New science shows that releasing big fish is crucial to maintaining healthy populations

After listening to Dr. Bruce Tufts, who heads up the Freshwater Fisheries Conservation Lab at Queen’s University, talk about why big fish matter on our most recent DOC TALKS FISHING podcast, our heads are still spinning in amazement. And judging from the emails and messages we’ve received from folks who listened to the podcast, we’re not the only ones who were spellbound. You can listen to the entire podcast by clicking HERE. And here are a few critical takeaways.

It’s incredible how much science is still coming out about the value of big fish in fish populations. In many different ways, they’re incredibly important. There’s a huge misconception about that, which is something we need to talk about.

As fish age, they’re putting less energy into growth and more energy into reproduction and the quality of those reproductive events. A 12-pound female is producing far more eggs than three, four-pound females. What it means is that as big females get older, their contribution of quality eggs is exponential in the population.

On why having fish die of old age is the sign of a high quality healthy fishery:

A lot of the challenging part of managing fisheries is figuring out what portion of the population is going to die from natural mortality, and what portion of the population is going to die from fishing mortality.  What we decide to take as selective harvest from a lot of these populations is in the hands of individual anglers.

If we’ve got forward-thinking managers, then we’ve got slot limits that are trying to protect the most valuable part of the population. But I think even in those cases we’ve probably got a lot of fine-tuning to do. I know that a lot of original slot limits allow people to take big fish at the far size spectrum—really, really big fish. And they would call it a “social” part of the slot. So it isn’t even biologically determined. We’ve only got a few of these big fish.

On the dangers of thinking about fish in human terms:

I spend so much time when I’m teaching trying to dispel myths that we have from that traditional perspective. We call it anthropomorphism: looking at things through our human lens. And there are so many animal examples where that’s the wrong way to look at things.

Fish can learn from each other, whether it’s where to go to eat, what to eat and how to avoid predators. Following older fish to important areas for feeding or on migration routes is something that’s coming out more and more in the scientific literature on fish. In many populations, the younger fish are learning their roots from older fish.

A fascinating example is that when we’ve really damaged some commercial fish stocks, when they collapse, the migration areas change. So younger fish are basically growing up on their own without any adult guidance. We’re finding that some of these populations don’t use the same spawning areas as they did when older fish were plentiful. 

On the amazing “storage effect” of BOFFFFs being able to outlive periods that are unfavourable for reproduction and then spawning successfully when the conditions are right.

In terms of their ability to survive challenging environmental conditions, old fish have more energy reserves. And we’ve talked about the fact that they may have more knowledge of where to go for wintering areas, etc. Another reason why they’re so valuable is that they are still there, and ready, and have survived some of these challenging conditions. Then they can produce an incredible number of high quality eggs when the time is right.

On why Tufts had t-shirts made for his Queen’s University biology students with the slogan BIG FISH MATTER emblazoned on the sleeve.

My lab crew was going to a lot of competitive fishing events, a lot of bass tournaments. And I think what a lot of tournament anglers needed to learn, and we’ve worked away at it, and the t -shirts were one part of that, was the value of the fish they’re bringing into weigh-ins for the fish population.

I spent a lot of time as a fish physiologist earlier in my career trying to teach anglers how to look after those big fish in their livewells, so that they can be released alive at the end of these live-release bass fishing tournaments.

At the same time we were showing tournament anglers the ages of the fish they’re weighing in, and trying to educate them on the value of those fish to the overall population. Trying to get them to be extra vigilant of the fish in their live wells. To how to look after them properly. They’re not just a commodity. We’re lucky to use them and we need to look after them.

We became famous for cleaning up after a bass tournament that went badly down here. That’s not normally the case, which is a good thing for the industry. But we had to bring a number of dead fish back to Queens. When we aged the fish that didn’t survive at this badly run tournament we determined that the population had lost 1,700 years of growth.

To listen to the entire podcast with Dr. Bruce Tufts click HERE.