Cases of capture of Atka mackerel, Pleurogrammus monopterygius, transplanted to the Barents Sea from south-eastern Kamchatka

Atka mackerel, Pleurogrammus monopterygius was proposed for acclimatization to the Barents Sea long ago (Russ, 1958) and has been thoroughly studied in this regard. However, the number of experimental works by the transplantation of Atka mackerel from Kamchatka to the Barents Sea was small and their scale is insignificant. A total of 2 attempts were made in the 70s and 80s. The last time in 1982-1984, 6.5 millions of Atka mackerel caviar was transported from Kamchatka to Murmansk. Unfortunately, the systematic works by introduction was stopped. Meanwhile, the experience of acclimatization of Atka mackerel is very valuable not only for its practical orientation, which has in the future the additional production of fish in the Barents Sea, but also for a certain contribution to the development of the theory of acclimatization. The article provides information on the two repeated capture of Atka mackerel in the Barents Sea and six repeated in the White Sea. It is advisable to purposefully check the information on the White Sea; it is possible that the short time of the stay of adults Atka mackerel in the reservoir during the breeding period does not allow them to be identified during the annual ichthyological survey of the White Sea. It would be useful to catch of the Teribersky Cape of the Barents Sea, where adult Atka mackerel can be found during the breeding season. If the facts will not be confirmed, then our supposition remains true that the scale of work on the transplantation of Atka mackerel caviar was insignificant and the amount of imported caviar is small

The first evidence of intersexuality in Atka mackerel Pleurogrammus monopterygius (Hexagrammidae)

Summary Histological examination of Atka mackerel ovotestes reveals the possibility of intersexuality. Individuals with bisexual gonads have been caught in the North Pacific near the south-east coast of the Kamchatka peninsula. While intersex appeared to be normal females with developing ovaries, histological analysis showed the presence of both female and male tissue in the same gonad. Specifically, primary growth, cortical alveolar and primary vitellogenic oocytes were located among spermatogonia cysts. The prevalence of intersexuality in the population was less than 0.1%.

About the forced and later spawn of Atka mackerel Pleurogrammus monopterygius Pallas, 1810 (Scorpaeniformes: Hexagrammidae) in the waters of the North Kuril Islands

Results of the research indicate that the eggs of Atka mackerel are a part of forage for this speciesis from May to December. Captures of the Atka mackerel individuals spawning and feeding on the own eggs far from the coast indicate that a certain part of the stock spawns at the depths considerably lower than normal spawning grounds. Spawning individuals of Atka mackerel is were observed in research from June to December. Emergence of larvae from the eggs laid in November–December is expected in spring.

STATE OF STOCKS AND MODERN FISHERY OF ATKA MACKEREL PLEUROGRAMMUS MONOPTERYGIUS (PALLAS, 1810) IN THE OLYUTORSKY-NAVARINSKY AREA OF THE BERING SEA

Atka mackerel Pleurogrammus monopterygius is one of the mass species of fam. Hexagrammidae that inhabits the boreal and subarctic waters of the North Pacific and forms two large populations in its western and eastern parts. Reproductive range of the eastern, Aleutian population extends from the Gulf of Alaska, along Aleutian Islands to Commander Islands, with the main spawning grounds at the Aleutians and in the southeastern Bering Sea. From these areas, the fish at early stages of ontogenesis spread widely in system of the Bering Sea currents to the western-southwestern Bering Sea, where the atka mackerel aggregations are formed on the external shelf at prominent capes, as Cape Olyutorsky. Dynamics of the atka mackerel stock in the Olyutorsky-Navarinsky area in 1994–2019 is presented on the base of bottom trawl surveys, fishery statistics, and open NOAA data. After the period of low stock in the middle 1990s, the atka mackerel abundance increased sharply to the maximum in 2006–2008, when the spawning stock in this area was about 9.5 . 103 t and the commercial stock about 14.0 . 103 t. Since that time, trend to decreasing is observed, with the spawning stock 3.6 . 103 t and the commercial stock 5.6 . 103 t in 2013, and recent stabilization at the low level with slight decline continuing. A possible reason of the sharp increase in 2000s could be the intensive transport of the atka mackerel juveniles from the main spawning grounds at Aleutian Islands to the area at Cape Olyutorsky. The catches of atka mackerel in the Olyutorsky-Navarinsky area in 1994–2018 corresponded well with its stock dynamics.

