Experimental determination of residence time for sockeye salmon spawners on spawning grounds in the littoral zone of Lake Nachikinskoye (Kamchatka)

State of the spawning part of the sockeye salmon population in Lake Nachikinskoye is characterized. Adults of the early race enter the lake from the sea in spring and early summer, mature at a depth and spawn from July to late August in three different loci — creeks, springs and lake, forming the corresponding ecotypes. The late race representatives enter the lake in July-August, mature, and spawn until December in the same loci. The races differ in age structure, size and fecundity. Males dominate in both races, with a growing proportion of small-sized individuals. According to the materials of aero surveys, the number of fish on the spawning grounds decreased gradually until 2016. Recent data are presented for the number of sockeye salmon belonged to early and late races on certain spawning grounds in the lake basin, based on results of quadrocopter surveys in 2018–2021. The number of the early race spawners was ~100–400 × 103 ind., late race ~300–500 × 103 ind.; the fluctuations were not synchronous between the races. These great spawning stocks require reliable protection and detailed annual monitoring to predict further changes.

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Migration behavior for sockeye salmon adults of early race in the tributaries of Lake Nachikinskoye (western Kamchatka)

Zaporozhets,

Zaporozhets

2024

Izv. Tihookean. naučno-issled. rybohoz. centra

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Several stages are determined in the early run of sockeye salmon into tributaries of Lake Nachikinskoye: i) maturation of adults at depth, ii) concentration of adults in the mouths of the main tributaries, iii) entry of small flocks of the spawners into tributaries over a short distance, iv) upstream movement of lager flocks, v) thinning of flocks and formation of pairs, vi) spawning, and vii) death of spawned fish. In the large, stable accumulations formed in the mouths of tributaries, salmon choose paths for onward movement in the process of homing, by decoding imprinting information. There, aggregations of spawners are differentiated into separate flocks going to spawn on different spawning grounds. A peculiarity of this population of sockeye salmon is the retention of individuals not ready for spawning in many pits and catches of the rivers, with formation of well-visible compact schools, which dissipate as the fish mature. Filling of the spawning grounds in tributaries is determined by their characteristics, and typically occurs with a dome-shaped dynamics of intensity. The upward long-term trend in filling of the spawning grounds is observed in the lower Taburetka River (before its tributaries), while the downward trend — in the tributaries. Data on the filling for the last 5 years are presented. The greatest contribution to reproduction of the early sockeye salmon in Lake Nachikinskoye is provided by the lower reaches of the Taburetka River (41 %), whereas its tributary, the Verkhnyaya River, contributes 20 % and inputs of other tributaries are noticeably lower. In conditions of degradation for a part of the spawning grounds due to increased anthropogenic impact, all existing subpopulations should be preserved as productive as possible.

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Experimental determination of residence time for sockeye salmon spawners on spawning grounds in the littoral zone of Lake Nachikinskoye (Kamchatka)

Cited by 3 publications

References 10 publications

The Biology and Abundance of Sockeye Salmon Spawners in the Nachikinskoye Lake Basin (Southwestern Kamchatka)

The Biology and Abundance of Sockeye Salmon Spawners in the Nachikinskoye Lake Basin (Southwestern Kamchatka)

Sockeye salmon spawners in the basin of Nachikinskoye Lake (south-western Kamchatka): biology and abundance

Migration behavior for sockeye salmon adults of early race in the tributaries of Lake Nachikinskoye (western Kamchatka)

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