Fish Management

Duration:

30 minutes, 58 seconds

Native Fish Conservation Program Leader Todd Koel talks about the past, present, and future of fish management in Yellowstone National Park.

 

As early as 1889, soon after the park was established in 1872, park managers started planting native fish in fishless waters and bringing nonnative species into the park. In the mid-1930s, the park stocking policy changed to exclude the stocking of nonnative fish species and selected waters were left “barren of fish.” In the 1950s, the large-scale stocking of native species for recreational purposes was stopped in favor of wild fish management and native species conservation. However, by then over 300 million fish had been stocked in park waters and, nonnative species were firmly established in many lakes, rivers, and streams. To this day, nonnative fish are the biggest threat to the persistence of native fish in Yellowstone National Park and its surrounding waters.

An example of the significant negative consequences nonnative fish can have on an ecosystem is highlighted by the take-over of non-native lake trout in Yellowstone Lake. In 1994, lake trout were discovered in Yellowstone Lake. Soon after, park biologists confirmed that lake trout, a voracious predatory fish, were reproducing and proliferating at a rapid rate in Yellowstone Lake. It was also confirmed that larger lake trout were feeding heavily on native Yellowstone cutthroat trout, decimating the population of this native species in the lake. An expert panel suggested gillnetting would be the most effective method to remove lake trout to protect native Yellowstone cutthroat trout, although it would a require a long-term, possibly perpetual, commitment. The National Park Service agreed, and the lake trout control program was started.

 

 

Our Goals

We reduce the long-term extinction risk for Arctic grayling, westslope cutthroat trout, and Yellowstone cutthroat trout.

Nonnative brown, brook, and rainbow trout all compete with native species for food and habitat. Rainbow trout pose the additional threat of hybridizing with cutthroat trout. Lake trout are a primary predator of young fish, including Yellowstone cutthroat trout, in Yellowstone Lake.

We restore and maintain the important ecological role of native fishes.

Bald eagles, ospreys, pelicans, otters, grizzly bears, and other wildlife eat native fishes. Nonnative lake trout live and spawn in waters too deep for most of Yellowstone’s predators.

We create sustainable native fish angling and viewing opportunities, delivering a world-class visitor experience.

Yellowstone Lake and the Yellowstone River together are home to the world’s largest inland population of Yellowstone cutthroat trout. They’re the most prized and highly regarded by visiting anglers.

 

Native Fish Conservation Plan

To reverse the decline in native fish populations in Yellowstone and restore ecosystem integrity, the National Park Service is implementing targeted actions to promote native fish recovery. The actions aim to conserve native fish species from threats of nonnative species, disease, and the impacts of climate change. Guided by scientific peer review and informed by an environmental assessment completed in 2010, the Native Fish Conservation Plan uses the best available methods to address threats to Yellowstone’s native fisheries. The plan focuses on direct intervention and welcomes the assistance of visiting anglers.

Efforts in Yellowstone Lake Ecosystem

Since 1994, over 4.5 million lake trout have been removed from Yellowstone Lake. Gillnet operations provide important data about lake trout population, age, maturity, and potential spawning areas, which help control them more effectively. Accidental catching of native trout is minimized by fishing in deeper waters not typically used by Yellowstone cutthroat trout.

The Future of Lake Trout Control

Although complete elimination of lake trout in Yellowstone Lake is not possible with today's tools, ongoing efforts can significantly decrease their numbers. Continued strong suppression efforts will reduce lake trout to a level where they have only minor impacts on Yellowstone cutthroat trout. Since lake trout can reproduce rapidly, their numbers are likely to rebound quickly without sustained suppression efforts.

Currently, gillnetting is the main method used to decrease lake trout numbers. Alongside partners at the U.S. Geological Survey (USGS) Montana Cooperative Fishery Research Unit and Montana State University, methods to destroy lake trout eggs at their spawning sites are being explored. Several techniques have been tested, with spreading plant-based pellets over spawning sites to suffocate the eggs being the most promising. Early research suggests these pellets are easier to manage than other substances and effectively kill the embryos. While this method alone may not reduce overall lake trout numbers, it could be crucial for keeping their population down once control targets are reached and gillnetting can be reduced.

 

Duration:

1 minute, 23 seconds

A priority of Yellowstone is to maintain healthy, functioning ecosystems: not just on land, but in the water as well. Yellowstone cutthroat trout are a major part of food webs in the park, but they have been in decline due to predation from introduced lake trout. That's why we put out more than 6,000 miles of gillnet each summer and catch hundreds of thousands of lake trout in order to reduce the long-term extinction risk and restore the ecological role of cutthroat trout. "If the Yellowstone cutthroat trout were to disappear, and we were to allow the lake trout to thrive within the lake, many of the animals that depend on the cutthroat trout would also be displaced or gone." - Native Fish Conservation Program Leader Todd Koel

 

Efforts in Other Park Streams, Rivers, and Lakes

Competition, predation, and hybridization are the primary challenges posed by nonnative fish in other park streams, rivers, and lakes. Other concerns include habitat changes, diseases, and the impacts of climate change. Work involves isolating the project area, removing nonnative fish, and reintroducing genetically pure native species.

Using this method over 200,000 westslope cutthroat trout and 400,000 Arctic grayling have been introduced to 67.2 stream miles and 281 lake acres in the Gallatin and Madison watersheds since 2007.

 

Duration:

1 minute, 26 seconds

In partnership with Montana Fish, Wildlife & Parks, Yellowstone resumed the Soda Butte Creek Native Fish Restoration Project to remove newly discovered, nonnative brook trout.

 

Isolating a Project Area

Headwater refuges are important for native inland fish survival because in many instances, they offer isolation from nonnative fish. To create refuges where they don't exist, natural waterfalls are enhanced or artificial barriers are constructed to block fish from moving upstream.

