“There are a lot of things that are changing in the background that aren't visible to us and yet are profoundly affecting these fish populations," said Peter McIntyre, an associate professor of natural resources and the environment at Cornell University.

Brook trout are the official freshwater fish of New York state. They, and other types of trout, may be in trouble.

Researchers are finding that although many trout persisted through issues caused by acid rain in the Adirondacks, Adirondack lakes specifically are becoming too warm for trout.

“In the summer, they will dive deep into the water where it stays cool. And as long as the oxygen concentrations are high, they're fine there. Right now, there's about roughly 50% of Adirondack lakes where there is very little of that habitat," said Stephen Jane, a postdoctoral researcher, previously at Cornell University.

Jane said following legislation, acidity in areas in the Adirondacks has declined, but through a series of events, this is causing dissolved plant matter to go into lakes, making them browner.

Extreme precipitation is also contributing.

The browner water traps heat in the lakes.

“Fish are going to be squeezed into a smaller and smaller zone through time. And so that is just going to because you have less habitat available, that's just almost certainly going to reduce populations. Sizes in many of these lakes and many of these lakes will likely lose robust populations," said Jane.

The work done by the researchers indicates only about 5% of Adirondack lakes may continue to maintain water suitable for cold-water species.

“There's a lot of invisible threats to the health and status of these fish populations that are so important for so many different reasons," said McIntyre.

To help stop issues with local waterways and lakes, the researchers encourage people to not spread invasive species.