06/17/2026
"When it comes to fish reaching maximum size," says Dr. John Casselman, Adjunct Professor of Biology at Ontario's prestigious Queen's University. “Slow and steady wins the race. In conditions that are warm, fertile, and almost too perfect, they grow quickly, almost burn out in a sense and achieve a smaller ultimate size.
"On the other hand, if the water is too cold and there aren't enough nutrients, they grow too slowly to reach their maximum size. We see this in lake trout populations in the extreme Far North. Fish with a moderate growth rate and moderate food supply tend to reach maximum size. This is true for muskies and it may be true for crappies living in the northern half of their range."
The dynamics of fish growth is a subject Casselman has spent much of his life exploring, studying data gathered by observing under a microscope the cleithrum bones of muskies from across North America. The pioneering research he carried out with his friend, the late Dr. Ed Crossman, is for many in the science community, the definitive word on the subject of fish age, growth, and ultimate size.
In a nutshell, fish are cold-blooded, growing best within a narrow range of optimal water temperatures. When those temperatures remain warm and constant throughout the year, fish like crappies grow quickly, continuously, and mature early. But all of that growth comes at a cost. The fish die of old age — burn out — early.
When cooler optimal temperatures prevail, fish like crappies grow more slowly and mature later in life. Cooler water and slower growth allow the fish to live far longer. But despite a long lifespan, crappies still don't achieve maximum size. Somewhere between these two extremes lies the quintessential moderate growth that Casselman says allows the fish to live to their maximum life expectancy, and thus achieve maximum size.
It's important to note that the two divergent growth strategies don't necessarily involve north-to-south geographical differences. Two lakes can literally lie across the road from one another, if one is a shallow, warm, eutrophic environment, and the other a deep, cold, oligotrophic ecosystem.
The potential for a body of water to produce numbers of fat, platter-size crappies appears to be dependent on water temperatures and fertility that allow them to flourish and grow at a moderate rate.
"It could be," says Casselman, "what we're seeing in New York, Wisconsin, Minnesota, and Ontario is that with climate change, water temperature has increased just enough that crappie growth rates have been stimulated enough that the fish are now reaching, or almost reaching, their maximum age and ultimate size."