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Seasonal fish species composition, catch rate and catch value in the small scale fishery of a tropical monsoon estuary along southwest coast of India

Ichthyofaunal survey was conducted in the Ib River (21°44’ to 22°50’ N; 83°56’ to 83°54’ E), an important tributary of Mahanadi, to evaluate the diversity and distribution of freshwater fishes along six sites on seasonal basis between February, 2016 and January, 2017. A total of 55 species belonging to 42 genera, 21 families and 9 orders were recorded from the study area. Maximum number of species belonged to the Order Cypriniformes (41.8%) followed by Siluriformes (21.8%) and Perciformes (21.8%). Maximum value of species richness was observed in downstream areas; Sundargarh and Barghat and least in upper stretches of Pamsala. Shannon–Weiner diversity index ranged between 2.47 to 3.68 at the six sites of Ib River indicating healthy state of the river. Bray-Curtis similarity cluster analysis suggests that similarities between sites decrease with increasing distance, with highest similarity found between Sundargarh and Barghat sites. Baseline data on fish biodiversity has been generated in this study which can now be periodically monitored and form basis for future conservation plans.

Rising crisis in marine environment is the presence of plastics in the water column and risk of their input and accumulation in the food web. The present study reports for the first time, the presence of micro and macro plastics in the gut of razor moonfish, Mene maculata. Moonfish plays a major role in the marine food web as prey of large pelagic fishes. The gut analysis of fishes collected from commercial vessels operating along eastern Arabian Sea was analysed to determine the occurrence and abundance of plastic particles with attempt to identify the diet component which might have contributed to the plastic intake in fish. The analysis revealed dominance of plastic particles in gut when dietary component was dominated by eggs. The present study forms baseline information for plastic accumulations in fishes along the eastern Arabian Sea

An attempt was made to establish association pattern between dimension of fish and otolith to expedite morphometric variations of geographically isolated stocks of Tenualosa ilisha (Hamilton, 1822), from three diverse ecosystems; viz., an estuarine (brackish water), a riverine (freshwater) and a lacustrine (freshwater) ecosystem. Sampling was carried out during the period from September 2017 to February 2019 and a total of 196 otoliths were sampled from Narmada Estuary (n=69), Brahmaputra River (n=75) and Ukai Reservoir (n=52) of India. Mean otolith length recorded was 3.55±0.14 mm, 5.18±0.09 mm and 3.85±0.07 mm for samples collected from Narmada Estuary, Brahmaputra River and Ukai Reservoir respectively. Otolith length-weight relationship (OLWR) from three ecosystems showed negative allometric b values ranging from 1.9046-2.5048, with significant difference between Narmada Estuary and Brahmaputra River (p<0.05). Power regression analysis of otolith dimensions (length and width) to total length of fish (TL) and otolith length (OL) to total weight of fish (TW) showed that data fitted well to the model as evident from R2 values (>0.6); except for relationship between otolith width (OB) and TL in samples from Brahmaputra River (R2=0.459). Present study provides first-hand information on association pattern of dimension of fish body and otolith of T. ilisha which can be used in geographical mapping of stock profile of the species.

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An analysis was carried out on monthly spatial distribution and unusual congregation of Indian squid (Uroteuthis (Photololigo) duvaucelii) off Maharashtra coast. Decadal, annual and monthly squid landing data were taken from National Marine Living Resources Data Centre (NMLRDC) of ICAR-CMFRI. Onboard fisheries information were collected from multi-day trawlers operating from Mumbai and Ratnagiri. Ocean environment parameters coming from Copernicus Marine Service Information with 1/12 degree horizontal resolution and 50 vertical depth level and OSCAR (Ocean Surface Current Analysis Real-time) near-surface ocean current estimates was derived using quasi-linear and steady flow momentum equations on a 1/3 degree grid with a 5 day resolution. In last decade, contribution of squid to total marine fish landing of Maharashtra rose from 2% to 7.3%. The decadal landing shows two peaks in 2012 and 2017. Indian squid landing in 2017 shows two peak, one during August to October confined to 15 0 N to 17 0 N latitude in 15 to 60 m depth off south Maharashtra and second in summer, during March-April months widely scattered in north and south Maharashtra. The unusual abundance of Indian squid during mid-October to mid-November 2017 were attributed to rise in coastal surface and subsurface temperature. Catch per hour of trawl and SST shows strong positive correlation (0.79) during the same period.

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