OTTAWA - Canadian conservationists say the federal government could dramatically weaken protections for fish habitats in lakes, streams and waterways across the country with proposed changes to the Fisheries Act.

Jeffery Young, a biologist with the David Suzuki Foundation in Vancouver, said the changes announced by Ottawa on Tuesday could add modest protections to bodies of water where there are established fisheries.

But he fears the revisions would narrow the definition of a fish habitat and strip away measures that now protect marine ecosystems that don't support active fisheries.

"It will result in reduced protection of streams, lakes and wetlands across Canada, particularly in areas that are more remote," he said, adding that he has yet to see details of the changes.

"The Fisheries Act is important to protect freshwater ecosystems, not just for the benefit of fisheries, but for the benefit of people and water quality."

Fisheries Minister Keith Ashfield announced the proposals Tuesday, saying they will identify and manage threats to the commercial, recreational and aboriginal fisheries, but his statement didn't elaborate on what those might be.

Officials with the Fisheries Department did not return messages seeking comment.

In his statement, Ashfield said the changes will allow officials to enforce conditions on projects, such as bridge or pipeline construction, that might destroy a fish habitat.

But a marine conservationist said that could weaken protections for all other habitats where fish exist -- but which don't support commercial, recreational or aboriginal fisheries -- by subjecting them to less rigorous environmental assessments before a project begins, or possibly none at all.

"It's focusing on areas where there are existing fisheries, but what about lakes and streams where there are not actual fisheries going on?" said Susanna Fuller of the Ecology Action Centre in Halifax.

"They're going to greatly reduce the areas where those habitat authorizations will be required."

The federal NDP immediately panned the proposed changes, also saying they will weaken environmental oversights when it comes to major projects, such as oil and gas developments.

"The Conservatives are putting the rush to development ahead of the tens of thousands of Canadians who depend on the fisheries," said New Democrat fisheries critic Robert Chisholm.

"They are once again making significant changes without having a transparent and respectful discussion with Canadians, especially those whose lives depend on sustainable fisheries."

In his statement, Ashfield said the existing rules treat all bodies of water the same, regardless of their contribution to the fishery.

He said the new measures will draw a "distinction between vital waterways that support Canada's fisheries and unproductive bodies of water."

Fin Donnelly, deputy fisheries critic for the federal NDP on the West Coast, accused the Tories of gutting habitat protection.

"It seems there is no limit on what they will do to help their big business friends avoid environmental responsibility," he said in the House of Commons.

"Does the minister not understand that selling out fish habitat is short-sighted and will damage both the fishery and our economy?"

Ashfield responded by insisting that the changes will protect fisheries from "real threats, such as aquatic invasive species and habitat destruction."