Bycatch, depredation and authenticity of tuna value chain

Tuna longliners play a very important role in the export-oriented fisheries sector in Sri Lanka while contributing a reasonable foreign income to the country. Hence, the objectives of the study were to investigate the issues of by-catch, depredation, and authenticity of the export-oriented tuna value chain while exploring the transport and logistics issues of tuna supplies and to propose strategies to overcome the issues identified. Primary data was collected from fishers in two fisheries harbors, Dikkowita and Gandara, in the Western and Southern provinces, respectively. A pre-tested, structured questionnaire was administered to the fishermen who used to fish in the high seas and the Exclusive Economic Zone. Boat owners or crew members of multiday fishing boats (IMUL) were interviewed monthly, covering 20% of the boats in each harbor. The depredation index was 15.60, with an attack interval of 3.46 and a damage rate of 0.29. Issues such as depredation of attached hooks or bait, hooking of unwanted catch, dissolving of fish schools, wastage of time, fuel, and energy, and loss of moral strength among fishers were recorded. The unwanted by-catch, such as sea turtles, sharks, seabirds, and sailfish, reduced the harvest, while these non-targeted damages adversely impacted marine life. As suggested solutions to overcome the issues, dolphin pingers could be used to repel the harmful cetacean species, the crew members could be trained for cetacean identification and record keeping, and satellite tagging could be used to closely monitor the predatory species.