Q&A: Can you eat crayfish from the North Saskatchewan River?

Caution: Due to mercury concentrations, Health Canadafish consumption guidelinesrecommend eating fish from the North Saskatchewan River no more than once a week. Children under the age of 15, pregnant women andwomen of child-bearing age should not consume the fish.

They are known as crayfish if you're in Canada. Crawfish or crawdads in the U.S. Yabbies in Australia.

Whatever you call them, the lobster-like freshwater crustaceans may be closer than you think. These critters have been scuttling and spreading in Alberta waters and in recent years have even settled into the North Saskatchewan River.

CBC's Edmonton AM checked in with Heather Proctor, a biologist at the University of Alberta to get the details on crawfish moving into Edmonton's waters.

This interview has been edited for length and clarity.

Are there crayfish in the North Saskatchewan River?

Yes, there are indeed. And that was a surprise to me when I first saw them there.

The history of the crayfish in Alberta is a complicated one. Even up to 1991, the crayfish were restricted to the Beaver River drainage, which is northeast of Edmonton. And even at that point, there were concerns that the crayfish species, Faxonius virilis, might actually go extinct in Alberta because it was so restricted in habitat.

So when I came back after a decade or so away and found them in the North Saskatchewan, I was totally surprised.

What happened with their survivability or their spread through the system? How did that happen?

Well, it's still in part a mystery.

For any standing water body, including many stormwater ponds in Edmonton, crayfish got there because people put them there. That was either deliberately, because people like crayfish they're sort of cute and possibly edible and also maybe through movement of like shore stabilizing material could potentially just accidentally move them around.

But in the North Saskatchewan and also in the Battle River drainage system, it seems that they, for whatever reason, walked up on their own.

Obviously, some species are native to the province and some are not. What is the risk of more crayfish in more bodies of water?

That's certainly a big concern to fish and wildlife and other ecological environmentally associated agencies.

The one species that we have in Alberta that is technically native is Faxonius virilis the northern crayfish and it's also native to Saskatchewan, Manitoba, Ontario, from probably also Quebec.

It's also native to northeastern U.S. So, that one has a legitimate claim to being in Alberta, although not in as many water bodies as it currently is due to human movement.

Other species, the rusty crayfish or Faxonius rusticus, and a lot of pet species that you might be able to buy in pet stores, it is a concern if they escape or are deliberately planted in places.

And you might wonder why: crayfish are very voracious eaters of everything. They can eat plants and animals. They'll happily eat any trout eggs that they might find on the bottom of the substrate. And when they eat the water plants, they can really make a water body quite mucky.

Now if people want to catch crayfish, are there any rules around that?

Basically fishing wildlife regulations say you can catch crayfish without a licence if you're just using a dip net or grabbing them. You need a licence if you are using a baited hook.

But you're not allowed to move crayfish alive out of the place that you captured them, you're actually required to kill them on site and not transfer them.

Edmonton AM6:46Are there crayfish in the North Saskatchewan river?

There's been some recent discussion on social media about crayfish appearing in Alberta waters. To learn more, Edmonton AM turned to Heather Proctor, a biologist at the University of Alberta.

So, how do you kill them?

If you have some amazing capacity to boil water at the place that you're fishing, then that would be the quickest and most humane way to do it. They, like almost all invertebrates, have a ventral nerve cord. So you might be able to stab them in the chest and put them to death immediately that way.

Now the crayfish in the North Saskatchewan River, can we eat them?

Yes they are edible, though I would not suggest making a bouillabaisse out of them straight away because of course they are all completely covered with guck of all sorts and they have their gut contents as well and who knows what they've been eating.

If you want to cook them, the recommended way from folks who live in real crayfish country in southeastern United States is to do what's called a purge. You put them into cool salty water which will make them void their bowels and also throw up. And then once they start to clean themselves that way, you could do a sort of bouillabaisse-type approach.

Or, you could just boil them and then crack them and eat them like regular lobster meat. And that's probably the safest way.