Submitted photo

A mountain whitefish from the Blitzen River. 

By Lauren Brown

The diversity of aquatic life in the Harney Basin can get overlooked in discussions regarding the overabundance of carp in Malheur Lake. However, the Harney Basin Wetlands Collaborative (HBWC), a collaborative convened and supported by High Desert Partnership, recently invested in a study to examine aquatic fauna in the basin with the goal of understanding where fish populations overlap and intersect with the basin’s carp populations. 

“All the partners decided that it was important to have a snapshot in time of the fish species- native and nonnative living in the basin,” Ben Cate, High Desert Partnership ecological coordinator, said. 

Cate noted that, because much of the work HBWC is doing involves infrastructure upgrades for flood-irrigation practices, knowing where fish species are helps determine diversion choices.

Jason Dunham, a research ecologist for the United States Geological Survey, implemented the study Fishes of the Harney Basin Revisited as a follow-up to the 1971 study The Origin and Distribution of the Fishes in the Harney Basin by Peter Bisson and Carl Bond. 

“I thought about those final outcomes that people wanted and realized that the last time we looked at fishes of the Harney Basin formally was 50 years ago,” Dunham said.

Basin geology

The Harney Basin’s geology is key in examining how fish populations are distributed. 

“Basically, it’s a closed basin that doesn’t flow out to any other drainages. It all flows to Malheur Lake, which is a terminal water body,” Cate said. 

Unlike the Snake or Columbia rivers, which eventually flow into the ocean, the Harney Basin is isolated. 

However, thousands of years ago, rivers in the Harney Basin likely flowed clear to the Pacific Ocean. About 30,000 years ago, the Malheur Gap, an event of volcanic eruptions, cut off the Harney Basin from the Malheur Basin.

“Until that point, presumably, the Blitzen River, Silvies River, and Silver Creek all flowed to the ocean,” Dunham said. 

Fishes of the Harney Basin

When looking at the diversity of fish in the basin, Dave Banks, the district fisheries biologist for the Oregon Department of Fish and Wildlife (ODFW) Hines office, said he divides the fish populations into native and nonnative species. 

The more well-known native species include redband trout and mountain whitefish. There are also native species of dace, minnows, tui chub, sculpin, and two different sucker species. 

Redband trout are a subspecies of rainbow trout, and Banks said they are on the sensitive species list at ODFW.

“The list was created with the development of our native fish management policy. That policy directs us to keep an eye on native fish species. They are a cold-water species preferring water temperatures in the upper 50s to low 60s. Typically, you find them in the Blitzen River,” Banks said.

They are also found in the Silvies River and Silver Creek tributaries. 

Mountain whitefish are found in the Blitzen system, though they are not as prevalent as the redband trout population. Banks said they are more sensitive to water temperature and need cold water to survive. For this reason, they are more active in the winter. Banks said they can get as large as 12 inches. 

He noted that the native speckled dace are durable and can tolerate warmer water temperatures. Therefore, you might find them in areas that are too warm for redband trout. Speckled dace grow to be 2 to 4 inches in length, and they feed on algae, diatoms, and macroinvertebrates. 

Suckers are generally bottom-oriented fish. 

“They are the vegetarians of the system, and they are usually scraping algae and diatoms off the rocks and substrate,” Banks said.

They can get quite large, up to 16 to 20 inches long, and they do well in the lower system, often utilizing the same habitat as carp.

In fact, Cate said suckers can sometimes be mistaken for carp, and people will throw them up on the bank thinking they are a trash fish.

“That’s not the right thing to do,” he said. “Those are native species that belong here, and play a key role in the ecosystem.”

Nonnative fish species in the basin include largemouth and smallmouth bass, brook trout, bluegill, crappie, yellow perch, brown bullhead, pumpkinseed, and of course, carp. 

Banks said there is a naturally reproducing population of brook trout, which originate from the East Coast, on Steens Mountain in Fish Lake. ODFW placed them there years ago, but they don’t stock them currently, and the fish now naturally reproduce. He noted that brook trout are a popular sport fish for anglers and can grow to be 12 inches. They spawn in the fall, unlike most other species in the basin that spawn in the spring. 

