Responsible harvesting of underutilised fishery resources

Abstract

In order to fill in the supply-demand gap for fish protein, in the context of downward trend in production from the conventional fish stocks, there is an imperative need to locate unconventional and underutilised fishery resources. Mesopelagics and Antarctic krill are considered to be promising underutilised resources, which have potential for future development. Mesopelagic fishes in the world oceans has been estimated at about 1000 million t and recent estimate of biomass based on acoustic data is reportedly between 11,000 and 15,000 million t. Myctophids which form a major component of mesopelagic resources have high prospects to become a major source of fish protein for direct human consumption and for meeting fish meal and oil requirements for the expanding aquaculture industry and in poultry and animal husbandry, when efficient harvesting and appropriate processing and value addition technologies are evolved. The decadal average (2006-2015) catch of myctophids is 8,284 t, ranging between 15 t (2006) and 21,393 t (2011) (FAO, 2017). The decadal average (2006-2015) catch of Antarctic krill (Euphausia superba) from the Southern Ocean is about 1,88,210 t per annum, ranging between 10,45,86 t (2007) and 3,17,615 t (2014) (FAO, 2017). The precautionary catch limits for Antarctic krill prescribed by Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) total over 8.6 million tonnes and hence it is one of ocean’s largest known underexploited resources. Recent developments in harvesting technology and in products being derived from krill indicate renewed interest in exploiting this resource. An aimed midwater trawl system designed to attain large mouth area, smoothly tapering trawl body with small meshes in the belly or a small-meshed inner lining and small mesh codend, which can be operated at low towing speeds is adjudged to be appropriate for trawling of myctophids and Antarctic krill, in view of their small size and low swimming speeds. Important factors influencing the successful performance of the trawl system for myctophids, would be size of the trawl mouth which should be maximum limited only by the towing power of the vessel; an auto-trawl system efficient and dynamic enough for positioning the trawl in alignment with the DSL, oxygen minimum zone (OMZ) and layer of availability according to diel vertical migration of the myctophid species, a stream lined trawl body with optimised body and codend mesh sizes based on selectivity analysis of the regional species, in addition to a better understanding of the spatial and seasonal abundance of the species. The possibility for developing continuous trawling system as developed and used for Antarctic krill, comprising of midwater trawl and a powerful pumping system for continuous pumping of the catch from the codend, can also be envisaged for harvesting of myctophids. The prospects, issues and challenges in operating a fishery based on myctophids and Antarctic krill from India would be discussed in this paper.