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NOAA Technical Memorandum NMFS-AFSC-334

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Spatial distribution, diet, and nutritional status of juvenile Chinook salmon and other fishes in the Yukon River estuary

Abstract

Surveys were conducted in the Yukon River estuary during the summers of 2014 and 2015.The primary objectives of this research were to evaluate the community composition and spatial distribution of fish in the distributaries and within the river plume, and to investigate diets and energetic condition of emigrating juvenile Chinook salmon.A shallow, sub-ice platform separates the shoreline of the Yukon Delta plain from the marine environment.This platform extends up to 30 km offshore with water depths between 1 m and 3 m.At the seaward edge of this platform, the bathymetry increases sharply along an area known as the delta front which marks the transition between fresh and marine waters. Sampling for this research was conducted in the three main lower Yukon River distributaries and along the delta front.Sampling in the distributaries occurred from near ice-out in May through the end of July, while sampling along the front was conducted during cruises in June, July, and August of each year.Juvenile Chinook salmon utilized all three lower Yukon River distributaries for emigration; however, higher CPUE was observed at front stations along the north edge of the delta suggesting that the salmon move north after leaving the river mouths.Temporal differences in prey consumption and energy density of juvenile Chinook salmon were observed in both the distributaries and on the front.Juvenile Chinook salmon were a small component of the overall fish catch in each year.Most species captured in the distributaries were juvenile or young of the year (YOY).The most common species captured in the Yukon river distributaries in both sampling years were juvenile and YOY coregonids (whitefish and cisco), juvenile sheefish (Stenodus leucichthys), juvenile Arctic lamprey (Lethenteron camtschaticum), and juvenile burbot (Lota lota).The most common species on the delta front were Pacific rainbow smelt (Osmerus dentex), saffron cod (Eleginus gracilis), Pacific herring (Clupea pallasii), and ninespine stickleback (Pungitius pungitius).



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