A form of invasive species known as the Charru mussel (Mytella strigata) is spreading quickly in the backwaters of Kerala. Originating from South and Central American coasts, reports indicate an alarming increase in their numbers in this part of India.
Reasons for the Spread
There are several reasons for how the Charru mussel found its way to Indian shores. One possibility is that they were attached to ship hulls or transported as larval forms in ballast water discharges. Ballast water is seawater that ships carry to enhance their stability. Cyclone Ockhi, which hit South India, Sri Lanka, and Maldives in 2017, possibly played a role in accelerating this invasion.
Areas Impacted
Surveys conducted in Kerala have discovered the presence of Charru mussel in numerous estuaries and backwaters, including Kadinamkulam, Paravur, Edava-Nadayara, Ashtamudi, Kayamkulam, Vembanad, Chettuva, and Ponnani. These backwaters comprise stretches of lakes, canals, and lagoons located parallel to the Arabian Sea coast. Ashtamudi Lake – a Ramsar site in Kollam district, is the area most impacted by the Charu mussel. The Charru has replaced local mussel and oyster species, significantly disrupting the ecosystem.
Concerns Raised
The rapid proliferation of the Charru mussel threatens the unique biodiversity of Kerala’s brackish water habitats. It ousts other mussel and clam species from the backwaters, thereby endangering the livelihoods dependent on molluscan fisheries. In light of its potential damage, the fast-breeding Charru mussel can be seen as a pest attack on clam fishery.
Ecolabelling and the Marine Stewardship Council
The short-necked clam fisheries in Ashtamudi lake have received an eco-label from the Marine Stewardship Council. About 3,000 people rely on fisheries in this region. Ecolabelling is a method of environmental performance certification. It identifies products or services that are environmentally preferable within a specific category. The Marine Stewardship Council is an independent non-profit organization advocating for sustainable fishing, headquartered in London.
Invasive Species Explained
An invasive species is an organism not native to a particular area that causes harm. They pose a threat to local biodiversity by causing extinction of native plants and animals, competing for limited resources, and altering habitats. They can be introduced to a new area through ship ballast water, accidental release, and often by humans.
Understanding Mussel
Mussel refers to numerous bivalve mollusks belonging to the marine family Mytilidae and the freshwater family Unionidae. Mollusks are soft-bodied invertebrates often enclosed in a calcium carbonate shell. They are most commonly found in cool seas worldwide. In India, two species of marine mussels, the green mussel and the brown mussel, are commonly found in coastal areas.
The Charru Mussel
The Charru mussel, native to the South and Central American coast, varies in color from black to brown, purple, or dark green. It can survive in a variety of salinity and temperature but struggles beyond 36 degrees Celsius.
Way Forward
Complete eradication of the Charru mussel from Indian waters may not be possible, making its containment crucial. There is a significant need for studies on invasion biology and for raising awareness about marine invasive species.
Last Modified: February 7, 2024