Most of you do not have to be told that the weather now is much different than it was a few months ago. Those of us in the northern climates are huddled around inside, looking out the window at a blanket of snow on the ground and ice on the ponds. This gives us an opportunity to engage in outdoor activities such as ice skating, ice fishing, sled riding or snowball fights. It’s easy for us to know that we have to be careful outside in freezing temperatures and dress warmer to make sure that we don’t freeze to death. But you may not think about what cold-blooded animals such as fish, frogs and turtles need when the water they are living in gets a sheet of ice on top.
Mammals and other warm-blooded animals transition differently than cold-blooded animals when the weather changes from mild to downright cold. Some mammals get ready for the cold by growing a denser and heavier winter coat. Others stash food in a hideaway for future use, and still others ball up and hibernate for a few weeks to a few months at a time.
The cold-blooded animals, including the fish in your ponds, do not have the ability to make these bodily changes due to physiological differences. Instead of having the luxury of growing a heavier coat, stashing food away or hibernating, they must adjust by changing their habits and changing the location of their home within their environment.
## A Change in Metabolism ##
In early fall, when the weather begins to cool down, the water also cools, resulting in a slower metabolic rate in the fish. A slowing metabolism means they will need less food and process food more slowly. At this point many pond owners will usually do one of a few things with their fish food: cut back on the feeding rate; change from a floating to a sinking food; change the nutrients, minerals or additives of their food and/or decrease the protein and fat content of the food. As the pond owner makes changes to the feed, the fish’s body automatically transitions from a growth phase to a maintenance phase. This means that they will need little or no feed to maintain a relatively even body weight. In a growth phase, they will consume more than their body needs for maintenance, allowing the excess food to be converted to muscle or fat.
At the fish farm here in south-central Pennsylvania, the fish begin their transition to a slower lifestyle at the bottom of the pond when the leaves begin their color change, so our feeding rates begin to get gradually lower. By the time you are reading this article, our ponds are probably frozen and there will be no feeding of the fish in the outside ponds. Winter feeding, or the lack thereof, has been the subject of many discussions between pond owners and fish farmers as to what the proper method might be.
In my opinion, your fish will give you subtle hints to tell you what they need. I have seen fish looking for food on a sunny, 50-degree day on the first of February; if your fish are looking for feed in the winter, feed them (but only lightly). I have also seen ponds where you wouldn’t even know there are fish present for a few months in the dead of winter. If you don’t see them, it’s because during the coldest periods of the winter, the fish will be at the bottom of the pond and not interested in feeding. That’s where the water is warmest after going through fall turnover. (Type “fall turnover” into a search engine after you are done reading this article; it is very interesting.) Although the water is warmest on the pond bottom, it still stays at a chilly 39 degrees Fahrenheit, which is why the fish are relatively lethargic there.
## Care Beyond Feeding ##
Although fish are not always being fed actively during the winter, ponds still need to be monitored to make sure the fish are maintaining their health and staying stress-free. A simple bubbler, fountain or stream running into the pond should keep an area of the water from freezing. Oddly enough, when fish get sick or stressed, they will seek out this area and you will know something is wrong.
Keep alert for signs of parasites or fungus such as flashing, red spots or fuzzy spots. You will also want to keep stressors to a minimum, including predators and steep changes in water temperature or chemistry. Since the fish are just resting and have not taken in any feed, their stress responses are lessened and their immune systems may be more easily compromised.
Those of you in the northern climates need to remember that your fish are not ignoring you during this time of year; they are merely resting on the bottom. Keep in mind that they have gone through a transition from an active feeding mode to a maintenance mode and they are just thinking about warmer weather. Observe your pond daily and correct problems as they arise so that your fish continue to rest comfortably. When the warm weather does come, they will be “looking for love,” so make sure you condition them properly by gradually increasing feeding to bring them through another season. Enjoy the winter!