ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01291

ABSTRACT: The Sindhudurg coast in Maharashtra, India, supports diverse fisheries and is a vital habitat for Indian Ocean humpback dolphins, a species also found nearshore along the west coast of India. Here, dolphins cause economic losses to fishermen by competing for catch and damaging fishing gear. Dolphins are also affected by entanglement in or ingestion of parts of fishing nets. There is a need for a systematic assessment of the distribution of risks to dolphins, and the specific fisheries most impacted by interactions with dolphins. To bridge this information gap, we: (i) analyzed the behaviour and locations of dolphin groups in the absence and presence of fishing vessels (2012-2015), and (ii) mapped the spatial overlap of dolphins and fishing vessels (2014-2015), to determine high-risk areas for dolphins. We observed 175 dolphin groups, of which 43% engaged in foraging behaviours (75 groups). Dolphins occurred in approximately 50% (164 km²) and fishing vessels in 100% of the total survey area (333 km²). The proportion of dolphin groups engaged in foraging behaviours was significantly higher when fishing vessels were present compared to when absent. Gillnet (55%) and trawl (32%) accounted for the majority of observed fishing vessels when dolphins were present. Gillnet vessels had a 95% spatial overlap with dolphin habitat and trawl and purse seine vessels, 86% each. We identified eight high-risk areas that were within ~500 meters of the coastline, coinciding with high-density dolphin habitat, near estuaries. These results have the potential to inform marine mammal conservation and fishery management in Sindhudurg.