An Erratum to this paper has been published: https://doi.org/10.1134/S1063074025010018

The Derzhavin's sculpin (Radulinopsis derzhavini Soldatov et Lindberg, 1930) is a psychrolutids species that leads a cryptic life in coastal waters of the Japan Sea and the southern Okhotsk Sea. To date, larvae of this species have remained unknown; therefore, their biology is poorly understood. In the present study, the early developmental stages of R. derzhavini are described for the first time. In Peter the Great Bay, Japan Sea, this species is characterized by a spring spawning season (May) and a short pelagic period of larval development, usually from mid-May to the last 10 days of June. Species identification of the described larvae was confirmed by incubation, rearing of larvae in captivity, and genotyping of a fragment of the mitochondrial cytochrome c oxidase I (COI) gene. In addition, the development of pigmentation in larvae of this and related species was compared. Morphological analysis of both adults and larvae, together with complementary molecular genetics, confirms the previously obtained conclusions that the species of the genera Radulinopsis, Radulinus, Asemichthys, and Astrocottus form a natural group with monophyly by all types of data.

Stichaeus ochriamkini (Stichaeidae) is common in the northern Japan Sea and the southern Okhotsk Sea. Among the five known representatives of the genus Stichaeus, early ontogenesis is the least studied in S. ochriamkini. In this study, the authors provide the first description of all larval stages of this species. In the north-western Japan Sea, larvae are found in plankton from early April to early June. S. ochriamkini larvae can be identified using the following characters: postanal-lateral pigment (PLP) lines present on the sides of the caudal part of the body and run along the anterior edge of hypaxial myomeres; 14-15 abdominal vertebrae; 32-34 rays in the anal fin; larvae disappear from plankton at a body length of L-T > 25.0 mm (L-S > 20 mm). Larvae of S. ochriamkini are very similar to larvae of Stichaeus punctatus. The melanin pigmentation in larvae of both species shows similar patterns of development. In the genus Stichaeus Reinhardt, 1836, two groups of species are distinguished by the presence/absence of PLP lines in larvae, and by significant divergence (clearly exceeding the species level) in the COI mtDNA gene. It is suggested the differences between these species groups is recognized at the generic level. Thus, the genus Stichaeus Reinhardt, 1836 should include S. punctatus and S. ochriamkini, whereas the other three species should be placed in the genus Dinogunellus Herzenstein, 1890: Dinogunellus fuscus, Dinogunellus nozawae and Dinogunellus grigorjewi.

The larval development of Chirolophis japonicus and Ch. saitone from the yolk-sac stage to the settlement on the bottom is described from waters of Peter the Great Bay, Sea of Japan. The pattern of distribution of melanin pigmentation over the body of larvae in these Chirolophis species is formalized for the first time. It consists of six rows, the aggregation on the top of head, and several single melanophores. Despite the similarity between the species, each of them has its specific features that are manifested mainly as a different number of axial skeleton elements (total number of vertebrae and number of rays in the dorsal and anal fins). A conclusion is made that a reliable diagnostic character to identify larvae of Ch. japonicus and Ch. saitone within the period of their development from hatching to settlement can be the number of melanophores at the base of the anal fin rays.

The ichthyoplankton of the upper epipelagic zone (0–50 m) was studied in the northern part of the Sea of ​​Japan in July–August 2017. Eggs of seven fish species and larvae of five fish species from five families were recorded off the coast of Primorye; eggs of six species from five families and larvae of 12 species from seven families, in the Strait of Tartary. Eggs and larvae of four species of the Pleuronectidae family ( Limanda punctatissima, Glyptocephalus stelleri, Cleisthenes herzensteini, and Acanthopsetta nadeshnyi ) prevailed everywhere. Off the coast of Primorye, Cl. herzensteini dominated, and in the Strait of Tartary, L. punctatissima . In comparison with the results of the Kuril-Sakhalin expedition performed the late 1940s, the eggs of pelagic fish species, such as Engraulis japonicus, Cololabis saira, and Scomber japonicus , was found in small quantities and only in the surface water layer. The results allow us to report on slight changes in the species composition relative to the middle of the last century, on the one hand, and significant changes in the dominant species, on the other.

In the laboratory experiment and in fish caught in conditionally clean and polluted areas, the presence of metabolites of polycyclic aromatic hydrocarbons in bile by methods of conventional and synchronous spectrofluorimetry was determined. The study showed that this approach is well suited for the detection of metabolites of polycyclic aromatic hydrocarbons with 2–3, 4, and 5–6 aromatic rings. If the content of metabolites of polycyclic aromatic hydrocarbons with 4 and 5–6 rings in bile is low, the method of synchronous spectrofluorimetry is less sensitive than conventional spectrofluorimetry. Both methods of monitoring are simple and fast and reflect the real picture of water pollution.

