Benthos elimination by juvenile red king crabs Paralithodes camtschaticus (Tilesius, 1815) in the Barents Sea coastal zone: Experimental data

Abstract

231 Study of the effect of the red king crab Paralithodes camtschaticus (Tilesius, 1815) on the local benthic biota is one of the main lines of research in the ecological consequences of its introduction to the Barents Sea from the northern Pacific region. The conditions of the new habitat proved suitable for the crab reproduction and growth. Food resources are believed to be the main limiting factor of the red king crab numbers in the Barents Sea [2]. Adult red king crabs inhabit the southern Barents Sea to a depth of 300 m, whereas juvenile crabs are most abundant in the coastal zone. Undoubtedly, both adult and juvenile crabs affect benthic communities. However, the details of this effect, especially regarding juvenile crabs, have not been studied. The numbers of immature (juvenile) crabs off the Murman coast at depths less than 40 m was estimated at 55 × 10 6 in 2003 [10]. These crabs inhabit communities of hard and soft grounds with benthos biomasses of 500‐3500 g/m 2 [1] and 40‐150 g/m 2 [8, 12, 13], respectively. The main food of juvenile P. camtschaticus is bivalves, gastropods, echinoderms, and polychaetes [5, 7, 9, 11]. To estimate the elimination of benthos by juvenile P. camtschaticus, quantitative data on their feeding are necessary, but these data are very few in the available literature. The traditional quantitative analysis of the contents of the crab gastrointestinal tract, which contains only crushed and considerably digested remnants of the food does not allow the number of the eaten representatives of zoobenthos or their weight to be determined. The calculation of the crab ration or the elimination of benthos by crabs based on these data yields incorrect