DNR: Fall Trout Spawn in Full Swing

It's your town. Your lives. Your stories. Make sure someone's telling them—donate to Decorah News now. NORTHEAST IOWA — Brilliant fall colors aren't only found in trees, but also in streams — and inside the Manchester Fish Hatchery. These underwater splashes of color signal that trout spawning season is in full swing. Thanks to an increase in self-sustaining, naturally reproducing brown trout populations, the Iowa Department of Natural Resources did not need to collect brown trout eggs this fall. Today, all brown trout caught by anglers have spent their entire lives in the stream. Past stockings of French Creek–strain brown trout helped establish wild fisheries throughout northeast Iowa. "Anglers like these wild, stream-raised fish. They are harder to catch than our hatchery-raised stocked fish," said Dan Rosauer, Iowa DNR trout hatchery manager. "Nearly all public trout streams have lots of brown trout in them." Years of work to protect and enhance the South Pine Creek watershed in Winneshiek County has allowed Iowa's only native trout — the brook trout — to thrive and continue to naturally reproduce there. Eggs are typically taken streamside in early November from wild South Pine Creek brook trout, fertilized, taken back to the Manchester Fish Hatchery, and grown to 2-inch fingerlings by the following June. Those fingerlings are then stocked throughout northeast Iowa to develop new brook trout populations in other streams. "The recent drought put additional pressure on our trout streams over the past couple of years, so we gave the South Pine Creek brook trout a bit of a break this fall," Rosauer said. Milt was collected from a portion of South Pine Creek and from another stream with a restored brook trout population. "The milt collected from wild male brook trout will be used to fertilize about 100,000 eggs from South Pine–strain female brook trout currently held at the Manchester Fish Hatchery," Rosauer said. The rainbow trout spawn—the backbone of Iowa's trout program—takes up much of December and January. Roughly 750,000 eggs will be collected this season. Crews check for ripe female broodstock once a week. After a brief sedative bath, each trout is held over a plastic bowl while workers roll a hand down her belly to release a stream of bright orange eggs — up to 6,000 per fish. The milk-white milt from two males is mixed in, and water is added to activate the eggs and milt, allowing fertilization to occur. The mixture is gently stirred to avoid bruising the eggs. The fertilized eggs are poured into an incubator tray and slid into place beneath a stream of 50- to 52-degree water until they hatch. Tiny sac-fry emerge about 30 days after fertilization. Dark clouds of small fish grow in raceways at the hatchery. They are hand-fed for the first month, then trained to eat from automatic feeders. As the trout grow, they are monitored and transferred to larger tanks and then raceways. The fingerlings will be kept at Manchester or moved to Iowa's two other hatchery stations near Elkader and Decorah to be raised for future stocking. In 13 to 15 months, they will reach about a half-pound and be ready to stock. Nearly 50 put-and-take streams across nine northeast Iowa counties are stocked from April through October, and nearly 20 community trout fishing locations are stocked during the cold-weather months. "We stock about 370,000 catchable rainbow trout from the hatcheries," Rosauer said. "We also stock about 60,000 brook and rainbow trout fingerlings each year to grow in the streams." There is natural spawning—mostly brown trout and some brook trout—in more than 100 northeast Iowa streams, thanks to improved habitat, strong trout genetics, and several years of above-average rainfall prior to the recent drought. Many trout caught, however, are spawned under the care of hatchery workers at Manchester. These cold-water fish are strong fighters and especially vibrant in their spawning colors this time of year. More information about Iowa trout streams and trout fishing tips can be found on the DNR website at iowadnr.gov/trout. Stay ahead of the curve! Subscribe to free newsletters for exclusive insights, local trends and analysis delivered straight to your inbox.