Nova Scotia lobsters still in sweet spot despite climate change
Group of scientists predicted impacts on Canada's most valuable fishery
For the first time, Canadian scientists have attempted to predict the impact of a warming ocean caused by climate change on the lucrative Nova Scotia and New Brunswick lobster fishery on the Scotian Shelf.
In most areas, lobster habitat in the offshore is expected to remain suitable or improve over the next few decades, according to a study published in the journal Frontiers of Marine Science.
Offshore is defined as beyond 19 kilometres from land.
"Some of the climate projections suggest that it may not have a big impact over the next number of years on adult lobsters," said Adam Cook, a lobster scientist at the Department of Fisheries and Oceans.
"There is still uncertainty of course around the young lobsters and egg production. But for the offshore adult lobsters, we're feeling like climate impacts in terms of temperature particularly aren't going to be a major negative driver."
Cook said the Scotian Shelf lobster fishery is somewhat insulated by location — it's in the middle of where lobsters are found on the North Atlantic coast — and water temperatures are cold enough to withstand projected temperature increases.
Managing a $1-billion fishery
Cook is one of nine scientists at the Bedford Institute of Oceanography who examined climate change vulnerability in Lobster Fishing Areas 27 to 41, which run from northern Cape Breton along the Atlantic coast of Nova Scotia and the Bay of Fundy. A scientist from the U.S. government's National Marine Fisheries Service also contributed to the peer-reviewed paper.
It's no coincidence the crustacean was selected for study.
The lobster fishery is Canada's most valuable — worth about $1.3 billion — with the lion's share caught in southwestern Nova Scotia.
Managers at the Department of Fisheries and Oceans wanted a tool they could use to understand the impacts of climate change at the local level, said research scientist Nancy Shackell, a lead author of the study.
"The key part is that we're putting the information on the scale of the fishery management area and that will make it really easy for anybody that is dealing with policy to start to think about how [lobster fishing area] 34 will be affected, how [lobster fishing area] 33 will be affected," Shackell said in an interview.
If the prediction is accurate, it's good news for inshore lobster fishermen, who have enjoyed record prices in recent years. Bigger and more powerful boats allow them to fish far from shore.
The study was restricted to offshore waters because it's where DFO has developed databases on lobster habitat after decades of its own surveys.
"The inshore is a more dynamic system that we have less fisheries independent information, less specific information on lobster habitat usage," said Cook.
He is cautious when asked if inshore waters will also remain a suitable habitat for lobsters.
"Overall I think the patterns will likely hold, but they are quite different ecosystems in the species compositions and how lobsters are making their living in these two different places," he said.
Good news for Clearwater Seafoods
North America's largest shellfish harvester, the Bedford, N.S.-based Clearwater Seafoods, would appear to be well-positioned.
The company holds a monopoly on Lobster Fishing Area 41, which is Canada's only offshore lobster fishing area.
The zone starts 80 kilometres offshore and extends to a 320-kilometre limit. It's the only lobster fishing area in Canada with a quota, a year-long season and no trap limit.
All of the company's annual total allowable catch of 720 tonnes — or nearly 1.6 million pounds of lobster — is caught off southern Nova Scotia, much of it near the 80-kilometre line.
Inshore fishermen have complained it's not fair that the fishing area is reserved for one company.
"The [lobster fishing area] borders within the DFO Maritimes Region impose constraints on the fishing industry and present challenges as a warming ocean increases productivity in areas such as [Lobster Fishing Area] 41, which currently has a single licence holder," the study noted.
Shackell said that is an issue for those who manage the fishery.
"That would be one instance where they would have to figure out, do we issue new licences, do we hold back new licences? That's their decision, I don't know anything about that, but it would be information for them to consider," she said.
How they came up with the prediction
The scientists created vulnerability indices for lobster and for coastal communities and assigned a number to indicate vulnerability to climate change.
On shore they looked at economic dependence on the fishery, the condition of harbour infrastructure, replacement cost of each harbour, increased sea level, flooding, impacts of wind, wave heights and sea ice.
They looked at the vulnerability of offshore lobster habitat to ocean warming and changes in zooplankton.
Two different ocean models projected ocean bottom temperatures up until to 2055.
Ocean climate expert David Brickman, who is married to Shackell, helped develop one of the high resolution models for the North Atlantic.
He said historically on the Scotian Shelf and in the Gulf of Maine, there is a "battle" between colder arctic water flowing down past Newfoundland and warm Gulf Stream water from the south.
"What our model shows in terms of changes in temperature in the future, the colder water is not predicted to have as big an influence in these areas. There seems to be somewhat of a natural barrier at the Laurentian Channel, the Grand Banks," he said.
Bay of Fundy more vulnerable
The study said the Bay of Fundy is more vulnerable than other areas of the Scotian Shelf.
"It does seem to be warming at a slightly faster rate, as a lot of the Gulf of Maine is as well. There is potential for some negative consequences looking at the overall patterns and that may impact the lobster populations sooner than in some of the other [lobster fishing areas]," said Cook.
Both scientists stress there are uncertainties about their study, including the impact of warming temperatures on lobster predators and prey, especially the tiny zooplankton known as copepods. In the first few weeks of life, lobsters float near the surface where they feed on copepods.
The copepods have started moving out of a warming Gulf of Maine.
"We're just looking at changes in thermal habitat. We can say that the animals like sort of a window of temperature and they like a window of depth and we see them there all the time and then using [Brickman's] model we say how much of that will increase or decrease," said Shackell.
Despite the caveats, scientists say the study is a step forward.
"It's a really neat collaborative piece of work that brings together multiple disciplines to be able to talk about some important patterns that we're seeing in terms of climate change, socioeconomic aspects and the biology of the lobsters," said Cook.