Banks said largemouth and smallmouth bass, which come from the Midwest and Southeastern United States, are also popular fish to target for anglers. They are found in the Silvies River above 5-Mile Dam and can get quite large, up to 15 inches. They are also found in Krumbo Reservoir.

According to Banks, while the bass are a great game fish and popular with anglers, they can be problematic in terms of their effect on native fish populations.

“They’re pretty voracious. Anything they can get in their mouth, they’ll eat,” Banks said. “We’ve seen where they have some negative impacts on native fish species. That is why we don’t have them everywhere. They’re not a native species, and we’re trying to make sure that none of our native species end up on the endangered species list.” 

Unintended consequences

When well-intentioned folks try to place nonnative fish in local bodies of water, it can have unintended consequences, Banks said. An example is Willow Reservoir, where yellow perch were illegally introduced a few years ago. The reservoir used to be a popular trout fishery, and ODFW had been stocking it with rainbow trout. However, after the yellow perch were introduced, they outcompeted the rainbow trout, producing an overabundance of yellow perch that were 3 to 4 inches in length.

“For the most part, nobody wants to keep those,” Banks said. As a result, ODFW ended up pumping all the water out of the reservoir to completely get rid of the fish. “That’s money and time that’s being used to fix a problem that could be used to monitor or make fisheries better,” he said. 

Similarly, the overabundance of carp in Malheur Lake has created a habitat that is not friendly to other fish species. For example, the carp behavior of rooting for food in the sediment, creates murky water. This makes it hard for redband trout, who rely on sight to catch their prey, to hunt for food. In turn, it also makes it hard for aquatic vegetation to flourish when sunlight cannot make its way through the turbid water to the plants that would grow in the sediment.

“A healthy aquatic system would include a lot of aquatic vegetation, and all of those pieces contribute to a system that would promote vegetation in the water column,” Cate said. As the Harney Basin is a major stop on the Pacific Flyway for migratory birds in the spring, this vegetation would also provide added incentive for birds to stop at Malheur Lake on their way north. 

According to Cate, controlling the carp population in the basin will make it a healthier aquatic environment for all the fish species here.

“Carp are really repressing all of the native species, but especially the really desirable ones,” he said.

All species have their role in the ecosystem, but when one multiplies in such great numbers as the carp have done throughout the basin and the yellow perch on a smaller scale in Willow Reservoir, it drastically alters the habitat and affects the other species in that environment, usually negatively. 

Banks said that if the carp situation were to be controlled, species such as redband trout, dace, and suckers would utilize Malheur Lake to a greater extent, and the result would be bigger fish, specifically bigger female fish, that would then produce more fish.

“If you could manage the carp at some level, you could have a big win for the native fish community and other fish species that are persisting in this system,” Banks said. 

Study revisited

As shared previously, HBWC invested in the Fishes of the Harney Basin Revisited study to take a current snapshot of the fish populations in the basin because much of the work they are doing involves infrastructure upgrades for flood-irrigation practices. It involves putting diversions across the Silvies River that create fish-passage barriers. As part of the state’s requirements to install diversions, they must also provide the ability for fish to pass through these barriers in the form of fish ladders. At this point, the collaborative has been able to obtain some exemptions from these requirements because of the need to control the carp population and restrict them to certain areas and limit their spread. When the carp population is under control, the collaborative may decide it needs to provide passage for the native fish to go back and forth. At that point, knowing where those native populations are will give them a baseline from which to operate and to understand the impacts of these changes in management actions. 

“All of the native fishes in the Harney Basin play roles in the ecosystem. They all feed in different ways and are able to convert the stream’s energy into fish,” Dunham said. “The Harney Basin in particular has many native fish that are just as interesting as other animals and plants in the basin. Because fish movements are limited by water, their histories are more reflective of how water has moved around the Harney Basin and the region in general for thousands of years.”

Since 2011, the Harney Basin Wetlands Collaborative is finding ways to improve the aquatic health and sustainability of Malheur Lake, and wild, flood-irrigated wet meadows across the Harney Basin. This effort is led by a diverse group of stakeholders, including local ranchers, conservation organizations, the Sovereign Nation of the Burns Paiute Tribe, government agencies, technical experts, scientists, area residents, nonprofit partners, and others who share a love and concern for the Harney Basin. For more information about HBWC, go online to highdesertpartnership.org.