It’s too early to make an accurate count but it’s estimated more than 100,000 fry have safely hatched and started feeding at the Manitou Rapids sturgeon hatchery.
“It’s hard to tell because we haven’t inventoried them yet,” aquaculture technician Joe Hunter said Monday, adding they had to wait until the fry are an inch long before it’s safe to handle them.
Then they’ll be able to get a more accurate number and use it as their benchmark or starting point, he remarked.
Hunter, who said the last batch of eggs hatched about two weeks ago, admitted initial losses seemed higher than normal since the fry were all clumped together in the hatching troughs.
“Now, it looks like a lot of fish,” he said, noting the young sturgeon have spread out a bit as they prepare to begin feeding.
“The real labour intensive part starts with feeding them the brine shrimp,” Hunter said, which began yesterday and will continue for three-five days before the fry can be switched over to artificial feed.
They faced extra complications during the egg harvest this year due to the extremely low river level. Although the hatchery’s main water supply is now pulled from a groundwater well, river water is still used for the spawning and hatching process.
“We had to put a secondary pump out there because the water level was too low for our main submersible pump,” Hunter said.
“We were getting some pretty muddy water,” noted Lorraine Cupp, a fellow aquaculture technician at the hatchery.
Another problem was the water temperature. Sturgeon eggs normally are incubated at 10-15 C (50-59 F) but on the last day of incubation in the hatchery, Hunter said the river water was up at 16 (61).
Hunter believed the higher water temperature was responsible for a lot of the yoke sacks on the eggs to swell up, causing some to hatch prematurely.
“We had a lot of premature ones,” he said. “There were high initial losses.”
And both Cupp and Hunter are still concerned the fry that did survive might have gone through the hatching process too fast.
“Our batch in Minneapolis at a recirculation facility had the same thing [with fast hatching],” Hunter said, noting mortality rates jumped enormously as the fish grew bigger than an inch.
“Something wasn’t developed right, something they needed at a later stage,” he remarked. “We’re kind of hoping we won’t have any problems.”
“But it’s a possibility,” Cupp warned.
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