Research Yukon River Tagging Project The Fairbanks Fish & Wildlife Field Office started a cooperative project with the National Marine Fishery Service in 1996 to learn more about the populations of fall chum salmon in the upper Yukon River. Objectives of this project are: To determine the number of fall chum salmon in the Yukon River drainage spawning above the Tanana River using a fish mark and recapture technique. To learn more about run timing of various salmon stocks in the Yukon River. Determining the total number of fall chum salmon traveling through the vast, muddy waters of the upper Yukon River drainage is a difficult task. Biologists at the Fairbanks Fish & Wildlife Field Office are using a method to calculate salmon numbers called mark/recapture. Fish wheels are used to capture salmon. Biologists insert a uniquely numbered and color-coded plastic tag in the fish's back near the dorsal fin, then release it back into the river. The same method is used to recapture fish at a point farther upriver. Biologists keep track of the total number of fish tagged, and the number of marked and unmarked fish recaptured. This information can be used in a calculation to estimate the total population size. One fish wheel is used to capture and tag migrating fall chum salmon. This is located in a narrow section of the Yukon River, called the Rampart Rapids. A recapture wheel is located about 30 miles upriver near the village of Rampart. Biological technicians tag and quickly release each fish as soon as it enters the fish wheel to minimize stress and holding time. All other fish species incidentally caught in the fish wheel such as sheefish, whitefish, and Chinook salmon are released. Biologists use dip nets to transfer the salmon from the fish wheel to a water-filled tub. This tub contains a padded cradle which safely immobilizes the fish to be tagged. Water is continuously pumped through the holding box to maintain adequate oxygen and temperature levels. The following information is recorded for each fish tagged. Tag number Release Time A biologist uses a sharp needle to insert the tag behind the dorsal fin and tie it in a knot. This is very similar to piercing an ear. Each tagged fish also has the adipose fin (located on the fish's back near the tail) removed for easier detection by the video crew at the recovery site farther up river. Each thin and flexible plastic "spaghetti tag" is individually numbered and color coded, and has the USFWS address on it. Fishers who later catch a tagged fish are encouraged to return the tag to the U.S. Fish & Wildlife Service along with information about when and where the fish was caught. The tagged fish are released back into the river. Total handling time of each salmon is less than 1 minute. A total of 5,532 fall chum salmon were tagged at the Rapids Site from July 28 to September 18, 2003. The recapture fish wheel at the village of Rampart sampled fish from July 29 through September 21. A video image capture system was used to record total numbers of tagged and untagged chum salmon and tag colors. What we are finding out? The average migration rate of tagged salmon is about 18-25 miles/day. This figure is determined by calculating the time, date, and distance where fish were tagged and later caught. The total population of fall chum salmon migrating past the study site declined between 1996 and 1998, but appears to have stabilized. The estimated abundance of fall chum salmon migrating through the mainstem of the Yukon River in 2003 was 485,102. Tagging and recovery information can be used to estimate the total population of fall chum in the upper Yukon River drainage. This allows the fish populations to be managed more effectively. Specific migration rates and run timing can be determined from tag returns from communities along the river. A breakdown of different spawning stocks between tributaries in the United States and Canada can also be assessed through tag recoveries. The fall chum salmon that spawn throughout the Yukon River drainage are important to the culture, economy and ecology of both Alaska and Canada. This research project will make managing this shared resource a much easier task. Text and graphics by USFWS Staff Last Modified 24 January, 2006