The life and times of crab

Emma
Emma Graney
Send to a friend

Send this article to a friend.

Fishing

Crab are interesting little critters - just ask Earl Dawe, research scientist for the Department of Fisheries and Oceans.

He's specialized in crab since 1986 and he knows a fair bit about the bottom-dwelling creatures who are about to be picked up for a ride to Newfoundland shores (and into our bellies).

Snow crab, the species caught off the coast of Newfoundland. Submitted photo

St. Anthony -

Crab are interesting little critters - just ask Earl Dawe, research scientist for the Department of Fisheries and Oceans.

He's specialized in crab since 1986 and he knows a fair bit about the bottom-dwelling creatures who are about to be picked up for a ride to Newfoundland shores (and into our bellies).

Talking to The Northern Pen last week, Dawe described the lifecycle of the snow crab, the species fished off the Northern Peninsula.

"They're very susceptible to temperature," he explained.

That susceptibility is what governs their size which, according to Dawe, means a carapace somewhere between 30 and 75 mm for females and 40 to 140 mm for males.

"There are other factors, as well, of course, but the main one seems to be temperature. We get smaller crab down here than you'd get further north in warmer waters."

Wait a second - warmer water north? That doesn't sound logical.

"Usually yes, but we're talking about the ocean bed which is their habitat," he explains, "and the water up there is deeper which makes it slightly warmer at the bottom."

Oh. And that makes them bigger because ... ?

"Well, it seems that crabs will stop moulting whenever they're comfortable, and they like the colder water, so in warmer water they will continue to grow and they'll reach terminal size when they're a lot larger."

Moulting is when a crab sheds the exoskeleton it has outgrown.

"For a little while after that they go through a soft-shell stage, where they're not as protected and, if they're picked up in fishing traps, generally are thrown back because there's not a lot of call from them on the market," Dawe said.

True enough - who wants to get a crab that's half-empty when you crack it open?

Older crabs are also undesirable because when they reach sexual maturity they stop moulting and keep the same shell for the rest of their lives.

"Like they're wearing the same old clothes, year after year," he says. "They end up with growths on their shells and ultimately they deteriorate and rot from the joints."

They rot? That's a horrible way to die.

"Do humans have it any better?" asks Dawe.

Fair point.

And how old are these crab with time-pocked shells and withered legs?

"No one's quite sure how long crab live for, but through our observations in labs it's thought that the oldest ones are about nine or 10 years old. But the ones that end up in the fishery are generally about four or five years old."

The cycle goes like this: in spring they hatch and then go through a larval stage when they're floating on top of the ocean. Eventually they sink to the bottom.

For the first few years they hang around on a rock or sandy-bottomed surface and moult each year in late winter. Eventually they move to a muddy-bottom habitat and from there grow to full maturity (which is when the males get those big claws), mate, breed and then get caught. Or eaten by cod. Or die from rotting.

And Dawe throws out another interesting tidbit about crab - they're cannibals. Small crabs that have recently sunk to the bottom and are just starting their journey through life will often get gobbled up by larger, older crabs.

It seems those little crab lack the ability to, when being attacked (or, say, held aloft by a scientist in a boat), drop a leg off.

"The strangest thing is that sometimes they grow a whole new leg back in its place, rather than just healing over the hole with shell," says Dawe. "It's very strange."

So, as crab fishermen head out from Northern Peninsula wharfs in the coming weeks, spare a thought for the crab that will be coming back with them.

Organizations: Department of Fisheries and Oceans

Geographic location: Northern Peninsula, St. Anthony, Newfoundland

  • 1
  • 2
  • 3
  • 4
  • 5

Thanks for voting!

Top of page

Comments

Comments