How warming waters around P.E.I. could affect snow crab and lobster

Scientists working with the Department of Fisheries and Oceans are keeping a close eye on how changing water temperatures might affect species like lobster and snow crab. 

Research scientist Joël Chassé says as the atmosphere warms, the ocean waters around P.E.I. are also heating up. 

"The winters are becoming milder and milder, meaning that the removal of the heat from the ocean is not as [great] as before. So the waters are warmer and warmer overall," he said.

"What we found out both from the surveys and from some modelling work that we have been doing within DFO, it's actually the Southern Gulf — and specifically the Northumberland Strait — warming at a faster rate than the rest of the Gulf." 

Chassé said there's a lot of variability from one year to the next. Surface water has been warming at a rate of between 1 to 1.2 degrees Celsius over 100 years — but that appears to be speeding up.

He said on average over 10 years, surface temperatures in the Northumberland Strait could see increases of 0.5 degrees in summer and 0.3 degrees in winter.

One degree could be significant for some species.— Joël Chassé

"Over the last 10 years or so, we have been warming a little bit more on average than the previous, let's say 20 years. So it's not a big change, but you know, one degree could be significant for some species," he said. 

"Changes are happening. It's not deniable anymore. And if the these changes don't slow down, we will have to adapt to these changes."

Chassé said there are implications for some fish species, some positive and some negative. 

Fisheries and Oceans biologist Tobie Surette said that while lobster is a warm water coastal species, snow crab prefer deeper, colder waters.

And those differences are key when it comes to climate change. 

"Lobster has largely benefited from the warming climates, at least so far," he said. 

Surette said they don't know exactly why that is. 

"It's just good, good conditions. I mean we're getting more and more small lobsters. So it's either that the survival of small lobsters is much better now that the water is warmer, or there's much more food available," he said. 

In the United States, he points out, the story has been different. 

"The most southerly distributions of lobster have in fact decreased because it's felt that the water is too warm there now," he said.

[Lobster] live very happily in waters that are 20, 20-plus degrees.— Tobie Surette

"They're very temperature tolerant. So they live very happily in waters that are 20, 20-plus degrees. But if the temperature gets too high, we can start to affect egg development and the survival of small lobsters as well ... which can then just lead to stock collapse.

"So there is an upper threshold, but the story here, up to now, we see absolutely no sign of that." 

Surette said P.E.I. and New Brunswick would likely see impacts first.

"It turns out that the Northumberland Strait is where the warmest waters are concentrated now ... So if one region was going to show issues with temperatures that are too high, it would be the Northumberland Strait. And so far we're not seeing that."

Snow crab more sensitive

Surette said snow crab live in a very small temperature range, with the species preferring waters that are less than 3 or 4 degrees Celsius. 

"It's a lot more sensitive to temperature changes. Now that being said, the water layer in which they live is a lot more stable," he said. 

And for now, they are doing well: "We're at the third-highest biomass in the history of the survey right now." 

But Surette knows that could change. He has been in contact with snow crab scientists from Alaska.

The snow crab fishery there was shut down after a massive loss of stock a few years ago, likely due to warmer than usual water. 

"I've seen it referred to as a marine heat wave," he said. 

"An influx of really warm waters swept in and basically caused a large mortality event and the crab surveys they had saw a decrease in snow crab stock of about 80 per cent over one to two years. So it was very dramatic."

It doesn't take much to affect a snow crab population. 

Snow crab would be the canary in the coal mine as far as a stock that is vulnerable to warming.— Tobie Surette

Surette said temperatures at the bottom of the Southern Gulf are generally colder than 2 degrees Celsius. If those temperatures edged closer to 4 or 5 degrees, there could be a decrease in snow crab stocks in certain areas. 

"Obviously we've been looking at the Alaska case very closely and I've been working with biologists from there as well. But yes, snow crab would be the canary in the coal mine as far as a stock that is vulnerable to warming.

"We can expect some pretty widespread ecosystem changes over the years if the warming trends continue."

Ready to sound alarm

Surette said scientists are monitoring and tracking lobster and snow crab so that they can provide a head's up if they see an important increase in mortality. 

Chassé said human activity around the planet has led to higher seawater temperatures and it would be difficult to slow the warming, let alone reverse it. 

"There is nothing else [other] than climate change that could explain this long-term trend," he said.  

"Scientists have been giving warning signs for the last 30 years about the fact that the climate is warming... How important that is for the common human being, I think, depends on what you do and where you live and all these things.

"But certainly I would say it's concerning that these changes are happening, and it's going to be hard to slow it down."