The term “hoot owl” originated in the early 1900s when loggers focused their work in the morning hours when it was cooler and more humid (and when owls could often be heard) hoping to avoid starting fires if their saws or other tools threw sparks. In the early 2000s, FWP began applying the term “hoot owl” to new restrictions on summer trout fishing that allowed anglers to fish only from midnight to 2 p.m.—the coolest hours.

That’s because trout can’t survive in water that is too warm, and even if most anglers release their fish, a certain percentage will die from the stress of being caught and handled. A 2008 Montana State University study showed that trout caught and released from water with a temperature above 68 degrees F were far more likely to perish than those taken from cooler water.

To reduce catch-and-release mortality when fish are most stressed, FWP restricts afternoon and evening fishing on some stretches of streams and river. This decision is not taken lightly. “It’s a last resort, and only when it looks like trout on a river are really in trouble,” said Bozeman-based FWP regional fisheries supervisor Mike Duncan, whose region covers the Big Hole, Beaverhead, Madison and several other popular trout rivers.

How FWP decides

The two most important criteria FWP uses to apply hoot owl restrictions on a stretch of river are water temperatures of 73 degrees or higher for three consecutive days or extremely low stream flows (below the fifth percentile of the mean historic flow for that river or stream). These criteria only apply to streams managed for trout and char, which have far less tolerance for warm water than other Montana game fish such as bass and sauger.

Area fisheries biologists monitor mountain snowpack during the winter then track flows and water temperature from United States Geological Survey (USGS) monitoring stations throughout spring and summer, all while watching short- and long-term temperature forecasts. If a river section nears dangerously low levels or high water temperatures, an area biologist notifies senior managers in the regional office and Helena headquarters, who then alert the Fish and Wildlife Commissioner whose region covers that water. In discussion with department staff, the commissioner makes the final recommendation to impose hoot owl restrictions. The FWP director signs the order.

Other factors also come into play when imposing or removing a closure. For instance, FWP may not lift restrictions if weather forecasts suggest that cooler water temperatures will be short-lived. A few rivers, like the Big Hole, have drought management plans that stipulate flows that trigger closures. FWP’s Statewide Fisheries Management Plan also highlights specific reaches of rivers that are likely to see high water temperatures and low flows in the coming years, which can be a useful guide for visiting anglers.

While most hoot-owl restrictions apply mainly to fisheries containing non-native brown and rainbow trout, the state’s native bull trout fisheries have even lower restriction thresholds due to the species’ even lower tolerance for warm water. Fisheries managers have begun discussing adapting more conservative hoot-owl closure criteria for fisheries containing Montana’s state fish—native westslope cutthroat and Yellowstone cutthroat trout, which also have especially low tolerance for warm water.

If long-term forecasts hold, conditions for trout will continue to be tough every summer, so it’s important that trout anglers ‘give a hoot’ and do all they can to protect this invaluable resource by fishing responsibly and ethically.

Before heading out to fish, visit the FWP website to check for current restrictions: fwp.mt.gov/news/current-closures-restrictions/waterbody-closures.