KOCHI: The charming and rustic backwaters of Kochi is facing a mussel calamity. American brackish-water mussel, known as Mytella strigata, an alien invasive species has been proliferating in backwaters, posing a danger to the native species of mussels. “This invasive species can modify the ecosystem, compete with native species, endanger local fisheries and aquaculture, introduce diseases and interfere with coastal facilities,” says Cusat Department of Marine Biology head S Bijoy Nandan.
According to him, the mussels might have reached Kochi by ballast water in ships, which is the water carried on board to provide stability to the ship, or by fouling on the hull of ships. There is a chance of the species reaching Kochi from other Asian countries like Singapore, Thailand and Philippines where it has been proliferating recently.
“All species occupy a niche in its native ecosystem. The invasive species will enter the niche and gradually displace the native species. The American mussels are competing with the native population of green mussels, Perna viridis, proliferating and adapting to the local ecosystem. It can survive in waters with a wide range of salinity between 5 to 35 ppt. The species is seen fouling on floating plastic bottles, wooden pilings, walls of fish cages, hulls of vessels and bottom sediment. Once they perish, these mussels sink and cover the bottom sediment resulting in the depletion of dissolved oxygen,” said Bijoy Nandan.
The study conducted by the Cusat team of researchers P R Jayachandran, B P Aneesh, P Graham Oliver, Joseph Philomina, M Jima, K Harikrishnan and S Bijoy Nandan has been published in the internationally peer-reviewed journal ‘Bioinvasions Records’. Earlier in 2018, researchers from Cusat had identified invasive black-striped mussels, Mytilopsis sallei, in the Kochi backwaters.
“Proliferation of this alien invasive species poses a serious danger to the ecology of endemic species of the fragmented brackish water habitats along the Kerala coast, considered as a stretch thriving with endemic species. Their rapid growth, early maturity and wide salinity tolerance make them a potentially alarming fouling species,” said Cusat postdoctoral fellow P R Jayachandran.
The general external colour of the shells of the species was uniformly black, while some rare individuals showed a bright green colour and a different colour pattern. Around 150-200 mussels were seen in one sq m and the flesh of the invasive species is not edible. But, some residents catch and eat them mistaking them for the endemic green mussels.