India’s first dugong reserve will help protect the world’s only herbivorous marine mammal

In an effort to protect the dugong, the Tamil Nadu government declared 500 sq km of the biodiversity-rich waters in the Gulf of Mannar and Palk Bay, where the marine mammal is found, as the country’s first dugong conservation reserve. Announced in September last year, the reserve is spread over the northern part of the region between Adirampattinam and Amapattinam, off the coast in southeast India.

The dugong is listed as vulnerable in the International Union for Conservation of Nature Red List of Threatened Species, though some studies show its conservation status is highly variable across its range.

According to studies by the Wildlife Institute of India, only about 200-250 dugongs remain in the oceans, and among them, 150 can be spotted in the Palk Bay and Gulf of Mannar, off the coast of Tamil Nadu, which is now the most significant surviving natural habitat for dugongs globally. There are reports that at least 75 dugongs are found near the Andaman and Nicobar Islands, and 50 can be spotted near the Gulf of Kutch in Gujarat.

“By protecting dugongs, we are not supporting that species alone,” Supriya Sahu, additional chief secretary with the government of Tamil Nadu, in charge of environment, climate change, and forests, told Mongabay-India. “The rich marine diversity of the Gulf of Mannar would completely come under the protection, and there would be new initiatives to address the challenges of climate change on marine animals and their ecosystem.”

She says the Gulf of Mannar and Palk Bay are habitats for a wide range of marine fauna, including rare fishes, sea turtles, seahorses, and sea cucumbers. The region is presently facing threats of climate change apart from destructive fishing practices and industrial pollution.

According to Chennai-based environmentalist G Sundarrajan, one of the promoters of the green movement Poovulagin Nanbargal, climate change has started impacting the sustenance of dugongs and the seagrass heavily, and that is why his organisation advocated with the Tamil Nadu government to declare the Gulf of Mannar and Palk Bay as a dugong conservation reserve.

Conserving seagrass

The dugong is currently the only herbivorous marine mammal in the world and it feeds exclusively on seagrass. It can eat up to 40 kg of seagrass every day, making the plant crucial to the survival of the animal.

Other than supporting dugongs, seagrass beds along the continental shelf play a vital role in protecting the fragile marine biodiversity of the Gulf of Mannar and Palk Bay, off the coast of Tamil Nadu in the southeast of India, and support the health of coastal ecosystems in the Bay of Bengal off the eastern coast of India. These submerged flowering plants can usually be seen in shallow marine waters and they help enhance water quality by absorbing carbon dioxide and generating oxygen. They also serve as breeding grounds for many fish species.

In the middle of last year, a decade long experiment to restore seagrass was successful with 14 acres of degraded seagrass being restored on the seabed in the Gulf of Mannar by the researchers from Suganthi Devadason Marine Research Institute of Manonmaniam Sundaranar University. Restoring seagrass beds through rehabilitation projects is the primary way to protect the dugongs and these beds give Gulf of Mannar and Palk Bay their identity. The region has thirteen different species of seagrasses, with Thalassia hemprichii, Syringodium isoetifolium, and Cymodocea serrulata identified as the dominant species.

According to researchers, manual transplantation of seagrass sprigs (shoots) was the best restoration option. Under their project, the researchers attached mature seagrass sprigs with intact roots to biodegradable jute twines and then tied the twines to PVC quadrats (frames). The quadrats were then taken underwater and fixed at the earmarked restoration sites. The project cost the university around Rs 10 lakh per acre for planting.

Seagrass rehabilitation helps not only to increase the seagrass cover but also to increase the associated biodiversity, said Suganthi Devadason Marine Research Institute director, JK Patterson Edward.

Seagrass beds in both the Gulf of Mannar and the Palk Bay are also essential for the livelihood of traditional fisher communities in the area. With this in mind, the social-ecological system prevailing in this biodiversity-rich and productive coastal region will be documented and considered one of the critical components in the preparation of the dugong conservation action plan, said additional chief secretary Sahu.

According to her, the Gulf of Mannar and Palk Bay, which fall in the Indo-Pacific region, are one of the world’s richest marine biological resource. The Gulf of Mannar has been chosen as a conservation reserve because of its biological and ecological uniqueness. As per studies, the Gulf of Mannar and Palk Bay are home to 3,600 species of plants and animals that make the region one of the biologically richest coastal regions in India. The area is also known for its corals, of which 117 species belong to 37 genera.

Reserve status

According to Sunderrajan, the destructive practice of bottom trawling to catch fish in shallow waters has caused large scale depletion of seagrass meadows in the region. The trawling has also adversely affected small-scale fish workers who depended on the fishery resources associated with seagrasses.

Additionally, the slow-moving dugongs regularly become victims of accidental entanglements in fishing nets and collide with boats and trawlers.

Sunderrajan said efforts are on to convince the government to ban trawling and gill nets in the area and permit local communities to continue their traditional fishing activities. He also stressed the need for a coordinated intervention by fisheries and forest departments.

Suganthi Devadason Marine Research Institute director Edward notes that the new dugong conservation reserve status would help end bottom trawling practices that are dangerous to the bottom-dwelling seagrass beds, apart from posing other threats.

Trawling also buries benthic organisms, uproots seagrasses and causes physical and biological damages to the seagrass ecosystem. According to him, mechanised trawling, push net operation, and shore seine are the bottom trawling operations carried out in the Palk Bay and Gulf of Mannar.

West coast seagrass

In the last week of December 2021, tourists and fish workers active on Kerala’s famous tourism destination Kovalam beach saw large-scale washing up of a particular kind of grass, unfamiliar to the western coast until then. Strangely, the livestock on the beach refused to eat them.

Somebody alerted the Department of Aquatic Biology and Fisheries at the University of Kerala. The experts there soon identified it as two seagrass species – Oceana serrulata and Syringodium isoetifolium. They noted that these species, not usually seen on India’s western coast, were the main food of the threatened marine mammal, the dugong, that is usually found on the eastern coast’s Gulf of Mannar and Palk Bay regions.

“An underwater species, seagrass is crucial in the survival of dugongs, known locally as sea cow or kadal pashu and these marine plants are different from the more common seaweed,” observes A Bijukumar, head of the department at the University of Kerala.

Noting the unexpected occurrence of seagrass in Kovalam, he said that it could have been intense wave actions that uprooted the grasses from the east coast and deposited them at the beach on the west coast. According to Bijukumar, the Kerala coast has not witnessed seagrass accumulation before and a detailed underwater study is needed to understand its occurrence here.

This article first appeared on Mongabay.