What happens to fish in the winter?
In 2020, we acquired this small pond from a neighbors rental. That required emptying the pond, removing all the rock and liner, transporting the three fish that came with it, digging a new pond base and reinstalling it on the property. It was back breaking work, but with everything shut down for Covid, we had the time, and it was so worth it! Those three fish soon provided us with hours of entertainment, nutrient rich fish water for our gardens, and many, many new little fish.
The first year was a learning curve, for sure, though we had loads of experience raising trout at our farm in Costa Rica. Down there the water is always warmer, so there is less to worry about the cold winter temperatures. We weren’t certain about how our school was going to survive the winter when we often have frozen temperatures on the Oregon Coast. So we bought a thermometer to measure air and water temp outside.
Fish are funny creatures. Did you know they essentially hibernate for the winter? Hibernation in fish, is called torpor. Torpor is a state of reduced physiological activity that allows them to conserve energy during unfavorable environmental conditions. During torpor, fish experience a significant decrease in metabolic rate, heart rate, and respiration, which helps them survive periods of cold temperatures, low oxygen levels, or food scarcity. This adaptive mechanism is especially common in species that live in environments with extreme seasonal variations, such as ponds or lakes that freeze over in winter. By entering a state of torpor, fish can essentially "pause" their normal bodily functions and wait out harsh conditions until their surroundings become more favorable again. This survival strategy is crucial for their ability to withstand and adapt to changing environments. This is how they can survive even when the ponds are frozen.
The above video is from a freeze in 2024, you can see Jonah the big orange/white Koi under the surface of the water completely inanimate. We thought perhaps we had lost all of our little friends, but as it warmed up, they again became more active. There is no need to feed the fish regularly during the winter, but we do monitor the temperature and as they are more active with warmer temperatures, we will throw a little food into the pond. This morning the temperature was 35 degrees, and the fish were responding appropriately- which is, not at all. Everything about their lack of movement indicates they’ve entered torpor.
Goldfish and koi typically come out of torpor when water temperatures consistently rise above 55°F (approximately 13°C). As the environment warms up, their metabolism and activity levels gradually return to normal, and they become more active and start feeding again.
Given that we use our nitrogen rich pond water to nourish many plants here at Urban Greens, we are always excited when spring comes, and our fishy friends once again become part of the symbiosis of this urban small farm. But they’re not just workers here, they are our pets too. Did you know goldfish and koi have facial recognition? They know exactly who we are, and respond to our presence, which is always flattering. Do you like the fish towers we have in place? These glass towers allow the fish to come above the surface level of the water so they can check out our world a little closer. It’s fun for them, and it’s fun for us. Follow UrbanGreensMicro on Instagram and facebook for fun fish tower videos come spring time!
