Thank you.
My name is Andrew Pershing and I'm the chief scientific officer at the Gulf of Maine Research Institute in Portland, Maine, U.S.A. I've been studying the oceanography and ecology of the Gulf of Maine for more than 25 years.
As you know, the Gulf of Maine is bordered by the provinces of Nova Scotia and New Brunswick as well as the states of Maine, New Hampshire and Massachusetts. The United States and Canada have a shared interest in the well-being of the Gulf of Maine. I'm honoured to be invited to share my perspective on how climate change has impacted and will impact ecosystems in the northwest Atlantic, especially the region's valuable lobster fisheries.
The earth's oceans have absorbed more than 90% of the excess heat trapped on the planet due to the burning of coal and oil. At the ocean's surface, temperatures have increased at an average rate of 0.01° Celsius per year since 1982. However, the warming of the ocean is not uniform. Over the last 30 years, the waters from Cape Hatteras to Newfoundland have warmed at nearly four times the global average rate. This makes this region one of the fastest-warming ocean regions on the planet.
The area of rapid warming encompasses the natural range of the American lobster. Over this period, the distribution of lobsters has shifted poleward by a rate of 11 kilometres per year. This shift has coincided with the dramatic increase in landings in Maine, New Brunswick and Nova Scotia, but a severe decline in catches in Rhode Island and New York.
There are two main processes that lead to range shifts in animal populations. First, individual animals can actively move to follow the environmental conditions that they prefer. This active movement is most common in large, mobile animals. A good example of a movement-driven range shift is the recent shift in the distribution of right whales from their summer feeding areas in the Bay of Fundy now to the Gulf of St. Lawrence. For less mobile species like lobsters, shifts in their distributions come from differences in reproduction and survival. Lobsters have not crawled from Rhode Island to Maine. Instead, lobsters in Rhode Island now produce fewer babies, and fewer of these survive, while Maine and Canada have seen a lobster baby boom.
The northward shift in lobsters has been driven by increased reproduction and survival in the north and decreased reproduction and survival in the south. Warming is an important part of this story. When lobsters are raised in warm water they grow fast and reach maturity in only a few years. But smaller lobsters produce fewer eggs and juvenile lobsters must run a gauntlet of predators. In colder water, lobsters grow more slowly and mature at a larger size.
When Dr. Arnault Le Bris and I compared lobster populations in the Gulf of Maine with those in southern New England, we were able to identify an optimal summer temperature for lobster recruitment near 16° Celsius. As waters have warmed, these optimal conditions have shifted from Massachusetts in the 1990s, to Maine and Nova Scotia in the early 2000s, to eastern Maine and New Brunswick in the last decade.
However, because we're talking about a shift due to differences in survival, we'd also need to account for fishing. In our modelling study, Dr. Le Bris and I contrasted the management strategies used in southern New England with those in the Gulf of Maine. Until recently, the lobster fishery in southern New England only had a minimum legal size, while Maine has long had both minimum and maximum legal sizes. This strategy, along with the practice of marking egg-bearing females with a v-notch, has been championed by generations of Maine lobstermen under the hypothesis that protecting larger lobsters would ensure a large brood stock and support high recruitment.
Our calculations support this hypothesis. We found that the lack of an upper size limit amplified the effect of warming in the south, turning a moderate downturn into a collapse. Similarly, protecting larger lobsters amplified the benefit to Maine from the recent warming.
But what about the future? Climate projections suggest that the northwest Atlantic will continue to warm at an above-average rate. By 2050, our region will likely be 1.5° Celsius warmer. At these temperatures, the western Gulf of Maine, the Scotian shelf and the southern Gulf of St. Lawrence will become less favourable for lobsters. When we put this rate of warming into our model, the number of lobsters in the Gulf of Maine decline to levels we experienced around the year 2000. Removing the protection on larger lobsters would result in a steeper decline. One of the most important messages of our recent paper is that protecting older, larger lobsters helps build resilience in this population.
In our study, we ran our model out to the year 2050. Beyond 2050, the fate of lobster will depend on global carbon emissions. If carbon emissions are reduced as envisioned in the Paris Agreement, then Maine and Atlantic Canada will likely hold on to valuable lobster fisheries. However, under business-as-usual emissions, these fisheries will be much smaller.
Our results for lobster underscore a major theme that emerged in the “Fourth National Climate Assessment” published last fall. In the “Oceans and Marine Resources” chapter, my colleagues and I highlighted how sound fishery management can help fisheries build resilience to climate change. We also identified clear economic benefits to fisheries from reducing carbon emissions, a theme that cut across all of the chapters in the recent U.S. “National Climate Assessment”.
As you consider policies for the future of Canada's lobster and snow crab fisheries, I would encourage you to learn from the experiences in the United States fisheries and to consider how your policies will fare in a warmer ocean.
Thank you.