South Fork bull trout fishery seeing angler increase, but OK so far

Despite increased angling pressure, the bull trout fishery in the Hungry Horse Reservoir and the South Fork of the Flathead continues to hold its own and the take is well below thresholds set by the U.S. Fish and Wildlife Service.

The bull trout is listed as threatened under the Endangered Species Act and the Hungry Horse Reservoir and the South Fork are the only place in the near 200 miles of the Flathead River drainage where one can legally fish for them.

In the reservoir, an angler can keep up to two fish each year. In the South Fork, the fish must be released.

But even in the reservoir, the harvest is pretty low, notes Montana Fish, Wildlife and Parks fisheries biologist Leo Rosenthal.

The fishery is tightly regulated. Fishermen pursuing bull trout are required to keep “catch cards” which document when and where they caught fish.

FWP has kept track of the number of fish caught and kept based on card data and surveys since 2004.

The most ever caught in the reservoir was 2,154 fish in 2005. The least, 348 in 2013.

From 2018 to 2013, the average has been about 507 fish.

But the number of fish kept is low, about 40 fish a year, according to a report by Rosenthal.

The U.S. Fish and Wildlife Service set a maximum take of 300 annually when it allowed the fishery. Anglers have never reported keeping more than 97 in one year and that was back in 2009.

On the South Fork of the Flathead, where the fishery is catch and release only, the popularity of fishing for bulls is on the rise.

In 2012, the number of angler days was estimated at 657. In 2018, that number had zoomed up to 1,662.

The year 2018 was the last report. The next two year report will come out later this year, Rosenthal notes. In 2018 it’s estimated that more than 650 bull trout were caught and released in the South Fork. In 2017, a little more than 500. In 2016, just under 600. But from 2011 to 2015, it was between 200 and 300.

“We’re seeing an increase in that fishery,” Rosenthal notes.

To make it easier on fish, FWP recently instated single-hook only regulations, which, in effect, bans treble hooks, which are harder on a bull trout’s mouth.

“We wanted to make it easier to release fish unharmed,” Rosenthal said.

So far, the increased angling pressure in the river doesn’t seem to have had an impact on spawning success and mortality — yet.

Rosenthal said redd counts — a way to track bull trout by counting their spawning beds — have been stable so far, but FWP is keeping an eye on it.

“Currently the population is doing just fine,” he said.

But FWP is monitoring the fishery closely, as more people use packrafts to float the South Fork. In addition, getting the necessary catch card is easier — they can be had at the Spotted Bear Ranger Station, rather than only at FWP offices in Kalispell.

“While the bull trout fishery in the South Fork and Hungry Horse Reservoir appears to be sustainable, the increase in participation, estimated pressure, and estimated catch does give some reason for concern. It is clear that more bull trout are being caught and released in the South Fork than in previous years. Recent literature suggests that post-release mortality of large bull trout can be as high as high as 15-33% in some streams because of anglers photographing memorable-sized fish,” the report notes.

Anglers are asked to hold fish gently with wet hands and keep them in the water — taking them out just a few seconds to take a picture.

The anglers mostly aren’t out-of-staters, either, the data shows. Most — more than 70 percent — are Montanans.