Vol 58, No 5 (2018)

Influence of biotic and abiotic environmental factors on feeding of the predatory fish in the Rybinsk Reservoir in 1953−2012 has been analyzed. It is revealed that the feeding spectrum of the majority of piscivores (sander Sander lucioperca, burbot Lota lota, pike Esox lucius and adult perch Perca fluviatilis) includes 16−18 fish species, while only seven in Volga sander Sander volgensis. Three aboriginal fish species (perch, ruff Gymnocephalus cernuus and roach Rutilus rutilus) and two invasive species (European smelt Osmerus eperlanus and Black-Azov tyulka Clupeonella cultriventris) are the main food items for piscivores. In some years, these species accounted for 97% of the total number of prey. Introduction and naturalization into the reservoir of smelt (during the period of climatic norm) and Black-Azov tyulka (during regional climate warming) considerably changed proportions of species serving as potential prey for predatory fish. During these periods, the share of invasive species in the ration of pelagic zone piscivores was increasing, but this increase was not proportional to the abundance of these prey species. After decline in abundance of smelt and tyulka (while, at the same time, these species were still dominant) their shares in the feeding of predators decreased, while the role of more available mass aboriginal species increased again. It is revealed that predatory fish are selective to certain prey items: sander, Volga sander, and large perch prefer to feed on perch yearlings; burbot, on yearlings of perch and on ruff; and pike, on roach.

The second, final part of the work contains a continuation of the annotated list of fish species found in the marine and brackish waters of Aniva Bay (southern part of the Sea of Okhotsk, southern part of Sakhalin Island): 137 species belonging to three orders (Perciformes, Pleuronectiformes, Tetraodontiformes), 31 family, and 124 genera. The general characteristics of ichthyofauna and a review of the commercial fishery of the bay fish, as well as the final systematic essay, are presented.

Evolution of schooling behavior in fish is discussed. For the first time, schooling was formed in early Teleostei ca 200–220 Ma years BP. There are no strict data on the presence of this form of social behavior in older Craniata. It is supposed that the evolutionary path of schooling followed from asociality to protoschools and then to true equipotential schools. The schooling behavior might disappear and appear again repeatedly and independently in different groups of teleosteans. Formation of schooling depended on Teleostei’s mode of life, first of all, on distribution to the pelagial, and it did not strictly depend on the evolutionary age or phylogenetic relationships of taxonomic groups or particular species. Schooling might be transformed into other types of social behavior. The scheme of evolution of the schooling behavior is suggested.

The morphological description of a rare species, Mekong blind sole Typhlachirus elongatus, from the Mekong River delta is described. Three species—T. lipophthalmus, T. caecus, and T. elongates—are considered as species included in the genus Typhlachirus. Unfoundedness of placing T. elongatus in the genus of Brachirus is shown.

The information on the size composition and distribution of the larvae and juveniles of polar cod Boreogadus saida on the shelf of Russian Arctic seas (the Kara Sea, the Laptev Sea, and the East Siberian Sea) is presented for the period of July–September 2015–2017. The larvae and juveniles are widely distributed here, forming the largest accumulations on the continental slopes in the areas least affected by the river runoff. Both seasonal and regional differences are observed in the size composition of the early developmental stages of the polar cod: the juvenile average length increases from summer through autumn and southwards.

The growth, the sequence of formation, and the features of the transitive states of skeletal elements (cranial bones and serial structures, such as teeth, gill rakers, fin rays and pterygiophores, vertebral bodies, predorsalia, and scales) have been studied in prelarvae, larvae, and fingerlings of the lacusrtrine-riverine morphs of the white charr Salvelinus malma complex from Lake Kronotskoe, Eastern Kamchatka, reared in a laboratory at a constant temperature and collected in the Uzon River, at a spawning ground and downstream. A comparative analysis of osteogenesis features in white charr and the original morph, the Northern Dolly Varden Salvelinus malma malma, has been carried out. A high variability in the rate of growth and development of white charr is noted. A delay in calcification of skeleton in prelarvae and a late onset of scale formation (at the end of the second and the beginning of the third year of life) and first annulus in otoliths (by the third year of life) have been revealed. The results indicate the high specialization of early ontogenesis in white charr, a fish endemic to Lake Kronotskoe.

The paper characterizes feeding of juvenile chum salmon Oncorhynchus keta and pink salmon O. gorbuscha during the fattening period in July 2013−2015 within the coastal zone of 0.5−1.5 km from the shores. The study revealed that both species exhibited diverse feeding in the pelagial, but older Neocalanus spp. and Pseudocalanus spp. copepodites were the main food items determining adequate covering of the fish demands for food. These invertebrates formed 78% of the total zooplankton biomass in the upper water layer (0−10 m). In 2013 and 2014, all juvenile fish specimens were feeding and were fed satisfactory. In 2015, feeding intensity of the juvenile fish was weaker and more than 1/3 of the fish were starving by the end of July. On average for three observation years, chum and pink salmons were feeding at the narrow shallows almost twofold better than over the wide shallows. Specific features of the fish feeding revealed in the present study are in agreement with the interannual and local fluctuations of the zooplankton abundance.

The bluelined hind Cephalopholis formosa (Shaw, 1812) belonging to family Serranidae inhabits in the coastal waters of Indo-West Pacific: western India to Philippines and Andaman Sea. For the first time one such specimen of this species was caught in the Odisha coast, Bay of Bengal, India. We reviewed its distribution after compilation with available literature.

The report outlines the research findings on White Blood Cell Count during the annual cycle of the bullhead notothen Notothenia coriiceps native to waters of Galindez Island (the Argentine Islands). We found a statistically significant reduction in lymphocyte concentration and an increase in the proportion of segmented neutrophils during the spawning season.

Data on the size-age and sex structure, as well as the magnitude, of Siberian taimen Hucho taimen population from the Tugur River basin are presented.