The Michigan Department of Natural Resources is seeking tips from the public in finding out who is behind the vandalism at Platte River State Fish Hatchery in Beulah, about 25 miles southwest of Traverse City. Coho are released in the Platte River near the hatchery, and stocking sustains the fish population.
"This is the first time in 45 years where we have had this type of incident at this facility," said DNR Fish Production Manager Gary Whelan. "It could have put our entire coho salmon program in serious jeopardy. ... We were exceptionally fortunate to have an above average coho salmon spawning run this year."
The DNR said hatchery staff arrived at work Oct. 5 to find the fish dead.
An investigation found that the previous night the fish were apparently crowded into a small area. That blocked water flow and created conditions in which dissolved oxygen levels became lethal for the fish, the DNR said.
Salmon carcasses were salvaged for use in the fishmeal industry, the DNR said.