Life cycles and somatic production of hyperiids in the Okhotsk and Bering Seas

Hyperiid species Themisto pacifica , T. libellula , and Primno macropa are widespread in the Far-Eastern Seas. They are an important element of trophic web in pelagic communities of these seas. Their food spectra are very broad and include copepods, euphausiids, arrowworms, and fish larvae. On the other hand, the hyperiids play an important role in the diet of large-sized marine organisms as walleye pollock Theragra chalcogramma , mackerels Scomber japonicus , Pleurogrammus monopterygius , and Pleurogrammus azonus , and japanese squid Todarodes pacificus . Life cycles and production of these hyperiid species are described on the base of samples collected in complex surveys conducted by Pacific Fish. Res. Center (TINRO) in the Okhotsk Sea and the western Bering Sea in 1984-2011. All three species have similar life history though the maximal life span is 2 years for T. pacifica and T. libellula but 3 years for Primno macropa . They spawn twice in their life in the period from May to October with the peak in July. Their weight increments also increase twice, usually when their size is 7-10 and 10-12 mm for T. pacifica and P. macropa and 10-15 and 20-30 mm for T. libellula . The average specific daily production of hyperiids in the Okhotsk Sea is estimated as 0.0410 for T. pacifica , 0.0273 for T. libellula , and 0.0101 for P. macropa ; but in the western Bering Sea - as 0.0492 for T. pacifica , 0.0361 for T. libellula , and 0.0094 for P. macropa . The most favorable feeding grounds for hyperiids are located at Kuril Islands, at West Kamchatka, and in the Anadyr Bay. Their summary annual production is estimated as 30.235 mln t in the Okhotsk Sea and 21.370 mln t in the western Bering Sea

On feeding of deep-sea crabs on the continental slope of northwestern Kamchatka

Mean index of gastrointestinal tract fullness for golden king crab Lithodes aequispinus is 15.5 ‱. Detritus occurs in 40.5 % of the cases, so it is a common food for this crab, Polychaeta, Ophiuroidea and Decapoda are 33.2 %, 32.1 % and 15.4 % of its ration, respectively, whereas Mollusca are only 11.5 % of the ration weight, despite of frequent occurrence. Triangle tanner crab Chionoecetes angulatus has the mean index of fullness 20.9 ‱, Polychaeta and Mollusca are two main components of its ration (31.4 % and 27.3 %, respectively) and Decapoda and Pisces are the secondary components (13.9 % and 12.2 %); detritus occurs in 11.2 % of the cases. Cannibalism is observed incidentally for the latter species