Trap survey on the fishing boats as a promising way to stock assessment of Red King Crab (Paralithodes camtschaticus) in the Barents Sea

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Red king crab was introduced into the Barents Sea by Soviet scientists in the 1960s and has developed a largest population in the world. Data on the stock abundance of red king crab in Russian waters of the Barents Sea are principally obtained via stratified, random trawl surveys, which have been conducted annually in August or September since 1997. Trawl surveys are generally associated with depths of more than 60-100 m in areas with predominately soft bottom. In 2004, commercial crab fisheries began in Russian Exclusive Economic zone. In 2003-2006, six diving surveys and four trap surveys were conducted by Russian Federal Research Institute of Fisheries and Oceanography (VNIRO) in cooperation with fishermen. Abundance in different sex-size groups was assessed on results of the trap surveys and with the help of new software developed in VNIRO and based on different mathematic methods for interpolation of spatially distributed data (Kriking, spline-approximation, the Delaunay triangulation and the Voronoi diagram). The resultant maps of the red king crab distribution were analyzed. Based on the results of trap and diving surveys in 2003-2005, the king crab stock in Russian waters of the Barents Sea was estimated to be approximately 100x106 individuals, including 40-50x106 mature crabs. It is shown that autumnal trawl surveys (August-September) led to a systematic error in the king crab stock assessment.