WHY BASS POPULATIONS GET STUNTED
New science shows that it's not a lack of food that stunts growth
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Have you ever wondered why your favourite bass lake doesn’t produce big brawny fish like you often see the pros catching? We have a jewel of a lake where we take folks who’ve never caught a lot of fish before, and it’s a hoot watching them hook one high-flying smallmouth after the other. But we’ve never seen a four pounder. Not even close. There’s a plethora of fish in the lake, but the population tends to be modest in stature. It must be a scarcity of food for the fish to grow big, right? Well, it could be, but as Dr. David Philipp explained on our recent Doc Talks Fishing podcast, food is rarely the limiting factor in most of our bass lakes.
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David is renowned in the science world, serving as the Director of the Fisheries Genetics Lab at the Illinois Natural History Society, an adjunct professor at the University of Illinois and the Chair of the Fisheries Conservation Foundation. In partnership with Queen’s University, Carleton University and the Ontario Ministry of Natural Resources, he’s been leading groundbreaking research into bass management in southeastern Ontario, accumulating over 30 years of data on certain populations, and snorkelling thousands of miles of shorelines following the fish.
“The life history of these bass is characterized by two specific things that are important for them,” Philipp told us. “One is sexual selection—female choice—and the other is male parental care. When bass are immature they grow quite fast, but when they mature, their growth really slows down. So a bass that matures at 12 inches at age three, might eventually grow to about 13 inches, then it spawns six years in a row. So that three-year-old male tops out at about 13 inches. One that wait to spawn until age six, when it’s 16 inches, then grows to about 18 inches. One that waits until age eight, when it’s 18 or 19 inches, then grows to 20 inches or so.”
The other fascinating things about how northern-range smallmouth bass mature—and the length and weight to which they may ultimately grow—is that the process is denominated by the female members of the population, because they choose which fish they want to spawn. Philipp says males can select their nesting area wherever they want and perform all of the courtship rituals, but if a female looks at him and says, “I don’t think so, you’re not what I’m looking for” the process ends right there.
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“And what the females are looking for,” says Philipp, “are big, bad, tough males in a good spot to defend their babies. So they’re looking for the most aggressive, biggest, toughest fish out there. But who gets caught by anglers in the spring? The biggest, toughest, most aggressive fish, right? We’ve seen it tons of times where there’s a male that will swim 15 metres away from his nest to slam the snorkel or mask and start biting it. He is that aggressive. They’ll bite your fingers. So the first lure that lands within 15 metres of the nest, he’s hooked. We see that all the time. So what happens with spring fishing, is that we’re removing these aggressive males.
“They’re the biggest bass and so we’re taking this population of big, old, maturing males down to smaller, smaller and smaller fish. That is how stunting happens in centrarchids. It’s not that they grow slowly, it’s that they mature early.” Removing big fish does this, Phillipp says, because if the big guys are gone, the remaining male fish can spawn when they’re smaller. “All you have to do is be the biggest one out there and you’re the one that’s going to get picked by the females.”
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You can listened to the entire Doc Talks Fishing Podcast with Dr. David Philipp on your favourite podcast provider, and spoiler alert, it’s hard to comprehend what he and his team have discovered after monitoring and tracking smallmouth bass in southeastern Ontario since 1990. For the first 15 years or so, the population stayed level, but since 2004 it has dropped off dramatically. There are now 30 per cent fewer males protecting nests that contain 40 per cent fewer eggs. To make matters even worse, the hatching success rate has dropped from 70 per cent down to 35 per cent. So the number of fry has decreased 70 per cent.
But that’s the glass half empty part of the story. The potential to restore and enhance northern bass populations is the flip side of the coin, and you can listen to David explaining how easily we can make that happen by clicking on the link below.