Kochi backwaters face threat from invasive mussels

The presence of invasive mussels in Kochi Backwaters has been confirmed. The scientific journal, Current Science, recently stated researchers at the Cochin University of Science and Technology (CUSAT) identified the genus of the mussels found in Kochi backwaters as invasive, posing a great threat to the aquatic life in Kochi.

Invasive species, also called as exotic/alien species or introduced species are those which are not native to a specific location, but if spread to other areas, pose a danger to environment, economy and human health. It can be a plant, insect, animal, amphibian or even a bacterium. As the name suggests, its main feature is "invasion."

Ever since our existence, the migratory band of humans have taken along with them, wide range of parasites and pathogens. The alteration of water bodies according to our needs also have contributed to spreading of invasive species. For instance, due to the development of St Lawrence Seaway System, a primitive fish named 'Sea Lamprey', native to North Atlantic Sea migrated to the Great Lakes region of North America . This fish uses a specially modified sucker to latch onto a game fish and drain its blood. This fish's entry resulted in imbalance of composition of aquatic life in the region. So, it is evident how fatal the invasive species can be.

The mussel is the common name that we use for members of several families of bivalve molluscs, from salt water and fresh water habitats. The mussel found in Kochi is the black-striped mussel, Mytilopsis sallei, which is native to the South and Central Americas. The main characteristic of this species is that they can survive in any adverse climatic condition, even in shallow water and multiplies rapidly. They also destroy the ecosystem in water bodies and result in death or displacement of fish and aquatic plants.

In recent years, the presence of this invasive species has been recorded in Hong Kong, Australia and Japan. In India, it has been seen in Mumbai and Vishakapatnam ports and now it has reached Kochi! How did these mussels come all the way? These mussels are said to migrate from one place to another through discharge of ballast waters of water vessels.

Ballast is is the material used to provide stability to a vehicle or machine. Ballast tanks in ship function to route the water in and out during transit. But, ballast water taken into tank from one water body and discharged in another can result in introduction of invasive species in the latter.

The International Convention for the Control and Management of Ships' Ballast Water and Sediments (2004) regulates the charge and discharge of ballast water. According to this convention, ships should discharge ballast water when they are in high sea, which has a depth of 2,000 meters or more, and during day time. But, these regulations are seldom followed.

The black-striped mussels can cause deterioration of coastal infrastructure. They accumulate on the water surface and cause ecological and economic losses. The native species of fish that we eat and upon which our fishermen survive for livelihood may get displaced or killed slowly. The aquatic plants will also die. The main issue is that there is very low research done on this matter.

People and the Government need to realise how much danger have reached our waters. The regulations regarding ballast water exchange should be strictly imposed. Better ballast water management systems must be implemented. Ways to terminate the multiplication of these mussels need to be found out. And, not to forget, funding and aids should be given for this research. Fishermen, students and common people should unite to address this issue as soon as possible. Or else, The Queen of Arabian Sea will have to witness the deadly alteration in the composition of her aquatic life and ecosystem.

(Reference: Study published in Current Science on December 25, 2018)