Hundreds of yellow ovals offset the brown and green coloration of each female brown trout ready to spawn at the Manchester Fish Hatchery. The splashes of color are signs that trout spawning season is in full swing.
Brook trout, Iowa’s only native trout, gave up their eggs in October. The Manchester Fish Hatchery maintains a domesticated strain of brook trout and has enough fingerlings to stock streams next spring through fall.
Brown trout are currently being spawned. Brood trout are brought to the hatchery from French Creek in Allamakee County. They are held at the hatchery across two spawning cycles then released back in French Creek, supplementing earlier generations of brown trout.
All brown trout are stocked as 2-inch fingerlings. “Anglers like these ‘wild’ stream raised fish. They are harder to catch than our put-and-take stocked fish,” explains Mike Steuck, Iowa DNR fisheries supervisor for interior streams. “Many of the public streams have lots of brown trout in them.”
Rainbow trout, the backbone of Iowa’s trout program, take up much of December and January. Roughly 750,000 eggs will be collected this season.
Crews check for ripe female brood stock once a week. After a quick sedative bath to quiet them, each big trout is held firmly 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. Mixed in quickly is the milk-white sperm from two males. 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 “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 12 to 14 months, they will be a half-pound and ready to be stocked. Nearly 50 put-and-take streams throughout nine northeast Iowa counties and almost 20 community locations are stocked through the cold weather months.
“We stock about 380,000 catchable rainbow and brook trout from the hatcheries,” said Steuck. “We also stock about 200,000 brown 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 75 northeast Iowa streams thanks to improved habitat and trout genetics, and an extended period of above average annual rainfall. Most 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.