In contrast, the survey results indicate some fish are declining.
“There has been a subtle decrease in species richness,” Donabauer said. “Our data suggest that the loss of one species from a lake over a 15-year period is the new norm.”
Species showing the largest declines are specie Donabauer describes as “cool-water” fish, or fish generally found in clean lakes where oxygen is present in deeper, cooler water.
“Northern pike is a good example of a cool-water fish,” Donabauer said. “They survive, grow, and reproduce best where water temperatures are less than 73 degrees and at least 3 parts per million of oxygen occur.
As lakes age and become nutrient enriched, they can lose their layer of cool-water habitat and stress fish.
Pike were found in 40 percent of our lakes in the 1980s. Now the figure has dropped to 30 percent, Donabauer said.
“This is the type of information we get from surveys and is crucial for us to understand what’s going on in lakes,” Donabauer said. “More important, it serves as a basis for taking corrective management actions and provides a way to measure their success.”
‘till next time,
Readers with questions or comments may contact Jack Spaulding by e-mail at firstname.lastname@example.org or by writing to him in care of this publication.