AUBURN – An algae problem in Lake Auburn has resulted in a salmon bonanza for fishermen this spring. In the past few weeks at the 2,200-acre lake, fishermen have hooked some fat landlocked salmon, the cousin to the famed Atlantic salmon.

“I was working last weekend and checked a number of anglers who had fish over 5 pounds and two over 6 pounds. There are some very large salmon being taken,” Game Warden Troy Thibodeau said.

Thibodeau said two weeks ago he walked up on one angler as he landed a whopper off Lake Shore Drive.

“It looked like he hooked a log. But there was a huge splash,” Thibodeau said. “He was pretty excited. He gets the rod going and then puts it down and gets this fish hauled in. That fish was at least 7 pounds.”

State regional fisheries biologist Francis Brautigam called the great salmon fishing a silver lining in the algae problem at Lake Auburn, which services the water district for Lewiston and Auburn.

Last summer an algal bloom depleted the oxygen in the deeper parts of the lake. The result was a large kill-off of the togue in the lake.

Lake trout depend on cold, well-oxygenated water, and without it suffer and die. However, salmon can tolerate warmer water with less oxygen. And a byproduct of the unexpected algae growth was a boon in the salmon fishing.

The algae led to a growth in the smelt population, and that population got a further boost by the loss of the togue, a major predator. As a result, the salmon benefited from the spike in the smelt population and grew fat.

This spring that’s drawn fishermen.

Robie Davis came from Bowdoin to fish for salmon on Wednesday but came up empty.

“Usually I fish Moosehead for salmon but thought I’d try here,” Davis said as he drifted around the deeper holes in the lake, which drop as deep as 118 feet.

Gard Scanlon fished the lake Wednesday as well but was tight-lipped about how he did.

“I have no complaints. It’s about the same as it always is. I’m catching fish,” said the Lewiston angler.

Meanwhile, the Auburn Water and Sewerage Districts has been monitoring the problem.

Biologists have tried to figure out the cause and gauge whether an algicide will be necessary to prevent it in the lake, which is part of a 10,000-acre watershed.

Algae thrives on phosphorus in the water column and for reasons that are not clear, there was a spike in phosphorus last June and again in September, according to the water district.

Why it occurred is still being analyzed. But if enough phosphorus in the deeper sediments is released under low oxygen conditions, it can fuel blooms toward the top of the water column.

“It’s an unusual event. (The oxygen levels) appear back to normal healthy levels. One of the key things we look for, one of the key nutrients is phosphorus. We are optimistic the lake is recovering,” said John Storer, superintendent of the water district.

Storer said the algae growth may have been caused by a series of perfect events that also may never be replicated.

“There is no smoking gun. It seems to be a perfect storm of events: a very, very warm 2011; a warmer spring in 2012; and a very early ice-out so the algae got a year of early production. Then in June there was massive flooding. We gained a foot of water on our lake. A lot of nutrients could have washed in during one storm. It was a very biologically productive time for algae,” Storer said.

Already the water district has spent more than $400,000 on the problem, including $150,000 toward monitoring that will be done this summer. On Wednesday, water district workers were spreading buoys anchored at five depths around the lake. Those will be monitored weekly to gauge the water clarity.

The water district also may consider an application of algicide to Lake Auburn if necessary.

A permit to apply an algicide is currently open for public comment until May 22.

“Nobody wants to do the emergency measure if it’s not necessary, but if the same kind of algae appears and causes the fish kill, it would be prudent for the ecosystem,” Storer said.

However, two weeks ago water district biologist Mary Jane Dillingham reported that the test for dissolved phosphorus indicated the lake has oxygen throughout the water column, a good sign.

By monitoring and working to prevent the growth of algae, water district officials hope to keep the drinking water clean and avoid the need for an algicide. And a lack of algal bloom will mean the togue stocked this spring will have a chance to grow, even if that also means an end to the fatter salmon in the lake.

The luck fishermen are having now is only a happy byproduct of the larger problem, Brautigam said.

Deirdre Fleming can be contacted at 791-6452 or at:

dfleming@pressherald.com

Twitter: Flemingpph