By Everett Clark and Briana Tippetts

Henrys Lake, situated on the north end of Island Park, is a hotspot for anglers in the area. It features a hatchery which stocks the lake with cutthroat trout. It also features tributaries for wild fish to spawn. To help protect the lake and keep it available for all the recreation it offers, the Henrys Lake Foundation has been crucial. They frequently work on improving and preserving the lake, including taking steps to avoid erosion and maintain wildlife populations. Two significant developments have occurred which the Henrys Lake Foundation have contributed to: a Lower Targhee Creek restoration project and Parental-based Tagging. 

Lower Targhee Creek Restoration

Land development rendered Lower Targhee Creek unviable as a fish habitat. The current landowner, Robert Keith, plans to improve that. He is collaborating with Henrys Lake Foundation to restore the creek to its original state as a rich spawning ground for local fish, including the cutthroat population.  

Efforts will include restoring the stream’s natural flow to reconnect it with its floodplain by adding woody debris to the stream and constructing Beaver Dam Analogs. The resulting overflow will heighten hyporheic flow, which is the circulation of the stream water with its neighboring groundwater system. Hyporheic flow creates a natural self-purification system and increases dissolved oxygen, which is essential to the survival of fish and wildlife. It also sustains water levels and maintains flow during winter, enabling fish to survive harsh weather. 

In its natural state, the stream will meander, creating riffle habitats connected to pools where fish can breed in ideal conditions. The Yellowstone Cutthroat Trout requires a decent layer of gravel to plow nests for their eggs. Cobble will be added to the stream to create these conditions. 

The foundation will also restore streamside vegetation. The vegetation will provide refuge for fish to conceal themselves from predators, natural breeding grounds, and plentiful feeding. Trees and other vegetation will also help regulate water temperatures.  

Henrys Lake Foundation is excited to team up with Robert Keith and begin work on the Lower Targhee Creek project. Their efforts, along with those of their cooperatives, aim to restore the creek into a thriving ecosystem where the Yellowstone Cutthroat can live and reproduce. The Foundation will provide updates on the project as they occur, and they have expressed thanks to current and future contributors for their significant investments. The cutthroat population saw a large increase in 2021 and continues to grow today. 

Parental-based Tagging

Another major change at Henrys Lake has been a development in how fish populations are tracked. For nearly a decade, the Henrys Lake hatchery has used Parental-based Tagging, a new technological advancement in the tracking of fish.     

Parental-based Tagging (PBT) is a method used to track fish genetically by analyzing their DNA. Because every individual fish has a unique genetic code, the data gathered from PBT is highly accurate and gives biologists a lot of useful information for managing the hatchery. Some of this information includes when and where the fish was spawned, and its parentage.     

PBT can track information very precisely, making it far more powerful than previous tracking methods, such as Telemetry and Floy tags, which use surgically implanted physical tags to track fish. PBT raises the bar, allowing tracking to be done for each fish spawned at the hatchery.    

So how does it work? Hatchery biologists take small, nonlethal tissue samples from each spawned adult fish before sending them to the lake. These samples are stored and sent to the Idaho Fish and Game facility in Eagle, where the genetic data is calculated. This facility processes samples from all over the state, giving IDFG a clear picture of the genetics across Idaho, including at Henrys Lake.     

The information is then stored in a database accessible to biologists studying the lake. For example, if an IDFG specialist catches a fish from a tributary, they can take a small sample and check it against the database. If the fish’s genetics are in the system, that indicates that the fish was spawned in the hatchery. If not, it’s a wild fish, and its DNA can be added to the database. This information is important because hatchery fish typically have a higher mortality rate than wild fish. Wild fish grow up facing the dangers of life in the wild, whereas hatchery fish are unprepared for those dangers. Additionally, PBT information helps determine the percentage of hatchery-spawned vs. wild-spawned fish in the lake, a task much more difficult before PBT.    

Experienced anglers know that many factors influence fish survival. Like lakes worldwide, Henrys is also affected by climate fluctuations. Being such a shallow lake, it’s more susceptible to these fluctuations, including increasing water temperatures. For the various fish populations at Henrys, water temperatures above 70 degrees can be dangerous, even deadly. These fluctuations are generally normal, but PBT proves especially useful for assessing fish populations during these critical periods.    

Though PBT is intensive, previous methods for aging fish and assessing parentage were even more challenging.

“Originally, aging fish was a little bit of science and a little bit of art, too,” says former Idaho Fish and Game fisheries biologist Damon Keen. He says biologists relied on scales, ear bones, and other visible details to make estimated guesses about the age and parentage of fish. “Kinda like rings on a tree,” he says.  

 PBT has been happening at Henrys since 2017, and the quality of the data gathered has consistently improved. PBT eliminates the guesswork about parentage, age, and spawning locations. Both freshwater fish and anadromous fish can be genetically tagged using PBT. Although this method has been implemented for anadromous fish in other places, Henrys Lake is the first to apply PBT to resident freshwater fish on a large scale.   

But as biologists like Keen know well, the data is just so valuable. When asked for the one thing people should know about PBT, he said, “I think it’s the most powerful tool that fishery biologists have to manage Henrys Lake.”   

Both the restoration and tagging projects are helping a beloved Idaho lake preserve its status as a wildlife habitat, making it a place where fish and anglers alike can expect longevity.