Non-target species interactions in tuna fisheries and its implications in fisheries management: Case of large-mesh gillnet fisheries along the north-west coast of India

Occurrence of non-target, associated and dependent species is a feature of tuna gillnet fisheries world-over, posing a great concern for fisheries management. Predominance of small-scale or artisanal fisheries in the region compounds the concern due to the uncertainty in data. There is dearth of information on the catches and the non-target species interaction in the tuna gillnets fisheries in India, especially from the north-west coast, where gillnet is the predominant gear targeting the tuna. We collected spatially explicit catch data with voluntary participation of fishermen from Veraval, Gujarat and quantified the species wise catches over space and time for 567 fishing operations spread across six years (2011-2016). Species composition, seasonal variation, nature and level of interrelationship in catch incidences, similarities among different groups of resources etc. were ascertained using various statistical tests like the Kruskal-Wallis rank test, Pearson’s correlation and principal component analysis (PCA). The study reveals spatial expanse of gillnet fisheries of Gujarat and their major fishing grounds together with variations in catches of different groups over space and time. Nature and strength of interaction of sensitive species like turtles and dolphins as well as the unicorn leatherjacket, an emerging catch in the gillnet tuna fisheries was ascertained and GIS maps depicting the areas of copious presence of these groups are presented. Management implications of such interactions as well as the potential of involving fishermen to gather spatially explicit fishery data, paving way for their active involvement in fisheries governance are discussed. The study can be replicated at national level to enhance the understanding on the gillnet fisheries to bring in pragmatic interventions to sustain the fisheries.