The desert rangelands of southeast Oregon may seem like an unlikely place to survey fish populations. But in the Whitehorse and Willow creek basins a population of native Lahontan cutthroat trout has defied the extreme conditions and has survived eons of floods, droughts and silty, alkaline water.
Lahontan cutthroat trout, now listed as threatened under the Endangered Species Act, were once found throughout desert basins in parts of California, Nevada and southeast Oregon.
ODFW biologists will use backpack electro-fishing devices to temporarily stun fish so they can be netted, measure and released unharmed. Scientists will count, measure and weigh the fish to help determine how well this population of Lahontan trout is doing.
To better quantify just how well these fish populations are doing, ODFW biologists will walk the length of Whitehorse and Willow creeks in July and August counting fish. They will use electro-fishing devices to send an electrical charge through the water that temporarily stuns the fish, allowing them to be counted and measured before being released unharmed.
“Currently, this is the only pure native Lahontan trout population in Oregon and we’re excited to see how it’s enduring,” said Shannon Hurn, ODFW district fish biologist in Hines.
Lahontan trout can grow to be the largest of all cutthroat trout and were once found throughout desert basins in parts of California, Nevada and southeast Oregon. In recent decades, many populations have disappeared due to dam construction, habitat destruction and the introduction of non-native brown, brook and rainbow trout.
“Hatchery programs still provide for popular Lahontan trout fisheries in several states, but there are very few self-sustaining, naturally reproducing populations,” Hurn said.
So few populations, in fact, that the species has been protected since 1973 and is currently listed as threatened under the federal ESA. In 2006, it was identified in the Oregon Conservation Strategy as a species in need of conservation.
In 1989 biologists counted only 8,000 Lahontan trout in the Whitehorse basin. During the most recent population survey in 2005, the number had increased to 13,500.
Hurn credits the population rebound in the 1990s to the work of the Trout Creek Mountain Working Group, a coalition of rangers, government agencies and other that has been working on Lahontan trout recovery since the late 1980s.
Hurn also cites the increased presence of beaver and modifications of grazing practices by the local ranching community for the uptick in numbers.
“Over time, changes in grazing practices have led to real improvement in riparian conditions,” she said. Streamside vegetation now stabilizes the banks reducing siltation, and shades the water keeping it cooler.
Populations have improved enough that a catch-and-release fishing season was opened on Whitehorse and Willow creeks in 2001.
Biologists will use data from this year’s survey to better define the trend in the population, as few assessments have been conducted. The data will also be used to determine how fish populations are responding to drought cycles and continued good management practices.
This year’s survey is being funded by a grant from the Fish Restoration and Enhancement Board with additional funding from ODFW, the Western Native Trout Initiative and the National Fish and Wildlife Foundation.