Rebecca Krogman on Advanced Fingerling Walleye Research
Walleyes stocked this week will help fisheries biologists in future stocking decisions.
Spawned this past spring then raised at the Department of Natural Resources’ Rathbun Hatchery, the 8- to 10-inch advanced fingerlings join walleyes already in Pleasant Creek Lake, Lake Macbride and five other Iowa lakes, introduced as tiny, recently hatched fry.
Each just-stocked advanced fingerling 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 the fingerling was stocked in an ongoing research project on Macbride and six other Iowa lakes.
In contrast, fry stocked in the spring are not clipped or marked each year. Due to their larger size at stocking, advanced fingerlings are expected to survive well and may provide more consistent recruitment of walleyes, year to year.
“We stock many more fry but they have a higher mortality rate than advanced fingerlings. These advanced fingerling walleyes are more expensive to raise; however, a larger percentage may reach (catchable) size,” said Rebecca Krogman, DNR reservoir research biologist. “We will be able to determine more clearly several years down the road whether one group grows faster, survives better and ultimately recruits to the fishery more successfully.”
The project will include study of the otoliths, scales and spines, referred to collectively as “age structures,” 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 ... click here to read the rest of the Globe Gazette article.