December is a transitional period for trout behavior, river conditions, and angling techniques. Here are some things to keep in mind when prepping for a day on the water this holiday season.
TROUT METABOLISM RATES DROP
Trout are cold blooded, meaning their body temperature will match their surroundings. As body temperatures drop, their metabolism slows down and they become less active, needing less nutrients to survive. Water temperatures in our “freestone” rivers are currently transitioning to their usual winter time average lows, which means trout metabolism rates are also transitioning. Some trout may still be more on the active side of the spectrum and aggressively foraging for food on warmer days, while others may be hunkering down for the winter and eating a bare minimum to survive.
First, let’s talk about a few food sources that will be taken off the menu in the near future; trout eggs and smaller fish. Brown Trout spawn during the fall months and quite a few of the eggs they lay end up drifting loose in the current. However, most spawning activity is coming to a close so loose drifting eggs will no longer be in the river systems until Rainbow Trout start spawning in the spring.
As water temps continue to decline, trout are less likely to expend precious energy chasing down prey, so small fish become a less frequent item on the menu. Aquatic insects will make up most of a trouts diet as they sit stationary in the current and wait for bugs to drift by, providing an easy meal. Many different species live in our river systems and most of these species “hatch” during the summer months, lay eggs back into the river to develop into nymphs or larva over the winter, and repeat the cycle. This means that only minuscule eggs, and immature nymphs or larva of most aquatic insect species will be in the water, and will not be large enough for trout to eat. One family of aquatic insect, the “Stoneflies", are an exception to this cycle because the nymph stage of these insects can take 2 to 4 years to mature and hatch, so their nymphs will be available for trout to feed on during the winter. “Midges” are probably the most important Family of aquatic insect for trout during the winter as they have shorter life cycles and will hatch and lay eggs during all months of the year.
Can an angler fish the surrounding rivers all winter long on the fly? Yes, as long as they are not covered with ice. Some rivers do ice over after prolonged periods of winter weather and most of these are classified as “freestone” rivers, or a river that is not originating directly from the dam release of a reservoir. A few examples of freestone rivers in the area are The Colorado River, The Eagle River, 10 Mile Creek, and the Arkansas. Currently our freestone rivers are ice free and very fishable, but this could change as we get into January and February.
“Tailwaters” are sections of river that lie directly below a dam release, and these stretches of river do not freeze due to the constant source of water being released from the reservoir at a consistent temperature, which is normally in the high 30’s through low 40’s (degrees Fahrenheit). Due to the consistently ice free water, a tailwater is always a good choice for the angler during winter because they will always be fishable. Another benefit of the consistent water temps in tailwaters is consistent behavior from trout, due to their metabolic rate fluctuating less. An angler can expect trout in most of our tailwaters to be actively feeding throughout the winter, and fish for them in many of the same lies where they are found in the summer.
On the other hand, trout in freestone rivers will endure a large drop in metabolic rates as water temperatures decline, which means they will have less energy in general. This causes trout to seek out water like deep pools and tailouts of runs, which provide cover, and also have a gentle current that does not cause the trout to expend very much energy to hold their place. The angler should seek out these calmer, deeper pieces of water, and concentrate on fishing them with nymphs close to the river bed. Often during the winter trout will “stack up” in prime pieces of holding water, so it is a good idea to spend a lot of time fishing the same zone once a fish has been hooked there.
In conclusion, all of our rivers are still fishable at the moment and trout are being caught, but as winter months continue some “freestone” rivers could potentially ice over in some areas. In sections of freestone river that stay ice free the angler can capitalize on the trout's lethargic winter nature, by concentrating on fishing calmer, deeper water. Rivers fed by dam releases, or “tailwaters” will stay ice free all winter, and are always a good place to search for feeding trout. The angler can enjoy more consistent action, and fish more typical lies for trout in these waters. In general, there will be less variety in food sources for trout in both freestone streams and tailwaters, with the midge providing a high percentage of most trouts intake. Happy hunting out there everyone, and enjoy the solitude of winter fishing which is one of the biggest perks of the season!