SPIRIT LAKE, Iowa - The Iowa Department of Natural Resources (DNR) discovered 26, 3- to 5-inch gizzard shad, in East Okoboji Lake on August 11 as part of routine sampling.
"We don't know how gizzard shad got into the lake," said Mike Hawkins, fisheries biologist for the Iowa DNR at Spirit Lake. "It is possible that someone intentionally put them in the lake."
This is the first time gizzard shad have been found in the Iowa Great Lakes. Gizzard shad were not sampled in West Okoboji Lake or Spirit Lake.
"The Iowa Great Lakes are at the northern edge of this species' range," Hawkins said. They do not tolerate long winters and are usually found in southern Iowa lakes and streams. "Mild winters the past few years may have allowed them to survive further to the north."
Gizzard shad are known to disrupt fisheries and compete with native fish like bluegill and yellow perch. "We can't predict their impact in the Iowa Great Lakes at this point. Because we are at the northern edge of their range our winters should hold their numbers in check. Gizzard shad can reproduce in large numbers and our continued mild seasons could favor this species," said Hawkins.
It is very important to never transport and release any fish species into any public water body. Introducing species like yellow bass, common carp and gizzard shad can reduce native fish populations, decrease water quality, and limit fishing.
Iowa DNR fisheries teams will monitor the population in the coming years to determine changes and impacts. "There is no way to eliminate gizzard shad from a lake without completely renovating and restocking the lake," Hawkins said.
Iowa law makes it illegal to possess live gizzard shad. It is also illegal to stock fish in any public water of the state, including game fish. The public is asked to report any of this illegal activity to their local conservation officer or by calling the Turn-in-Poachers (TIP) hotline 1-800-532-2020. Callers can remain anonymous.
Media Contact: Mike Hawkins, Fisheries Biologist, Iowa Department of Natural Resources, 712-336-1840.