- Associated Press - Monday, October 24, 2016

SPEARFISH, S.D. (AP) - The Belle Fourche Reservoir dodged a major environmental bullet in September when a barge that was to be used to dredge parts of the reservoir was discovered to be covered with zebra mussels.

That barge was inspected and sent for sanitation before it entered the water.

Zebra mussels are on the state’s least wanted list of aquatic invasive species as they can harm aquatic ecosystems and wreak havoc on pipes connected to the watershed.

Layer upon layer of mussels can line and clog pipes. That could be irrigation pipes, the plumbing of a dam, or a boat motor, clogging the cooling system and overheating the motor, said Mike Smith, aquatic invasive species coordinator for the South Dakota Game, Fish, and Parks.

As for damaging the ecosystem, Smith said each adult mussel can filter about a liter of water every day, siphoning out plankton and algae from the water.

“Plankton is the basis of the aquatic food web,” Smith said. “Pretty much everything starts with plankton.”

Small baitfish feed upon the plankton. They in turn are fed upon by larger game fish. And with mussel densities of a couple hundred thousand per square meter, the amount of water filtered can be staggering, the Black Hills Pioneer (https://bit.ly/2en9piw ) reported.

Worst case scenario, he said, without plankton feeding the ecosystem, the fishery could die out.

“It’s always tough to pinpoint one exact cause in the collapse of a fishery, but it can definitely have that effect,” he said.

The increase of the mussels in the state has been rapid. They were first discovered in the Great Lakes in the 1980s and have spread across the country.

“We had our first evidence of a zebra mussel in South Dakota in 2014 in the form of a single mussel at Lewis and Clark State Park. The following year, we noticed we had quite a few more mussels,” Smith said.

“This year we had a confirmed zebra mussel presence in McCook Lake in Union County, and the population at Lewis and Clark has expanded exponentially,” he continued.

In 2015, about 30 percent of the boats in the Lewis and Clark Reservoir marina had mussels on them. This year, mussels are on 85 percent of the boats, most with dozens or even hundreds of mussels on them.

“It is rapidly, rapidly expanding its population even beyond what we expected this year,” Smith said of the zebra mussel population.

Once the mussels and their cousins, the quagga mussel, are established in a body of water, little can be done to get rid of them.

“They reproduce so quickly, even more so than Asian carp,” Smith said. “Each female zebra mussel can release a million eggs per spawn, and they also spawn multiple times per year.”

Spawning times range pretty much any time the water is above 50 degrees and below 90 degrees, Smith said.

And even though there is a very high mortality rate, up to 95 percent of eggs, around 50,000 would remain.

Smith said that a chemical has been developed to kill zebra and quagga mussels in open bodies of water. However, to treat a lake the size similar to the Lewis and Clark Reservoir, chemical costs would range between $20 billion and $40 billion.

To put that in context, the state of South Dakota’s budget for 2016 was $4.8 billion.

“There is nothing we can do that is cost effective to take these out,” Smith said.

Asian carp also on least wanted list

Asian carp consists of four species, the silver and bighead carp are in South Dakota. Each female can produce more than 300,000 eggs per spawn, and they spawn multiple times each year, according to the GF&P.;

They are currently in all major tributaries of the Missouri River in the state.

“They rapidly reproduce and can pretty much get into pretty much any amount of water,” Smith said. “The juvenile get into really shallow areas, and that is where they stay until they mature into bigger-sized fish. They can grow really quickly, too. After that first year of growth, they are too big for our predator fish.”

Although the fish carry the name carp, they are not a bottom feeder.

“They actually eat plankton, which is what our juvenile game fish and forage fish eat,” Smith said. “When you have these big population growth, they can really consume a lot of plankton. There is very little food left over for those other species.”

Like the mussels, once the carp are established, there is little that can be done to stop the spread.

Smith said there are reports of Asian carp being in South Dakota dating back to the early 1990s and possibly as far back as the late 80s.

“We really didn’t see this huge expansion until 2010,” he said. “That coincided with a couple years of really high runoff. That’s one of the keys for them to have a really successful spawn; a high spring runoff. A lot of water will come down and flood areas and make backwater areas, which is perfect habitat for juveniles to live.”

In 2012, the state restricted fishermen from gathering minnows from most of the counties in Eastern South Dakota. That is because the Asian carp minnows look very similar to gizzard shad, a common baitfish. Transporting live carp to other bodies of water could lead to the expansion of the prolific fish.

Currently, the spread of Asian carp has stopped. Both silver and bighead carp can be found in the Missouri River below Gavins Point Dam, the James River, the Vermillion River, below the spillway, and the Big Sioux River downstream of Falls Park in Sioux Falls. On the James River, they made their way all the way to North Dakota, Smith said.

Smith said the GF&P; is not trying to stop the invasive species, since that is cost prohibitive. Rather, the department is trying to slow the spread. By following the regulations, you can help do this.

It is against the law to dump minnows into water. They should be placed into a fish grinder or thrown in the trash at the end of the day.

Boat plugs must be removed when not on the water.

“So many of these species are transported in water, and you don’t even know that they are in there. They are microscopic,” Smith said. “Just following the regulations is going to go a very long ways in slowing the spread.”

“We operate under the old adage ‘an ounce of prevention is worth a pound of cure,’” Smith said. “If we spend the money and educate people up front on what these things are, how they spread, and how we can stop or slow the spread across the state, that is where our money is best spent.”

He said more invasive species are on the horizon. The snakehead fish is moving in from the south and the New Zealand mud snail, which affects trout streams, is “knocking on the door from the West.”


Information from: Black Hills Pioneer, https://www.bhpioneer.com

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