Did You Know?
Humpback whitefish are distinguished from other whitefish by the pronounced hump behind the head in adult fish.
The humpback whitefish is a medium sized fish up to 20 inches in total length. Humpback whitefish are distinguished from other whitefishes by the pronounced hump behind the head in adult fish with an inferior mouth, which means that the mouth that points downward, with the upper jaw being longer than the lower jaw. Sometimes referred to as a sub-terminal or ventral mouth, the inferior mouth is often protrusile, meaning it can be extended forward, sometimes a significant distance. This allows the fish to grab food particles or prey that would otherwise be out of reach. This is an adaptation often observed in bottom feeding fish such as the humpback whitefish.
Adult humpback whitefish are generally dark brown to midnight blue dorsally fading to silver on sides with a white belly. The adipose fin is well developed and is often larger in male fish. The tail has a dark posterior edge. No parr marks are found on juvenile fish.
Growth and Reproduction
Some populations of humpback whitefish are anadromous which means it spends part of its life in the ocean and part of its life in fresh water. Humpback whitefish are known to rear in channel ponds, sloughs, estuaries, and the marine environment until mature, when they migrate upstream to spawn. Age at first maturity for adult humpback whitefish seems to increase with latitude and occurs as young as 4 years old (in the Kuskokwim River) to as late as 11 years old (near the Arctic Ocean). Sexually mature humpback whitefish older than 30 years of age have been found in a number of rivers located within the Kuskokwim River drainage. Adult humpback whitefish undertake extreme spawning migrations into freshwater systems, traveling over 500 miles up the Kuskokwim River and over 1,300 miles up the Yukon River. Depending on her size, a female humpback whitefish may release up to 50,000 eggs. Whitefish eggs are negatively buoyant and non-adhesive. The female broadcasts her eggs over loosely compacted gravel beds in turbid and swiftly flowing water. The eggs presumably hatch in the spring and the young descend downstream to feed and rear.
Juvenile humpback whitefish feed mainly on zooplankton, while adults feed mostly on benthic invertebrates including mollusks, crustaceans, and chironomid larvae. Adult humpback whitefish do not feed during spawning runs.
Anadromous humpback whitefish typically migrate into freshwater systems in late spring to late summer to spawn. Spawning can occur from September through November, depending on the system. Humpback whitefish are known to spawn in the mainstem waters and tributaries of the Yukon, Kuskokwim, Tanana, Kvichak, Susitna, Copper, and Alsek Rivers.
Range and Habitat
In Alaska, humpback whitefish is distributed throughout several water bodies within the Yukon River, Kuskokwim River, Tanana River, Kvichak River, Susitna River, Copper River, and Alsek River drainages.
Status, Trends, and Threats
Several studies have been conducted on humpback whitefish populations by a number of agencies over the years. Research indicates that Susitna, Kuskokwim, and Yukon River populations are quite distinct. Such information is very useful when conducting mixed stock analysis on fish collections of unknown origin. It is clear that an understanding of humpback whitefish genetic population structure is necessary to identify appropriate management units for maintenance of biodiversity and productivity.
Overall strength of humpback whitefish returns across the state between year and location seems quite strong based on anecdotal and harvest information. Although various state and federal agencies have conducted studies to estimate the relative abundance or model harvest impacts on local population of humpback whitefish, there is not sufficient data to assess the relative abundance of humpback whitefish within or between all known populations throughout the state.
Potential overharvest from commercial, personal use or subsistence fisheries is the main threat to the resource. The migratory behavior of humpback whitefish makes the species susceptible to obstructions such as dams or habitat alteration, disturbance, or degradation. Because these fish rely on long-distance dispersals, efforts should continue to protect and identify the movement corridors that link critical habitat areas to ensure the long-term survival of humpback whitefish.
The humpback whitefish is a medium-sized fish known to reach a length of 20 inches but is generally smaller.
In Alaska, the humpback whitefish is distributed throughout several water bodies within the Yukon River, Tanana River, Kvichak River, Susitna River, Copper River and Alsek River drainages.
Benthic invertebrates including mollusks, crustaceans, and insect larvae.
Variety of marine mammals, fishes, and birds.
Humpback whitefish have been observed returning to the same spawning grounds over several years.
Managed by the Alaska Department of Fish & Game in Alaska state waters
Did You Know?
- As with other whitefish, the humpback whitefish digs no nest or redd but broadcasts its eggs which lodge in the gravel.
- Humpback whitefish have been observed spawning under the ice in the Kuskokwim River as late as mid-November.
- Humpback whitefish are distinguished from other whitefish by the pronounced hump behind the head in adult fish.
- Humpback whitefish exhibit a wide variety of life-history patterns, including freshwater-migratory, anadromous-migratory, and non-migratory strategies.
The humpback whitefish is known to be an important subsistence fish species for coastal and riverine communities located within drainages of the Colville River, Kuskokwim River, Yukon River, and Kvichak River. The Chatanika River has supported a prolific and popular recreational spear fishery targeting humpback whitefish since the 1970s. There is a directed fishery for humpback whitefish and least cisco in the Chatanika River which occurs from late September through late October. As the fishery is managed by emergency order, an ADF&G permit is required, allowable gear is limited to spears only. Annual household limit is 10 whitefish (any species), with no size limits.
Both commercial, personal use, and subsistence fishers target humpback whitefish. The Commercial Fisheries Division of ADF&G manages these fisheries in Alaska. Subsistence surveys are conducted by both Commercial Fisheries and Subsistence divisions. There are no directed sport fisheries for humpback whitefish in Alaska.
Numerous research projects have been conducted on humpback whitefish throughout Alaska. The Alaska Department of Fish and Game, U.S. Fish and Wildlife Service, and University of Alaska have all studied humpback whitefish in recent years. ADF&G projects include abundance, size composition, fecundity, and stock assessment of Chatanika River whitefish. U.S. Fish and Wildlife Service projects have sought to identify spawning habitats and spawning migration patterns in some reaches of the Yukon and Kuskokwim River drainages. Many of these projects use radio telemetry (biologists place radio transmitter tags into fish and then follow the signal in order to track the fishâ€˜s movements). University of Alaska projects focused on population dynamics, movement patterns, and spawning habitat use.
There are a number of ways to get involved in the regulatory process for humpback whitefish. Since the State of Alaska is responsible for managing humpback whitefish fisheries throughout the state, you can participate by attending Alaska Board of Fisheries (BOF) meetings, local advisory committee meetings or writing proposals to the BOF.
Alaska Board of Fisheries
The Board of Fisheries meets four to six times per year in communities around the state to consider proposed changes to fisheries regulations. The board uses the biological and socioeconomic information provided by the Alaska Department of Fish and Game, public comment received from people inside and outside of the state, and guidance from the Alaska Department of Public Safety and Alaska Department of Law when creating regulations that are sound and enforceable. The public can submit proposed changes and comment on proposals prior to deliberation through written or oral means. The public is also encouraged to participate in their local advisory committee. Eighty-one committees throughout the state provide recommendations to the BOF on a variety of issues. For more information visit the Board of Fisheries section of our website.