The article provides a description of Davidijordania lacertina (Pavlenko, 1910) with a body length of 18.0–32.0 mm TL , collected from Vostok Bay, Sea of Japan. The total number of vertebrae (119–121) and the pigment pattern on the bodies of the examined juvenile fish correspond to those of D. lacertina .

The embryonic and early larval development of the Cherskii’s sculpin Cottus czerskii Berg, 1913 was studied. The duration of the embryonic period was 21 days at a water temperature of 9–10°C. Pelagic larvae of approximately 8.0 mm total length leave the egg envelopes, with a large rounded yolk sac with one large oil globule, 10–12 trunk and 30–31 precaudal myomeres and several large melanophores on the yolk sac, 2 melanophores in the peritoneal region, and 30 melanophores in a postanal ventral row. At 11 days after hatching at a length of 9.0 mm, the yolk sac is completely resorbed and the number of myomeres remains the same; seven rays become visible in the caudal fin. The fully formed larva of C. czerskii has an elongated body, a small head, a rounded snout, and an oblong tail part. The melanophores are located in the peritoneal area above the gut, in the abdominal area, and in the postanal ventral row. Armament in the form of spines on the top of the head is absent, pointing to the affiliation of the species that we studied to the Cottus–Leptocottus phenetic group.

Data on species composition of ichthyoplankton of the coastal zone of western part of Peter the Great Bay of the Sea of Japan are generalized. Here eggs, larvae, and fry of 77 species of fish belonging to 25 families occur, which comprises 24.4% of the total number of species inhabiting Peter the Great Bay. Among the studied water areas, maximum species diversity (60 species) was recorded in ichthyoplankton of the eastern site of the sea biosphere reserve. Seasonal dynamics of species composition of ichthyoplankton of the coastal zone of the western part of Peter the Great Bay was traced: number of species reduced from 52 in May to two in October.

This study revealed additional data concerning the spawning period of the Japanese anchovy Engraulis japonicus Temminck et Schlegel, 1846 in Vostok Bay (Peter the Great Bay, Sea of Japan). The spawning of E. japonicus in this area ends in September at a water temperature of 17.5 ± 3°C. Some important peculiarities of the embryonic and postembryonic development of E. japonicus in the natural environment are described. The anchovy larvae have characteristic upper and lower rows of melanophores and subcaudal paired rows of melanophores on the trunk. Regular alternating rows of long and short cones were found in the retina of the early larval stages (TL 5.5 ± 0.1 mm). The planes of the photoreceptive lamellae in the outer segments of the short cones are oriented parallel to the long cell axis, which evidently provides sensitivity to polarized light.

In the summer period of 2009, two species of warm-water fish—Japanese cutlass fish Trichiurus japonicus and frigate mackerel Auxis thazard —were found in Peter the Great Bay. Their description is made, and their main diagnostic characters are provided. It was established that both species of the genus Auxis are found in Russian waters of Far Eastern seas.

Two specimens of Liparis frenatus (Gilbert et Burke, 1912) of 30.1 and 55.5 mm in TL were recorded in Russian waters of the Sea of Japan for the first time. Five specimens of a poorly known species, L. kusnetzovi Taranetz, 1935, were found. Data on the areas of capture and counts of plastic and meristic characters are provided. The specimens of L. frenatus and L. kusnetzovi are described and compared to the closest species of the genus.

We summarize the results of a study of the taxonomic composition and seasonal variations of ichthyoplankton in Vostok Bay. Samples were collected during 2003–2008 at a stationary light station located on the mooring module of the experimental biological station Vostok (Institute of Marine Biology). Within the observation period, larval and juvenile fish of 67 species belonging to 11 orders and 30 families were found in 412 samples. The seasonal dynamics of species composition of ichthyoplankton were examined over the period from March to November. The number of species in the samples changed from 40–36 in April–May, respectively, to 6 species in October. The contribution of resident species and southern migrants to the ichthyoplankton samples was estimated. The light station sampling has proven to be most effective in studying the species diversity of the ichthyofauna in Vostok Bay. Using light station sampling, 18 fish species were found that were not recorded using other sampling techniques.

Five specimens of a rare fish Nautichthys pribilovius (12.5, 13.9, 15.0, 33.0 and 54.0 mm SL) were found in waters of the Far Eastern State Marine Biospheric Nature Reserve and in Vostok Bay. A description of the examined specimens and habitat data are provided. Literature data and our own observations show that as the fish grows from a larva into an adult, the length of the snout and head, as well as the size of the pectoral fin increase, the eye diameter diminishes, and the pigmentation pattern changes.