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A Pinch Of Salt

A Pinch Of Salt

As a child, the greyish-pink dolphins that visited the Kochi estuary fascinated Divya Panicker. As an adult she now studies them, and decodes some of their mysteries for Sanctuary Asia readers.

Despite high human use, the Kochi estuary is frequented by humpback dolphins. The author believes that the high salinity and abundant mullet fish could be the reason. Photo: Divya Panicker.

On a hot, humid afternoon, as I hop on to one of the government-run transport ferries from Ernakulam to Vypeen, the greyish waters dotted green with hyacinth are calm and steadily flowing. The tide is coming in and the estuary looks bloated. A couple of dolphins pop up next to the boat and I reach for my camera and begin clicking. No one bats an eyelid at first as they probably assume I am just another tourist enthused by this old estuary city. But then a couple of boys yell, “Are those dolphins?” and the excitement picks up, lasting till we pass the pod.

The coastal town of Kochi, home to over two million people, has grown around the Kochi estuary. The estuary links the Vembanad backwaters with the Arabian Sea through a narrow mouth spanning about 450 m. The variety of boats in the estuary reveal the multitude of anthropogenic interests in this area; large, swanky, white cruise liners carrying tourists from the world over, dredgers maintaining the channel’s depth, vanjis (canoes) with locals casting fishing nets, naval ships with Indian flags riding high, cargo ships with numerous stacked containers bringing in goods, double-decker tourist boats with blaring music, fancy speed boats swerving through and trawlers and purse seine boats returning from a hard day’s work at sea. While growing up here, I have often wondered what brings the dolphins into this busy estuary. They, I assume would spend most of their time dodging boats. Something must truly attract them to this place despite the high human traffic.

THE MOTTLED PINK DOLPHINS

The most common question I encountered while starting my field research was, “Do we have dolphins in Kerala?” Barring fishermen and a few others, almost all locals I met posed this question. At times, one could easily stand onshore in this region and observe dolphins feeding or playing just a few metres away. Through a number of stranding events, by-catch and sighting reports, we know that Indian waters have as many as 26 species of cetaceans (whales, dolphins and porpoises). One of the most commonly reported species is the humpback dolphin Genus Sousa, the same species one sees in the Kochi estuary. Records date back to as early as the 1800s and their presence has been established in all coastal states except Lakshadweep and the Andaman & Nicobar Islands. Being strictly a coastal species, these dolphins are often seen in and around estuarine areas.

KADAL PANNI IN KOCHI

In Kochi, this species is called ‘kadal panni’ in the local language of Malayalam, which translates to sea pig. Somehow, the hump did not make it into the name here. The pig did, fishermen tell me, because the meat of this dolphin is fatty and tastes more like pork than fish. At present, with government bans in force, dolphins are not hunted, but fishermen are all too familiar with the species as they frequently encounter them and often complain that they steal fish from their nets out at sea. But the dolphins within the estuary do not steal from nets. Some fishermen do not think the animal deserves to be called a dolphin; maybe people didn’t like their thieving nature. Or maybe, people didn’t think the humpback to be as beautiful or acrobatic as its well-known cousin, the bottlenose dolphin.

Nevertheless, these mottled dolphins and their use of this highly human-modified estuary was extremely intriguing. Over the year 2012-2013, my team and I studied dolphins in the estuary and collected data on environmental characteristics, boat traffic, fishing intensity and dredging activities to obtain clarity on when, where and why dolphins come to this estuary. During the monsoon, when estuary waters were almost fresh, dolphins were only occasional visitors. Rarely did they venture in, choosing instead to linger at the mouth of the estuary. However in other seasons (especially the dry season) they used the estuary extensively, almost daily. They would never stay permanently and would always return to the sea after a few hours. Something special was happening in the few hours they picked to visit the estuary.

Apart from existing perils such as fishing net entanglement, habitat loss, prey depletion from overfishing, collisions with boats, and polluted waters, the humpback dolphin faces yet another threat from proposals to expand the port’s facilities.
Photo: Katrina Fernandez.

