RACINE (WITI) -- Scores of dead fish were found this weekend and early this week in the Root River in Racine. The fish are mostly salmon, and a lot of them surfaced near a DNR processing station -- and now, officials are trying to determine what killed them.
Salmon are not native to the Great Lakes. They were introduced about 60 years ago to eat smaller, invasive fish. The DNR collects their eggs every Fall, and salmon naturally die once they've spawned.
Richard Oukrust went fishing on Monday, but didn't see any fish headed upstream. He walked over to the DNR's release point, and found dozens of dead fish.
"I've seen dead fish along the river and everything but nothing, nothing like this," Oukrust said.
After 17 years of fishing the river, Oukrust isn't surprised the fish died, but says he can't understand why they barely made it up the river.
"I understand these fish are on a mission to die, I do understand that -- but they should be dead upstream, not here," Oukrust said.
The DNR says water levels help determine how long the fish can survive.
"We haven't had a lot of rain this fall except for last weekend, so when we did release these fish, they encountered relatively low water and because they're at the end of their lifecycle, they ended up dying right near the facility," Brad Eggold with the DNR said.
Oukrust wonders whether CO2 is also to blame. The DNR gases some of the water inside the facility -- relaxing the fish and making it easier to collect eggs. Officials say that's not a factor in this incident.
"We do have another tub in the facility that we actually put oxygen back into. We wait for them to recover in this setting before we put them upstream so they're fully recovered when we put them upstream," Eggold said.
The DNR says ultimately, a combination of biology and bad timing are responsible for the scene in Racine.
The DNR says another factor is the size of this year's Chinook salmon. Eggold says they're the biggest he's seen in about 10 years. Of course, the bigger the fish, the more they're affected by low water levels.