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Two near shore small cetaceans occur commonly along the Maharashtra coast, the Indian Ocean humpback dolphin and Indo Pacific finless porpoise. These cetaceans frequently interact with fisheries in this region due to overlap in space and resource use. Besides stranding records, little ecological information is available about these species from Maharashtra. We conducted 143 semistructured interviews to document local ecological knowledge and community perceptions of small cetaceans in 30 coastal fishing villages in Sindhudurg. Perceptions of finless porpoises were largely neutral, whereas humpback dolphins were negative. A classification regression tree (CART) analysis (root node error: 60%) showed that the annual cost of gear damage was an important predictor variable of humpback dolphin perceptions, followed by occupation (gear type) and age. Entanglements were reported for both species in large and small gill nets, and shore seines. Perceived net damage and catch loss due to humpback dolphins was six times greater than that of finless porpoises. However, finless porpoises were reportedly more frequently entangled in gear than humpback dolphins. We provide an insight into the perceptions of cetaceans in the local community and the fisheries‐cetacean interactions that shape them.

The Indian Ocean humpback dolphin (Sousa plumbea), a common cetacean species in India, has a diverse vocal repertoire, which to date has not been described in detail. This study focused on analyzing their whistle vocalizations. Humpback dolphins were recorded off the Sindhudurg coast of Maharashtra, India, and 2,260 whistles were analyzed for their acoustic characteristics. Whistles spanned a wide frequency range between 2.3 kHz and 33.0 kHz, with durations ranging from 0.01 s to 1.60 s. Whistles were categorized into seven contour classes based on their qualitative properties. A classification and regression tree (CART) analysis was used to quantify variability between the seven contour classes using the measured acoustic features. Based on the CART analysis, frequency gradient, minimum slope, maximum slope, beginning and ending slope accounted for most variability between whistle types. CART resulted in an overall classification accuracy of 89.5%. This study provides a detailed description of acoustic features and qualitative properties of humpback dolphin whistles from the northwestern coast of India. Further comparisons of acoustic data from Sousa populations along the Indian coast are necessary to determine possible geographic variations in whistle characteristics and whether the variations are driven by environmental or genetic factors or a combination of both.

Arabian Sea humpback whales (Megaptera novaeangliae), listed as “Endangered” on the International Union for Conservation of Nature’s Red List, remain resident throughout the year in the waters of the Arabian Sea and constitute a genetically isolated population. In the eastern Arabian Sea, information on humpback whales off the Indian coast has largely been limited to stranding records, local ecological knowledge, and opportunistic visual sighting data. These data, along with information from a long-term study off Oman, suggest that humpback whales migrate across the Arabian Sea into Indian territorial waters from October to March. To study the presence of Arabian Sea humpback whales in Indian waters more comprehensively, passive acoustic monitoring (PAM) was initiated along the west coast of India in 2019. Male humpback whales produce complex songs with a stereotyped structure; these songs are shared within a population, and song patterns are known to evolve progressively over time. In this article, a structural analysis of humpback whale song recorded over four days off the coast of Netrani Island, Karnataka, India, in December 2019 is presented. Time-frequency features of 2,641 individual call units were analysed. Call units had a fundamental frequency bandwidth ranging from 149.98 to 541.65 Hz, with a duration ranging from 1.19 to 5.5 s. The call units were used to identify phrases and themes required to construct the structure of the song, which can potentially help identify the population to which singing individuals belong. This study indicates the need for a long-term PAM program across the Arabian Sea to compare whale songs across the region. Simultaneous recordings over multiple seasons will best assess population connectivity, seasonal occurrence, and movement patterns within and between populations across the Arabian Sea and the Indian Ocean.

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