catch composition of landing data registered in NEAS waters toward carnivore spectrum.