A proposal to limit fishing quotas on ailing snow crab populations has left the fisheries union reeling, warning that a "precautionary approach" suggested by the federal government to improve stocks has gone overboard.

Fish, Food and Allied Workers-Unifor, which represents 15,000 workers in Newfoundland and Labrador, argues the Department of Fisheries and Oceans could be using its precautionary proposal to determine how many crab fishers can harvest this year, without listening to workers and businesses about how that approach would affect them.

The DFO says otherwise, assuring harvesters the incomplete proposal won't have any effect on its annual quota decisions this April.

But scientists stressed in a briefing Tuesday that some fishing areas were "severely depleted," alarming businesses and prompting the union to express concern over a further reduction in quotas.

The industry saw a 17 per cent cut in crab quotas last year, with a similar slash in 2017.

The department first announced its intent to move toward a precautionary approach last fall, following a report showing snow crab stocks at their lowest in a quarter-century.

Darrell Mullowney, a DFO scientist who took part in that study, told CBC in October that the department harboured concern over exploitation.

"We are not sure that [stocks] can continue to sustain the levels of fishing pressure that have been imposed upon it in recent years," Mullowney said.

A month later, the department announced 80 per cent of snow crab were below fishable size, and warned pressure from high quotas would threaten the long-term health of the stocks, impairing their reproductive ability or even triggering genetic damage.

When too many large males are removed from a snow crab population, smaller male crabs stop growing. DFO's research suggests too many large males have been caught.

The department maintains that limiting quotas can improve stock size, and points to previous research showing that when fishing pressure was reduced in certain areas, stocks grew within two or three years.

Tony Doyle, a crab fisherman and vice-president of the union's inshore council, disagrees with DFO's assessment.

He says some areas aren't as bad as others, and worries his income will take a considerable hit if DFO follows through with its proposal.

"Every dollar I've made since 1975 … has come out of the water," said Doyle. Most of that income in recent years, he said, has depended on the snow crab.

He said that only gives him added incentive to ensure stocks aren't overfished.

When the resource looked like it was on a downturn, he said, he would limit his harvest in kind.

"We want to keep it as a sustainable fishery," Doyle said, pointing to decisions such as introducing biodegradable twine to allow any crab caught in lost traps to crawl free, and establishing no-fishing zones in some areas to allow crab to reproduce undisturbed.

"We've been doing lots of things in the last 20 years to sustain the fishery," he said.

"It's just Mother Nature giving us a kick up the behind."