If the mild winter weather this year carries over through spring and summer, fish populations in northeast Indiana lakes could benefit.
DNR biologists say weather has a big impact on lake temperatures, oxygen levels and water clarity—key factors that determine how much habitat is available for fish.
“Our data show that more habitat and better habitat is present when overall conditions are warmer and drier,” said Jed Pearson, DNR fisheries biologist. “Less habitat is present in colder, wetter years.”
Habitat includes the space fish have to swim and forage in, and areas where temperature and oxygen are more to their liking.
Based on a nine-year study of summer habitat conditions at Crooked Lake, north of Columbia City, the depth where fish can live varies as much as 30 percent from year to year.
In an average year, suitable habitat extends from the surface down to 24 feet. Below 24 feet oxygen levels drop too low for fish to breathe.
During 2012, a warm and dry year, habitat was present down to 28 feet. In contrast, fish were confined to the top 21 feet of water in 2014, a cool, wet year.
“These variations can also affect where fishermen find fish,” Pearson said.
Each summer, most area lakes stratify into three layers: a surface warm-water layer, a middle cool-water layer, and a bottom cold-water layer.
Water is a great insulator, so once these layers set up in spring they usually persist through summer. Oxygen levels, however, can vary within these layers depending on the amount of sunlight, water clarity and abundance of aquatic plants.
At Crooked Lake the warm-water layer typically extends from the surface down to 18 feet. This is where anglers usually catch bluegills and bass. Plenty of oxygen is always available.
The cool-water layer is narrower and sets up between 18 and 20 feet where water temperatures range from 68-73 degrees, which is where perch typically hang out.
The bottom habitat layer usually sits between 20 and 24 feet deep. It is where the lake’s ciscoes, a native fish species related to trout, can be found.
The cold-water layer at Crooked Lake was thickest in 2010, 2012 and 2016 but virtually disappeared in 2014. In some years, as conditions deteriorate, cisco die-offs have occurred when the fish were unable to find cold water with enough oxygen.
In addition to studying habitat at Crooked Lake, Pearson is looking at data from two other lakes: Adams Lake in LaGrange County and Waubee Lake in Kosciusko County.
“We’re seeing the same sort of variation in each,” he said. “All three lakes had more habitat in 2012, the warm, dry year, and less habitat in 2014, the cold, wet year. All three followed a similar pattern in other years.”
So if the warm weather conditions continue, barring any heavy rains, 2017 could be a very good year for fish— and fishing.