Are lakes running out of whitefish, ciscoes?
Spooner, Wis. — Inland cisco and lake whitefish populations – important game fish forage species and also sought for eating by some anglers – are declining in Wisconsin, and more research is needed on the impact that may be having on walleye and muskie populations, as well as water quality, according to a state fisheries research report.
Gill-net surveys conducted between 2011 and 2014 by the DNR found that 29 percent of the lake systems that historically held ciscoes and 33 percent that once had lake whitefish no longer do, based on deep-water sampling nets.
In addition to documenting abundance and distribution of the two species, the study also examined age and growth of the captured fish to help explain why some lakes have smaller, or “dwarf” specimens, and others have much larger, thriving populations.
“This is the first time we’ve used a standardized approach for studying those species,” said Jeff Kampa, one of the DNR’s fisheries researchers who worked on the netting study.
Funding of $90,000 for the study was provided by a federal Sport Fish Restoration grant generated by excise taxes on sportfishing gear.
The report said that of Wisconsin’s some 15,000 inland lakes larger than 2 acres, only 188 – about 1.25 percent – have had ciscoes. Only nine once had lake whitefish. The list of about 150 accessible study lakes was chosen after review of historical records, other isolated studies, and anecdotal local angler reports. Most of the lakes were in the northern third of the state.
However, the highest average cisco catch rate per night of netting was from Elkhart Lake in southeastern Wisconsin’s Sheboygan County, where the catch ranged from zero to 137 fish. Average whitefish catches were low, the most ranging from zero to three per night of netting in Forest County’s Franklin Lake. Maximum size of captured adult lake whitefish varied from 14 inches in Franklin Lake to 26 inches in Vilas County’s Manitowish Lake Chain.
Ciscoes and whitefish require deep, well-oxygenated cold water. They play an important role in a lake’s ecosystem. The chrome-colored fish are native species. Ciscoes eat zooplankton and determine the types and abundance of these microscopic animals that are present, and that, in turn, can influence the type and amount of microscopic algae in a lake, affecting water clarity. The same zooplankton also are food for many young fish, including walleyes, yellow perch, bluegills, and crappies.
Whitefish consume some zooplankton, but focus mainly on bottom-dwelling aquatic insects, mollusks, other invertebrates, and occasionally other fish or fish eggs.
Kampa said studies in Canada have demonstrated that ciscoes, and to a lesser extent whitefish, are prey for walleyes, northern pike, muskies, and lake trout, and help produce trophy-sized fish.
Ciscoes are fairly oily and tasty when smoked, and whitefish are a delicacy when boiled, fried, baked, or grilled.
The report also said:
• The future of ciscoes and whitefish in Wisconsin’s inland lakes is far from certain. As the shorelines and watersheds of many lakes have become developed, increased runoff of sediment and nutrients has reduced water quality and oxygen levels in lake bottom-waters, making less habitat suitable for ciscoes and lake whitefish.
• Rising air temperatures over the past 50 years have increased lake water temperatures, shrinking desirable habitat for both species.
• Non-native rainbow smelt have invaded several inland lakes, to the detriment of ciscoes and lake whitefish.
Kampa said more research is needed on relationships between ciscoes and whitefish and game fish species. That research would help identify environmental factors that might explain why some cisco/whitefish populations are thriving and others are not. But, he said, those efforts might be reduced to “low-level monitoring” until impacts of looming state budget and research personnel cuts are known.
The complete report containing names of all the lake systems surveyed and the catch rates is on the DNR’s website.