Decline in Lake Arthur muskellunge fishing has anglers, state trolling for answers
Sunday, October 09, 2011
By John Hayes, Pittsburgh Post-Gazette
Pennsylvania Fish and Boat Commission
Fisheries biologist aide Matt Gordon holds a 50-inch muskie during a 2011 survey of Lake Arthur.
PORTERSVILLE -- The waters of Lake Arthur were calm Monday evening. But in a meeting room at Mount Zion Baptist Church, on the shoreline of Shannon Run Bay, a maelstrom of controversy swirled as anglers, the state Fish and Boat Commission and Moraine State Park management clashed over what's happening beneath the surface.
The 3,225-acre Lake Arthur impoundment has long been considered one of Pennsylvania's premiere muskie lakes, stocked yearly by the state with 3,300 young muskies averaging 6 inches. Survival rates are low, but good forage, a stable weed mass for cover and catch-and-release practices resulted in higher than normal catch rates for what has been called the "fish of 10,000 casts."
But in recent years, anglers have noticed a decline in catches. In a routine survey this summer, Fish and Boat biologists found lots of muskies at Lake Arthur, particularly big ones, but were startled to log a total absence of entire year classes of muskies, those from 26 to 32 inches.
No doubt something is changing at Lake Arthur. The mystery grows as anglers and the agencies that maintain the lake spar over what's to blame for the missing muskies.
At last week's meeting, members of the Moraine Muskie Association presented enterprising informal research they believe shows the impacts of aquatic herbicides used to control weed growth at the lake. Tim Wilson, the Fish and Boat biologist who manages the Lake Arthur fishery, shared research that confirmed some of the anglers' concerns but challenged their conclusions. Following the meeting, park manager Dan Bickel defended the use of herbicides to control the plants, and inferred possible linkage to Moraine's ongoing problems with municipal sewage processed by the park.
Herbicides
"We've noticed a sharp decline in muskie numbers in Lake Arthur. Probably four years ago it started," said Fombell muskie guide and Moraine Muskie member Howard Wagner. "We wanted to see the effects of herbicide use on places we knew had good weed beds, so we went from bay to bay. Portersville Bay, Bear Run, Osprey, under the Route 528 bridge, the five fingers including Muddy Creek Bay -- wherever we went, we found no weeds or poor weed growth."
The group's main concern is the park's use of two aquatic herbicides (trade names Reward and Navigate) to clear the water for boaters. Group members presented photos of de-weeded areas and charts comparing muskie stocking rates and harvest reports. Some feared muskies were directly poisoned by herbicides; others were convinced the weed-control policy destroys habitat for forage fish.
Since Moraine State Park opened in 1971, the state Department of Conservation and Natural Resources has used Reward and Navigate to clear weeds from the swimming beach, 10 boat launches, marinas and other areas.
"We have to manage for multiple uses -- fishing, swimming, pontoon boats, sail boats, canoes and kayaks, hydrofoils," said Bickel. "We had a lot of complaints from the marina this year from people having trouble getting out of their slip spaces due to aquatic weed growth. . . . When we use it, we use the minimum amount of herbicide that we possibly can."
Since 1971, DCNR has treated as many as 43 acres of Lake Arthur per year, at 1 gallon per acre, depending upon need. In 2004, a year with a high muskie population, no herbicides were used. But in another peak year, 2007, 39 acres were treated. In 2010, DCNR used herbicides on about 12 acres. This year control agents were used on nearly 23 acres of the lake.
The herbicides used at Lake Arthur are common. Neither directly kills the plants -- they cling to plant surfaces and disrupt growth. Both are approved by the U.S. Environmental Protection Agency and used by some 40 states, other governmental bodies and private landowners. Both are used by DCNR throughout Pennsylvania. Fish and Boat does not use the herbicides in the wild, but employs far higher doses at its hatcheries.
Sewage
Like many parks in Pennsylvania's state park system, Moraine's sewage processing system takes in pre-processed sewage from a nearby municipality. At Moraine, outflow from Prospect Borough is processed in the park's system and released below the dam into Muddy Creek.
Bickel said cement-encased sewage pipes cross the lake bottom at two places before entering the park's processing system, which is inspected monthly by park staff. But long-standing problems with the municipality's incoming sewage remain unresolved.
"Faulty equipment in Prospect's system before it comes to us -- yes, that's an ongoing problem," said Bickel.
Prospect Borough sewage officials did not immediately return calls from the Post-Gazette.
It's unclear, however, how potential sewage releases might relate to Lake Arthur's muskie problem. PFBC biologist Wilson said if biological matter was leaching into the lake, it would be a problem for all fish, yet only the muskies are experiencing sharp losses of entire year classes. Biological waste would likely decrease water clarity, he said, which would in turn impact aquatic vegetation.
Habitat
For many years, Lake Arthur's forage fish, game fish and angling success rates were directly linked to the aquatic plant milfoil. An invasive species that choked out native growth, milfoil nevertheless provided perfect cover for little fish. Big fish lurked under and at the edges of weed beds waiting for a snack, giving anglers an easy casting or trolling target.
Since about 2007, when muskie catch rates began to decline, a new invasive plant species has quickly spread through Lake Arthur. Hydrilla, sometimes called Esthwaite waterweed, entwines in thick beds on the bottom, crowding out the less dense milfoil.
"It's too thick. The little fish can't use it to hide, and the big fish don't use it as a point of ambush," said Wilson. "Like other game fish, muskies are cannibalistic. Baby muskies need weeds to survive and without the good milfoil, they're more susceptible to predation from big muskies."
In fact, Wilson said the 2004 and 2007 spikes in muskie population that anglers sorely miss could be responsible for the current absence of later year classes. He cited a Wisconsin study showing that in lakes with unusually large numbers of big muskies, little muskies were eaten at such levels as to cause the collapse of the entire muskie population.
Wilson theorizes that the loss of some weed beds to herbicide is small potatoes compared to the sea change that rocked Lake Arthur with the arrival of hydrilla and subsequent demise of milfoil. The resulting muskie cannibalism, he speculated, may have caused the population changes experienced by anglers and detected in PFBC surveys.
Wilson said he will recommend doubling the number of young muskies planted in the next state stocking, but it may take a while to get the muskies back on track.
"Even with the hole in the population, it's still a pretty good muskie fishery now," he said. "The population is about the same as it was before those two really good years. The guys who adapt to the new conditions and change their gear and tactics will eventually come upon a formula that works."
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