Yukon River Chinook Run Timing

Yukon River Delta. Image by Earth Observatory, NASA.

Location of Data

Yukon River Chinook are predicted to arrive on the delta slightly later than average in 2021. The first significant pulse (15% point) is expected by June 15th and 50% of the run is expected to have arrived by June 23rd. See the complete forecast for more information.

Background

This forecast is intended for use by fishery managers, residents of Yukon River communities, and others to estimate when the Chinook salmon run will arrive on the delta and how it will develop through June and July 2021. The forecast is based on historical catch and environmental variables identified by Mundy & Evenson (2011). This page shows (1) the modeled and estimated cumulative daily percentage of the 2021 Chinook salmon run, (2) the cumulative CPUE of the delta test fisheries, as reported daily in 2021 by ADF&G compared to a selection of cumulative CPUEs of historical runs. As data on the fish migration develop, they will be plotted on Chart 1 so it can be seen how well the actual run matches the model and forecast. If the fit between the modeled and estimated catch diverges considerably, an updated forecast may be issued and posted to this page.

Chart 1. Forecast of the cumulative percent of the Chinook run in Y-1 on each date from June 1 through July 15, 2020. Blue bars are forecasts of the 15%, 25% and 50% run percentiles derived from a model that approximates the migration of 1985. Once the run starts, a cyan-colored line will show the 2020 cumulative CPUE converted to estimated run percentages.

Use this link if you can’t see the graph.

Chart 2. Historical CPUE data provided by Arctic-Yukon-Kuskokwim Region, Alaska Department of Fish and Game. The blue line at the center of the graph shows the average of all runs between 1989 and 2011, excluding 2009 and 2010.

Use this link if you can’t see the graph.

The Need

Known for navigating the longest annual freshwater migration route of any salmon to reach their spawning grounds, Chinook salmon can start arriving on the Yukon River delta at almost any point in June. Over the past 50 years the first pulse of Chinook has occurred sometime between June 6 and June 26. Traditional knowledge on the Yukon holds that spring weather conditions, including ice, temperatures and wind determine when in June the fish enter the river, but each spring brings a different combination of conditions, so pinning down a schedule for the arrival of the first pulse can be tricky. Twenty days can be a long time to wait to find out when the fish are actually coming and if there are enough of them to harvest.

Management of the Chinook salmon fishery is closely linked to expected time of arrival in harvest areas. When the migration begins earlier than expected, it’s reasonable for fishery managers to conclude that the run is stronger than it actually is, possibly resulting in over-harvesting near the river’s mouth and loss of harvest opportunities upriver. Likewise, in years when the first pulse of fish comes late, it is reasonable for fishery managers to conclude that the run is very weak, perhaps so weak that fishing needs to be slowed or stopped altogether.

Project Location

The Yukon River (Gwich’in: Ųųg Han or Yuk Han, Yup’ik: Kuigpak, Inupiaq: Kuukpak, Southern Tutchone: Chu Nìikwän) is the longest river in Alaska and the Yukon Territory (Canada) at 3,190 kilometers (1,980 miles). The Yukon River’s headwaters are in British Columbia, which then runs (including its many tributaries) through northwestern Canada into interior Alaska, and towards the Yukon-Kuskokwim delta at the Bering Sea. 

Project Details

Researchers from NOAA Fisheries and the Alaska Department of Fish and Game, with the support of the Alaska Ocean Observing System, identified a combination of spring conditions that are closely related to the timing of Chinook salmon on the Yukon delta.  Using percent spring ice cover between St. Lawrence Island and the Yukon delta, April air temperatures in Nome, and marine surface temperatures just offshore of the delta in May.

This timing and environmental information is intended for use by fishery managers, residents of Yukon River communities, and others to estimate when the Chinook salmon run will arrive on the delta and how it will develop through June and July. The outlook and its associated forecast are based on the historical fish and environmental variables. 

The Forecast includes (1) the modeled and estimated cumulative daily percentage of the year’s Chinook salmon run, (2) the cumulative catch-per-unit-effort (CPUE) of the delta test fisheries, as reported daily by ADF&G compared to a selection of cumulative CPUEs of historical runs, and (3) marine environmental data (see charts in the forecast) that are used as inputs to the year’s outlook and forecast model. As data on the fish migration data develop, they are plotted on Chart 1 so it can be seen how well the actual run matches the model and forecasts. When the timing model doesn’t match the actual run, the timing model and forecasts may be updated.

On the left, a US Fish and Wildlife Service employee measures smolt, or juvenile salmon, on the Yukon River. On the right, another employee counting salmon salmon from an underwater camera as they pass through the weir and migrate upstream to spawn. Photo Credit: US Fish and Wildlife Service

Project Highlights

The Chinook Run Timing model and forecast is a valuable tool that has provided important information to fishery managers since 2015.  

Resources

Read the Post-season analysis from previous years’ Yukon Chinook Run Timing Forecasts.

Publications

Mundy, P. R., & Evenson, D. F. (2011). Environmental controls of phenology of high-latitude Chinook salmon populations of the Yukon River, North America, with application to fishery management. ICES Journal of Marine Science, 68(6), 1155-1164.

Mundy, P. R., & Evenson, D. F. (2011). Environmental controls of phenology of high-latitude Chinook salmon populations of the Yukon River, North America, with application to fishery management. ICES Journal of Marine Science, 68(6), 1155-1164.

Murphy, James, Howard, Kathrine, Cosden Gann, Jeanette, Cieciel, Kristin, Templin, William, Guthrie III, Charles. (2016). Juvenile Chinook Salmon abundance in the northern Bering Sea: Implications for future returns and fisheries in the Yukon River. Deep Sea Research Part II: Topical Studies in Oceanography. 10.1016/j.dsr2.2016.06.002. 

Principal Investigators

Bryce Mecum
Consultant
Phil Mundy
NOAA Fisheries
Profile photo for Will Koeppen
Will Koeppen
Axiom Data Science