CHATSWORTH, MURRAY COUNTY, GA (WRCB) - The Georgia Department of Natural Resources is investigating why several thousand fish have died in one Murray County lake.

Georgia DNR biologists say they've been getting complaints since Saturday from boaters, fishers and swimmers on Carter's Lake.

It doesn't take long to spot fish belly up on Carter's lake. Silver sprinkles cover the blue water from end to end.

"Dead fish just floating, I just wondered what was causing it," boater Jana Manous said.

"I noticed that a lot of shad were dead," fisherman Carl Melear added.

It's the first time frequent Carter's Lake fisherman Carl Melear says he's ever seen this many dead fish.

"I don't know what might be causing a kill like that," Melear said.

With lingering questions, intense heat and several hours with no catch, he decided to pack up early.

A few days into their investigation, DNR officials say they're leaning toward it being natural causes instead of toxins in the water. That's because all the dead fish seem to be the same species.

"If it was a toxin in the water or low oxygen in the water, it would be killing all different types of species," said Jim Hakala, Georgia Dept. Of Natural Resources Fisheries Biologist.

State biologists came out to the lake this weekend to look into the reports and after seeing it for themselves, say nearly all of the dead fish are eight to ten inch gizzard shad.

"On the dead fish, there were no sores or anything like that so it's looking at this point, natural in origin," Hakala said.

They say this type is prone to die off, just not this many at one time. They say it could mean a variety of things-- possibly an increase in spawning made the species sick.

Channel 3 talked to a family over the phone who's among those that alerted the DNR to the situation this weekend. They rely on the fish they catch there for a lot of their meals so they say they're keeping them in the freezer as a precaution until the DNR rules a definite cause.

The DNR is going back out on Carter's Lake to continue the investigation later this week. They say the gizzard shad population will rebound quickly because of their high reproductive rate.