HELENA – Bears might be sleeping, but guess what? FISH NEVER SLEEP!!

Well at least not technically. They do slow way down though. When it gets cold out, most fish across Montana start to behave a bit differently. Fish tend to move into areas that resist daily temperature swings (whether that’s a deeper part of the lake or calm pool section in a river or stream), and into areas that might actually be slightly warmer than surrounding habitats and more well oxygenated.

Freshwater reaches a maximum density at about 4°C. So at a point where water is cooling with cooler air temperatures, many fish might find themselves thermally attracted toward the bottom of a lake or river.

Additionally, as water cools, it holds more dissolved oxygen (thus, the reason an ice-cold fizzy drink stings with carbonation and a warmer one goes down a bit smoother).

Finally, water turbulence from flow or wind might literally mix these factors up, so another winter attractor is spring upwellings and hyporheic flows (areas where water flows through the substrate and interacts with shallow groundwater sources).

This is not to say it’s all snug and cozy. In lentic environments (lakes and ponds), long, cold winters with little influence from the sun lead to thick ice, which leads to vegetative die-off, which leads to reduced photosynthesis and increased decomposition, a deadly squeeze from top and bottom for fish in lakes and ponds.

In lotic environments (rivers and streams), conditions are dynamic as well, with shifting flows as anchor ice and slushy ice develop, habitats can suddenly become inaccessible or worse – way colder. So, while deeper areas and areas along the bottom of a waterbody might be more suitable for metabolic processes, the change in habitat often comes with a change in diet.

Many fish require fewer calories with reduced metabolisms (and might stop foraging altogether) and are often a bit more sluggish (read as efficient). A fish’s winter diet might change substantially to take advantage of what’s simply around them, or it might just be they don’t need as much energy and are taking advantage of calorically-more-efficient prey (e.g., lots of nutrition without a lot of effort).

This can often explain why it’s the slow retrieval of a colorful lure or a slight wiggle of a maggot or just the stationary attraction of cut-bait on a tip-up that catches the eye of a not-so-hungry fish under the ice.

So, it’s safe to say that during the depths of winter, most fish across Montana just plain chill. But there’s always an exception, and in these circumstances, that is the burbot Lota lota. This unique, and singular freshwater member of the cod family (Gadidae) thrives under the ice. Burbot are one of the few species in Montana that actually aggregates and spawns during the coldest months with writhing globs of burbot forming in late January and reproduction commencing in early February. While this species is typically more active at night, during the winter the shorter days and thick ice contributes to lower light underwater and brings out its hidden voracity.

So, this winter don’t be caught sleeping. Get out and slowly forage for what you can get – the fish won't mind.