A Fish’s Life in the Winter

December 5, 2020 9:05 AM

Temperature has a direct effect on fish metabolism, feeding, and survival. No other physical factors affects the development and growth of fish as much as water temperature. Metabolic rates of fish increase rapidly as the temperature rises. Conversely, as temperature decreases, so does the fish’s demand for oxygen and food. Many biological processes, such as spawning and egg hatching, are geared to annual changes in environmental temperature. Each species of fish has a temperature range it can tolerate; within that range, there is an optimum temperature for growth and reproduction, which may change as the fish grows.   It is important to remember that in addition to fish that other forms of life continue to exist in frozen ponds including aquatic invertebrates, algae and even some plants.

Shallow, productive Iowa lakes and ponds may suffer from winterkill. Winterkills result in lower winter dissolved oxygen levels and diminished populations of many sport fish the following spring.  To address the causes of winterkill, the landowner should restrict nutrient flow into the pond, increase pond depth, or install aeration devices. Lake aeration may take place in summer, fall, or winter. Fall or summer aeration reduces the amount of decomposing organic wastes that results in decreased oxygen demand in the winter. Winter aeration may be dangerous due to the resulting hazardous opening in the ice or management practices during inclement weather. Aeration devices come in a variety of forms and prices. It is important to match a suitable aeration device to the appropriate pond size to maximize aeration. Numerous publications are available that list sizes and prices of aerators.

What about ice fishing? It is recommended that there should be a minimum of four inches of clear ice for ice fishing and at least five inches for snowmobiles and ATVs.  Always check ice thickness before venturing onto the ice and do not assume as ice conditions do change over time.