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Fall trout spawn in full swing

  • 11/14/2023 11:41:00 AM
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Brilliant fall colors are not only found in trees, but also in streams and the Manchester Fish Hatchery. These underwater splashes of color are signs that trout spawning season is in full swing.

Thanks to an increase in self-sustaining, naturally reproducing brown trout populations throughout Northeast Iowa, there was no need to collect brown trout eggs this fall. In past years, brood trout from the French Creek genetic lineage were collected from French Creek in Allamakee County or Spring Branch Creek in Delaware County, raised at the hatchery then stocked in streams as 2-inch fingerlings.

“Anglers like these ‘wild’ stream-raised fish. They are harder to catch than our hatchery-raised stocked fish,” said Mike Steuck, Iowa DNR fisheries supervisor for interior streams. “Many, if not 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 to thrive and continue to naturally reproduce in that stream. Eggs are typically taken streamside in late October and early November from wild South Pine Creek brook trout, fertilized and taken back to the Manchester Fish Hatchery to be raised and stocked as 2-inch fingerlings in June. 

“With low water levels in most trout streams, we gave the South Pine Creek brook trout a break this fall,” said Steuck. Milt was collected from a self-sustaining population established by stocking fingerlings hatched from eggs collected from South Pine Creek.

“We focused on improving our hatchery techniques with hatchery-raised South Pine Creek female brook trout and wild South Pine Creek brook trout males to expand the numbers of fingerlings available,” explains Steuck.

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 quick sedative bath to calm them, each big trout is held over a plastic bowl, as one of the workers rolls a hand down her belly to force out a stream of orange-golden eggs—up to 4,000 to 6,000 per fish. The milk-white sperm from two males is mixed in. Water is added to activate the eggs and sperm allowing fertilization to occur. The ingredients are gently stirred with a turkey feather to avoid bruising the eggs.

The fertilized eggs are poured into an incubator tray and slid into their place below a stream of 50 to 52-degree water until they hatch. Tiny sac-fry hatch about 30 days after fertilization. Dark clouds of tiny fish grow in raceways at the hatchery. The fish are hand-fed for the first month, then “trained” to eat from automatic feeders.

As the trout develop and grow, they are monitored and transferred to larger tanks, then raceways.  The fingerlings will be kept at Manchester or transferred to Iowa’s two other stations, near Elkader and Decorah, to be raised for future stocking. In 13 to 15 months, they will be a half-pound and ready to be stocked.  Nearly 50 put-and-take streams throughout nine northeast Iowa counties are stocked from April through October and almost 20 community trout fishing locations are stocked through the cold weather months.

“We stock about 370,000 catchable rainbow trout from the hatcheries,” said Steuck. “We also stock about 60,000 brook and rainbow trout fingerlings each year to grow in the streams.”

There’s natural spawning, mostly brown trout and some brook trout, in more than 80 northeast Iowa streams thanks to improved habitat and trout genetics, and an extended period of above average annual rainfall prior to the drought these past two years. Many trout caught, though, are spawned under the eyes of hatchery workers at Manchester. These coldwater fish are great fighters and beautiful in their spawning colors this time of year.

Find more information about Iowa trout streams and tips for trout fishing on the DNR website at www.iowadnr.gov/trout.

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