Chinook Migration Research

Throughout August, our Wildlife Resource Manager Brandon was on the Yukon River assisting William Twardek, a PhD Candidate with the Canadian Wildlife Federation and Karlie Knight the Lands Coordinator of the Carcross Tagish First Nation. They were busy collecting data on the impacts of the Whitehorse dam on salmon dispersal and spawning success. Shifts were spent fishing along the handful of small eddies that line the Yukon River downstream from the dam in Whitehorse. With the approval and assistance of local first nations and the Department of Fisheries & Oceans, gill nets were used to catch migrating salmon. Each net was 100-feet long and had a mesh size that was suitable for Chinook. Nets were checked every 30 minutes. Given the lackluster run through the dam this year, many hours of work yielded few fish. Once they finally caught one, they had to act fast as to minimize stress on the fish and gather data. Each fish was carefully removed from the net and placed in a holding tank on the boat that was supplemented with oxygen from a pressurized tank. They then drove the boat further up stream and began data collection. Will or Karlie were in charge of applying an acoustic tag into the mouth of the fish while Brandon or another crew member assisted with measuring length, sexing the fish, identifying hatchery or wild and taking temperature of the water. Once they had their data the fish was released upstream so it could continue its journey to the fish ladder and beyond. This entire process was a blur of movement and averaged 8 minutes from capture to release as to minimize air exposure and handling. All in all they tagged 7 fish, far below the desired 30 they initially anticipated but given the low run, a few fish were better than none. The tagged fish will trigger receivers along the river that were placed early in the season. This data will help researchers understand fish movement through the dam and to their natal grounds.

September gave way to yellow aspen trees and the final step in a Chinook’s life cycle. Once again, Brandon assisted on the river, this time conducting carcass surveys along both the Yukon and Teslin Rivers to determine spawning success. During scouting of the Teslin River, they were lucky to encounter a small group of spawners digging their redds before fertilization. Nearby, a half dozen carcasses slowly drifted downstream. By examining the cavity for remaining eggs, they could do a calculation of the egg volume in a graduated cylinder to determine how many eggs each female likely laid. As for the males, they could examine the gonads for milt (sperm) and assuming even part of the sacs were empty, they were deemed successful spawners. Lastly, they took note of the condition of the carcass in terms of level of decay and length to determine age class. The carcasses were then returned to the river so their nutrients could be used by eagles, bears or aquatic invertebrates. Once spawning season was over, the crew had to collect receivers placed back in July and begin cleaning and preparing equipment for next season. Data will be analyzed throughout the winter by William and will go towards his PhD and future research. This research is vital in understanding the impacts human structures such as dams have on wildlife dispersal and reproductive success and will shape how future infrastructure projects are implemented.