Thanks to improved land use practices, habitat restoration, and a focus on wild trout management, Southeast Minnesota, is blessed with a great abundance of trout. This great abundance is most obvious on our streams that have a special regulation called a “Slot-Limit” placed on them. The slot limit you will find is Southeast MN is a 12″ to 16″ protected slot. This means that you must release all fish you catch that measure between 12 to 16 inches in length. For the exact wording of the regulation, and which streams have it, see this MNDNR page.
When fishing these slot limit streams, an angler may actually be doing the trout population a favor by keeping a limit of trout. This is because these streams typically have such a high population of trout, that they can’t grow to their greatest potential. So, by protecting the trout that have grown to a larger size, while at the same time reducing the numbers of smaller trout, we hopefully end up with a more balanced size structure with more large trout. That’s the theory. The reality is that there just aren’t enough trout harvested to make much of a difference. And that’s the bottom line: there’s just not a lot of harvest going on on many of our streams to negatively impact the overall trout populations.
Of course there are scenarios where harvest could possibly affect a trout population: Streams that have low populations of trout may be negatively affected by over harvest. This is not common here in MN. Another scenario is that when anglers harvest too many larger (over 12 inches in our case) trout. This has the effect of eliminating the stronger, faster growing fish from a stream, while leaving the smaller fish to reproduce, effectively stunting the overall fish population. And this is another reason we have the slot limit protecting these larger fish.
So, next time you are planning a trout fishing trip to Southeast MN, consider fishing one of the streams with a slot limit, and plan to keep some trout. Not only are these wild fish of gourmet quality on the plate, they need to be thinned out in order to better balance their populations. At the very least, you won’t be hurting anything by keeping them.