As the temperatures drop, the fish go deep.
As we head indoors for the winter, finding refuge and warmth in a comfy chair by the fireplace or wrapped in a blanket in front of the TV, fish and other aquatic life also look for a good place to hunker down for the winter. Those “good places” include deep pools and slow runs (flat water areas with slow moving water) in the stream, places with root wads and vegetation or backwater areas. The greater diversity there is in habitat features, the more options fish and bugs have to find just the right spot.
Each animal has its own strategy to survive the cold winter months. Finding places where the water is slower, like in a backwater area, allows fish to expend less energy and just “hang out.” Many fish will gather or school in deep pools or runs, particularly where groundwater upwells into a stream providing warmer water to swim in. The bugs will crawl down in the crevices between the rocks or in the vegetation or detritus on the bottom of the streams. Our freshwater mussels burrow down into gravel, sand or sediments.
The Season of Slowing Down
Many fish and bugs survive the winter by slowing down their heart rate and metabolism as the temperatures go down. They move slower and eat less – digestion is slowed so a meal lasts a little longer. Growth slows or even stops during the winter.
Under Thin Ice
Ice can provide a layer of insulation between the slightly warmer waters below and the colder air above. As our weather changes from both the effects of climate change and natural fluctuations, we have seen more freezing and thawing throughout the winter replacing the extended periods of frozen water. This can cause stress for aquatic life as conditions change, forcing them to expend more energy to find suitable habitat.
Inconsistent weather makes the need for diversity in habitat that much more important. Healthy rivers and streams equip fish, bugs, and crustaceans with what they need to hunker down and survive the winter. A primary goal of local restoration projects is to provide varied and complex habitat while restoring form and function to the river channel.