WHY ESTUARIES?

Clearly, salinity influenced when and where the dolphins were found in the estuary. Apart from being most visible during the dry season when salinity was at its acme, dolphins were actually selecting areas in the estuary that were most saline in this season. From other studies and our own experience of spotting them during the monsoon when salinity was extremely low, we know that dolphins can tolerate a wide range of salinity, so this could not be a key physiological barrier.

Examining dolphin behaviour gave us a clue to what might be happening. The dolphins spend most of their time foraging, so the more saline waters may actually be attracting their prey and, as a consequence, the dolphins themselves. A few interviews with experienced fishermen quickly made it clear that mullet was the most abundant fish catch in the estuary. Interestingly, mullet catch was also reported to be highest in the dry, and lowest in the monsoon, directly proportional to dolphin sightings in these two periods. Asking the fishermen for their views on what dolphins are feeding on, most answered without much hesitation that although they have seen dolphins feeding on different types of fish, their attraction within the estuary was the tasty mullet aggregating here. On numerous occasions, we saw for ourselves, dolphins gorging on mullet. It may very well be that dolphins are dodging boats and risking collision even, to get to their favourite meal!

SHARED LIVING

Living so close to the coastline, humpback dolphins come in frequent contact with human activity. Perils can be diverse such as getting entangled in fishing nets, competing for the same food sources, colliding with boats and disease as a result of polluted waters. The International Union for the Conservation of Nature (IUCN) has classified humpbacks as ‘Near Threatened’ on the Red List. Estuary destruction and prey depletion are certainly the most imminent of these threats.

The status of this species in Indian waters is unknown, and population estimates and threat assessment are much needed to guide conservation decisions. Kochi is one of the largest ports along the west coast of India. Proposals to expand the port’s facilities through various developmental projects are being examined today. Some of the plans include the construction of two breakwaters and reclamation of land (~3000 acres) for an outer harbour at the estuary mouth. It is imperative for Environmental Impact Assessments to take into consideration the fact that the estuary mouth is prime dolphin habitat. Modifications in this area could not only result in direct habitat loss but would also probably cut off access to other parts of the estuary used by dolphins. The narrow mouth is the only corridor for dolphins into the estuary. Dovetailing of the estuary mouth’s ecological significance in all future development schemes by concerned authorities is crucial to ensure the survival of this apex predator in these waters.

After packing up the day’s observations, I watch the sun set over the horizon across the estuary mouth. The beautiful purple-pink light bathes the Chinese fishing nets and the boats and everything else in it. The lights on the cranes of the port are coming on. The strains of ‘Kolaveri di’ fan out across the estuary from a huge, white, swan-shaped boat. The dolphins are still there. Unexpectedly, a humpback, typically non-acrobatic, leaps out of the water five times in a row sending a pulse of excitement through me. In a way, I am glad the light is too low for photographs, I can just soak it all in without peering through the viewfinder. I think to myself what anincredibly unique field site this is.

Divya Panicker’s field study was supported by the Rufford Foundation, U. K. and the Wildlife Programme at National Centre for Biological Sciences, Bengaluru.

The humpbacks derive their name from the characteristic bulge on their back under the dorsal fin. Their geographic range arcs South Africa, India, China and Australia. Although calves are completely grey, adults vary in colour across this geographic spread. African humpbacks are mostly grey, Chinese variants are nearly all pink and Indian humpbacks are a motley mix of both. In fact, these morphological differences are an indication of underlying genetic variations. Presently, there is much debate in the scientific community on the taxonomic status of the Indo-Pacific humpback dolphin, with at least three separate species being recognised under it. Two of these species S. plumbea and S. chinensis are expected to be found along the Indian subcontinent and further genetic investigations are required to ascertain this. Until recently, all humpbacks in India had been clumped under S. chinensis, now the ones along the Kochi coast are called the Indian Ocean humpback dolphin, S. plumbea.

Author: Divya Panicker, First appeared in: Sanctuary Asia, Vol. XXXVI No. 2, February 2016.

 
 
 

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