What Are Hoot Owl Restrictions (and Do They Work)?

Fly fishermen who live or frequent the northwest have likely had to reckon with Hoot Owl restrictions in some way, shape, or form.

The term originates from the early 1900s when loggers in western forests were required to operate their heavy machinery in the cool, dewy period of early-morning in order to reduce the risk of sparks starting wildfires during hot, dry summer days. As it happens, owls also tend to be active in the early morning, and the work period became known as the “Hoot Owl”. The term has since stuck around in reference to activities conducted early in the day to avoid the hottest hours of the afternoon.

This includes the seasonal restrictions that go into effect in some northwestern states that prohibit fishing between 2 p.m. and midnight each day.

The reasoning behind them is fairly simple: heat-stressed fish have a higher mortality rate, so only fishing during the coolest parts of the day is thought to help reduce overall fish mortality during the hottest periods of the summer. But are they actually effective?

Before we take a stab at answering that question, it pays to understand a bit more of what’s happening beneath the surface during those summer heat waves.

How do hot, dry conditions impact trout?

In the northwest, high heat and dry conditions go hand in hand. As the temperatures rise and water levels drop in mid-summer, trout seek out the deep holes in order to stay as cool as possible. This bumps up the competition for space and food, leaves trout more vulnerable to predators, and can allow disease to spread more easily—placing stress on the population as a whole. In addition, a host of secondary effects can impact trout. Water temperature is often a trigger for hatches (higher temperatures can throw off the timing of said hatches) and can affect growth of other organisms, including algae and various pathogens.

While this may not kill a significant number of trout in the immediate term, it can result in spawning failures and lead to increased predation on young fish—both of which have the potential to stunt a population’s ability to sustain itself.

When water temperatures are high enough for long enough, trout can become even more vulnerable. Different trout species prefer different temperature ranges, but none of them are particularly well adapted to water temperature over 73 degrees Fahrenheit. At such temperatures, dissolved oxygen levels in the water decrease, making it harder for fish to respire aerobically.

Aerobic respiration is the process of utilizing glucose and oxygen to generate adenosine triphosphate (ATP)—the main source of energy used by living organisms to carry out everything from the building of proteins to the generation of electrical impulses in nerves. Aerobic respiration is a particularly effective way to generate ATP for two reasons: it’s incredibly efficient (resulting in 38 molecules of ATP), and its byproducts, carbon dioxide and water, are largely benign.

When oxygen becomes less available to trout, they can temporarily make up the difference in energy production using anaerobic respiration. Once again, glucose is the base starting ingredient, but a lack of oxygen triggers a less efficient chemical pathway that results in only 2 molecules of ATP and a potentially harmful byproduct: lactic acid.

This has a number of effects on trout. The reduction in energy production requires those precious ATP molecules to be reserved for the most essential functions—which means digestion, reproduction, and growth are all put on the back burner. A lack of available ATP can also leave the trout’s immune system less functional. In an environment where hot, dry conditions have already forced fish together, increasing the risk for disease spread, this can be particularly deadly. And finally, if forced to rely on anaerobic respiration for an extended period of time, the lactic acid produced as a byproduct can simply kill the fish by creating hyper-acidic conditions in cells.

The impetus for Hoot Owl restrictions is to reduce the number of added stressors already impacting heat-stressed fish and (in doing so) prevent an overall increase in fish mortality due to angler activity.

Do Hoot Owl restrictions improve trout survival?

This is an important question. It impacts how we manage our trout populations. It influences when we plan our fishing vacations. It has very real implications for guides, fly shops, and other businesses that make a living off the water. It is understandable, then, that it is the source of a fair amount of controversy.

There was a study performed by Idaho Fish and Wildlife back in 2021 that suggests there is no significant difference in fish mortality due to catch and release fishing in high water temperatures.

As mentioned above, heat stressed fish have trouble producing enough energy to carry out normal physiological functions, such as reproduction and digestion. A fish that isn’t digesting isn’t going to be eating much either, which suggests that very few of them will actually rise to the temptation of your fly to begin with. The data gathered in the study seemed to confirm this principle and Idaho Fish and Wildlife drew the following conclusion:

“…while mortality of individual trout goes up at higher water temperatures, angler catch success goes down at the same time. Because catch rates drop as the water temperatures climb, anglers are causing as much fishing mortality at the lower water temperatures as they are at higher water temperatures because they just catch fewer trout.”

