Vol 63, No 2 (2023)

A new species of golden loach is described from the Don River basin. This species is distinguished from all other Sabanejewia species by the following set of characters: a midlateral row of relatively large 9–16 (more often 13–14) dark blotches along flank usually well developed; no black line along flank; interspaces between midlateral blotches usually with dark pigmentation; some individuals with uniform dark lateral coloration; dorsal fin origin usually in front of pelvic fin origin; body relatively low: body depth noticeably less than the length of the caudal peduncle, usually does not reach 17% standard length—SL, it is contained more than 6 times in SL; dorsal adipose crest on caudal peduncle very weakly developed, ventral crest poorly visible; two black spots at caudal fin base usually merge with each other. Previously, this species was considered conspecific for S. baltica distributed in the Black and Baltic Sea basins, but recent phylogenetic studies have shown that they belong to separate mtDNA phylogenetic lineages

Carrying a gravitational load requires modifications of the skeletal system during water-to-land transition of vertebrates. Early stages of the transition are little known due to incomplete and scattered fossil deposits which can be fulfilled by examining extant amphibious fishes facing analogous conditions. In the present study, we compared vertebral morphometrics of eight oxudercine gobies (Parapocryptes serperaster, Pseudapocryptes elongatus, Oxuderces nexipinnis (low terrestrial); Boleophthalmus boddarti and Scartelaos histophorus (moderate terrestrial), Periophthalmus chrysospilos, Periophthalmodon schlosseri, and Periophthalmodon septemradiatus (high terrestrial)) to gain understanding of the vertebral modifications during land invasion. Results show that the higher terrestrial species possess higher flexibility of the vertebral column, heavy ossification of the neural and haemal spines in the caudal region, and the dorsal twisting feature of the caudal base which could serve effective terrestrial locomotion and allow to perform various body postures. The flexibility of the anterior portion of the caudal region could serve the tail standing and leaping of some mudskippers. We tentatively presume that terrestrial locomotion of oxudercine gobies is endowed by flexibility of the vertebral column and heavy ossification of the caudal vertebrae.

Fishes of the genus Eleginus (Gadidae) are typical representatives of the ichthyofauna of the Northern Hemisphere; they play an important trophic role in the marine ecosystems of the Arctic and North Pacific and serve as targets of commercial and artisanal coastal fishing in many areas of the Russian North and Far East, as well as in areas of the coast of Alaska and northern Japan. The level of knowledge about the intraspecific organization of representatives of the genus Eleginus that is necessary for the rational exploitation of their stocks remains insufficient and their interspecific relationships have so far been analyzed using limited materials. This paper presents the first study of the interspecific relationships and intraspecific structure of navaga (E. nawaga) and saffron cod (E. gracilis) using a large-scale material (986 specimens in 29 samples from most of the species ranges) based on analysis of the polymorphism of mtDNA gene Cyt b. It is shown that they are independent, genetically differentiated species and their comparison with representatives of the genus Microgadus indicates that both species of the genus Eleginus might originate from a common ancestor close to M. proximus, while the divergence in the genus Microgadus occurred much earlier. Data on the haplotypic composition of saffron cod samples inhabiting areas from the Peter the Great Bay to Alaska waters and navaga samples inhabiting areas from the White Sea to the Ob Bay of the Kara Sea are given, which makes it possible to consider the phylogeographic history of both species and their intraspecific organization within the studied areas. Three groups can be distinguished for saffron cod: (1) Pacific–Japanese–Sakhalin group, (2) Chukchi–Bering seas group, and (3) intermediate group, which includes samples from the Sea of Okhotsk and waters of the northern Kurils.

The research outcomes of spatial and bathymetric distribution of dragon poacher Percis japonica are reported based on the bottom trawl surveys carried out in the Russian territorial waters in the Sea of Japan. The species can be found in the waters along the entire coastline. However, its spatial distribution pattern is variable. Thus, its distribution is sparse off the coasts of West Sakhalin, especially off the southern part of the island, while the species tends to congregate in the Peter the Great Bay and the Tatar Strait, where the locations of the species across these water areas remain almost unchanged throughout the year. With respect to the Northern Primorye Coastal Zone, the even distribution is typical for the entire water area, without any high congregation locations. Therefore, the dragon poacher can be found in wide ranges of depths and temperatures. However, its preferable ranges are substantially narrower. The highest values for available biomass resources are typical for the water areas off the Northern Primorye Coastal Zone.

Based on the materials collected in the course of longline fishing in the area of the Emperor Seamount Chain, new data on the occurrence, distribution, and some features of the biology and ecology of Hozukius guyotensis have been presented. It has been shown that it is a common species in the ichthyofauna of the studied area. It is observed on the peaks and in the slope area of the Nintoku, Lira, and Koko seamounts at depths of 385–1015 m; its largest catches are typical for the range of 500–700 m. In the catches, H. guyotensis was represented by individuals 32–73 cm long and weighing 0.45–5.27 kg. Presumably, the species begins to mature at a length of 44–46 cm; the main stage of its reproduction takes place in spring.

