Strategies to control invasion of Sailfin Armoured Catfish, Pterygoplichthys spp. in wastewater-fed aquaculture bheries of East Kolkata Wetland, India with suggestion of a modified barrier based on the biological and behavioural characteristics

Abstract

Sailfin armoured catfish ( Pterygoplichthys spp.), an alien invasive species of family Loricariidae has invaded extensively in wastewater-fed large aquaculture ponds (locally called ‘bheries’) of East Kolkata Wetlands (EKW), West Bengal, India. As there is no viable controlling method at present, commonly these fishes are removed by different physical methods and discarded. In the present study, we investigated the effectiveness and suitability of different in-practice Pterygoplichthys spp. control methods, based on on-field sampling, biological and behavioural study of the fish and also response analysis of the stakeholder’s of EKW. The results indicate that in-practice eradication efforts, like ‘repeated seine netting’ with or without removal of Eichhornia sheath of the pond periphery and ‘dewatering of pond’ aiming to reduce or eradicate Pterygoplichthys spp., are not fully effective, because of the capture avoidance ability and burrowing habit of these fishes. We found deep and branching burrows of Pterygoplichthys spp. in aquaculture ponds of EKW, with maximum burrow depth of 58 cm, and water in that burrows even after 12 days of dewatering. Hence, it is suggested stakeholders to keep dewatered pond exposed to sunlight for at least four weeks or above to ensure complete water-out from the burrows in which Pterygoplichthys spp. take shelter or lay their eggs. ‘Multilayer bamboo fencing’ or ‘combination of bamboo fencing and net barrier’ use by the stakeholders of EKW to prevent intrusion or re-intrusion of Pterygoplichthys spp. were found only partially effective, because of the capability of these fishes to damage net-blocking through their hard dorsal and pectoral spines or entry through the holes dug across the barrier in beneath or banks of the sewage intake channel. Based on learning on the biological and behavioural characteristics of Pterygoplichthys spp., we then suggested a modified version of barrier to the stakeholder’s of EKW, incorporating a sewage feeder pipeline, a concrete collection chamber with size separation arrangement made of hard materials like wire mesh and a dam of specific dimensions across the channel, for effective prevention of intrusion of these fishes in their aquaculture bheries.