Unaccounted mortality of red king crab (Paralithodes camtschaticus) in deliberately lost pots off Northern Norway

During the 1960s, adult and juvenile red king crab (Paralithodes camtschaticus) were introduced to the Kola Peninsula with the aim of establishing a commercially exploitable stock in the Barents Sea. The stock has steadily increased and there is now a red king crab research fishery using pots. For various reasons, pots are occasionally lost, and concern has been expressed about whether lost pots could still catch crabs and thus contribute to a significant unaccounted mortality. An experiment was set up whereby pots were deliberately lost for periods of between 5 days and 1 year. A new design of rectangular collapsible pot was the main gear used, but in a single 5 days trial the traditional conical pot was used. All crabs caught were tagged and their lengths measured before they were returned to the pots. The crabs gradually left the pots and new ones entered. In a string of four pots, for example, all 92 tagged individuals left the pots after 4 months, while 61 new crabs entered them. Very few dead crabs were found in the pots. The size of the crabs increased with soak time in the rectangular pots, while it decreased with soak time in the conical pots. A relationship between soak time, crab catch and associated mortality was established. (C) 2003 Elsevier B.V. All rights reserved.