Vol 58, No 3 (2018)

The second specimen of Eumicrotremus brashnikowi was found in collection materials of ZIN RAS. The species was placed in the genus Eumicrotremus on the basis of the following diagnostic characters: bone plaques spread all over head and body, including caudal peduncle; two pores in the infraorbital canal of the seismosensory system; pores of the seismosensory system are situated on the ends of long skin tubules on the chin and the lower part of a gill cover. The validity of E. brashnikowi is confirmed by the presence of bone plaques in the form of flat plates covered with very thin and short bone spines forming the rosette. The similar structure of bone plaques was not revealed in juveniles and adult specimens of other species of the genus Eumicrotremus. The redescription of E. brashnikowi is carried out. The considerable similarity of the external skeleton structure of E. brashnikowi and E. phrynoidesis is confirmed. The synonymy of E. phrynoidesis and E. asperrimus is not supported.

Information about the sites of catches of the sea lamprey Petromyzon marinus in the western Barents Sea and Arctic lamprey Lethenteron camtschaticum in the Barents and White seas is presented based on the data of trawl surveys performed in 2004−2016. It is demonstrated that sea lamprey is occasionally encountered in the western Barents Sea; nine specimens have been recorded during the entire period of surveys. The northernmost point of a capture of sea lamprey is located near 76° N and the easternmost point is at 31°15′ E. Arctic lamprey is not numerous in the Barents and White seas; a total of 66 and 17 specimens have been caught, respectively. Its local aggregations are found in the southeastern part of the Barents Sea and in Dvina Bay in the White Sea. Arctic lamprey penetrates to the north to 76° N and into the central part of the Barents Sea.

A single specimen of African angel shark, Squatina africana (Regan, 1908) was caught off Lakshadweep (11°5′47″ N; 72°2′21″ E), India in September 2016. The present study is a new report of the above species from Indian waters. In addition to classical methodologies, DNA barcoding was also adopted for species identification. The 650 bp-long region of mitochondrial Cytochrome Oxidase subunit I was sequenced to obtain the DNA barcode for the species under study. The sequence divergence value within species and between species was calculated using MEGA V.7.0, where Kimura 2 parameter (k2p) model was chosen as a distance model. The average k2p distance separating individuals within species was 1.76% and inter specific divergence was 8–10%. A neighbour joining network was constructed to provide a graphical representation of divergence between the species. Using the maximum identity with Gen Bank database, K2P divergence distance, NJ-network and traditional morphological approach, we could identify the given specimen as a mature male African angel shark.

To date a considerable amount of data on sympatric diversification of the laсustrine fish has been accumulated and many important advances made. However, the evolutionary mechanisms of the process still remain unclear. The paper discusses fish polymorphism in the water bodies of different latitudes, but the major focus is the question of sympatry in the charrs of the genus Salvelinus across the northern lakes. Numerous cases of diversification were comparatively analyzed, which provides evidence for the existence of several main pathways of evolutionary process. The pathways are controlled by environmental factors, which determine the structure of the lake ecosystems in the northern latitudes.

Two color morphs of freckled goatfish Upeneus tragula with different Vietnamese names and mainly black and red body coloration of fresh dead exemplars are found off Hon Thóm (Thom Island), the largest island of An Thoi Archipelago located to the south of Phu Quoc Island, Gulf of Thailand, South China Sea. The presence of the morphs may be connected with the occurrence of two sympatric stocks or with color variation within a single stock. To test these hypotheses, red color content on the body (based on digital analysis of images) and gonadal condition is compared in both morphs. Body coloration does not depend on the sex of the fish. The black morph differs from the red morph in a smaller body size (12.7 vs. 16.4 cm FL on average), and it is represented by mainly immature individuals of both sexes (mean gonadosomatic index of the females 0.5 vs. 2.0%). It is proposed that the change of body coloration is associated with sexual maturation, and it occurs in the ontogeny within a single stock.

Data on the age and growth of the roughhead grenadier Macrourus berglax from waters off Southwest Greenland have been obtained based on the analysis of otoliths. Specimens with a preanal length of 5−39 cm, a weight of 7−5275 g, and age from 2 to 22 years are recorded in trawl catches. Roughhead grenadier exhibits a similar rate of linear growth in waters off Southwest Greenland and other parts of the range in the Northwest Atlantic. No considerable differences from the rate of the linear growth calculated earlier from scales for the species in waters off West Greenland have been found. In the recent period, the rate of weight gain in roughhead grenadier in waters off Southwest Greenland has been lower than in the Northwest Atlantic in the first half of the 1980s. The age of mass maturation in males (7–9 years) and females (16–17 years) in waters off West and East Greenland is somewhat higher than in coastal waters of Norway and the Northwest Atlantic.

The saddleback syndromes were observed in several commercial fishes obtained from Saudi Arabian coast of the Arabian Gulf. These deformities resulting in missing dorsal spines or rays, sometimes accompanied by a depression in the dorsal profile, were found in ten fish species from seven families. Other morphological abnormalities such as scale disturbances, lateral line deformity, and kyphosis, the presence of a lesion, slight ambicoloration, and supraneural deformities accompanying the saddleback deformity were also observed. The occurrence of similar deformities across such a spectrum of fishes from the same location suggests that the abnormalities were induced by something in the environment common to all these species.

Regulatory effect of surfagon—a synthetic analog of gonadotropin-releasing hormone—on the gonad state of rainbow trout (Kamchatka steelhead Parasalmo mykiss (=Oncorhynchus mykiss)) juveniles is investigated. The juveniles were 2.5 months old and were exposed to brief (4 days) heat stress (19–20°C). The increase of water temperature was followed by anomalies of gonads after 1 month (destruction of sex cells and hypertrophy of connective tissue). In females, the increased water temperature activates sex redetermination: in ovaries, cysts containing destroyed spermatogonia are found. In 1.5 months, the exogenous application of surfagon was followed by acceleration of spermatogenesis in gonads of experimental fish (2.5 months old) and by a slight decrease of fraction of anomalies in structure of their testes compared with the gonads of fish not exposed to surfagon. Exposure of rainbow trout to surfagon prior to sex differentiation is more efficient than after it is completed.

Information on the distribution of small-headed clingfish Apletodon dentatus (Gobiesocidae), which is a rare species in the Black Sea, off the southeastern coast of the Crimean Peninsula is presented along with morphological characteristics of the sampled individuals.

Daily and seasonal cyclicity, directivity, and area of the fish migration in the main ecological zones of Lake Glubokoe have been revealed with the help of hydroacoustic complexes. Mass appearance of fish in the epipelagial and profundal of the water body is observed at dusk and at night, and they return to the littoral and sublittoral with the dawn. In the summer, vertical migrations of fish occur mainly in the near-surface layers of the water column, and the fish also occupy the profundal in late autumn.