Nfld. & Labrador

80% of N.L. snow crab are below fishable size

Too many large males have been removed from the snow crab population, and DFO scientists warn the fishing pressure on the species could cause lasting, serious harm.

DFO warns fishing pressure could lead to long-term harm to stocks

DFO shellfish biologist Darrell Mullowney measures the shell of an undersized snow crab. (Jane Adey/CBC)

Eighty per cent of the snow crab in the province's waters are now smaller than fishable size, and new biological research from the Department of Fisheries and Oceans says fishing pressure on the already strained stock is the main problem.

"There is a major biological concern here," said DFO biologist Darrell Mullowney.

A pile of mostly undersized snow crab on display in a lab at the Department of Fisheries and Oceans. (Jane Adey/CBC)

Scientists say continuing to fish at high levels could lead to long-term serious harm to stocks through genetic change or impaired reproductive capacity.

The news comes just as the Department of Fisheries and Oceans is set to meet with harvesters about snow crab in a series of meetings being held across the province between November 19 and 29. 

Mullowney said managers and scientists intend to be forthright at that meeting about the seriousness of the situation.

"There's a state of concern on this stock and, you know, the department is open in sharing the fact that we're concerned."

Not enough large crabs

The new research reveals that too many large male crabs have been removed from the population. When there are fewer large males, the smaller male crabs terminally molt — that is, they stop growing. 

"[Small] crab used to have to grow large to compete with the larger individuals. In the absence of the larger individuals, there's no need for them to grow large anymore so they would sense that there's no big guys around anymore," he said. 

Only male crabs that meet or exceed the minimum legal size (95 mm carapace width) may be harvested during the fishing season. (Jane Adey/CBC)

The new research shows just how important large males are for the overall health of the snow crab population.

"[They] are superior breeders and do things like maintain the genetic hierarchy in the stock. So they're quite important," Mullowney said.

Potential long-term harm

Mullowney says fishers may be shocked by the DFO findings because it's not what they see when they haul in their pots.

"They're not allowed to use small mesh pots like we did, which can capture these undersized crabs, so they don't see this for the most part," he said.

They only see the big crab in the population. They do see that there's fewer and fewer in their pots, but they don't see the fact that 80 per cent of them are terminally molting and a small size."

There is a major biological concern here.- Darrell Mullowney

Mullowney is optimistic the situation can improve with the right management approach.

"If our interpretation of the situation is correct and this reflects the lack of competition from big males in the population, the answer is to reinstate some big males into the population," Mullowney said. 

"That would mean at least a reduction in fishing to at least promote that process."

In fact, the DFO has supportive evidence for that approach from the province's south coast crab fishery. When fishing pressure was reduced there a few years back, size and maturity for the snow crabs started to increase. It took two-to-three years for the turnaround to occur.

When snow crab terminally molt (stop growing) their shells are darker and often have encrusting organisms. (Jane Adey/CBC)

Scientists are hopeful that the cause of the smaller crabs is situational, and not genetic.

"This is not irreversible harm or anything being done at this point that these things can't again grow large, and hopefully quite quickly, if we're able to re-establish a healthy population of big crabs," Mullowney said.

With files from The Broadcast

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