Yellowstone Lake
Update on Yellowstone Cutthroat Trout Recovery in Yellowstone Lake and the Upper Yellowstone River System.
Overview and History
Wyoming Trout Unlimited (WY TU) and the East Yellowstone Chapter of TU (EYCTU) have collectively been focused on recovering the Yellowstone Cutthroat Trout (YCT) population of the upper Yellowstone River and Yellowstone Lake system (YL) since 2008. Our focus has been on aiding and encouraging the National Park Service (NPS) in their efforts to suppress the
invasive and predacious lake trout (LT) that were introduced into that systemaround 30 years ago and in aiding the US Geological Survey (USGS) in their multi-pronged efforts to locate the LT spawning beds in that system, to learn about LT spawning behavior, and to develop alternative suppression techniques focused on LT ova and fry. The primary focus of the USGS/TU joint effort is a major telemetry study of LT movements through the use of hydro-acoustic telemetry transmitters. Trout Unlimited in Wyoming has been the major fundraising source for the USGS efforts along with the Greater Yellowstone Coalition (GYC), the
National Parks Conservation Association (NPCA), the Federation of Fly Fishermen
(FFF), and TU chapters and councils in many states but especially Colorado, Montana
and Idaho.
Yellowstone Lake Working Group:
The Yellowstone Lake Working Group which consists of representatives from all of the above agencies and non-governmental organizations (NGO’s) along with representatives from Montana State University Fisheries (MSU), and the Yellowstone Park Foundation which is now named Yellowstone Forever (YF, the major funding source for the gill netting on the Lake). This Working Group along with several contract researchers meet on a regular basis to review progress in the effort and to set the agenda for future efforts.
Overall Summary of the Progress:
The efforts to remove LT from the YL system and recover the YCT population is a long term project that has no simply and quick fix. The LT is a voracious predator and has high reproductive potential in the YL system. Its population numbers roughly 700,000 age two and older fish. YL itself is a huge lake with great depths (up to 400 ft.) making suppression a difficult and lengthy process. The effort has at its core a major netting campaign to remove both adult and juvenile LT. Longer term suppression is focused on finding the LT spawning beds through telemetry and then developing specific techniques aimed at cutting off LT recruitment by targeting the LT ova and fry.
The netting campaign is now over 20 years old, although only in the last 6 years has it reached the level that is acknowledged to be sufficient to reverse the population expansion. The telemetry study is currently 6 years old.
The population of LT in the system is in decline although only modestly so. A crash has not yet occurred although it is still anticipated. It is most heartening that the adult LT population is definitely showing signs of decline. The telemetry study has met its primary goal of identifying many (although certainly not all) of the LT spawning areas. Due to funding limitations, this telemetry study is scheduled to be discontinued for the 2017 season. Ova and fry suppression studies are progressing on several fronts and results are encouraging although the “silver bullet” for LT ova and fry suppression has not yet been found. Meanwhile, the YCT population is showing signs of recovery. Every metric studied to monitor this population is on a positive trend. Included are: angling catch rates, spawning stream monitoring studies, distribution netting results, by-catch rates, and visual observations in critical YCT spawning areas. The population of YCT in the system is not yet where it should be; progress is being made.
The ecosystem that depends upon the YCT population as a food source has been negatively and in some cases, severely impacted. But there are signs of recovery. In 2016 and for the first time in many years, a grizzly was filmed while feeding on YCT during the spring spawning run.