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Vladivostok, Russia

Zavolokin A.V.,Pacific Research Fisheries Center
Russian Journal of Marine Biology | Year: 2010

The seasonal and interannual trends in the distribution and abundance of jellyfish (Scyphozoa and Hydrozoa) in the epipelagic and mesopelagic areas of the Sea of Okhotsk during 1992-2005 were examined on the basis of trawl survey data. The area of occurrence, biomass, and the numbers of Scyphozoa in the epipelagic layer were the smallest in spring; in summer and fall their abundance sharply increased and then decreased in winter. In contrast to the epipelagic zone, the numbers of scyphomedusae in the mesopelagic layer were significantly lower in the summer than in the winter and spring. This probably indicates that a part of scyphomedusae winter in the mesopelagic. Hydrozoa in both the epi- and mesopelagic areas were more numerous in the winter and spring. Jellyfish biomass and abundance greatly changed from year to year. Thus, in fall the biomass of scyphomedusae and hydromedusae in the epipelagic zone varied from 166 to 1271 and from 6 to 49 kg/km2, respectively. © Pleiades Publishing, Ltd 2010.

Zavolokin A.V.,Pacific Research Fisheries Center
Journal of Ichthyology | Year: 2011

Based on complex epipelagic surveys in the western Bering Sea, a comparative analysis of food supply of Pacific salmon (Oncorhynchus spp.) was conducted in summer and fall from 2002 to 2006. Nine indirect indices of food supply used in the study were as follows: feeding similarity, width of the feeding spectrum, diet feeding ration, diet feeding rhythms, fraction of accessory food in the ration, growth rate of the fish, abundance of food resources, and abundance of salmon. The food supply of salmon is lower in summer 2003 and fall 2006 in comparison to the food supply in other years of the study. However, well expressed feeding selectivity, consumption of prey items of certain type, and small proportion of accessory food (copepods and chaetognaths) prevailed in plankton, suggests the presence of sufficient food resources for Pacific salmon in the western Bering Sea. © 2011 Pleiades Publishing, Ltd.

Hirpo L.A.,Pacific Research Fisheries Center
Livestock Research for Rural Development | Year: 2012

Food and feeding habits of Carassius carassius in Melkawakena reservoir were studied. Samples of C. carassius were collected monthly during August (2009) through to July (2010) using gillnets of different mesh sizes. C. carassius was found to ingest a variety of organisms of plant and animal origins, as well as items including detritus and sand grains. However, insects, zooplankton and phytoplankton were found to be the most important food of the fish in the reservoir. Thus, the fish is considered to have a mainly omnivorous feeding habit. The major food items ingested were insects when the size of the fish is increase. However, the importance of phytoplankton and zooplankton tended to decrease where as that of insect tended to increase with the length of C. carassius. Thus, it appeared that the fish feeds progressively more insect as it grows larger. High incidence of empty stomachs was observed during the whole sampling period. But, the frequency of empty stomach was high during the rainy season, which could be associated with breeding activity.

Volvenko I.V.,Pacific Research Fisheries Center
Russian Journal of Marine Biology | Year: 2012

In the virtual multidimensional space of integral biocenotic characteristics, such as abundance, the sizes of individuals, and the components of species diversity, which are scaled on corresponding coordinate axes, the points that represent samples from various biocenotic assemblages, form similar multi-layered hill-shaped figures. The examples we considered are the pelagic macrofauna of the Bering Sea, the Sea of Okhotsk, the Sea of Japan and the adjacent waters of the Northwestern Pacific Ocean; the phytoplankton, zooplankton, and zoobenthos of Lake Ladoga, the Neva Bay, and the Gulf of Finland in the Baltic Sea; the beetle guild in the rainforest of Borneo Island on the Malay Archipelago; and the bird taxocenes and biotope groups of soil mites in North America, among others. The obvious similarity of the composed diagrams results from the close interrelationships of all the integral characteristics and also from the universality of the structure of links between them, which is tolerant to movements in the real space-time continuum and invariant towards the subject of the studies. The multidimensional domain of the analyzed variables is a set of points that are aggregated along a segment, whose length and orientation relative to the coordinate axes determine the general rules of the biocenotic organization of the living matter. © 2012 Pleiades Publishing, Ltd.

Volkov A.F.,Pacific Research Fisheries Center
Russian Journal of Marine Biology | Year: 2012

The mass occurrence of the large hyperiid Themisto libellula was recorded in both the western and the eastern Bering Sea within 2007-2011. Those were the years of a relatively long 6-year period of cold, which was caused mainly by the inflow of cold waters from the north; this is confirmed by the distribution of bottom and surface temperatures and also by the ice-cover values. This hyperiid became dominant in the diet of salmon, walleye pollock, herring, and several other nekton fish species. T. libellula periodically spreads southward with cold northern waters, finding favorable conditions in "new" areas. Being a rapidly growing species with a short life cycle, within 1 or 2 years it reaches a high abundance, which then gradually declines and remains at a mean or low level, as usually occurs with species that were introduced into a new habitat. After the environmental conditions deteriorate, as a "warm" period arrives with changes in the general circulation and a growing inflow of warmed Pacific waters, the southern boundary of the species range moves back far northward and it completely disappears in the areas where it prevailed in the plankton and was a main forage item in the diet of many fish species. Taking into account the durations of warm and cold periods from 1980 until 2010, an event like this in the Bering Sea can be expected within 1 or 2 years. In the eastern Bering Sea, the abundance and dominance of a number of zooplankton species may vary simultaneously. This effect is more pronounced in T. libellula and for this reason the species is considered as a biological indicator of the described climatic changes in the Bering Sea. © 2012 Pleiades Publishing, Ltd.

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