Towards a more selective Patagonian toothfish fishery

Abstract

The Patagonian toothfish (Dissostichus eleginoides) fishery in the South Atlantic Ocean, also known as the Argentine Sea, began in the mid-1980s. It is conducted using two types of demersal fishing gear: bottom trawl and bottom longline. In 2000, a concerning situation was detected that threatened the sustainability of the fishery due to the high proportion of juvenile specimens present in the catches. Given the large size of juvenile fish, which exceeds 80 cm, and the particular shape and size of their mouths, managing selectivity through fishing gear regulations proved to be difficult to implement. Thus, any such regulation was expected to be of limited effectiveness. However, the issue of excessive juvenile Patagonian toothfish in catches was resolved thanks to a particular biological characteristic of the species, which allowed for selectivity to be managed by limiting accessibility to the juvenile fraction of the stock, thereby modifying the exploitation pattern. The species exhibits a differential size distribution by depth: larger and older specimens inhabit depths of up to 2,500 m, while juveniles are predominantly found in shallower waters, typically ranging from 600 to 800 m. Regulating the depth at which both fleets could target the species proved to be a management measure easily accepted by the fleet, as it did not entail additional costs or gear modifications and also facilitated control by national fishery authorities. A series of complementary measures were established between 2001 and 2002, including management elements addressing various aspects of the fishery. The result of this strategy was almost immediate, with juvenile catches in the following years dropping significantly, generally remaining below the established threshold. In general, CCAMLR-managed fisheries lack specific measures to avoid or minimize juvenile catches. The increasing number of immature fish in South Georgia Islands D. eleginoides fishery catches has drawn special attention from CCAMLR since 2021. The impact of fishing on the juvenile fraction of a population is a critical factor for both resource sustainability and fishery yield. The practical implementation of measures to reduce juvenile mortality, within a precautionary and ecosystem-based approach, is essential for ensuring the long-term productivity and sustainability of the resource and its fishery.