Cetaceans (whales, dolphins, and porpoises) are as iconic and critical to the oceans as tigers are to the terrestrial ecosystem. Cetaceans play a vital role in maintaining healthy marine ecosystems and serve as early warning indicators of oceanic changes due to natural disturbance or human-induced changes. Much of what we know about cetaceans off India’s coast is based on stranding records and more recently, from sporadic coastal cetacean research. In both resource-rich and resource-constrained environments, biological data collected from stranded animals can significantly enhance our understanding of cetacean natural history and threats affecting them. In India, where cetacean research is in its infancy, data from stranded animals is a scientific treasure. However, stranding data provide only a partial profile of cetacean populations that inhabit India waters.
To fully grasp the uniqueness and diversity of the northern Indian Ocean cetaceans, we need to systematically assess cetacean populations at sea. One of the best ways to study at sea populations is through broad-scale, ship-based standardized surveys. Such surveys are standard practice globally to study multiple cetacean populations with the ultimate goal of estimating abundance, density, and understanding distribution. Without this fundamental knowledge, actual impacts on cetacean populations from human or natural threats cannot be determined. An understanding of actual impacts can help with stakeholder engagement and facilitate effective marine resources management by assessing the risk to protected marine species from multiple users of the marine environment.
Recently, a multispecies cetacean systematic survey and training was conducted on the Ministry of Earth Sciences (MoES), Centre for Marine Living Resources and Ecology (CMLRE) fisheries research oceanographic vessel, FORV Sagar Sampada, from December 15 to 18th, 2017, off Kochi, India. This first of its kind broad-scale, line-transect survey training provided 10 trainees from various institutions across India with skills to systematically collect, record, and report cetacean visual data by highly experienced NOAA Fisheries trainers. This is also the first time a systematic offshore survey of cetaceans has been conducted in the Arabian Sea off the west coast of India.
This is an example of a successful Indo-US resource and funding collaboration involving Indian institutions – MoES/CMLRE, Wildlife Conservation Society- India (WCS), and the National Centre for Biological Sciences (NCBS) and US institutions - NOAA Fisheries, Office of Naval Research (ONR) Global, Woods Hole Oceanographic Institution (WHOI), and the University of Washington.
Data were collected using two 25 x 150 long-range binoculars or “Big-Eyes” (photo) positioned on either side (port and starboard) of the ship’s flying bridge, donated generously to NCBS by the WHOI, USA to conduct systematic cetacean surveys. During the roughly 2.5 day cruise, a total trackline distance of 205 nautical miles was covered at an average speed of 5.9 knots. Despite severe weather and visibility issues impeding survey effort, a total of 12 cetacean sightings were recorded during an actual trackline effort of about 127 nautical miles during the training cruise. Species sighted include Stenella longirostris (spinner dolphin), Stenella attenuata (pantropical spotted dolphin), Grampus griseus (Risso’s dolphins), Globicephala sp. (pilot whales), and Balaenoptera edeni/Balaenoptera omurai (Bryde’s whale/Omura whale), Tursiops sp. (bottlenose dolphin), as well as some unidentified cetaceans. Survey effort covered both shallow inner and middle- shelf waters (< 150 m) and deeper outer-shelf/slope waters < 2,000 m.
The results of this pilot survey are extremely promising and suggest that longer and systematic cetacean surveys in combination with fisheries, oceanographic, and acoustics research could provide us with a comprehensive assessment of these charismatic and influential predators in the marine ecosystem and advance India’s capabilities to protect its unique and rich marine biodiversity that is unparalleled in the world.
