THOOTHUKUDI: In order to conserve endangered dugongs, researchers at Gulf of Mannar Marine Biosphere Reserve along with other marine experts have restored 14 acres of degraded seagrass on the sea bed of the Gulf of Mannar region over the past 10 years. The conservation of dugongs assumes significance as numbers of the mammal have drastically fallen over the years with only 250 remaining in India, according to the Wildlife Institute of India (WII).
Of the 250 dugongs, about150 of them are found along the Gulf of Mannar and Palk Bay between Indian and Sri Lanka, 75 near the Andaman & Nicobar Islands and 25 in Gujarat's Gulf of Kutch.
The endangered dugong, also known as the sea cow, is an essential part of the marine ecosystem. According to experts, the seagrass beds in the Gulf of Mannar and Palk Bay are the habitat for a wide range of marine fauna, including fishes, sea turtles, sea horses, sea cucumbers, as well as the dugong. Dugongs which depend on underwater seagrass meadows are the world's only vegetarian marine mammal. With the increasing challenges such as climatic changes, destructive fishing practices and industrial pollution along the Gulf of Mannar and Palk Bay, seagrass meadows had shrunk leading to a fall in the dugong population.
Researchers attached to the Suganthi Devadason Marine Research Institute (SDMRI) affiliated to the Manonmaniam Sundaranar University said that the restoration of seagrass beds through rehabilitation projects was the only way to conserve the dugongs which are the flagship animal for the Gulf of Mannar and Palk Bay. Seagrass also plays a vital role in carbon sequestration and thus helps fight climate change. While dense seagrass beds are seen between the mainland and the islands in the Gulf of Mannar, few patches of seagrass occur beyond the islands. The Gulf of Mannar had recorded over 13 different species of seagrasses with Thalassia hemprichii, Syringodium isoetifolium and Cymodocea serrulata found to be the dominant species.
The researchers felt that the destructive practice of bottom trawling to catch fish at the shallow waters had greatly depleted the seagrass meadows in the Gulf of Mannar region. According to a survey conducted in 2016, the extent of seagrass beds in Gulf of Mannar was 152 square km while it was 209 square km in the Palk Bay, a researcher from SDMRI said. Describing the stress factor, the researchers added that several thousands of small-scale fishermen depend on the fishery resources associated with seagrasses.
SDMRI Director Dr JK Patterson Edward, who spearheaded the rehabilitation project, told The New Indian Express that bottom trawling is very dangerous to the bottom dwelling seagrass beds, apart from posing other threats, as the practice buries benthic organisms, uproots seagrasses and causes physical and biological damages to the seagrass ecosystem. Mechanised trawling, push net operation and shore seine are the bottom trawling operations being carried out in Gulf of Mannar and Palk Bay, he pointed out.
Apart from destructive fishing practices, there are other factors such as pollution, coastal development, elevated sea surface temperature, sea level rise and sedimentation that also threaten the survival of seagrasses, said another researcher.
Seagrass restoration project
The SDMRI researchers said that manual transplantation of seagrass sprigs (shoots), was found to be the best choice for seagrass restoration in the Gulf of Mannar, through various experiments. Accordingly, the mature seagrass sprigs with intact roots are attached to a biodegradable jute twine and the twine is tied to a one square metre PVC quadrat, which is immediately taken underwater and fixed at the earmarked restoration site, they said.
Patterson explained that the ecological functions of the rehabilitation sites are attained within two years as the rehabilitation sites look similar to natural seagrass areas in terms of seagrass cover and the density of associated biodiversity. It costs about Rs 8 to Rs 10 lakh per acre for planting, monitoring and maintaining. "A total of 14 acres of degraded seagrass area has been restored in the Gulf of Mannar and Palk Bay from 2011 to 2020 with a success rate of 85-90 percent,” he said.
Seagrass rehabilitation, not only helps to increase the seagrass cover, but also increases the associated biodiversity, he added.
35 Dugongs rescued in India
Expressing concern about the dwindling number of dugongs, Wildlife Institute of India (WII) scientist F Dr K Sivakumar said, "Right now, we have only one species of dugongs in the world but ancient India had four more species of sea cows that are extinct. India has the highest diversity of sea cows in the world, he said.
Poaching of dugongs has drastically fallen and sightings of dugongs have increased in Indian waters in the past five years, following massive awareness programmes. "So far, we have saved 35 dugongs from illegal fishing, which approximately saves Rs 350 crore, as one dugong can help us get fishes worth Rs 2 crore a year by facilitating the breeding of fishes in the seagrass habitats," he said. The World Dugong Day (May 28) initiated by India has now been accepted worldwide, Sivakumar said.
A senior Gulf of Mannar Biosphere Reserve official, seeking anonymity, said that the population of the mammal would have increased as no poaching case was reported in the past three years due to expansive awareness programmes along 252 coastal villages in Thoothukudi and Ramanathapuram districts, besides improving of its habitat. "We have also rescued two live dugongs and released them into the sea", he said.
Cash award for rescuing dugongs
On May 28, 2020, the Gulf of Mannar forest authorities announced a cash prize of Rs 1,000 for those who released dugongs from fishnets into the sea. Although none have come forward to claim the award, authorities have doubled the prize this year.