Voprosy ihtiologii

A new species of the tubenose goby is described, found in some rivers and lakes of the Black Sea coast of Georgia and Abkhazia. In contrast to the widely distributed in the basin of the northeastern part of the Black Sea Proterorhinus marmoratus s. stricto, the new species typically has no more than 16½ branched rays in the dorsal fin (typically no less than 17½ rays in P. marmoratus), typically 13½ rays in anal fin (typically no less than 14½ rays in P. marmoratus); total number of scales along the mid-lateral is no more than 50 (varies from 47 to 57 in P. marmoratus); in specimens SL 40 mm or more, the distance from the anterior tip of the snout to the origin of the second dorsal fin longer than 50% SL (typically shorter than 50% SL in P. marmoratus) and the distance to the origin of anal fin longer than 56% SL (shorter than 56% SL in P. marmoratus).

The European barracuda Sphyraena sphyraena (Linnaeus, 1758) is occasionally recorded in the Black Sea, however its findings in the 21st century have become more frequent. This paper presents the results of biological analysis of a mature female barracuda with a total length of 35.4 cm and weight of 196.4 g, aged 4+ years, caught off the coast of Crimea (Sevastopol) in 2022. Oocytes in the ovaries (weight of 1.999 g) are at the resorption stage. Fragments of the spine of an unidentified fish have been found in the digestive tract of the specimen. Based on literary data, biological characteristics of barracuda individuals previously recorded in the Black Sea are presented. The prospects for the development of the Black Sea waters by this species are assessed; if the climate change trend towards warming persists, the possibility of successful naturalization of the barracuda will increase.

The results of the study of the distribution of whitespotted char × Dolly Varden hybrids (Salvelinus leucomaenis × S. malma) and their parental species in the Utkholok River (northwestern Kamchatka) are given. The localization of sexually mature individuals after spawning in the river channel in the pre-winter period (September–October) is presented. Qualitative differences have been revealed in the characteristics of the water flow and bottom substrate in the biotopes preferred by the chars and their hybrids. A characteristic feature of fish distribution is the position of individuals in a water flow, which provides maximum access to drift food particles for effective post-spawning recovery and preparation for wintering. It has been found that the biotope of whitespotted char × Dolly Varden hybrids is unique and differs from those of their parental species: the three groups were able to reduce the tension of feeding relationships based on spatial distribution. The results provide additional evidence of the successful course of microevolutionary processes, including the adaptation of the hybrids to their own biotope in the ecosystem. There is reason to believe that the interspecific relationships of the hybrids and parental species in the Utkholok River are nonantagonistic and their stable coexistence with continued selection, as well as the stabilization of the developed adaptations, are possible.

The underwater studies of the typical spawning ground of the masked greenling Hexagrammos octogrammus conducted in the northern part of the Sea of Okhotsk at a depth of 0.8–3.0 m revealed the confinement of the species to the biotopes of rocky underwater plateaus in the macrophyte belt during the spawning season. The average density of males was 0.17 ind./m2. The sites with the optimal conditions for spawning of greenlings are located in the central part of the macrophyte belt (1.5–1.7 m) on medium-sized boulders. Of the three size groups of males, significant differences in the conditions were noted only between large and small ones. Small males were located at shallower depths and closer to the shore line. Large males were located on the horizon with the dominance of brown algae at the lower boundary of macrophytes. The medium-sized greenlings (16-19 cm) showed preferences which were characteristic of both small and large individuals. An assessment of the abundance and distribution of males of masked greenling and a description of the environmental conditions at the spawning grounds (data on relief, sediments and macrophytes) made it possible to characterize the spatial organization of the spawning grounds of this species.

Late embryonic and early larval development (until first feeding) of Monodactylus argenteus have been studied. The chronology of development and a detailed morphological description of the eggs, embryos, and early larvae are presented. The eggs of M. argenteus were obtained from ichthyoplankton catches from the coastal waters of Central Vietnam and incubated under laboratory conditions at a temperature of about 24°C. The taxonomic identification was performed using the molecular-genetic method of DNA barcoding based on gene cytochrome oxidase 1 subunit (COI) from mitochondrial DNA.

Three immature specimens of Indo-Pacific sailfish Istiophorus platypterus have been found in a catch using a fixed net from the Sea of Okhotsk side of Kunashir Island on September 27, 2023. Data of morphometric measurements of one of them are presented. The total length of the studied specimen was 1101.3 mm, fork length (FL) was 973.8 mm, standard length (SL) was 966.6 mm, lower jaw–fork length (LJFL) was 82.15 cm, and body weight was 2.25 kg. The temperature of the water surface layer in the catch site was 21°C on the date of the capture.