By Dr. Rob Neumann
Select Science—Do pike under ice cover choose the same types of habitats they use in summer? Are daily activity periods similar between these two seasons? Research conducted in a German lake contrasted movements and habitat choice of pike, using the same tagged individual fish radio-tracked during four 24-hour periods in midsummer and midwinter.* The study was conducted on a 62-acre lake about 50 miles northeast of Berlin. The natural lake, Kleiner DÖllnsee, has an average depth of 13 feet and a maximum depth of about 25 feet. About 14 percent of its surface area was covered by emergent vegetation such as Phragmites, or common reed, and cattails, and 27 percent of the lake bottom contained submergent vegetation such as pondweed and coontail.
During summer trackings in July, average water temperature was about 70°F. Winter tracking occurred in February, with the lake completely ice covered by the beginning of January. Submerged vegetation began to disappear from the water column, laying over on the lake floor, in mid-October.
Pike were found to be more active in summer, with activity peaks in twilight periods, while no pronounced daily activity peaks were found in winter. In summer, pike selected areas of submerged vegetation and negatively selected open water (areas deeper than about 13 feet). Pike chose habitats significantly closer to shore in winter, negatively selecting shallow open water, and also avoiding deeper open water. Average distance to shore was higher in summer than winter. Larger pike generally had greater movement and used areas farther from shore.
The researchers found that during the dusk activity peak in summer, pike were also farther from shore, suggesting diel “horizontal” movement patterns, possibly due to pike following prey using various depths from shallow to deeper open water throughout the day.
While pike used certain areas with submergent vegetation in summer, those locations lost their attractiveness in winter as the vegetation withered and settled on the lake bottom, the researchers found. Decaying plants and those laying over on bottom, however, were more attractive to pike than shallow open water in winter. The researchers say these findings suggest pike favored areas with some form of plant cover, regardless of season, which in winter in the study lake mainly was emergent plants in the littoral (shallow near-shore) zone.
*Kobler, A., T. Klefoth, C. Wolter, F. Freidrich, and R. Arlinghaus. 2008. Contrasting pike (Esox lucius L.) movement and habitat choice between summer and winter in a small lake. Hydrobiologia 601:17-27.