Idaho Fish and Wildlife goes on to argue that even in ideal conditions when trout are feeding voraciously and more likely to take an angler’s fly, the percentage of the trout population actually caught by anglers remains in the low single digits. Catch and release anglers, therefore, account for a relatively small proportion of overall trout mortality. Which begs the question: should we be restricting fishing during hot weather?

Montana has been implementing Hoot Owl restrictions since 2008. The criteria? Any time the maximum water temperature reaches at least 73 degrees Fahrenheit three days in a row. This often occurs at some point in July, and the restrictions will usually remain in place until sometime in September (or whenever the maximum daily water temperature falls below 73 degrees for three consecutive days). Other factors can influence whether Hoot Owl restrictions remain in effect, including angler pressure and water flow data.

As a 2022 review from the Maine Department of Inland Fisheries and Wildlife noted, there is a distinct lack of studies proving the effectiveness of heat-related fishing restrictions:

“Ecological theory would suggest that if there are enough thermal refugia to allow the entire population to shelter during high temperatures than temporary closure of thermal refugia to angling would increase survival, as deaths would only occur from predators. However, if there is a lack of thermal refugia then competition for space and oxygen due to overcrowding will increase natural mortality and increased angler induced stress or harvest could reduce competition and increase survival for remaining fish.”

The authors of this particular review go on to admit that the impact of fishing restrictions is likely to vary across river systems (and even within a single waterway) due to a variety of factors: the availability resources (shelter from heat, access to food, etc.), angling pressure, compounding environmental stressors (drought, algae blooms, etc.), presence of stream-side vegetation, and overall trout population health to name but a few.

“Any analysis is complex, and the best approach is likely to vary considerably… Unfortunately, without research into the effects of temperature-based closures, there is little to scientifically direct efforts, and biologists can only apply their best guess based on theory, experiences, and observations.”

Suffice it to say, there is a gap in our current knowledge of how to best protect trout populations from the pressures imposed by heat and drought. Is there a better solution, one that protects our trout more effectively and meets the wants and needs of recreators and businesses alike? Possibly.

Education is one route. Using barbless hooks, having the proper equipment to land fish quickly, reducing the time fish are handled and out of the water, taking care not to touch their gills, choosing to fish deeper waters or high mountain streams where water temperatures are more likely to be within normal ranges—these are all ways for anglers to reduce their impact on individual fish.

Habitat enhancement projects have also shown some promise. Create more deep-water refuges, increase stream-lake connectivity, and improve tree cover along a waterway and you would expect trout to fare better when the temperatures begin to rise. That said, such projects tend to be expensive, take time to realize results, and likely aren’t possible along all waterways where fish populations are endangered by increasingly hot, dry conditions.

Ultimately, there seems to be no one-size fits all answer. In the absence of actual data, perhaps the best we can do as individuals is to try and be responsible and respectful of our rivers, the fish, and one another.

Where are Hoot Owl restrictions in effect?

Currently, only Montana and Yellowstone National Park are actually instituting official Hoot Owl restrictions, though other states, including Oregon and Washington have used them in the past. It’s also worth noting that other states may implement seasonal or temperature-based restrictions on fishing that don’t fall under the category of Hoot Owl restrictions.

Remember to take a look at your state’s Department of Fish and Wildlife for information on fishing closures and restrictions. At the time of writing this article, there are currently Hoot Owl Restrictions in place on 14 Montana waterways.

Whether you agree with these restrictions or not, they are actively enforced by Fish and Game Wardens. A failure to adhere to them (even accidentally) could result in fines, penalties, and the loss of your license—which is enough to spoil anyone’s fishing trip.

Our advice? Get out there, enjoy the summer, and use responsible fishing practices regardless of whether or not restrictions are in place.

Questions? Opinions? Interesting studies you’ve come across in your own research on the subject? Share them in the comments below!