Regional fish biologist John Cassinelli says it was an ordinary day last fall when a Fish and Game crew was surveying the river near the Warm Springs Golf Course. They were looking for baby rainbow trouts, called fry.
“We noticed some shrimp in our nets as we were attempting to capture the fry,” says Cassinelli.
After some investigation, they figured out they were Mississippi “grass” or “ghost” shrimp, which Cassinelli says is a common aquarium species and food species that can be found and purchased in pet store around the Treasure Valley.
More were found in the same area this spring, which means they were able to survive the winter.
“Someone released them into the river live, and they’ve been able to survive and there’s at least a small population of them in that part of the river."
One of the female shrimp had eggs that were ready to hatch. So Cassinelli says they’re able to reproduce.
He says the species is native to the Mississippi River drainage and the only other place on the West Coast where they’ve been introduced and are surviving is the Sacramento River Delta in California.
“This was only the second identification of them in the wild west of the Rockies,” says the biologist.
He says they likely will be popular with the trout population which might snack on them because they’re small, less than an inch in size. That may help keep them from spreading too much.
“Because we have a lot of large predatory trout in the river, it’s hard to imagine them taking over the Boise River," says Cassinelli. “My guess is they will exist in some small numbers and probably be there for some time but probably won’t become a problem. But it’s hard to say until we get a better idea how widely distributed they are.”
That information may come next fall when Fish and Game conducts another survey of the river after the water drops down again. In the meantime, Cassinelli strongly encourages folks not to dump shrimp or fish into the river.
“We don’t want these exotic species in any of our rivers and it’s a common problem. You’ll find all kinds of weird, introduced species that come from people just dumping a lot of aquarium fish, so we discourage people from doing that.”
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