Breeding Superior fish
HARVEY – It’s the busy season at the Marquette State Fish Hatchery.
Captive broodstock egg takes began this week at the hatchery, located on Cherry Creek Road, with more planned in the upcoming weeks. Staff started gathering lake trout eggs that will be raised at the hatchery for eventual release into the wild.
Jim Aho, Michigan Department of Natural Resources fisheries biologist, said wild-strain lean lake trout were the focus of the egg take on Tuesday, with the parent fish taken from Lake Superior in 2001-2004. These fish, he said, are disease-resistant and contain better genetic material than other strains of lake trout.
The fish raised from stock will be added mainly to Lower Peninsula lakes such as Higgins, Crystal and Gull lakes and Lake Leelanau.
“Lake Superior is on its own with wild reproduction,” Aho said. “It doesn’t need artificial stocking.”
The parent fish, according to Aho, were kept in isolation at the hatchery for two years to lessen the chance of disease.
Raising fish can be a lengthy process because the lake trout must be 6 years old before they spawn.
Science plays a part, too. Hatchery personnel must cross lots from different years to prevent inbreeding, Aho explained. This time they were crossing 2003 stock with 2004 stock, and 2001 stock with 2003.
“Genetics are playing a big part in our operations now,” he said.
In the typical take process, technicians remove the eggs from the females. However, squeezing the eggs from the trout isn’t too stressful for them.
“They’ve been handled a bunch of times,” said Jan VanAmberg, hatchery manager. “We rarely ever lose one.”
Aho said each female produces between 3,000 and 5,000 eggs, witih 80 percent of them viable.
These eggs soon after are mixed with milt from the males. Aho said saltwater is added for sperm mobilization.
Then the miracle of science takes over.
“It’s basically instantaneous fertilization from there,” he said.
The eggs are left to sit in an antibiotic, and later put inside the hatchery for incubation. Aho said the eggs should hatch between Dec. 20-25 and be ready for transfer outside in June.
The fish will need to be in the hatchery between 14 and 16 months, Aho noted, before they can be released into the wild.
Aho said egg takes for brook trout are next on the list, with takes for splake – a lake trout-brook trout hybrid – mixed in.
During the one-year rearing cycle, hatchery personnel expect to raise 150,000 lake trout of the wild strain, plus 210,000 of the Seneca strain of lake trout for Lake Huron and southern Lake Michigan, Aho said. Also to be raised are 220,000 splake and 106,000 brook trout.
Not only is understanding genetics important when dealing with hatchery fish, knowledge of fish habitat comes into play as well. Trout, according to Aho, prefer rocky bottoms and streams.
“Michigan doesn’t have that environment,” he said.
So, the hatchery has to provide a little help.
Aho said, “If we didn’t stock brook trout into smaller lakes and lake trout into larger lakes, there would be no natural production.”
That would mean no trout fishery in inland waters, taking away a pastime enjoyed by many.
Christie Bleck can be reached at 906-228-2500, ext. 250.