Removing Nonnative Fish

Fish toxins (piscicides), like rotenone, are often used to control nonnative fish. Rotenone is toxic to gill-breathing organisms but relatively safe for humans and wildlife. To minimize the impacts to other aquatic life, park biologists conduct surveys to ensure the lowest effective concentration is used, time chemical use after amphibian metamorphosis, and neutralize the chemical at the end of the desired treatment area. Native fish are also temporarily removed using electrofishing and reintroduced once the water is safe.

Reintroducing Native Fish

Remote site incubators and live fish stocking are the two methods used for native fish reintroduction, each with advantages and limitations. To ensure long-term sustainability, park biologists monitor progress at project sites through population surveys. Different age classes of fish are collected to evaluate population health and confirm natural reproduction in years following stocking.

 

Duration:

1 minute, 32 seconds

To maintain the natural biodiversity of the Yellowstone ecosystem, sometimes you have to start small. Fish biologist Todd Koel discusses efforts to restore native fish in Grayling Creek, a cup of eggs at a time.

 

Remote Site Incubators

Gametes are obtained from native fish populations within and outside of the park. After fertilization, eggs are raised in hatcheries outside the park. Once reaching the eyed (near hatching) stage, the embryos are moved to remote site incubators (RSIs) in the park, where they will hatch and swim into the stream system. RSIs allow the fish to imprint to these streams, encouraging them to return as spawning adults. RSIs also make it possible to stock large numbers of fish with minimal effort.

Stocking

Stocking live fish involves transporting young fish (fry), juveniles, or adults from a hatchery or wild population to the project area. This method is low maintenance, swiftly restores recreational fishing, and is less susceptible to disturbances. However, it can be expensive in remote areas when helicopters are needed to transport fish. Additionally, stocked fish may have lower survival and reproductive levels since they weren't imprinted within the project area waters.

 

Sport Fishing

Yellowstone supports some of the world’s most famous fisheries and has been a destination for generations of anglers for over 150 years. Fishing regulations are designed to maintain native fish abundance and genetic integrity, the park’s overall ecological integrity, and a recreational fishery for park visitors. Examples of recent regulation changes include a “must kill” for lake trout and other nonnatives when caught in areas where they are harming native fish, “drought fishing” closures during periods of heat stress, and a ban on felt-soled wading boots to prevent introduction of harmful aquatic invasive species.

The Yellowstone Fly Fishing Volunteer Program

There are an estimated 2,650 miles of streams and 150 lakes with surface waters covering 5% of Yellowstone’s 2.2 million total acres. The Yellowstone Fly Fishing Volunteer Program engages in “fly fishing for science” to aid fisheries biologists in their efforts to identify, maintain, enhance, and restore native fish populations throughout the park. Established in 2002, this approach allows Yellowstone’s biologists to acquire data without having to travel to distant locations with electrofishing or other sophisticated gear. Please contact the coordinator, Paul Weamer, to inquire about volunteer opportunities.

Special thanks for Yellowstone Forever for their sponsorship of this important effort.

 

Questions & Answers

 

How many Lake trout were removed from Yellowstone Lake in 2023?

In 2023, the National Park Service and commercial crews removed a total of 236,845 lake trout. Although the overall catch decreased by 15% from 2022, the catch rate of larger fish was the highest since 2016 due to two strong year classes which first showed up in nets in 2019. Even so, suppression effort has reduced the lake trout spawning population by 85% since 2012. Efforts will continue to focus on these larger fish, aiming to reduce their numbers before they reach reproductive ages.

How much support has Yellowstone Forever Provided to the Native Fish Conservation Program?

Since 2018, Yellowstone Forever—Yellowstone’s official nonprofit partner—has provided a total of $4.3 million to the program.

Why don’t Yellowstone predators eat lake trout?

Lake trout differ from cutthroat trout as potential prey because they are generally not available: they can grow larger, occupy deeper areas of the lake, and spawn in the lake instead of in shallow tributaries.

How did lake trout get into Yellowstone Lake?

Lake trout were introduced to Yellowstone Lake by unknown means in the mid-1980s and first appeared in angler catches in 1994. Otolith microchemistry and genetics research suggest they came from Lewis Lake.

How do you locate lake trout spawning sites in Yellowstone Lake?

We use a combination of likely habitat, relocations of lake trout equipped with acoustic transmitters, and gillnetting results.

How many miles of gillnet are deployed each year?

In recent years, miles of gillnet ranged from 5,000 to 6,000 miles per year.

What is a Judas fish?

A “Judas” fish is one who betrays his friends by leading others to them. In our case, it’s a lake trout equipped with an acoustic transmitter who can help us find where concentrations of lake trout may be spawning.

How many people volunteered for the Fly Fishing Program in 2023?

In 2023, 53 volunteers spent 1,173 hours capturing, tagging, and recording Yellowstone cutthroat trout, rainbow and hybrid trout, in Slough Creek and Lamar River. Nonnative rainbow and hybrid trout were removed to support native fish recovery and assess angling as a method for long-term population monitoring. Volunteers also gathered data on the grayling population in Ice Lake and the upper Gibbon River watershed.

 

Duration:

1 hour, 2 minutes, 6 seconds

Todd Koel, leader of the Yellowstone Native Fish Conservation Program, and Mike Canetta, Yellowstone AIS biologist, provide an annual update about the program and fishing/boating regulations in the park. This is a recording of a live public meeting held April 30, 2024.

 

More Information

 

 

Contact Information

307-344-2282 (phone)
307-344-2211 (fax)

Native Fish Conservation Program
Yellowstone Center for Resources
PO Box 168
Yellowstone National Park, Wyoming 82190