Fishing for spring walleye? This fascinating new science will help put you on those early-season ‘eyes

With the walleye season opening across the country in the upcoming days, we spent some quality time on our Doc Talks Fishing podcast this week with longtime friend, Nick Baccante, who was the Senior Research Biologist in the Ontario Ministry of Natural Resources’ Walleye Research Unit.

Nick literally helped write the book on walleyes, with Dr. Peter Colby, who penned the Synopsis of Biological Data on the Walleye for the United Nations. So it was super-cool to talk with him about Canada’s most popular fish. Here are a few of our favourite takeaways from our conversation with Nick.

• I can’t think of too many other species (at least in freshwater), that span such a huge amount of the landscape as walleye. I mean, when you think about it, down to the Gulf of Mexico and Louisiana, all the way up to the Arctic Circle.

• This native range is pretty astounding, because when you look at the differences in environmental conditions that they have to survive in and adapt, it’s taken many years for the adaptation to work.

Nick then filled us in on the fact that first-time spawning walleyes don’t know where to go to lay their eggs. They learn from the older fish.

• That’s why we’ve always promoted the idea of maintaining a balanced population in terms of the age groups. Those older walleyes have a lot of learned behaviour in terms of where feeding and spawning grounds are. As you know, walleye are a schooling fish. They tend to congregate in schools at different times of the year. And spawning is one of those physiological requirements that the fish has to go through.

• For the most part, the young walleye just coming into maturity start to get the pheromones and all the cues that tell them to start looking for spawning grounds. So the schooling behavior is very important. They tend to follow the older mature fish.

Equally spellbinding, Nick said that younger walleye even learn from the older more mature fish about what prey species to target. This also emphasizes the importance of always having mature walleye in the population.

• The behavioural side of things is important in identifying preferred prey species. Walleye will go towards where these schooling prey fish are.  The value of the mature fish is beyond producing a large number of eggs. It’s that behavioural aspect as well.

• It’s so important to maintain that balanced age structure in the population, because it has all kinds of implications. That’s why sometimes we see the demise of a wildlife population if we lose one age group, or some age groups disproportionately to others. You need to have all of these components for it to work.

Knowing how walleye anglers love to fish near spawning areas when the season first opens, we asked Nick to spell out what makes the perfect walleye spawning grounds. Among the many things he mentioned was:

• At the top of the list I would say it’s the availability of oxygenated water.  So if we think about oxygen as a key factor, then you look at creeks and rivers where walleye might spawn and think, oh, well, that’s gonna be a preferred habitat. Well, it’s only preferred if it has moving water with ripples and rapids, because that’s what oxygenates the water.

• Now, in lakes, where’s the oxygenated water? Well, typically they tend to spawn on the windward side of the lake. So in the spring, if you look at where the prevailing winds are coming from, if they’re coming from the west, as they do here, it is on the eastern side of the lake.

Speaking of the walleye spawn, we were curious to know how many eggs a female walleye lays each spring and how many survive to adulthood.

• You might have to shut me up on this one, because it’s one of my favourite topics. I spent five or six years studying walleye fecundity. We use something called growing degree days above five Celsius. Above five degrees Celsius is a way to signify that biological activity will start. When you look at the map that I mentioned, if you look down into the Gulf of Mexico, you’re talking 5,000 growing degree days per year. And when you go up to the Arctic, you’re less than 1,000. That might not seem like a lot to people, but when you look at the implications it’s a tremendous difference.

• In terms of relative egg production, let’s say eggs per kilogram, we’re talking about anywhere from about 40,000 eggs per kilogram of fish in the northern part, and doubled at about 80,000 eggs per kilogram in middle attitudes.

• It is super high mortality…  At Savanne Lake, where I worked, we had the data and egg production was somewhere around 84 million eggs total. By age zero, which is from the time they hatch it’s about 99-percent mortality. Ninety-nine percent mortality from egg to hatching. So from 84 million eggs you’re looking at 10,000 age zero walleye, about 7,000 age one. By the time you get to where they start to mature you’re down to 2,000 fish. So it’s a huge mortality gradient.

To listen to the entire spring walleye interview with Nick Baccante, tune into Doc Talks Fishing on your favourite podcast provider or click HERE.