RESEARCH TECHNOCHEMICAL PROPERTIES OF JAPANESE MACKEREL AND ATKA MACKEREL

Исследованы технохимические свойства скумбрии японской (Scomber japonicas) и терпуга северного одноперого (Pleurogrammus monopterygius). Установлено, что скумбрия и терпуг являются ценным пищевым сырьем, богатым биологически ценным белком, в котором содержатся все незаменимые аминокислоты. Аминокислотные составы мышечных тканей скумбрии японской и терпуга северного одноперого существенно не отличаются, однако в скумбрии выше содержание гистидина и изолейцина. Общее количество моно- и полиненасыщенных жирных кислот (ЖК) в скумбрии составило 63,99%, а в терпуге их содержание выше – 75,56%. Из мононенасыщенных ЖК липидов скумбрии и терпуга преобладает олеиновая, которой в терпуге почти в два раза больше, чем в скумбрии. Терпуг более богат полиненасыщенными ЖК, содержание которых составляет 35,45%. В скумбрии их содержание ниже – 25,60%. Липиды скумбрии и терпуга имеют достаточно высокие коэффициенты метаболизации – 1,57 и 1,50 соответственно. Соотношение ω-6 : ω-3 ЖК у скумбрии составляет 1 : 5, у терпуга 1 : 3, т. е. содержание ω-3 ЖК по отношению к ω-6 завышено, что необходимо учитывать при производстве пищевых продуктов из данного сырья, комбинируя его с другим для сбалансированности жирнокислотного состава. Результаты исследования показывают перспективность использования скумбрии и терпуга при производстве широкого спектра рыбопродукции, в том числе полуфабрикатов. Technochemical properties of Japanese mackerel (Scomber japonicas) and Atka mackerel (Pleurogrammus monopterygius) were investigated. It is established that Japanese mackerel and Atka mackerel (terpug) are valuable food raw materials rich in biologically valuable protein, which contains all the essential amino acids. Amino acid compositions of the muscle tissue of mackerel Japanese and the terpug not differ significantly, however, mackerel higher content of histidine and isoleucine. The total amount of mono-and polyunsaturated fatty acids (FA) in mackerel was 63,99%, and in terpug their content is higher – 75,56%. Among monounsaturated FA of lipids mackerel and terpug dominated by oleic, which in terpug is almost two times more than in mackerel. Terpug is more rich in polyunsaturated FA, the content of which is 35,45%. In mackerel their content below – 25,60%. Lipids mackerel and Atka mackerel have relatively high coefficients of metabolization and 1,57 and 1,50 respectively. The ratio of ω-6 : ω-3 FA from mackerel is 1 : 5, the Atka mackerel 1 : 3, i. e., the content of ω-3 FA in relation to ω-6 are too high, it is necessary to consider in the production of food products from this raw material, combining it with others to balance the fatty acid composition. The results of the study show the prospects of using mackerel and terpug in the production of a wide range of fish products, including semi-finished products.

Diet of endangered Steller sea lions (Eumetopias jubatus) in the Aleutian Islands: new insights from DNA detections and bioenergetic reconstructions

The endangered western stock of Steller sea lion (Eumetopias jubatus (Schreber, 1776)) still declines in the western Aleutian Islands and accurate diet information is vital to test leading hypotheses. We undertook the first bioenergetic diet reconstruction using both molecular and hard part prey identifications from >600 scats collected in March–April 2008 and 2012. Atka mackerel (Pleurogrammus monopterygius (Pallas, 1810)) remained a primary prey (17%–27% by energy), but large (mean 60 cm) Pacific cod (Gadus macrocephalus Tilesius, 1810) also emerged as important prey (20%–24%) in a more diverse diet than previously reported, with Cottidae and smooth lumpsucker (Aptocyclus ventricosus (Pallas, 1769)) also contributing ∼10%. DNA detections highlighted a potentially important and previously underestimated prey, giant Pacific octopus (Enteroctopus dofleini (Wülker, 1910) (diet contribution 2%–15%, dependent on prey size assumptions). Although 504 unique DNA identifications resulted in significant increases for cephalopods, Pacific cod, and smooth lumpsucker, hard part alone species rankings were similar to composite ones and bioenergetic species rankings similar to occurrence-based ones. Retention or regurgitation of large cephalopod beaks, the removal of large cod heads, and skeletal fragility of lumpsuckers may explain these differences. DNA identifications provide valuable comparative and complementary prey occurrence data for pinnipeds, but composite diet estimates are optimal.