By Emily Davis
Each year, Oregon Department of Fish & Wildlife (ODFW) fish biologists brave the chilly spring waters to count steelhead nests, or “redds,” in the Middle Fork and South Fork John Day River, and their tributaries. These hard-won data are used to estimate the number of spawning steelhead in each basin, which in turn will help biologists determine how well the steelhead in each river are faring. Steelhead in the John Day River are listed as threatened under the Endangered Species Act.
These fish make the 400 mile swim from the mouth of the Columbia to the Middle Fork John Day River and spawn by using their powerful tails to dig redds in the gravel where the female lays her eggs and the male fertilizes them. After covering the eggs with gravel to protect them, the steelhead head back down the river: Unlike the Chinook salmon that will spawn in these same streams later in the summer, some steelhead don’t die after spawning. They head back out to the ocean, potentially returning in following years.
ODFW chose to compare the Middle Fork to the South Fork as a large-scale, long-term ecological experiment: Both rivers are important spawning and rearing habitat for the threatened Mid-Columbia Steelhead. But the Middle Fork is undergoing extensive stream habitat restoration meant to enhance steelhead and salmon populations. So, biologists can compare redd counts and other data from the two rivers to factor out influences common to the two rivers—like ocean conditions, weather, and disturbance—to analyze whether restoration is having a positive impact on the steelhead population in the Middle Fork.
This year’s counts are in, and it turns out 2015 was a big year for steelhead redds! ODFW biologists estimated 524 redds in the Middle Fork John Day River IMW area during March-June 2015. This is a 180% increase from 2014 and the highest on record since surveys were started in 2008. The estimate in the South Fork John Day River was higher than 2014, but not the highest on record in that basin.
Don’t get too excited just yet, though—a 180% sounds great, but higher redd counts do not necessarily translate to more spawning fish. A higher redd or fish count in just one year does not automatically mean restoration is working, either—biologists need many years of data to find a pattern they can link to a cause. Using an equation to translate redds to number of fish, ODFW biologists estimated a total of 3,784 steelhead spawners in the Middle Fork in 2015—actually lower than the 2014 estimate. Similarly, total spawner estimate for 2015 were lower than those in 2014 in the South Fork John Day River.
What accounts for this paradox of more redds, but fewer fish? It is likely that the low water conditions made it easy to view redds. Low flows also mean that redds remained visible longer because high flows didn’t scour them away. The Spring of 2015 had very low streamflows, which contributed to this year’s record redd counts.
What do all these redds mean for the future of the steelhead population in the Middle Fork? It is too soon to tell. More redds may mean more juvenile fish hatching, but biologists know that habitat for juvenile steelhead is very limited in the Middle Fork. More juvenile fish competing for limited resources may therefore not translate to more steelhead surviving and returning, because the already-small pie will have to be divided up into more pieces.
Currently, there are more questions than answers, but ODFW is on the case. Stay tuned for an upcoming news item on juvenile steelhead abundance and survival in 2015 and how it fits in with the year’s redd count.