Results of The Fish Ageing Study Undertaken by Aikens
Feb. 10, 2021
At Aikens, we have been the stewards of the lake for over 30 years (the lodge has been in existence since the 40’s). We were one of the first fly-in lodges in the late 80’s to voluntarily switch to a category known as “High Quality Management Lakes” in the province of Manitoba. This distinction introduced slot-size limits and reduced take-home limits. Nearly twenty years later, we took it one step further by eliminating take-home fish in 2005 at the suggestion of the new partner, Chris Jensen. Sure, both those future-looking decisions cost us a few short-term groups at the time, but as we enjoy the bounty of the lake today, we are happy for the leadership shown in the past.
In 2016, we started chatting with the fisheries biologists in the Manitoba government, and they wanted to work with us to get some data on Aikens Lake. The province had not looked at it since the 60’s and 70’s. In terms of sustainable harvest, it was quickly identified that the lake was already within allowable ranges below the 1kg of walleye per hectare which is the standard ratio.
But the biologists also wanted to go once step further in analyzing Aikens. Could we tweak the slot size to really promote the best conditions for long-term sustainability? They suggested we do a fish ageing study on our walleye population. Understanding how long it takes for fish to become mature enough to reproduce is crucial in proper lake management, and they never had any data on Aikens before. Size is not always indicative of maturation and the ability to lay eggs… in some lakes it can be 15” and in others it is 20”. At the time, and at the suggestion of the biologists based on the size and depth of our lake, we voluntarily dropped our slot size on Aikens from 21” to 19”.
One line we remember clearly from that meeting was “we feel it is a shame when walleye struggle to survive for years to finally reach spawning age, just to have them end up in a frying pan!” We could not agree more, so we dropped the slot with the understanding that we would reassess once we had scientific data to do so. We needed to find out how fast walleye reached that age to guide the eventual decision on slot size.
Our guides, led by head guide Austin Los, were huge contributors to the effort. A total of 125 walleye were analyzed (mostly using shorelunch fish). The way to determine age is with the otolith bones (small bones in the cranial cavity that show years like the rings in a tree). Ages ranged from 3 to 20, with the bulk (75%) falling within the 5-to-8-year range. The majority of fish over the 450 mm (~18”) range were females.
Despite the majority of walleye falling within the 5-to-8-year range there was a significant lack of individuals represented for age 6 suggesting a poor year class strength. Only seven walleye, less than 6%, were age six suggesting that in 2013 walleye spawning success may have been reduced. The alternative to this would be that 2014 and 2012 were extremely successful years in terms of walleye spawning success. It is common for successful spawn years to be two years apart, as new fry and fingerling fish tend to fight for territory and diet, and so it is rare for two spawn classes to thrive back-to-back. There were no apparent consistent differences between the age frequency distributions of males and females.
A cool part of the study is that it showed that walleye on Aikens can live to be extremely old… upwards of 30+ years! This means they can grow big and stay healthy for a long time… longer than most lakes when their life expectancy is in the low-to-mid 20-year range. The slower growth is explained by the fact that Aikens offers a lot of cool, deep water for walleye to hide and live in – even during summer months.
It has been proven that fish will grow at a slower pace when they live in water cooler than 10 degrees Celsius (50F). While they still feed normally, most of their energy is spent surviving as opposed to growing. So, the window for growth every summer is shorter on Aikens than in shallower lakes where the water warms up more quickly in the spring… but they tend to live longer as a result. Proper management to allow smaller walleye to reach maturation (and beyond) is the key to the long-term health of the fishery to ensure there is always a new supply of big spawners, which is why we were so appreciative that province took interest in Aikens Lake. It has helped explain why we have so many healthy and chunky walleye!
Conclusion: The data shows that in Aikens Lake, walleye tend to grow more slowly. It takes a female on average about 8 years to reach maturation, and at that point they are about 18” in Aikens Lake. As a result, we voluntarily adjusted our shorelunch slot size to represent this fact. For 2020 and beyond, we introduced a slot size of 18” and below are allowed to be kept for shorelunch, while everything that is bigger is put back in the lake to lay their eggs and ensure the long-term success of the fishery.
We would like to formally thank the province of Manitoba, and their lead biologists Derek Kroeker and Lee Murray, who helped us analyze the data. A special thank you Derek – your leadership and hands-on guide training was paramount in getting this done. We know that with strong science-based data, current and future generations of anglers at Aikens Lake will be thanking you as well!