Humpback Whitefish are an important subsistence fishery resource for local communities within the upper Tanana River drainage. Community members have expressed concerns to Tetlin National Wildlife Refuge staff on perceived declines in size and abundance of Humpback Whitefish in the area. To address these concerns, we conducted a study to evaluate demographic changes in local spawning populations of Humpback Whitefish over a 20-year time period. We compared length distributions, weight at length statistics, survival, and growth of Humpback Whitefish using data collected during two time periods separated by about two decades. The results of this study indicate that present-day Humpback Whitefish are, on average, 16 mm (approximately 4%) smaller, slightly heavier at length, exhibit slower growth, and attain smaller maximum sizes than fish sampled 20 years ago. Despite declining in size in recent years, Humpback Whitefish are currently experiencing greater survival than those 20 years ago. These results support local concerns that Humpback Whitefish appear to be getting smaller, but greater survival indicates that abundance is relatively stable or increasing over time. We hypothesize that late in life density-dependent effects and (or) changing environmental conditions may be influencing size and growth dynamics of these populations. To further evaluate the relationships between high survival, environmental conditions, and growth, it is recommended that otolith growth chronologies be developed and analyzed to determine if regional environmental changes may be influencing the different growth patterns we observed here. In addition, these types of sampling events and analyses are recommended every 10–15 years to develop a longer record of population variation for this important subsistence resource.

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A bright blue sky obstructed by fluffy white clouds reflected off of a stream shot from inside a kayak
The U.S. Fish and Wildlife Service manages an unparalleled network of public lands and waters called the National Wildlife Refuge System. With more than 570 refuges spanning the country, this system protects iconic species and provides some of the best wildlife viewing opportunities on Earth.
Juvenile Northern Pike in aquarium at Gavins Point National Fish Hatchery, South Dakota
The Fish and Aquatic Conservation program leads aquatic conservation efforts for the U.S. Fish and Wildlife Service. We are committed to tackling the nation’s highest priority aquatic conservation and recreational challenges to conserve, restore, and enhance fisheries for future generations.


a sweeping view of trees in a valley with mountains in the distance
Tetlin National Wildlife Refuge is nestled within the Upper Tanana River Valley, the abundant wetlands and forests of the Refuge welcome thousands of birds and people crossing the border into Alaska each year. The public lands and waters of the Upper Tanana offer opportunity for people to enjoy...
Mountains and rivers from aerial view
Based in Fairbanks, and in collaboration with our Utqiaġvik (Barrow) Satellite Office, we work with others to deliver conservation over approximately 338-million acres of Alaska. Our responsibilities generally range from the Yukon River Delta region in southwest Alaska, eastward to the Canadian...