Journal of Ichthyology

On the basis of statistical treatment of the data for 1946–2003 (correlation analysis and analysis of variance) on the biomass of the spawning stock (SSB) and of the resulting recruitment (R), expressed as abundance of three-year-old fish (N3), of the Northeast Atlantic cod Gadus morhua, the relationship SSB → N3 is revised and the extent of the influence of SSB on the formation of R is assessed. The relationship of SSB → N3 turned out to be significant only at SSB ≤ 250 000 t. The influence of SSB is only 4.3–14.7%, in comparison to the other background factors controlling R. This casts doubt on the adequacy of the so-called precautionary approach in fishery management, popular in international fishery organizations, which is based on efforts to support the spawning stock at a certain level (Bpa) taken as the optimum one.

Bài báo trình bày dữ liệu về thành phần loài và sự phong phú của sinh vật phù du cá được thu thập trong các năm 2012, 2014 và 2015 tại vùng biển Đông Bắc Sakhalin; những dữ liệu này được thực hiện trong các cuộc khảo sát định kỳ để ước lượng nồng độ trứng và cá sinh sản của cá thu Alaska (Theragra chalcogramma). Các khu vực có nồng độ trứng và ấu trùng của một số loài cá thương mại chính đã được xác định, sự biến đổi giữa các năm trong sự phong phú của chúng đã được phân tích, và sự phân bố của sinh vật phù du cá đã được liên kết với một số tham số môi trường như độ sâu, nhiệt độ và dòng chảy chính. Trong suốt thời gian nghiên cứu, 30 loài thuộc 11 họ đã được ghi nhận trong sinh vật phù du cá. Nồng độ trung bình của sinh vật phù du cá dao động trong khoảng 113–201 cá thể/m2. Trứng cá thu chiếm ưu thế tuyệt đối với tỷ lệ từ 78–89%; tiếp theo là trứng cá bơn Bering (Hippoglossoides robustus) (5–8%). Đã phát hiện rằng số lượng trứng và ấu trùng của cá bơn cùng với một số loài cá khác ở phần phía Bắc khu vực nghiên cứu tăng trong những năm có lượng nước xả lớn từ sông Amur.

The diversity of life strategy, population structure, size, age and sex composition, growth and variability of 11 microsatellite loci in mykiss (rainbow trout) Parasalmo mykiss of the Utkholok River (Northwestern Kamchatka) were studied. The mykiss population represents a system of groupings with different types of life strategy: anadromous fish prevail in the population, while river and semi-anadromous (estuarine and riverine-estuarine) fish are less common. Each of the groupings has specific size, age and sex composition, the ratio of the first time-maturing and re-maturing fish. At that, the individuals with different types of life strategy reproduce together on the same spawning grounds and there is no isolation between them. Analysis of the variability of microsatellite loci revealed no significant differences for any locus between the observed genotypic distributions and the theoretical Hardy – Weinberg distributions. The genetic differentiation of mykiss in the Utkholok River relates to the differences between fish with a river-estuarine life strategy and the others in three loci (Ots3, One108, and One112). The results of clustering show the maximum value of the probability of belonging to the same cluster of all mykiss individuals with different life strategies. Significant differences at the some loci are not evidencing their reproductive isolation. It has been found that mykiss population of Utkholok River is an integrated dynamic system of groupings with different types of life strategies, which are formed in each generation because of the cumulative impact of environmental factors and heredity.

The response of hydroxylase activity of cytochrome P-450 from the microsomes of fish liver depends on fish species and on the kind of pollution. Differences in activity of the enzyme in whitefish Coregonus lavaretus and Pike Esox lucius depend on differences in ecology and in sensitivity of species to industrial effluents. Whitefish reacted to pollution by decrease in the activity of cytochrome P-450. In pike the activity of the enzyme increased under the influence of industrial wastewater. Males of both species are less resistant than females to the aforementioned pollutants. With consideration to the obtained results, the determination of activity of cytochropme P-450 may be recommended as the indicator of pollution level of the aquatic environment with industrial waste products, including those containing heavy metals.

The hydrothermal vent in Frolikha Bay and the methane cold seep “Saint Petersburg” in Baikal Lake are characterized by the highly productive communities of the aquatic invertebrates and cottoid fish (Cottoidei). The benthic and pelagic ichthyofauna of the vent comprises twelve key species belonging to eight genera, while that of the seep comprise eight species (six genera belonging to three families). The only one obligate hydrothermal species, N. thermalis, has been found; it dominated by abundance (91.6% of total abundance) in Frolikha Bay. N. werestschagini dominated in the cold seep community (39.5%). The spatial distribution of the fish around the hydrothermal vents and the cold seeps was patchy. The largest schoolings has been observed in two biotopes, in the areas of the silty bottom sediments and at the areas covered by the bacterial mats, as well as in the near-bottom water layer.

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.

Eosytchevskia nom. nov. (type species: Parabarbus mynsajensis Sytchevskaya, 1986) has been proposed as a substitute name for the oldest known genus of cyprinids, Parabarbus Sytchevskaya non Franz. The generic name Parabarbus Franz, 1910 is synonymized with Puntius Hamilton, 1822, and its type species P. habilis is, in all probability, a junior synonym of Puntius brevis (Bleeker, 1849).