Kildin cod Gadus morhua kildinensis is a subspecies of Atlantic cod with extremely small population size, listed in the Red Data Book of the Russian Federation, which inhabits the waters of a small meromictic lake on the Kildin Island (Barents Sea). Comparative studies of morphobiological characteristics and feeding habits of Kildin cod in the juvenile period were conducted for the first time. Comparison of sample sets of adult Kildin cod and fingerlings on the basis of multivariate analysis of variance demonstrates a high degree of differences in the complex of morphometric characters. The diet of the analyzed sample set of Kildin cod fingerlings consisted of ostracodes (Ostracoda), larvae of polychaetas (Polychaeta), cladocerans (Cladocera), and gammarids (Gammaridae). The special features of changes in the diet of Kildin cod in the early ontogenesis are discussed.

Mixed-stock fisheries which simultaneously cause mortality amongst several populations of a species of fish may occur where separate stocks partially or completely overlap in the geographic area of harvest. This study aims to analyze the population-of-origin of adult and subadult adfluvial lacustrine brown trout Salmo trutta, exploited in a mixed-stock fishery in Upper Tuloma Reservoir in Eastern Fennoscandia, using otolith microchemistry. To evaluate the origin of migratory brown trout captured in these mixed-stock harvest fisheries, we undertook otolith sampling of brown trout juveniles in fluvial spawning and rearing habitats in the reservoir watershed, including 13 natal tributaries across the catchment of the reservoir in both Russia and Finland. Harvested adult and subadult brown trout otoliths were sampled from the impoundment in the central area of the reservoir and we analyzed for stock-related character differences to compare with known populations, using trace element signatures, with fish from the mixed stock fishery. The assignments-of-origin in the mixed-stock fishery-harvest samples did not follow the known distribution of populations sampled from natal streams in the watershed. For example, brown trout from the largest tributary catchments of Lotta River and Nota River were less represented in the mixed-harvest sample, which was contradictory to their contribution to the overall spawning and rearing areas of the catchment. These results point towards the importance of maintaining the diversity of different spawning and rearing tributaries required for brown trout recruitment into mixed stock fisheries, and the potential of the existence of population structure of brown trout in the reservoir catchment. Our information suggests that it is important to develop conservation and management strategies for natal habitats in multiple streams utilized by adfluvial lacustrine brown trout populations inhabiting various catchments and that are harvested in mixed-stock fisheries.

The occurrence of erythrocytes with micronuclei and DNA damage was detected by the comet assay in freshwater bream, Abramis brama, of age 3–4, and prussian carp, Carassius gibelio, of age 4–5 from Volga delta in September 2021. The average frequency of erythrocytes with micronuclei in the studied fish es was within the normal range for cells formed during spontaneous mutagenesis (0.5–1.0‰). Further, 25% freshwater bream and 26.6% Prussian carp exceeded this limit. The genetic damage index (GDI), which reflects primary DNA damage, was 0.21 ± 0.03 and 0.26 ± 0.02 in freshwater bream and Prussian carp, respectively. Further, it correlated (r = 0.71, p < 0.05) in Prussian carp with the occurrence of erythrocytes with micronuclei. Hematological and biochemical parameters of the mentioned species were within typical limits for fishes residing in water bodies with a weak anthropogenic load. The results allow considering the existing conditions of the freshwater bream and Prussian carp in the Volga delta as quite favorable in relation to the genotoxic situation.

A new species, Chromis oligactis from the coast of Khanh Hoa province (Vietnam, South China Sea) has been described, which is characterized by a moderately deep body (contained 2.2 times in the standard length), fin formula D XIV, 10; A II, 10; P i, 15–16; three spiniform procurrent rays of the caudal fin, 26 gill-rakers in the outer row on the first arch, and 19 perforated scales in the anterior lateral line. The holotype of the new species was caught at shallow depths, which is not typical for Indo-Pacific species of Chromis with 14 spinous rays in the dorsal fin.

The False Pike Conger Eel, Congrhynchus talabonoides Fowler, 1934 (n = 5) was reported for the first time from the southwest coast of India, Arabian Sea, previously the species was known only from Taiwan, Philippines and Andaman Sea. Diagnostic characters for the species have been provided. Further, the mitochondrial COI gene was generated and the phylogenetic position of C. talabonoides is discussed.

The cellular composition of leukocytes in the peripheral blood, head kidney and spleen was studied in individuals of three species of chars of the genus Salvelinus, white char S. albus, long–headed char S. kronocius and long-nosed char S. schmidti, as well as two forms, small-mouth and large-mouth chars living in Lake Kronotskoe. In the studied individuals, the proportion of lymphocytes of leukocytes in the peripheral blood was significant. The forms (species) of chars differed in the proportion of cell types, the size of leukocytes, as well as the intensity of leukopoiesis. The most significant differences in the proportion of different forms of leukocytes were found in the large-mouth char compared to other species and small–mouth char: high content of lymphocytes in blood smears, low content of monocytes in all tissues and organs, blast forms in the blood and neutrophils in the pronephros.