Story Submitted by: Korbin Proctor, Fisheries Management Student
Natural Resources Management Technologies Program,
University College of the North

It finally happened, you’ve been fishing in this spot since you were a child, always believing the monster Walleye you’ve been after has been lurking deep below. You’ve finally captured it. After taking a few pictures and measurements, you release it back into the cold September water and reminisce on the experience you’ve just encountered. An odd thought pops into your mind; “I wonder how long that fish has been down there? How old was that thing?” – Well we’ve done the math!

Natural Resource Management Technologies students at University College of the North conducted an exercise that will allow you to estimate the age of your walleye using some simple measurements. All you need to do is measure the length of your walleye from the tip of the mouth to the inside fork of its tail, otherwise known as the total fork length (Figure 1), and input that number into the prediction equation we have created.

Figure 1: Total Fork Length Measurement Location

The equation was made by collecting the age and growth information from walleye gathered from a Northern Manitoba Lake, in September 2019. Walleye dorsal spines have a similar structure to that of a tree, in the sense that for each year of its life, a new growth ring called an annulus will appear in the cross section. We examined, measured and counted these annuli for 54 walleye and related them to their respective lengths. By measuring the distance between annuli, we were then able to predict the total fork length of each Walleye at every year of its life. We then plotted the correlation between total fork length and age to get this equation:

Fish Age = 0.0271x – 3.0936

Where x is total fork length in millimeters. For example, imagine the monster fish you caught in the beginning of this article. You measured it to be just over the measurements required to be considered a Manitoba Anglers’ Guide master angler: 716mm. So, using this equation you would get the following:

Fish Age = 0.0271(716) – 3.0936
Fish Age = 16.31 years

So, the answer to the question posed at the beginning is that fish has been down there for a little over sixteen years. This equation is not limited to larger fish, although some inaccuracies can arise when attempting to use it for walleye that are under 100mm in length.

You may now be thinking: “So what? How can this information be useful?” Well aside from simply being an interesting talking point, fisheries managers can use this information to guide management efforts for angling lakes. More specifically, age, growth, recruitment, and mortality data can be used to set slot and bag limits, and inform stocking goals. Next time you are fishing, try it out for yourself! You might be surprised by how old some of these Walleye may get.

Korbin Proctor was born and raised in the Swan Valley. He is currently enrolled in the second year Natural Resource Management Technologies Program at University College of the North. His interests include hunting, fishing, and anything outdoors. He has spent the last few summers working for Mountain Forest Section Renewal Company in Swan River, while attending post secondary classes in the winters.