HAY RIVER, N.W.T. - RCMP say all viable search options to locate four fishermen missing on Great Slave Lake have been exhausted.

Northwest Territories' Mounties say the probability that the men survived is low.

Searchers, including Canadian Coast Guard and Department of Fisheries and Oceans vessels, have been scouring the lake for four days.

The fishermen's partially submerged boat was found on Tuesday, but there was no trace of the men who left from the town of Hay River on Sunday to check fishing nets.

Missing are Daniel Courtoreille, 51, Michael Courtoreille, 50, and Jason Fulton, 40, all from the Lesser Slave Lake area of Alberta.

The fourth missing fishermen is Stacy Linington, 59, from Hay River.