A few traditional fishermen of Cheppanam village, near Panagnad, woke up to a surprise last week when an adult octopus landed in their stake net.
Besides the octopus, identified as Octopus vulgaris , a few individuals of squilla, a mantis shrimp, also got trapped last week in the stake nets set up in the backwaters. The octopus species, also known as common octopus, is usually found up to a water depth of 200 metre.
Fishermen in the Koch backwater region had reported earlier the presence of marine aquatic animals in the backwaters during peak summer season. This year, the marine species have started appearing during the early summer months.
The octopus, it is believed, might have travelled at least 10 km from the bar mouth, the point where the sea meets the backwaters, to be entrapped at Cheppanam. The animal weighing 530 gram, had a body length of 34 cm, including the length of its tentacles, said S. M. Raffi, Assistant Professor, Kerala University of Fisheries and Ocean Studies. Though of not much demand in the local market, frozen octopus meat is exported from India.
The animal samples were collected and analysed by researchers, S. Athul and T.M. Sreenath, for a research programme run by the Centre for Excellence in Aquatic Resource Management and Conservation of the University.
Usually, the salinity of seawater in the Kochi region is around 35 parts per thousand. In Cheppanam, the salinity was found to be 27 ppt. The gut examination of the animal revealed that it fed on estuarine species of fishes and prawns. The animal, it appeared, was actively feeding on the estuarine grounds and survived in the area, said Dr. Raffi.
K. Sunil Mohamed, the Head of the Molluscan Fisheries Division of Central Marine Fisheries Research Institute, Kochi, suggested that the animal might have been driven in the strong tidal currents and reached the area or it might have followed a group of its prey to ended up in the area where it was netted. Salinity in the region should be conducive for its survival, Dr. Mohamed said.
Mr. Raffi felt that the increased salinity levels of backwaters and the opening of fresh feeding grounds might have prompted the marine species to explore new habitats. If the species succeeds in establishing itself in the new ecosystem, it could pose threat to resident species, he said.
