Spatio-temporal analysis identifies hotspots of marine mammal strandings along the Indian coastline: implications for developing a National Marine Mammal Stranding Response and Management policy

Marine mammal strandings provide vital information on their life histories, population health and status of marine ecosystems. Opportunistic reporting of strandings serve as a potent low-cost tool for conservation monitoring of these highly mobile species. We present the results of spatio-temporal analyses of marine mammal stranding events to identify hotpots along Indian coastline. We collated data over a long-time frame (~270 years) available from various open access databases, reports and publications. Given the inadequacy in data collection over these years, we grouped data into four major groups viz. baleen whales, toothed whales, small cetaceans and dugongs. Further, we described the trends in data for marine mammal sightings, incidental mortalities, induced mortalities and stranding events using the last group for spatio-temporal analysis. Annual strandings along the Indian coast has increased considerably in the recent years (11.25 {+/-} 9.10 strandings/ year), peaking in the last two years (2015-17, mean = 27.66{+/-}12.03 strandings /year). We found that number of strandings spiked in June- September along the west coast and December- January along the east coast. We identified several sections of coastline which have consistently received comparatively higher number of stranded animals (0.38 - 1.82 strandings/km) throughout the study period. Use of novel geospatial tool Emerging Hotspot Analysis revealed new and consecutive hotspots along the north-west coast, and sporadic hotspots along the south-east coast. Despite the challenges of working with an opportunistic database, this study highlights critical areas to be prioritized for monitoring marine mammal strandings in the country. We recommend establishing regional marine mammal stranding response centres at the identified hotspots coordinated by a National Stranding Monitoring Centre with adequate funding support. Regular conduct of stranding response programs for field veterinarians, frontline personnel focused around identified stranding hotspots would help develop a comprehensive picture of marine mammal populations in Indian waters.