Feeding habits of masu salmon Oncorhynchus masou in the Okhotsk Sea is investigated. Its main prey in fall season is fish, amphipods, and euphausiids. However, the diet composition depends on the area: for masu with size of 30-40 cm it is mainly fish in the biostatistical districts 8 and 11 and zooplankton in other areas; besides, the zooplankton prey is replaced by fish for elder and larger salmons. The stomach fullness has significant circadian rhythm with one main maximum (70-700 ‱) and one minor peak. The main maximum was observed at 21 o’clock in 2002 but at 15 o’clock in 2006 and at 18 o’clock in 2009 and 2015 (local time).
Smoothtongue Leuroglossus schmidti is a small mesopelagic fish species common for subarctic waters. It rises to the upper epipelagic layer at night for feeding and preys mainly on euphausiids, copepods and amphipods. Its mean index of stomach fullness reaches 68 ‱ in the epipelagic layer, but it almost doesn’t feed deeper than 200 m, judging by a little food in the stomach. In the Bering Sea, euphausiids dominate in its diet and the portion of copepods is small. In the Okhotsk Sea, each of these two groups provides a half of the diet. In the North Pacific, the portion of copepods is 63 % on average, euphausiids are the second important prey, and amphipods occur in the diet occasionally. Daily ration of smoothtongue is about 1.4 %.
Feeding habits of adult sea bream are considered on the samples collected in the North Pacific and Bering Sea in the last several years. This species is a predator with the diet highly dependent on its habitat and composition of prey (small-sized fish and squids). It has two or three peaks of consumption daily, which change seasonally and year-to-year; anyway, the morning (3-6 a.m.) is usually the time of the lowest consumption, at least in summer and autumn, and the daytime is the normal time for feeding. The sea bream does not eat zooplankton usually, but Euphausia pacifica was a significant portion of its diet (34 %) in the southern part of surveyed area in the summer of 2009, possibly because of high concentrations of euphausiids in that area. Daily ration of adult sea bream is 2.5-3.5 % of its body weight.
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