• warning: Parameter 2 to ed_classified_link_alter() expected to be a reference, value given in /home/soloneconomist/www/www/includes/common.inc on line 2968.
  • warning: Parameter 2 to ed_classified_link_alter() expected to be a reference, value given in /home/soloneconomist/www/www/includes/common.inc on line 2968.

Fresh fish

IDNR stocking Lake Macbride, Pleasant Creek with larger walleyes
DNR fisheries biologist Paul Sleeper watches as a hatchery tanker unloads 8-inch walleye into Lake Macbride this month (Oct 21). The young walleye have a fin clipped, to identify them in a multi-year project to determine whether advanced fingerling or day-old fry stocking is more effective in getting the popular game fish to a catchable size in many Iowa lakes. (photo by Joe Wilkinson)

DES MOINES– Walleyes stocked this week will help fisheries biologists in future stocking decisions. Spawned this past spring, then raised at the Department of Natural Resources (DNR) Lake Rathbun hatchery, the eight-inch advanced fingerlings join walleyes already in Pleasant Creek Lake, Lake Macbride and five other Iowa lakes introduced as tiny, day-old fry.
Each just-stocked walleye has its left pectoral fin clipped to identify it as it shows up in future population surveys or on the end of an angler’s line. Each year a different fin will be clipped, to mark the year a fish was stocked in an ongoing research project on Macbride and six other Iowa lakes. The larger fingerlings should show a more consistent recruitment of walleyes, year to year.
“We stock many more fry, but they have a higher mortality. These advanced fingerling walleyes are more expensive to raise. However, a larger percentage will reach (catchable) size,” explained Rebecca Krogman, DNR reservoir research biologist. “We will be able to determine more clearly, several years down the road, growth rate, age structure; whether one group is growing faster.” The project will include study of the otoliths from a sample of walleyes. The otolith is a sort of fish ‘ear bone’ which shows a record of growth; similar to tree rings.
About 9,400 fingerlings went into Lake Macbride this week. Pleasant Creek received about 4,100. They will grow alongside survivors from 2.8 million Lake Macbride fry and 1.2 million fry in Pleasant Creek. “Every few years, we hope to get a big walleye year from the fry stockings,” noted DNR fisheries management biologist Paul Sleeper. “If the food source is there, typically zooplankton, the fry get a good start. If we have a cold front moving through, reducing zooplankton growth, we will have poorer survival.”
Natural reproduction is extremely rare on impounded lakes in Iowa, assuring that virtually all ‘unclipped’ walleyes in future surveys there were stocked as fry. Both stockings are now about seven to eight to inches in length. They should reach about 12-14 inches by this time next year… and 16-18 inches by fall 2016.
Other lakes in the research project include Big Creek, 12 Mile, Manawa, Little River and Icaria. Big Creek has a one year head start, with similar advanced fingerlings stocked last year, wearing a freeze brand to identify them. The study should conclude in 2019.