Reader mailbag: What’s with dead, white trout in the Owyhee River?

My inbox has been busy with mail from readers. I get lots of ice fishing questions this time of year, and people are also asking about the unusual-looking dead trout showing up in the Owyhee River. So, it’s time to break out the first reader mailbag of 2020. Thanks for the questions — they are always welcome!

What’s killing trout on the Owyhee River?

Local anglers are concerned about an unusually high number of dead fish in the Owyhee River this winter. The fish are white, making them easy to spot as you look across the river.

I spoke with Dave Banks, a district fish biologist who manages the Owyhee River for the Oregon Department of Fish and Wildlife. Banks and his colleagues have identified the culprit — a water mold called Saprolegnia.

“This mold is something that’s always in the water,” Banks said. “But when fish become stressed and get cuts and scrapes during the spawning season, they become more susceptible to it. We do see a few fish die from it every year, but this year is the most I’ve seen.”

Unfortunately, the dead fish are large, adult brown trout — fish that make the Owyhee a trophy trout stream and attract anglers from across our region. Browns are nearing the end of their spawning cycle, which means fish are more tired and stressed than usual. Spawning also causes openings in the skin — females scrape their bodies against the river bottom while building nests, and males aggressively nip at their mates and each other with sharp teeth — where the mold can cause its deadly infection.

There is a silver lining, though. The mold isn’t affecting juvenile fish, which is good news for future populations. Rainbow trout haven’t been impacted, either — they are sterile in the Owyhee, so spawning injuries aren’t a concern.

“We don’t anticipate this will have a major impact on the fishery,” Banks said. “There are still lots of healthy fish, and it’s not affecting younger fish that will fill in the adult population going forward.”

There’s not much anglers can do for now. Banks said Saprolegnia doesn’t have any known impacts on humans, but since browns are catch-and-release only, harvesting infected fish isn’t an option anyway.

All in all, it’s a bummer, but it looks like this fish kill shouldn’t be too harmful in the long run.

How’s the slush on Lake Cascade?

The recent warm spell combined with heavy snowfall has resulted in unfavorable conditions for ice anglers. While Cascade still has safe ice in most spots, much of the lake is covered in a thick layer of slush that makes getting around a hassle.

According to the folks at Tackle Tom’s in Cascade, slush depth varies from just a couple of inches to more than a foot, depending on location. Poison Creek, Boulder Creek and Van Wyck are the clearest access points. Four-wheelers are not recommended — they get stuck easily in the slush. Snowmobiles fare better, but anglers should avoid deep, wet patches of slushy snow and ice.

The good news? For those willing to brave the conditions, the bite has been picking up for rainbow trout (mid-water column) and jumbo perch (on the bottom, in 30 feet of water). Tackle Tom’s reports good fishing at nearby Horsethief Reservoir, too. Anglers are catching rainbow trout, brown trout and Kokanee salmon. Be prepared for slush on Horsethief, but it’s a smaller lake, so vehicles aren’t needed.

For comfortable fishing in slushy conditions, I recommend wearing waders or a pair of high, waterproof boots. Be safe out there, and tight lines!

Jordan Rodriguez has been fishing Idaho waters since he was a teen. Share your fish stories, adventures, tips and tricks with him at tightlinesboise@gmail.com or visit www.tightlines208.com.