Vol 59, No 1 (2019)

The structure of some muscles, ligaments, the aponeurotic system, and osteological traits of the visceral apparatus in silver carp Hypophthalmichthys molitrix is considered in detail. A number of the revealed traits of the jaw apparatus indicate its adaptation to pulsed suction filtration. The functional features of the feeding apparatus are analyzed based on the anatomical study and data published in literature.

The reproduction period of the sea raven Hemitripterus villosus were studied by visual SCUBA-diving methods in 1997–2016 in Peter the Great Bay, the Sea of Japan. It has been found that the beginning and the end of the spawning period shifted to a later date (5–12-day shift) in particular years, which is explained by the increased water temperature at the spawning grounds by 1.6–2.5°C in September–October. The degree of damage of the open egg masses has greatly increased (from 35.2 to 60.4%), the main predator is the sea urchin Mesocentrotus nudus. The observed changes in the timing of reproduction and an increase in the degree of egg consumption by predators are not critical factors for reducing the abundance of the sea raven.

Information on stone cockscomb Alectrias alectrolophus diet in Avacha Bay (eastern Kamchatka) are presented, and seasonal, local, age, and interannual changes in the composition of its food are considered. This species is benthophagus, so the main objects in Avacha Bay are Amphipoda.

Samples of Greenland halibut Reinhardtius hippoglossoides (Jordan and Snyder, 1901) from the Atlantic, Arctic, and Pacific Oceans were compared using eight microsatellite loci and the Cyt b mtDNA gene. The data obtained revealed a population connectivity of the Greenland halibut from the Laptev Sea to those from the Atlantic Ocean that is result of considerable eastward range extension due to recent climate change. Genetic differences between the Greenland halibut groupings of the Atlantic and Pacific Oceans, according to F_st values (0.141–0.197), reach a high level. Given the genetic differences revealed by both nuclear and mitochondrial markers, the taxonomic status of the Greenland halibut inhabiting the Pacific Ocean requires reevaluation at least to the rank of subspecies. It is suggested that the Greenland halibut populations of the Atlantic Ocean basin originated from those of the North Pacific. The time and conditions of Greenland halibut penetration from the North Pacific to the Atlantic Ocean are discussed.

By means of electronic microscopy, the structural distinctions of epithelial cells are revealed in three species of cartilaginous fish differing in their foraging: spiny dogfish Squalus acanthias (a typical fish predator), common stingray Dasyatis pastinaca, and thornback ray Raja clavata (benthos eaters-facultative fish predators). In the spiny dogfish, the length of microvillu in the brush border of enterocytes in the medial region of the spiral intestine is smaller than in Dasyatis pastinaca and Raja clavata (0.66 ± 0.05 vs. 1.16 ± 0.07 and 1.04 ± 0.10 μm) and their diameter, on the contrary, is greater (0.10 vs. 0.08 and 0.07 μm). In Dasyatis pastinaca, there is a well-developed glycocalix and the distal decrease of microvilli length. The role of the brush border enetocytes in the increase of digestive and transport surface of the intestine, as well as the role of particular organelles in digestions and transport of nutrients in the investigated fish, is discussed.

The work examines the food supply of the Azov anchovy Engraulis encrasicolus maeoticus in 2006–2013, while the level of salinity of the Sea of Azov was rising from 9.3 to 12.6‰. The food supply was assessed based on the lipids and essential polyunsaturated fatty acids (eicosapentaenoic and docosahexaenoic) accumulated in the body of the anchovy at the end of the feeding stage (October–November). As salinization of the sea progressed, the level of the total lipids in the anchovy body increased from 15.5 to 18–18.7% owing to triacylglycerol content; absolute amounts of eicosapentaenoic and docosahexaenoic acids grew 1.9 and 2.6 times respectively (from 576 to 1091 and from 594 to 1540 mg/100 g of wet weight). Along with this, anchovy stock increased multifold, which equally indicates a significant improvement in food supply of the fish. Qualitative composition of the anchovy diet was found to shift towards the dominance of the Black Sea migrants and an increased share of the animal-source food in the intake. In addition, we discuss the correlation between the interannual variability in food supply of the anchovy in 2006–2013 and stock of its main trophic competitors in the Sea of Azov, namely, tyulka Clupeonella delicatula delicatula and ctenophore Mnemiopsis leidyi.

In consideration of literature, it is concluded that it is necessary to restore the validity of Paragaleus longicaudatus (Bessednov, 1966) and of its synonymy with P. randalli Compagno et al., 1996.

Catching of extremely large (520 cm) specimens of smalltooth sand tiger Odontaspis cf. ferox (Odontaspididae) near the southern part of Walvis Ridge (Southeastern Atlantic open waters) is documented for the first time. This species was found earlier in the Atlantic Ocean in the near-continental waters and island regions of the northeastern Atlantic from the Bay of Biscay to Morocco, including the Mediterranean Sea. In the open waters of the southeastern Atlantic, the species was not recorded previously.

A method for computer-based determination of the motility characteristics of fish spermatozoa using ImageJ software and a number of original Excel macros that help optimizing the processing of the data obtained using the wrMTrck_Batch plugin are described. The described method has been tested on sperm of the Black Sea turbot Scophthalmus maeoticus.