Food composition of Red King crab Paralithodes camtchaticus (Tilesius 1815) (Crustacea, Decapoda, Anomura) of the Zelyonaya inlet of the Barents sea in the summer of 2015 and 2016

Food composition of the Red King crab Paralithodes camchaticus (Tilesius 1815) collected in the Zelyonaya inlet of the Barents Sea has been studied. The studied samples include 44 specimens that were collected in August 2015, and 24 specimens – in July 2016. The crab size varies within 40-200 mm. Red King crab is an epibentophagus. Among its food mollusks (mainly bivalves), brown and red algae, and echinoderms are dominated. In addition, foraminifera, polychaetes, amphipods (Caprellida), barnacles and detritus have been found. The Froerman coefficient (the average number of food’s taxon in one stomach) varied in the range of 5.91-6.06, which is almost 3 times higher than in shrimps (predator-gatherers). Based on this data, P. camtschaticus can also be attributed to the predator-gatherers. The inter-annual variations in the food composition of the studied crab in the Zelyonaya inlet are insignificant and it had exercised only for the secondary food items. Among food, crabs, nemerteans, sea anemones, egg capsules (accidental food items) were absent. However, the ratios between some food items in different crab age groups had slightly changed. Based on this criterion, the dominant and secondary food items can be divided into the following groups. On the one hand, these are mollusks (the frequency of which has decreased by one third), which occupy more than half of its volume in the virtual food bolus in juveniles and only one third in adults, on the other hand, foraminifera and bryozoans, which have completely disappeared from it. On the contrary, the frequency of occurrence of seaweed has increased three times, and fish – two times, but their role in the crab's diet has not changed. The frequency of occurrence of algae, detritus and sea urchins has not changed, but despite this, their role in the composition of food, judging by the proportion of volume occupied by them in full stomachs, changes dramatically in mature specimens. Algae, for example, occupy a quarter of its volume, (not 7,1 % of the VEL), i.e. three times more than in 2015. This is probably a consequence of the spatial separation of relatively small and large crab groups.

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