Living in far northern latitudes or high up in the mountains means dealing with long, harsh winters. The deep freezes brought about by such climates leave limited options for keeping outdoor fish. However, you can keep a variety of cold-hardy fish like trout and carp, if you have a deep enough lake.
What are cold-water fish?
Cold-hardy fish thrive in ponds and lakes where summer water temperatures seldom exceed 70 degrees Fahrenheit. Such waterbodies are typically only found at very high latitudes and altitudes. If you experience warmer summers but still freeze every winter, you can expand your fish population to include cool-water fish like perch and pike.
As water warms, it holds less oxygen. This can make ponds in hot climates uninhabitable for true cold-water fish species, such as trout, which are sensitive to hypoxia. These fish require higher oxygen saturation in a deep-water habitat containing a diffused aeration system.
Cold-Water Fish Species
Trout and other salmonoids are the undisputed kings of cold-water lakes. Rainbow trout are among the easiest to source and grow quickly, providing excellent angling in no time. Brown trout prefer the coldest waters and can be stocked together with rainbow trout. Brown trout are less ideal for lake stocking due to aggressive predation on other fish species. Remember, true cold-water fish species like trout require deep lakes and are generally unsuitable for smaller ponds.
Another family of cold-hardy fish that may be suitable for lakes and ponds that do not freeze entirely is carp. Carp, including koi and some goldfish, can endure a wide range of temperatures from 35 to 85 degrees Fahrenheit. Koi fish in winter enter a state of hibernation called torpor, where they slow their metabolisms and expend very little energy. They can survive long winters as long as you supplement oxygen and maintain a vent hole in the ice with an aerator.
Cold-Hardy Fish Care
Maintaining a thriving lake ecosystem with ample angling opportunities can present challenges in any climate. Ensure your fish can weather the coldest winters and warmest summers with seasonal fish care advice from our Pond Coaches. Contact us online or call 866-POND-HELP today!
Read more cold-water fishkeeping tips in these related guides:
How do fish survive in frozen lakes?
How to Prevent Winter Fish Kills
Last Updated: July 29, 2025