St. Paul, Minn. (WCCO) - The spring weather brought with it something pretty unsightly near St. Paul. Hundreds of fish recently died in Beaver Lake, and many of them ended up all along the shoreline.

Fish kills are not unusual this time of year, but this one has Ramsey County officials worried. The fish died even though there is an aeration system in Beaver Lake.

Ruth Klabunde walks her dogs around the lake about three times a week. The first thing she noticed was the smell.

"This is a really fun little lake to walk around," Klabunde said. "And the stench was kind of bad."

And then Klabunde says she saw the source.

"This whole little bay area here was thick with dead fish," she said.

When the ice finally went out on Beaver Lake a week and a half ago, it left behind schools upon schools of dead fish.

It's estimated that more than 7,000 pounds of dead fish - mostly catfish, sunfish and bass - have been taken out of Beaver Lake. But what caused this unusually large fish kill is still a mystery.

Beaver Lake has an aeration pump that can be turned on when oxygen levels get low. Ramsey County turned the pump on in February, but it only reaches a small part of the lake.

Terry Noonan is a water resources manager for Ramsey County public works. He said the DNR stocks the lake with fish. But instead of reeling in panfish, they had to hire someone to pull them out by the truckload.

"For whatever reason this year the aeration system did not perform as we'd hoped," Noonan said.

He thinks the cold spring and too many fish seeking oxygen caused Beaver Lake to go belly up.

"It could be that just so many fish accumulated in that relatively small area, that that's a stresser in and of itself," said Noonan.

The extent of the fish kill won't be known until the DNR can get out and do some sampling. There are still fish in the lake, but Noonan said there is little doubt that this could temporarily hurt recreational fishing.

It's possible the DNR may have to restock the lake if fish numbers get too low.

Beaver Lake has an aeration pump that can be turned on when oxygen levels get low. Ramsey County turned the pump on in February, but it only reaches a small part of the lake.

Terry Noonan is a water resources manager for Ramsey County public works. He said the DNR stocks the lake with fish. But instead of reeling in panfish, they had to hire someone to pull them out by the truckload.

"For whatever reason this year the aeration system did not perform as we'd hoped," Noonan said.

He thinks the cold spring and too many fish seeking oxygen caused Beaver Lake to go belly up.

"It could be that just so many fish accumulated in that relatively small area, that that's a stresser in and of itself," said Noonan.

The extent of the fish kill won't be known until the DNR can get out and do some sampling. There are still fish in the lake, but Noonan said there is little doubt that this could temporarily hurt recreational fishing.

It's possible the DNR may have to restock the lake if fish numbers get too low.