page_title: Koyukuk River
section_title: Flora and fauna
hierarchical_section_title: Koyukuk River / Flora and fauna
caption_attribution_description: English: Zane Hills and Koyukuk River. Koyukuk National Wildlife Refuge
context_page_description: The Koyukuk River is a 425-mile tributary of the Yukon River, in the U.S. state of Alaska. It is the last major tributary entering the Yukon before the larger river empties into the Bering Sea.
  Rising at the confluence of the North Fork Koyukuk River with the Middle Fork Koyukuk River, it flows generally southwest to meet the larger Yukon River at Koyukuk. The river, with headwaters above the Arctic Circle in the Endicott Mountains of the Brooks Range, drains an area north of the Yukon River that includes part of the Gates of the Arctic National Park and Preserve, as well as Kanuti National Wildlife Refuge and Koyukuk National Wildlife Refuge.
  The main stem of the river is lined by the communities of Evansville, Bettles, Alatna, Allakaket, Hughes, and Huslia before reaching Koyukuk. Its headwaters tributaries include the Koyukuk's south, middle, and north forks, the Alatna River, and the John River. Major tributaries further downstream include the Kanuti, Batzu, Hogatza, Huslia, Dulbi, Kateel, and Gisasa rivers. Of these, the Alatna, John, and North Fork are National Wild and Scenic Rivers, as is the Tinayguk River, a tributary of the North Fork.
context_section_description: Vegetation along the Koyukuk River, sparse along the upper reaches, consists of tundra plants such as dwarf willows and other shrubs, sedges, and lichens. Further downstream at lower elevations, taiga and boreal forest plants are common except in the Koyukuk Flats near the mouth, where sedges and other herbaceous plants dominate the poorly drained muskeg. Trees found in more well-drained areas along the river include mountain alder, trembling aspen, white, and black spruce.
  Fish species frequenting the lower Koyukuk include Arctic lamprey and sockeye salmon. The sockeye and other salmon species, including Chinook and chum, also thrive along the upper reaches and tributaries.
  Caribou migrate across the upper part of the Koyukuk watershed. Other major vertebrates in the region include bald eagles, brown and black bears, mink, beaver, marten, and river otter. Beluga whales sometimes visit the lower Koyukuk.
  Moose herds, which thrive in parts of the watershed, especially in riparian zones downstream of Hughes, attract local and non-local hunters, bears, and wolves. A consortium of moose hunters and state wildlife officials work to keep the moose population at sustainable levels.
  Through 2005, no one had published a study of invertebrates of the Koyukuk or its larger tributaries. General information included in a study related to pipeline construction through the watershed suggested the  presence of a variety of true flies, midges, black flies, mayflies, stoneflies, and caddisflies.
caption: Zane Hills and Koyukuk River
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