Relationship between fish size and otolith size of four deep-sea fishes from the Western Bay of Bengal, India

The present study provides the otolith morphology and morphometric relationships with fish size of four deep-sea fishes (Parascombrops pellucidus Alcock, 1889, Alepocephalus blanfordii Alcock, 1892, Lamprogrammus niger Alcock, 1891, Pterygotrigla hemisticta (Temminck & Schlegel, 1843)) collected from western Bay of Bengal during March 2020. Among these, the equations were derived for the first time for three species (P. pellucidus, A. blanfordii, L. niger). Sampling was done as a part of deep-sea exploratory survey of FORV Sagar Sampada along the deeper shelf regions of the Bay of Bengal at a depth range of 200 – 1000 m using high-speed demersal trawl (HSDT-CV). The numerical relations established using regression between fish size (TL) and various otolith morphometric measurements (otolith length (OL), otolith height (OH), otolith weight (OWe), otolith area (OA) and otolith perimeter (OP)) can be used to predict the prey size in food and feeding studies for studying the food web dynamics of less-studied deep-sea fishes. LWR of the otolith of selected species showed a negative allometric growth (t-test, p < 0.5). The higher r2 value (> 0.70) obtained for the relationship between fish size (TL) and various otolith morphometric measurements indicates the robustness of the model. The representative images of otoliths of these fishes will be helpful to the taxonomists for the species confirmation and reconstruction of past species assemblages in the palaeontological studies.