Fishing the Portneuf River in Idaho

The Portneuf River is a long and fertile waterway in southeastern Idaho that empties into the American Falls Reservoir. From end to end the river is 160 miles (257.5 km) long. Though significant parts of the river fall under special regulations or are closed to fishing completely. Still, the waterway offers a lot of opportunity for anglers to catch a number of fish.

The Portneuf rises along the Portneuf Range. It flows through reservoirs and miles of cultivated and uncultivated land along with golf courses and campgrounds. The river also runs through several towns and cities including Pocatello.

This river has been heavily impacted by human activity. It is high in nutrients and nitrates. A channel built by the Army Corps of Engineers designed for flood control has also altered the flow of the river. Still the main stem of the river continues to produce fish. Those are joined by others introduced to the river each year through stocking programs.

Fish in the Portneuf River

The Portneuf is home to a number of species of fish including both game and so-called rough fish. Wild brown trout and cutthroat trout can be found in the Portneuf River. A limited number of rainbow trout are also stocked into the river.

Other fish known to swim the Portneuf include the bluehead sucker, brook trout, cutbow, longnose dace, mottled sculpin, mountain sucker, redside shiner, speckled dace, Utah chub and Utah Sucker.

Both brown trout and Utah suckers seem to be most prevalent in the Portneuf. Some micro species like shiners and dace can also be found in large numbers. There are a lot of fish in some parts of the river. In other stretches however the water is not nearly as lively. The Portneuf is a river where it pays to move around and seek out active fish.

Fishing the Portneuf River

The Portneuf River is suitable for spin, fly and microfishing. Tenkara fishing could also work but would be better in the faster stretches of water. Much of this river has high soft banks that can give you a good look at the fish in the clear water below. But beware, it is also easy to cast a shadow over the water from these high banks and spook the fish. So try to maintain a stealthy approach.

The big bends, deeper holes, runs, undercut banks and spots under overhanging trees are most likely to hold fish. The large Utah suckers can often be spotted by sight fishing. But the big brown trout in this river are unlikely to make themselves known. So if you’re targeting trout, simply fish the likely spots and be prepared.

portneuf river brown trout

For spin fishing you can’t really go wrong with a red worm or nightcrawler on a size 8 octopus hook. When it comes to lures, I’ve had a lot of luck with the perch colored original Floating Rapala in size 5 or 7. Either can be fished on a long light pole rigged with clear 4 or 6 pound monofilament.

When fly fishing the Ponteuf a 5 or 6 weight pole with floating line and a hopper pattern on a 4x or 5x tippet is a good choice in the warmer months. It’s hard to go wrong with either a woolly worm or a San Juan Worm in sizes 10 to 16 any time of year.

Portneuf River fishing regulations

A portion of the Portneuf River in the town of Lava Hot Springs is closed to fishing year round. This is a popular area for swimming and tubing. The regulation seems to be meant to eliminate conflicts between anglers and those swimming in town.

The section of Portneuf River from the East Main Street bridge in Lava Hot Springs all the way up to the Chesterfield Reservoir is under special regulations. From December 1 to the Friday prior to memorial day trout fishing is limited to catch and release with artificial lures on barbless hooks.

Parts of the Portneuf River that flow through the Fort Hall Reservation are under the jurisdiction of the Fish and Wildlife Department of the Shoshone-Bannock Tribes.

USGS Water-data graph for site 06025500

The rest of the Portneuf River is under general regulations for the Southeast Region of Idaho. The daily limit on brown, rainbow, cutthroat and hybrid trout is 6 fish, with no more than 2 being cutthroats. The daily limit on brook trout is 25. The bluehead sucker may not be possessed. There’s no limit on other “non game fish.”

This is accurate as of the time of writing to the best of my knowledge. Of course regulations are subject to change. For current regulations be sure to check the Idaho Department of Fish and Game website.

Portneuf River fishing at a glance

Fish species present: Brown trout, cutthroat trout, rainbow trout, cutbow, brook trout, bluehead sucker, longnose dace, mottled sculpin, mountain sucker, redside shiner, speckled dace, Utah chub, Utah Sucker
Closest tackle shops: Dave's Tackle and Sports
Recommend line: 4-6 lb monofilament / 3-5x leader
Recommended bait / lures: Original Floating Rapala, Spearhead Ryuki, nightcrawlers, red worms
Recommended flies: San Juan Worm, squirmy worm, woolly worm, woolly bugger
Nearby hotels: Home Hotel Lava Hot Springs, Cobblestone Soda Springs

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