Is Your Catch Stocked or Wild?

The crisp morning air fills your lungs with oxygen and your soul with serenity and anticipation all at once. The water is flat and calm, depicting a perfect mirror image of the brilliantly colored foliage intermixed with deep evergreen that skirts the lake and makes you feel like you just fell into a watercolor painting. Each time you cast the line your heart jumps a little with anticipation of a bite and a sense of wonder surrounding what you might pull in from the depths. A familiar tug hits and you’re off on a glorious battle, give and take, between angler and fish. Finally, your finned rival has exhausted itself enough to allow you to gently net it into the boat. Now comes the age-old question as you admire its flaming orange belly, hooked jaw, and cloud white leading fin edges on immaculate fins: is this Maine brook trout stocked or wild?

I know what you’re thinking because it’s the same misconception that most people fishing Maine waters have: if it has all of its fins (did you look for that little adipose fin, too?) then it’s a wild fish. Alas, this may not be an accurate assumption. It’s actually a myth that all stocked fish in the state of Maine have clipped fins, thus the absence of a clipped fin does not indicate that this beautiful beast you’ve just landed is in fact wild. Only a small percentage of fish stocked by the state of Maine have clipped fins.

As you may be able to guess, fish actually utilize most of their fins for various purposes, such as their ability to maneuver throughout the water. For this reason, MDIFW does not clip fins unless there is a necessary reason for it, and there are a few reasons and instances where we might clip fins.

The first example is if we are stocking a species (i.e. a brook trout) in a water where a wild population of that species already exists, and we need to know, for biological tracking reasons, if fish caught post stocking are wild or stocked. An example of this is in Sebago Lake. Sebago has a wild population of landlocked salmon, where the management goal is to fully restore the wild population to support a fishery comprised of all wild salmon. We stock landlocked salmon into Sebago as well with the purpose of attempting to take some of the fishing pressure off the wild fish so that they may survive to spawn, while providing angling and harvest opportunities. Both the wild and the stocked populations of salmon in Sebago are closely monitored and because of that, it’s important for biologists to know if the salmon being caught and kept are stocked or wild, so salmon stocked in Sebago Lake have permanent fin clips, otherwise referred to as being ‘marked’. It’s important to note, there are very few waters where we stock a species that already has an existing wild population of that species.

Another example is if we are stocking a new water or a reclaimed pond. If this is the case, the stocked fish (usually brook trout) are marked so biologists can assess the development of a wild population and determine when stocking programs can be suspended when there is a sufficient wild population.

Another example is if we plan to study the stocked fish in the future, and we need to know the strain (this is the base genetic make-up) and/or age of the fish. Often if this is the information we seek, the fins clipped will be on a rotating schedule, so that the biologist need simply look at the fish, note which fins are missing, and immediately know what they need to know about the fish’s age or strain.

The previous two examples are where we would use permanent marks. These fins are quickly and cleanly removed while fish are young and anesthetized and the fins will not grow back. There is, however, another type of mark anglers might see, and that’s a temporary mark or clip. The purpose of this mark is to allow biologists who are studying the fish population in a given water to immediately tell if the fish has already been caught and measured recently or not.

With this information biologists can more accurately estimate fish population size and age make-up in a body of water. The most common temporary mark is a small clip on the tail (caudal) fin. This is temporary because when only a small piece of a fin is removed, it will grow back fairly quickly (depending on how much was clipped off, it may grow back in a few months). These clips do not affect the fish’s ability to maneuver or survive in any way.

Maine has eight hatcheries and two rearing stations to raise and stock over one million fish every year. All but two of these facilities raise as many fish as they can in concrete pools, called raceways. Every year it seems anglers want MDIFW to raise and stock more and more fish, but there remains only so much room in which to grow these fish. Thus, each facility is at or over rearing capacity for the species and ages of those species that they raise. Because of this, fish are a little more crowded than they would be in the wild and as all of the fish in a raceway vie for the best hang out location (usually at the top of the raceway near where the water is coming in), they sometimes rub their fins on the concrete as they maneuver, or nip at the fins of surrounding fish as they try to stake out territory. This causes the fins to wear down over time. Many anglers see this fin wear and believe it is a clip, indicating a stocked fish. While fin wear certainly may indicate a stocked fish, many stocked fish have no fin wear at all. Also, as the fin wear is not a clip, and most of the fin remains intact, then the fin will regenerate and heal itself quickly (usually within a year or less) after the fish is stocked. If you combine this information with the fact that we only clip a small percentage of the fish we stock, there’s a good chance that a lot of those fish you caught and thought were wild because they had nice fins, were actually stocked.

Now how will you know for sure if that beautiful fish you just reeled in was stocked or wild? Unless you are fishing a water that is being studied, you won’t! And that’s the way it should be. For more information about fish fin clips and study waters, call your local MDIFW fisheries biologist. For more information about our hatcheries, click here.