City lake suffers natural fish kill

Thousands of fish, most of them gizzard shad and small crappie, washed up on the banks of Dexter's City Lake over the weekend, the result of what the Missouri Department of Conservation and Dexter Parks Director Lawson Metcalf say was a "natural event," primarily due to the recent extreme heat.

"This is a natural event that occurs when the pond is deprived of oxygen," Reed explains. "It's not that unusual. It occurs in a lot of farm ponds that aren't in the public's eye, and many are never noticed."

It is unusual for Dexter's City Lake, however. Lawson says the kill is the first one of its kind since the pond was renovated 15 years ago, and perhaps in the pond's history. The five-acre pond, referred to as the Dexter City Lake, is about 11 feet deep at its deepest point near the fishing dock, but only about five feet deep in the center.

the scope of the damage can be seen on the northeast bank of the pond. Extreme heat, algae bloom, and the shallowness of the pond all apparently contributed to a lack of oxygen for the pond's inhabitants Saturday. More photos appear in Photo Galleries at www.dailystatesman.com

Reed and Lawson went to the local pond after a local resident fishing there Sunday morning witnessed several fish surfacing.

A natural fish kill occurs when a number of factors are in its favor, and for the local pond, all circumstances were in the kill's favor Saturday.

"We were set up to fail with conditions being what they've been," Metcalf confirmed Monday. "We had the extreme temperatures and the pond is shallow, plus we have an algae bloom which also contributes to this happening."

The algae, Metcalf explains, puts off a toxin when it blooms.

"Even though the water is a couple of feet deeper this year than last year due to the placement of rip-rap to solve the muskrat problem, the heat, the pond levels, and the algae bloom combined to make this happen. All of those factors caused the dissolved oxygen in the water to become depleted."

And when fish lack oxygen, fish die. When they die, they lie at the bottom of the lake for about 10-12 hours before surfacing. So, the kill is believed to have occurred Saturday night sometime.

Another factor working against the local pond was the population of shad and crappie there. Neither species were introduced to the city pond when it was originally stocked because neither is beneficial to a pond the size of the city's.

"We believe some anglers probably threw some in thinking it would be beneficial," Metcalf says, "but you can see by the numbers on the bank how they've multiplied and they're using much of the pond's oxygen. Those fish are massively over-populated. The lake is too small for those numbers. That, I believe, also contributed to the fish kill."

"With the hot temperatures, the lake is not going to retain oxygen like it does when it's cooler," Reed further explains, saying that typically a fish kill will only affect a portion of a pond or lake, and that's the assumption regarding the local weekend kill. There is no clear way to determine if that is what occurred, however.

Oxygen levels were tested in the lake Monday morning and were determined to be at 2.8. The desirable level is between six or seven in the summer months, Reed says.

The first step in restoring needed oxygen to the pond and its remaining fish was to begin aeration. Fire Chief Don Seymore directed a tanker to the east bank of the pond early Monday and immediately began pulling water out through a pipe on the bank and recirculating it back into the pond. Pumping 1,200 gallons per minute, the water gains oxygen in the process, and as it's sprayed back into the pond, it furthers the oxygen supply there.

Also utilized was a well on the east bank. Water was pumped from the well throughout the day Mon-day in a further effort to supply oxygen to the lake.

"The well water actually doesn't contain oxygen," Metcalf says. "But it gains oxygen as it's pumped through the air and enters the pond."

Catfish could be seen coming to the surface Monday morning where the cooler well water and oxygen were entering the pond.

"Anytime you can break up your spray of water and expose it to the air, you can pick up a little oxygen and carry it into the water," Reed says.

It is yet to be determined just how much damage occurred to the lake over the weekend. Signs were posted Monday that restrict any fishing activity there until further notice. An MDC biologist, Mike Reed, (Mark Reed's brother), is in the process of making several determinations regarding the city's lake. Those will be made public as soon as they are released. Mike Reed will also be visiting the pond to get out on the water and determine the extent of loss.

Authorities believe most of the fish affected by the lack of oxygen have already died. Reed says typically within a few days following the natural kill, the fish stop coming to the surface. Monday afternoon, there was no shortage of fish to be cleaned up at the lake. Literally thousands of them were packed against the northeast bank of the pond and several near a jetty further west on the north edge. Several more continued to float toward the bank.

Three recent DHS grads working for the Park District this summer spent their afternoon Monday donned in waders, scooping the dead fish with wire baskets and placing them in a backhoe bucket to be loaded on a truck and transferred to a grave on the pond's south edge.

With temperatures threatening to reach the 100 mark once again, it was a task none of the three will soon forget.

"I don't ever want to eat another piece of fish in my life," said Ryan Windham, who for several hours shoveled the dead fish toward Joe Lovins and Dylan Acevedo to dump into the backhoe bucket for burial.

"It's not pretty, but it's not catastrophic," Reed said as he witnessed the clean-up from the bank. "There's a lot to be determined down the road."

Several good-sized channel cats, bass, and some large crappie were among the dead fish, but by Lawson's calculations, about 75 percent of the dead fish are shad.

"One thing about a fish kill," Reed laughs, "is that you can say, 'See, I told you there were fish in that lake.'"