by Rahul Muralidharan
The sun was supposed to rise at 6:30 am.
But that day it did; fifteen minutes later.
At the break of dawn, a narrow strip of sunlight raced
through the sea surface reaching the shore.
And voila! A group of dolphins traveled along the coast.
stranded dolphin (Sousa chinensis) on the shores of Kovalam, near Chennai. cyanotype print by Sudharshan. smokingblues.wordpress.com
This is how my friend described to me his experience after seeing a pod of dolphins go past Injambakkam village in Chennai. Dolphins are not new to our coast. They have been there for a long time. Fishers observe them frequently during their fishing trips or from the shore. My first experience of observing a pod of Indo-Pacific humpback dolphins in Chennai was very similar to my friend’s. Out in the sea on a near shore fishing trip, at a distance, I could see tiny triangular fins pop in and out of the water, as if a blade was cutting through water.
The Indo Pacific humpback dolphin or Sousa chinensis as it is scientifically known – derives its name due to the dolphin’s presence in the Indian and the Pacific Ocean. Distributed along the entire east and west coast of India, a distinct hump on its back gives it the name ‘humpback dolphin’. Since humpback dolphins are coastal species, they prefer to stay within 25m depth feeding on near shore fish such as madavai (mullets), mathi (sardines) and nethili (anchovy). Fishermen call it paru vedan (paru meaning small, tiny | vedan meaning hunter) because humpback dolphins are found in the presence of small shoaling fish.
The stories that you hear about dolphins are vivid in the memories of the men who share their fishing grounds with them. For instance, the Coromandel coast and the Gulf of Mannar fishermen refer to them as karai kadavul (shore god). The legend believed is that Kutti Andavar an influential figure from the Chola dynasty era protected these dolphins. The story is told so:
Once, Kutti Andavar made a ring out of clay and threw it into the water, asking the dolphins to search for the ring. As clay melts in water instantly, it is believed that until this day the dolphins have been searching for the ring.
Coincidentally, this ring searching gesture is very similar to the feeding behavior of humpback dolphins. Mud plumes rise up to the water surface when dolphins nudge their snouts into the sea bed searching for tiny fish, crabs and shrimp. Fishers observe this behavior when they are at the same location, like the dolphins, fishing for shrimp or crabs. The blend of traditional cultures and ecology supports the long persistence of humpback dolphins from its immediate threat – fishing!
With the development and mechanization of Indian fisheries in the early 1950’s and 1960’s, new types of nets started replacing the old ones. Transiting form cotton nets to synthetic nets, moving from sustainable to unsustainable fisheries. Cotton fishing nets could not be soaked for a long time. They would disintegrate. Every time the nets were used, they had to be dried out in the sun at least for few hours before the next fishing trip. However, nylon nets could be soaked for a longer time, which means, more effort and more fish.
Dolphins, unlike other animals, see their environment through sounds. Bats do that on land. This is called “echo-location”. A bulbous structure on their head, known as a melon, produced high frequency sounds. When sounds hit an object, it bounces back and is known to be received by the lower jaw bones. This transmission and bounce back of sounds produces a mental imagery of a given environment, to the dolphins. They receive information on the shape, size and depth of objects. Moreover, recent research shows that humpback dolphins possess signature whistles. It is as if each dolphin’s name is coded with a unique whistle pattern, which helps them recognize each other underwater. Each dolphin has a name, each whistle has a dolphin. Additionally, they also use their eyes to hunt for fish.
Dolphins live in a three dimensional environment, submersed with blue light during the day time and the nights are as dark as space itself. Synthetic/nylon nets are designed in such way that they are almost invisible once soaked in the sea. Gillnets are one such example. These nets don’t give an opportunity for the fish to escape, neither to the dolphins which go in search of fish. Dolphins are air-breathing mammals, which require them to surface every 5-10 mins to catch a breath of air. But once entangled in fishing nets, they die out of drowning. Sometimes, dolphins get entangled while taking fish from nets. However, often-times fish nets entangle swimming dolphins, as the nets are not visible to them.
The Indo-Pacific humpback dolphins are placed under Near Threatened (NT) category in the IUCN red list of threatened species. We know next to nothing about their population status in India, although their range in other parts of the world show very few population estimates. Fishing mortality is identified as one of the greatest threats to humpback dolphins. Since these dolphins prefer near-shore, coastal zones, they face dire threats due to development pressures such as urbanization, coastal infrastructures and pollution which ultimately lead to habitat loss. Heavy metal pollutants like mercury and lead have been documented from the bodies of humpback dolphin along several parts of their range, especially from highly urbanized coastal cities.
Conversely, on the positive side, humpback dolphins have secured an iconic position in the hearts of the Coromandel Coast fishers. Fishermen in Nellore district of Andhra Pradesh in the east coast of India believe that they can communicate with humpback dolphins. When fishing nets are laid and in case if the fishers spot dolphins approaching toward the nets, they give out loud warnings to the dolphin not to approach on the same path. To their belief, dolphins switch directions and swim around the nets without entangling themselves. Some fishing communities along the Coromandel Coast consider dolphins as their ancestors who are out in the sea. Cultural beliefs, traditional knowledge and science are enmeshed in these stories; which makes it difficult to tease out the scientific parts. Somehow humpback dolphins have symbolic presence amidst the fishing populations of the Coromandel Coast. Interestingly, these stories have helped in conservation and long persistence of the humpback dolphins in our coast. For this reason, we need to develop methods to understand the nature and attitudes of various fishing communities toward the humpback dolphin. This search could involve anybody with an interest including students, fishers, researchers, general public, scholars, artists, teachers and list goes on.
Many people are surprised to know that dolphins inhabit our coast. If you would like to see them for yourself, then go out to the beach one morning. Who knows you might spot them against the breaking light of dawn; when it is the dolphins’ day out in the sea.
For more information, photos and details about Humpback dolphins of the Chennai coast – please click on this link to access a scientific research paper published in the Journal of Threatened Taxa.
Thanks to Sony RK for critical comments.
Rahul Muralidharan is a marine biologist currently pursuing his PhD at ATree. a slow baby turtle and two ghost crabs was his first field notes from the beach for Chai Kadai. He is an integral part of the ideas and activities we do. We hope he will continue to bring more of the ocean in to this space.