Invasive Fish

What is the difference between non-native and invasive?

Non-native species are those that were introduced to an area but may not necessarily cause problems to the natural environment. Non-natives can adjust to a new environment and call it home, even though they would not naturally exist there. Invasive species can be native or non-native but cause damage or prolonged issues to the environment. More often, invasive species are non-native and are introduced to an environment where they are not naturally occurring. Park biologists and managers actively try to reduce the quantity of the invasive species in the environment, while non-threatening non-natives are left since they do not pose as much of a threat.

 

Aquatic Invasive Species

At Lake Roosevelt, managing aquatic invasive species is critical for the sustainability of the lake. Mutiple partners work together to achieve these goals, depending on the gravity and the species. In some cases, the goal is to prevent the introduction of a new invasive species, while others may be to reduce the quantity of invasive species that already exist at the lake. Group efforts, boat inspections, self-certification forms, and bounties are some of the means of achieving these goals.

 

Primary Invasive Fish at Lake Roosevelt

 

Northern Pike

Ryan Hagerty/USFWS

Northern Pike

Esox lucius

• Originally native to patches among the mid-west United States and Alaska

• Introduced in many locations as a sport fish, and in some cases, done illegally

• On average, grow to 26 inches after 6 years; potentially can grow up to 50 inches over 20 years

• Aggressively preys on other fish (rainbow trout, sunfish, salmon, etc.), significantly reducing the population of native fish; this can change the dynamics of the entire lake, as some species will be more abundant, and others greatly reduced

• One female can lay up to 250,000 eggs, causing the population to grow very quickly

 

Refrigerated cooler where anglers can drop off northern pike heads as part of the Colville Confederated Tribes reward program.

Credit Scott Leadingham

Efforts to Reduce Northern Pike

Northern pike were originally introduced in this area on the Dry Fork Reservoir, in Montana in 1953. Since then, people have brought Northern pike to other areas of the Columbia Basin, including Lake Roosevelt. The Grand Coulee Dam helps to block Northern pike from accessing important salmon spawning habitat in the state of Washington; if they had access, they could cause further damage to salmon populations in Washington State.

Northern pike are relatively new to Lake Roosevelt, however, that has not stopped managers from attempting to reduce their population as quickly as possible. The first documented northern pike at Lake Roosevelt was in 2010. Collaboration between the Colville Confederated Tribes, Spokane Tribe, and the Washington Department of Fish and Wildlife began in 2015. Their efforts have helped keep Northern pike numbers lower through specialized gill nets designed to capture Northern pike and let other fish bypass the net. Additionally, the Colville Confederated Tribes offers a bounty program for Northern pike: $10 per fish head turned in.

Research and suppression efforts are ongoing and programs in the Columbia River Basin are actively working through early detection, rapid response approaches.

 

Common Carp

Credit Ron DeCloux

Common Carp

Cyprinus carpio carpio

• Native to Europe and parts of Asia; likely introduced to the United States in the 1800s

• Found in all US states except for Alaska

• Gold to brown color with red-tinted fins; head is triangular, and scales cover the entire body

• Grow up to 47 inches and a maximum weight of 88 pounds.

• Adapted to living in salty, brackish, and fresh water; water can be standing or flowing

• Primarily feeds on small crustaceans, gastropods, and aquatic plants

• Tends to disrupt aquatic vegetation and toss up dirt, making the water more turbid and causing plants to rip out of the ground

 

Common Carp

USGS/Kaitlin Kovacs

Efforts to Reduce Common Carp

Successfully reducing populations of invasive species requires a group effort. In the spring, the Colville Confederated Tribes Fisheries crew sets up large scale gill netting for common carp as a direct reduction of invasive species. On a smaller scale, the Washington Department of Fish and Wildlife does not require a fishing license to catch common carp, nor is there a limit on how many of them can be caught. While fishing at Lake Roosevelt, the National Park Service does require common carp to be caught on hook and line by anglers. These efforts will benefit the lake environment by reducing numbers of common carp over time, hopefully allowing for less destruction of aquatic vegetation and turbidity in the water.

 

Northern Crayfish

Patricia Thompson/USFWS

Northern Crayfish

Faxonius virilis

While technically not fish, Northern crayfish (a crustacean) are listed as a fish according to Washington state regulations, which are adopted by Lake Roosevelt National Recreation Area.

• Native to Montana, Wyoming, the Great Lakes, upper Mississippi River, and Hudson River

• Likely introduced while being used as a form of bait by anglers

• Grow up to 5 inches long; color varies but is generally a light brown with dark brown markings on abdomen

• Prefer bodies of water with flowing water and turbidity (dirt, sand, mud that makes the water hard to see through)

• Compete with native crayfish in the area for food and habitat; can also impact fish in the lake through competition and predation

 

Comparison between native signal crayfish (left) and invasive northern crayfish (right).

© Environment Agency 2011

Efforts to Reduce Northern Crayfish

The Northern crayfish is invasive along the Columbia Basin. Their presence affects the livelihood of the one native crayfish in this region: the signal crayfish. Being able to properly identify the differences is critical to the removal of invasive species. The signal crayfish (native) has smooth uniform brown color claws with white markings. Northern crayfish, on the contrary, have bumpy claws. Additionally, crayfish are often used as bait by anglers. One method of managing the spread of invasive crayfish is to ensure that anglers are knowledgeable about what types of crayfish are native vs non-native or invasive in an area. For this reason, educational programs are essential to ensure that anglers, students, and the public are familiar with various crayfish species.

Crayfish fishing season is from the first Monday in May through October 31, throughout the state of Washington. Signal crayfish have fishing limits and more regulations, whereas the invasive and non-native crayfish species have different regulations. The latter must be kept in a separate container and be dead before being removed from the general area they were fished from. No license is required and there is no limit to the number of Northern crayfish caught in a day.

Trained National Park Service staff are also involved in the removal of northern crayfish, using their expertise to identify them from the signal crayfish.