Hydrological regime and morphodynamics of the outlet part of the Kamchatka River, dynamics of mixing zone, patterns of juvenile Pacific salmon distribution and migration in the coastal waters of Kamchatsky Gulf in the zone of operating trap nets were analyzed on the results of complex field works prowided in summer period in 2018–2019; fishing and specifics of sockeye salmon spawning run in the river was described. In the course of analyzing the entire complex of available long-term data, an assessment of the likely impact of some key factors on the dynamics of anadromous migration of sockeye salmon in the Kamchatka River was made; biological statistics of spawners and current state of reproduction of this stock was demonstrated. It is found, that natural environmental factors, neither abiotic nor biotic (including fish health as population internal factor), could not cause disturbance of sockeye salmon spawning run dynamics in the Kamchatka River in recent years. Smoller body size and physiological imperfection of the spawners before the anadromous migration due to effects of high number of pink salmon in recent years are suggested to be the most likely cause of spawning run delay in late sockeye salmon morph. Regime of commercial use of the stock and general increasing pressure on the spawning stock by coastal fisheries are demonstrated to be the strongest outer factors to affect modern state of the resources and sockeye salmon population structure in the Kamchatka River, causing permanent escapement deficiency on spawning grounds in the river basin (first of all in the late morph), and also infact lead to disballance between different subpopulation groups in the composition of the stock. Recommendations in order to provide recovery and sustainable level of the Kamchatka River sockeye salmon stock are given in the perspective of more efficient commercial use of the stock next several years; highlights for further researches are outlined.
The paper represents results of longterm analysis of the state of the Pacific salmon stocks in Kamchatka River. It is admitted, that high-level effects of fisheries resulted in degradation of the spawning stock (stock abundance) of major local salmon stock units in the basin of Kamchatka River. Commercial importance and previous reproduction potential of all Pacific salmon species has been lost in the mediate and upper parts of the river. This situation was especially noticable in 2018–2020.In view of the trend in the dynamics of salmon stocks in the Kamchatka scientists of KamchatNIRO suggested additional measures of fishery regulation in the Kamchatsky Gulf and Kamchatka River basin. A target strategy of management of fishing Pacific salmon in Kamchatka River was developed as a result, including a complex of limitations to start fishing (catches), a system of stop-fishing days and periods of full stop fishing to provide escapement for spawning.Moreover, regular annual biological monitoring of Pacific salmon of Kamchatka River, provided by KamchatNIRO, was noticeably strengthened with additional hydroacoustic counting and control fishing at the fishery plot № 832. Hydrological-hydroacoustic surveys in Kamchatka Gulf began in 2018 also were to improve the regional scientific monitoring.Results of the surveys 2019–2021 allowed to evaluate current effects of hydrological regime and fishing in Kamchatka Gulf on formation of salmon spawning stocks in Kamchatka River. It has been found, that the changes of the morphodynamics of the Kamchatka River mouth in 2021 resulted in wider area of freshwater effects in Kamchatka Gulf. That was a trigger of redistribution of prespawning salmon aggregations on their migration routs to the river mouth, what eased press of fishing in the area of plots of marine fixed gill nets. In this way the spawning escapement of Pacific salmon into the basin of Kamchatka River this year increased.
Статья основана на результатах собственных полевых работ, выполненных летом 2018 г., а также на архивных и литературных данных. Представлены сведения о пространственно-временной динамике уровня, солености и температуры воды в эстуариях. Обсуждаются вопросы трансформации приливных колебаний уровня воды, структуры и динамики зоны смешения, динамики вод и водообмена, а также нагрева воды внутри эстуариев. Приведены сведения о пространственных характеристиках зоны смешения в прибрежной части Охотского моря около устья р. Крутогорова. Сообщается о морфодинамике баров (кос), отделяющих эстуарии рек Ича и Крутогорова от моря, и влиянии этого процесса на гидрологический режим обоих эстуариев. Фактические данные, имеющиеся в статье, могут быть полезны при сравнении исследуемых объектов с другими эстуариями.
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