Record redd counts on Metolius River

June 26, 2018
Record redd counts on Metolius River

Fisheries biologists have found a record number of redband trout redds, or nests, during their 2017-2018 surveys on the Metolius River. This indicates that the river's trout population remains strong and healthy.

"We have found that the primary spawning areas on the Metolius River for redband trout are from the mouth of Spring Creek to the headwaters, and in Lake Creek and Abbot Creek," said Nate Dachtler, assistant district fisheries biologist for the Deschutes National Forest's Sisters Ranger District.

Surveyors documented 1,947 redds in those stream reaches for the 2017-18 spawning surveys. For 2016-17 they located 1,244 and 1,174 for 2015-16.

These redd surveys were begun with the 1995-96 redband spawning season, which on the Metolius runs from December through May, although most of the fish spawn between January and March, peaking in February.

The surveys are cooperatively done by the U.S. Forest Service, Oregon Department of Fish and Wildlife and Portland General Electric, but volunteers play an important role. According to Dachtler, they typically get about 20 volunteers helping out each year, and many are recruited from the ranks of the Central Oregon Fly Fishers, Native Fish Society and Trout Unlimited.

Before wading out into the river's 45- to 50-degree water, volunteers get a quick course on how to identify a redband trout redd. The hen fish digs her nest in the gravel river bottom by turning on her side and undulating her body, which creates a depression revealing light gray finer sediment and a mound of heavier gravel immediately downstream of the redd. In this depression she will lay her eggs, then the male will move over the eggs and fertilize them with his milt. That light gray area on the river bottom is the giveway that helps the surveyors spot redds, although the fisheries biologists will double-check until they are sure the volunteers have gotten the hang of redd identification. The surveyors typically work in teams of three so they can cover the entire width of the river in one pass. When they find a redd, they mark it with a rock painted white so that it will not be counted more than once during subsequent surveys. The river from Spring Creek to the headwaters, and Lake and Abbot creeks, are surveyed every two weeks through the spawning period.

While this year's redd count was a record high, Brett Hodgson, Oregon Department of Fish and Wildlife district fisheries biologist based in Bend, cautions that it doesn't necessarily mean that the Metolius River redband trout population is currently increasing as the numbers have fluctuated over the years. But the data does create a picture of the river's redband population as robust and healthy. Based on the redd count, Hodgson estimates that it represents about 5,000 adult, spawning-age fish, although there are certainly many more younger fish in the river as well. There is no official estimate for the Metolius redband population.

However, there is no question that the river's wild redband trout numbers have increased over the decades, where surveys in the mid- and late 1980s found fewer that 200 redds compared to nearly 2,000 30 years later.

"That's been a result of the excellent habitat projects on the river and the discontinuing of the hatchery stocking program," says Hodgson.

For many years the Oregon Department of Fish and Wildlife stocked the Metolius River with hatchery fish raised at Wizard Falls Hatchery. But over time, research found that stocking hatchery fish has a detrimental effect on wild fish that includes competing with them for space and food, and if they interbreed they produce less-fit offspring. Studies in the 1990s found that wild Metolius River redband trout were hybridizing with hatchery rainbow trout that also made them more susceptible to diseases.

"There were some pools that had hundreds of hatchery fish that were outcompeting the smaller, wild fish," said Dachtler.

The state ended the stocking program in 1996, allowing the native, wild redbands to reclaim the Metolius River as their own once again.

Habitat improvements on the river have been another important factor. There were some early habitat projects just above Bridge 99 in the late 1980s, but the big push came in 2010, when the Forest Service put 900 trees in the river, the largest habitat project ever done on the Metolius, according to Dachtler. Those trees offer a number of benefits for the trout including shade, places to hide from predators, and as the logs decompose, create insect habitat that increases the food supply for fish.

While the strong redband population is good news, the Metolius remains a difficult river to fish. It's clear water makes it easier for the fish to see anglers and spook, and it often requires anglers to "match the hatch," determining what kind of insect the fish are feeding on at the time and presenting them with the proper imitation fly. According to Hodgson, there is a core group of regulars who have the river figured out and do pretty well, but for the casual angler it remains a challenging place to connect with a trout. Nevertheless, said Hodgson, "We're very happy with the redband population on the Metolius."

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