What’s a Trout to do?

By Brandon

Brandon fishing in the fall snow.

Brandon fishing in the fall snow. Photo by Bill Vanderford

It’s late November now at Vista Verde Ranch. As I gaze through the window of the fly shop out across the open pasture snow is falling slowly…almost hypnotically. The occasional whinny of a horse stands out in stark contrast to the otherwise still and silent ranch-scape. While the winter-white scenery and tranquility never seem to lose their luster, these can be cold and lonely times for a fishing guide. Okay, I’m being a bit melodramatic here, but even though I will soon be joyfully touring the backcountry on skis with our beloved winter guests, I find it hard to say goodbye to the warm summer days spent standing in the cool waters of the Elk River with guests casting to shy cutthroat trout. So, here’s the segue into my intended topic… As the snow grows deeper and temperatures fall and ice begins to form along the edges of the river, where do the trout go? What do they eat? Can they still be fooled with a fly? If you were hoping for a shorter blog post, I’ll sum it up succinctly for you.

1) Not terribly far

2) Certain types of aquatic invertebrates, and

3) Yes (albeit with a somewhat more tedious approach).

For those still interested, please read on.

To properly understand a trout’s wintertime behavior, we must consider a few things. Water temperature, water levels and flow rate, and insect activity all play into what trout are doing and where they go during winter months. Allow me to first describe two different types of river systems found here and across the country; Freestone and Tail Water rivers. Freestone rivers are classified as those which flow freely from source to confluence or termination without impediment from dams, reservoirs or other obstacles. The Elk River, for example, is a “freestoner” as it flows unhindered from its genesis below the Zirkel Mountains to its confluence with the Yampa River. The Yampa River, through Steamboat Springs, however, is a tail water since its flows and temperature are largely determined by releases beneath dams at both Stagecoach and Catamount Reservoirs. Classic tail waters will generally experience less wintertime fluctuation in water temperature and flows due to the fact that they draw water from the bottom of a reservoir where the water is less affected by air temps and in a more consistent supply. This creates a more consistent and stable aquatic environment for both the fish and the insects they eat. Conversely, a freestone river is very much affected by ambient conditions and can often fluctuate broadly based on air temps, ground water supply, snowmelt and freezing. For the sake of this blog, we’ll focus on how fish behave in a freestone river system.

For any of you with whom I’ve had the pleasure of fishing, we likely spoke about some of the key requirements of trout in order to better determine where they “hang out”. Food concentration, protection, water temperature, and resting places are some of the most important. The same needs hold true in the winter as in the spring, summer and fall with some changes to the individual importance of these requirements.

Food: As I often say, “It all begins with the bugs”. As water temps decrease, so do the activity levels of aquatic insects. Where, in warmer months, we experience bountiful hatches of caddis flies, mayflies, stoneflies and midges, the winter months can seem almost devoid of any real “bug life”. While this isn’t exactly the case, most species of aquatic insects do tend to hunker down a bit and await warmer water temperatures to pupate and eventually morph into winged adults. With the exception of chironomids (midges), some small stoneflies, and even smaller mayfly species, much of the insect world takes a noted break during the winter. So where does that leave our hungry fish? Not to worry. Trout, in particular, have a biological response to these conditions. As water temperatures near the point where insect activity drops off, trout experience a sharp decrease in their metabolic rate, therefore requiring much less food to sustain life. While they won’t likely experience much growth during this time, it allows them to hold out until the feeding season resumes in the spring.

Protection:  Just as in the summer, trout must be hyper vigilant of predation. Larger fish, eagles, and predatory mammals are typically more than willing to make a meal out of vulnerable trout, especially in the winter when other food sources are less accessible. Overhanging rocks and logs, ice shelves, submerged brush and vegetation all provide a level of protection for fish; however, deeper water often provides the best safeguard from overhead danger. As water levels drop throughout the winter due to freezing and lack of runoff, trout may find it more difficult to locate deeper water and thus will need to relocate to sections with deeper pools. This is often a reason for fish migrating downstream during the frozen months.

Water Temps: Fish are cold blooded animals and therefore lack the internal mechanism to self-regulate their body temps. They require their environment to be within a certain sustainable temperature range. Trout thrive in water that is typically too cold for many other fish species, but they still have their limits. The general temperature range for rainbow trout survivability is 35 – 75 degrees F. however, optimum temps are somewhere between 50 and 68 degrees (cutthroat and brook trout prefer water slightly cooler and brown trout are comfortable in slightly warmer water). While these numbers are a good guideline, it’s interesting to note that trout will often become conditioned to their home environment. For example, it’s not uncommon to find fish doing quite well in the Elk River when the water temperature is only a degree or two above freezing. When targeting trout in the winter, an excellent starting point to be on the lookout for is where a groundwater seep or spring enters the river. Because spring water maintains consistent temperatures independent of the seasons, it can often be just the few degrees of warmth the trout are looking for.

Rest: While resting places aren’t often included in the “must haves” section of a trout’s house hunting criteria, they become paramount to a trout’s survival during the winter. As mentioned before, when a trout’s metabolic rate is greatly reduced it becomes crucial that the minimum amount of calories be expended in its day-to-day efforts. Expending energy fighting the current in shallow and swift sections of river is far from a trout’s agenda during these cold times. While in the summer fish can be found broadly distributed feeding across many areas of the current, it’s more common in the winter for fish to congregate in greater numbers in slower deeper water where the velocity of the current is diminished. They are more concerned about conserving energy together than competing for food.

So, now that we understand just what it is that trout are seeking during this time of year we can better determine where they are, what they’re doing and whether or not they’re being forced elsewhere in the river system. And, if still bound and determined, as I am, to brave the elements and cast a fly in the winter around here, just fish where the fish are and be accurate with your drift because trout will be far less willing to expend the energy to move toward your fly. Also, if you’re fly fishing from atop the ice please check it first for stability. Better yet, let us fit you for some skis and join in on an epic Colorado backcountry ski adventure!

Whether in the backcountry or on the icy river, I hope to see you soon up here at VVR!