On the question of survival of the red king crab in trawl bycatches in the Barents Sea

Abstract

   The aim: Investigation of the survival rate of the red king crab during trawl fishing under the conditions of a research survey.   The methods: The paper based on works which were completed in 2020–2021 through the trawl survey in the Barents Sea. King crabs were overexposed on the open deck of the research vessel and after that they were keeped in traps and dropped out in the sea water of 15 m depth and keeped there more than 1.5 hours. Crabs heath conditions were checked after the experiments. We also used data on the state of the environment in the area of work and data on the number of injured individuals in the catches.   The newness: This is a first comlex research of king crabs survivability on the Barents Sea during the trawl catch. The same works were provided on the Barents Sea through traps.   The results: On an open deck at an air temperature of 3 to 12 °C and overexposure of less than 3 hours, the mortality of crabs was extremely low, amounting to a maximum of 2.5 % of the number of individuals in the experiment. Over the next 3–5 hours, up to 40 % of crabs could die, and if overexposed for more than 5 hours, up to 59 %. The average proportion of dead crabs during overexposure of 3–5 hours was 5.4 ± 0.3 %, more than 5 hours — 23.4 ± 1.2 % and increased with increasing air temperature: under conditions above 10 °C 100 % survival were never seen. The average delayed mortality in the simulation of release of crabs into the sea was 11 percent.   The practical significance: The results could be used for improving of fishery rules on the North fishery basign and red king crabs stock assessement. The article is not intended to calculate possible damage based on the results of control activities.