The Science of Stocking

By Doug Leier, NDG&F Dept.

There’s more than meets the eye when it comes to stocking a new lake for fishing. Just having water doesn’t equate to having fish, or being able to sustain or grow a population of fish.


When fisheries biologists are asked to “stock this lake,” it begins a process. The first step in establishing a new lake is to ensure that the public has access.


According to an article written by State Game and Fish Department fisheries management section leader in the July 2017 issue of North Dakota Outdoors magazine, wild fish are considered a public resource in North Dakota. The Game and Fish Department will not stock a lake unless there’s some public benefit. It doesn’t make sense to create a fishery with public resources that is inaccessible or unusable to licensed anglers.


All lakes on the Game and Fish Department’s list of fishing waters, published annually in the March/April issue of North Dakota Outdoors, and also provided on the agency website at, have some form of public access. Some have public lands and park-like access areas, some are accessible from a public right-of-way, such as a section line.


Others have easements with willing private landowners, who agree to allow the public to access the water across their land in exchange for the Game and Fish Department stocking fish and managing the lake.


Then biologists want to learn as much as possible about the resource before preparing a formal easement or writing a management and stocking plan. Biologists will typically assess the size of the lake and measure depth and oxygen levels to see if it can support fish over winter. In some instances, they may set nets to determine what kind of fish, if any, are already present.


Then, like a farmer planning which crops to plant, they use the information gathered to select fish best suited for the lake. While anglers may want walleye or perch, the limiting factors on the water body may bode well for some other species instead.


For instance, a small water body may support panfish and not a predator like northern pike. Or, if the water has no fish, they may stock yellow perch, which can thrive on aquatic insects and amphipods when there are no other fish to compete with.


But if the water is already full of fathead minnows, walleye may be the best option for producing quality fishing in a short amount of time because they grow well in that type of environment.


Once fish are selected and stocked, the lake is left alone for a time to let the fish grow to catchable size. Periodic test netting is done to evaluate survival, growth and possible reproduction.


When the fish become abundant and large enough for anglers to catch, the lake is added to the fishing waters list for anglers to see.


Fortunately in North Dakota, this process has taken place dozens of times over the past decade, and who knows, there might still be a few waters out there with potential for adding to the list.

Leier is a Biologist with the North Dakota Game & Fish Department.

(Featured Photo: There’s more than meets the eye when it comes to stocking a new lake for fishing. NDG&F Photo)


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