Fertilizing salmon eggs
Keeping salmon on the run
Collecting and hatching eggs steers salmon on course in an unending drive to survive.
David L. Sperling
The instinct to return home is a powerful, driving force. Salmon and trout imprint on their home streams, endure life in the ocean or the inland seas of the Great Lakes for years, then return in one of nature’s great upstream adventures. Mature fish give their all working their way back up tributary streams after years of traveling great distances, hunting for food, fending off predators, and surviving disease, environmental challenges, weather and manmade impediments. On the journey home, they stop eating and rely on fat reserves, great strength and willpower. When they arrive to spawn they are spent and die soon thereafter.
In the Great Lakes system, some of these fish complete their life cycle naturally. More than half of the Chinook salmon found in Lake Michigan breed successfully in well-aerated waters. On the Michigan side of the lake in the Lower Peninsula, glaciers left lighter, sandier soils and reliable groundwater flow that feeds the rivers and streams with a steady, stable supply of cool water. The Chinook spawn in fall and their fry grow into smolt and return to the Great Lakes the next spring.
It's a bit different on the Wisconsin shores. In the Badger State many of the small tributary streams peak and flash. They rely more heavily on spring rains and snowmelt for water flow. Tributaries that are fed more by runoff carry sediment that can smother eggs. Other salmonids, like coho and trout, hatch out and grow very slowly. They reside in the tributary waters for a year or more before flowing downstream. On the Wisconsin tributaries, few of these fertilized eggs live long enough to become fry and fingerlings. They often succumb to the summer heat or are preyed upon as these shallow streams warm up.
Fish biologists have learned how to increase the odds of survival. For instance, each fall Chinook salmon return to spawning grounds on Strawberry Creek at the southwest shore of the Sturgeon Bay Ship Canal after spending two to four years swimming the open waters of Lake Michigan and Green Bay. In some years, natural water flow in the creek is too low and slow to allow fish to swim upstream. During the spawning run, a pump system draws water from the canal and sends it bubbling through a quarter-mile pipe to maintain adequate depth and flow in the creek. Returning salmon work their way upstream to a collection pond. Here, DNR fisheries crews set up in late September and early October to gather fish, strip eggs from ripe females and milt from mature male salmon. They take the fertilized eggs to state hatcheries where they will be raised under controlled conditions until spring. By then the three- to four-inch fingerlings are stocked to jump start the next year-class of Great Lakes king salmon.
Egg and milt collection is hard, physical work. On a typical harvest day at Strawberry Creek up to a thousand muscular fish weighing up to 20 pounds apiece and averaging 34 inches long are handled by DNR staff and volunteers. Once the eggs and milt are removed, flesh from the fish smaller than 36 inches that contains fewer environmental contaminants is iced down and sent to food pantries in northeastern Wisconsin. For one of the pantries, experienced anglers volunteer to fillet and vacuum pack the fillets. Larger fish are sent to fertilizer plants and surplus eggs are sold to a bait contractor. In 2008, more than 20 tons of edible salmon harvested at Strawberry Creek and the DNR's Besadny facility at Kewaunee were distributed to food pantries. Over 10 tons of fish were processed into fertilizer and two tons of surplus eggs or eggs that were not suitable for hatchery use were processed by a bait company.
In past years, school groups and families visited DNR's three fish spawning/egg-taking facilities by appointment in season. Visits are still possible, but unfortunately, guided tours are a casualty of budgetary cutbacks. Chinook salmon will still be collected at Strawberry Creek from late September through mid-October. Steelhead (rainbow trout), coho and Chinook salmon will be collected at the Root River Steelhead Facility in Racine County from March through April and September through October. The C.D. Besadny Anadromous Fish Facility in Kewaunee is still open for public visits from March through December. It includes a big window to watch steelhead, brown trout, coho salmon and Chinook salmon moving upstream. The best viewing is during annual migrations in late September through early October and again in March through April. Interpretive displays at the facilities also tell the story of these annual migrations and visitors are welcome.
Find driving directions and more details about the facilities at Fish Spawning (Egg-Taking) Facilities. Join the swim and get caught up watching fish on the move.
David L. Sperling edits Wisconsin Natural Resources magazine.