Abstract
Marine mammal strandings provide vital information on species’ life histories, population health and status of marine ecosystems. Opportunistic reporting of strandings also serve as a powerful low-cost tool for monitoring these elusive mammals. We collated data over ~ 270 years available through various open access databases, reports and publications. Annual strandings along the Indian coast (mean = 11.25 ± SE 9.1) increased in the last two years of the study (2015–2017, mean = 27.66 ± SE 8.5 strandings /year). We found that stranding events spike during June—September along the west coast and during December–January along the east coast. We identified several sections of the coastline, such as Mumbai (0.38 strandings/km), Kozhikode (0.28 strandings/km), Tuticorin (0.4 strandings/km), Rameswaram (1.82 strandings/km), Chennai (0.32 strandings/km) and Bhubaneshwar (0.26 strandings/km) with a higher number of stranded animals reported. Emerging Hotspot Analysis located new and consecutive hotspots along the north-west coast, and sporadic hotspots along the south-east coast. We recommend establishing regional stranding response centres at the identified hotspots coordinated by a National Stranding Centre with adequately trained personnel and central funding support. Regular stranding response training programs for field veterinarians, and frontline personnel of State Forest Departments near stranding hotspots would provide an improved understanding of marine mammal health and threats in Indian waters. Further, the suggested National Stranding Centre needs to maintain a ‘National Stranding Database’ for long-term marine mammal conservation planning in India.
Highlights
Marine mammal strandings provide vital information on species’ life histories, population health and status of marine ecosystems
Highest incidence of sightings was for Dolphins and Finless porpoise (DFP) followed by dugongs, Baleen Whales (BW) and Sperm and beaked Whales (SBW)
The dataset used in the study was compiled from scientifically vetted databases, primary surveys, government reports and newspaper articles providing a comprehensive synthesis of long-term marine mammal stranding records in the country
Summary
Marine mammal strandings provide vital information on species’ life histories, population health and status of marine ecosystems. Shipping lanes intersect with movement corridors leading to collisions[26–28] and noise pollution can cause ‘auditory masking’ and permanent or temporary acoustic injuries29,30 Physical factors such as coastal topography (e.g. Cape Cod in Massachusetts, Golden Bay in New Zealand1,31,32), near shore surface currents, local wind patterns[33] may cause geographic clustering of stranding e vents[13]. Factors such as gently sloping beaches, known as ‘acoustic dead zones,’ distort acoustic signals of cetaceans, confounding navigation and leading to stranding[13]. Mammals along the Indian coast, primarily due to lack of broad-scale visual and acoustic surveys to estimate their population abundance, marine mammal stranding events can be a cost-effective and useful substitute to obtain data on local marine mammal occurrence patterns and potential threats
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