EDDINGTON – For nearly seven years salmon anglers on the Penobscot River waited for their river to be reopened to fishing.

On Saturday afternoon – less than two days after the 30-day experimental fishing season began – it was shut down temporarily after water temperatures in the river reached dangerously high levels.

Richard Dill, a Maine Atlantic Salmon Commission biologist, said he expected the river to remain closed to fishing until at least Tuesday, when cooler weather is forecast to arrive in the Bangor area.

Dill said ASC commissioner Dick Ruhlin of Brewer made the decision to close the river when water temperatures topped 20 degrees Celsius (68 F) on Saturday afternoon.

Warm water is a concern for salmon conservationists because fish caught in warmer water have lower survival rates than those caught in cool water. Anglers who checked the water temperature in the early Saturday fog said it ranged between 64 and 66 degrees.

The experimental season on the Penobscot, which lasts until Oct. 15, is entirely catch-and-release, and no fish can be legally removed from the water for any reason. ASC staffers crafted a precise set of regulations they hoped would prevent fish from dying during the season.

Dill made the rounds of the Bangor-area salmon clubs after the decision was made, replacing the green “fishing allowed” flags with red “no fishing” flags. Dill closed the Penobscot at the Eddington Salmon Club at about 4:30 p.m.

“We hate to do it, but we’ve got to err on the side of being conservative,” Dill said.

Dill said that even if the water temperature dropped a bit overnight, it would likely reach dangerous levels again early on Sunday, and rather than keep opening and closing the river, the ASC would wait until cooler weather arrived before allowing anglers back in the water.

A single angler was fishing the Penobscot just upriver from the Eddington club when Dill hung the red flag, and he scrambled out of the water as Dill went to the water’s edge to speak with him.

Across the river in the Wringer Pool, another solitary angler was visible when Dill put up the red flag.

Earlier in the day, as anglers celebrated the river’s reopening at an Eddington Salmon Club breakfast, Ruhlin stood on the club’s deck and said he would be keeping a close eye on the water temperature as the day progressed.

Ruhlin said at that time that the water temperature had been 64 degrees earlier on Saturday morning, but he suspected it might top 68 later in the day, forcing a temporary closure.

“We’ll keep an eye on it, and do what we have to do,” Ruhlin said.

The air temperature approached 80 degrees in the Bangor area on Saturday, and Dill said the continued warm, humid conditions would likely preclude ASC staffers from reopening the river until a cooler weather pattern pushed into the area.

Temperatures in Bangor again approached 80 degrees on Sunday.