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Poltev Y.N.,Sakhalin Research Institute of Fisheries and Oceanography SakhNIRO
Journal of Ichthyology | Year: 2011

According to data obtained off the eastern coast of the Northern Kurils in October-December 1998, the body length of spawning females of the longfin thornyhead Sebastolobus macrochir is 26-41 cm (on average, 31. 5 ± 0. 27). Mass spawning is recorded in females 28 cm in length and longer. The individual absolute fecundity of females is 69355-411710 (on average, 189086 ± 13662) eggs. The reproductive potential of females of the longfin thornyhead is estimated as 189 million eggs. It is supposed that all females participate in spawning. © 2011 Pleiades Publishing, Ltd. Source


Kaev A.M.,Sakhalin Research Institute of Fisheries and Oceanography SakhNIRO
Journal of Ichthyology | Year: 2015

Results of the study on the structure of scales in pink salmon, Oncorhynchus gorbuscha performed in 1997 and 2011 in six reproduction regions on Sakhalin and Kuril islands are presented. The study revealed no statistically significant correlation between the fish body length and number of sclerites on scales, but the correlation between gain of the body length and width of intersclerite distance is significant. The latter finding allows for using the scales for studying the patterns of growth in pink salmon. Comparison of the scleritograms of the first year growth revealed statistically significant differences in the relative width of intercirculi distances in pink salmon from different reproduction regions. In all cases, the difference between the groups of sclerites characterizing fish growth in the sea coastal regions were more pronounced. The changes in configuration of the scleritogram fragments characterizing growth of the juvenile fish from the open waters of the Sea of Okhotsk suggest that isolation of the regions of active feeding of the fish of various local populations remains, to a certain extent, after migration from the sea coastal waters. © Pleiades Publishing, Ltd., 2015. Source


Poltev Y.N.,Sakhalin Research Institute of Fisheries and Oceanography SakhNIRO
Journal of Ichthyology | Year: 2013

In waters of southeastern Sakhalin (Sea of Okhotsk), clutches of snailfishes of the genus Careproctus containing eggs at different stages of development or prolarvae were found on gills of the largest individuals (mainly in males) of three species of crabs (Lithodidae)-Paralomis verrilli (clutches were found in 1.4% of individuals), P. multispina (0.8%), and Lithodes covesi (11.6%). With an increase in the carapace width of lithodid crabs, the amount of eggs of snailfishes deposited in them and their diameter increase. More frequently, clutches are located from the left side of the carapace of crabs. Two-side clutches occur in larger individuals of crabs. No direct relationship between the presence of clutches of snailfishes on gills of lithodid crabs with necrosis or reduction of gills was revealed. The form of relations between lithodid crabs and Careproctus snailfishes was defined as "lodging" with different degree of impact on the host. © 2013 Pleiades Publishing, Ltd. Source


Kaev A.M.,Sakhalin Research Institute of Fisheries and Oceanography SakhNIRO
Journal of Ichthyology | Year: 2012

Characteristics of early and late migrants of pink salmon Oncorhynchus gorbuscha that spawned in the rivers of the coast of Aniva Bay (southern Sakhalin) and Iturup Island (southern Kuril Islands) are described. Upstream migration of the late form is characterized by the presence of large exemplars, especially males, and increasing proportion of these fishes in the catches. Absolute fecundity of the females of the early and late forms can be similar (Iturup Island) or different (Aniva Bay), but relative fecundity is lower in the females of the late form in both regions. Production of a larger number of eggs by the females of the early form is associated with a larger level of mortality: the abundance of the early form is comparatively low, and substantial annual variation of the abundance is registered. Relative abundance of pink salmon from the temporal groups depends mainly on reproductive conditions during the freshwater part of their life cycle. Analysis of size composition of the fish conducted over many years shows a trend in the ratio between the body lengths of males and females: unfavorable foraging conditions (and slower growth rate) lead to the appearance of females that are larger than males. To take into account a positive correlation between the body length and fecundity of females, this feature is regarded as a compensatory reaction of the population directed to more intensive reproduction at poor foraging conditions. © 2012 Pleiades Publishing, Ltd. Source


Kaev A.M.,Sakhalin Research Institute of Fisheries and Oceanography SakhNIRO
Environmental Biology of Fishes | Year: 2012

In the Sakhalin-Kuril region hatchery culture of pink and chum salmon is of great importance compared to other regions of the Russian Far East. During the last 30 years the number of hatcheries increased two-fold, and significant advances were made in hatchery technologies. As a result, chum salmon capture in regions where hatcheries operate (southwestern and eastern Sakhalin coasts, and Iturup Island) was 9 times as high during 2006-2010 than during 1986-1990, whereas wild chum salmon harvest markedly declined. Recent dynamics in pink salmon catch appear to track trends in natural spawning in monitored index rivers, suggesting natural-origin pink salmon play a dominant role in supporting the commercial fishery. It remains uncertain as to whether hatcheries have substantially supplemented commercial catch of pink salmon in this region, and I recommend continued research (including implementing mass marking and recovery programs) before decisions are made regarding increasing pink salmon hatchery production. Location of hatcheries in spawning river basins poses problems for structuring a management system that treats hatchery and wild populations separately. Debate continues regarding the existence and importance of density-dependent processes operating in the ocean environment and the role hatcheries play in these processes. Loss of critical spawning habitat for chum salmon in the Sakhalin-Kuril region has lead to significant declines in their abundance. I conclude by recommending increases in releases of hatchery chum salmon numbers in the region to help recover depressed wild populations and provide greater commercial fishing benefits in the region. © Springer Science+Business Media B.V. 2011. Source

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