Jon Ewert has more than two decades behind him at Colorado Parks and Wildlife (CPW), where he plays a crucial role in managing the fish populations at Lake Granby. Since becoming the area’s fisheries biologist in 2007, Ewert has focused on maintaining the health and sustainability of Lake Granby's renowned lake trout population.

“This is the most prolific lake trout population in the state,” Ewert says. “It has the highest density and the highest absolute number of lake trout living in it. It's a very high-quality fishery. And we don't stock lake trout — they're entirely self-sustaining through natural reproduction.”

Jon Ewert
CPW Aquatic Biologist

His work involves meticulous documentation and analysis of the fish populations to ensure that the lake continues to support a thriving ecosystem. This includes conducting randomized netting surveys to monitor the density and health of the fish, and making management decisions based on the data collected.

A significant part of Ewert’s efforts centers on balancing the predator-prey dynamics within the lake. However, maintaining an adequate prey base, primarily kokanee salmon, is essential to support the large predator fish population. Other management strategies also address the challenges posed by invasive species, such as rusty crayfish, which could threaten the fishery's ecological balance.

Through collaboration with agencies like the US Forest Service and local guides and outfitters, Ewert also works to enhance recreational fishing opportunities while safeguarding the lake’s biodiversity. His comprehensive fisheries management reports serve as valuable resources for both the public and his colleagues, while reflecting his commitment to preserving Lake Granby’s quality waters for future generations of anglers and other recreationists.

Help Protect Our Fisheries!

“One of the things rusty crayfish are known for is fish egg predation,” said Ewert. “One possible impact they could have is egg predation on these naturally reproducing fish. Public awareness of the fact that you can't move live species around; you can't move live crayfish around; and you can't move live fish around is really important. We have rules against those things for a reason and there are certain species that we just don't want in our waters because they could have a huge negative impact.”