A group representing Gulf of St. Lawrence lobster fishermen says frustration is mounting after the federal government rejected its proposal for a shallow water exemption to fishery closures aimed at protecting endangered North Atlantic right whales.

The Department of Fisheries and Oceans says it considered the proposal by two groups including the Maritime Fishermen's Union, but will not exempt waters of up to 10 fathoms — or 18 metres — in depth.

Union president Carl Allen says the federal decision makes no sense because there have been no documented instances of right whales venturing into shallower waters of the Gulf.

Allen says lobster fishermen could lose about 25 per cent of their income this year because of fishery closures.

He says although his membership has been willing to co-operate with the measures so far, there may come a point where they say they've "had enough."

The department says the closures are the most effective way to protect right whales from entanglements in fishing gear.

The lobster and snow crab fisheries are scheduled to end in the Gulf of St. Lawrence at the end of this month.