BAR HARBOR — A new study provides more evidence that climate change in Gulf of Maine has pushed the endangered North Atlantic right whale out of its traditional foraging grounds in search of food, reduced the population’s calving rate and exposed the whales to greater risk from ship strikes and fishing gear entanglement.
The study, published in Oceanography earlier this month, analyzed plankton, oceanographic and whale sighting data and found that whales increasingly ventured out into new areas, such as the Gulf of St. Lawrence in Canada, as temperatures in the Gulf of Maine rose and their main food source declined.
In 2010, the Gulf of Maine underwent unprecedented changes as the warmer waters of the Gulf Stream pushed farther north than usual, consistent with models of human-driven climate change. These warmer waters came into the Gulf of Maine and created poor conditions for Calanus finmarchicus, the zooplankton that right whales eat.
Zooplankton monitoring showed a decline in summertime food abundance for the whales and they eventually started abandoning the traditional foraging habitats and migrated to the Gulf of St. Lawrence, where they were killed at high rates by ship strikes and fishing gear entanglement.
“This paper demonstrates that just as these mortalities in the Gulf of St. Lawrence are caused by humans, the reason that right whales were driven from their typical foraging habitat pre-2010 is most likely human-caused as well,” wrote Erin Meyer-Gutbrod, an assistant professor at the University of South Carolina and a member of the team of researchers who published the study, in an email interview.
She said the research indicates that climate-driven reduction in prey is lowering the calf rates for right whales and is making their habitat use less predictable. Part of the issue in St. Lawrence was the whales were unexpected and there were not enough protections in place to help them.
“If we can’t predict where and when a right whale is going to occupy an area, it’s much harder to develop effective protective policies to reduce anthropogenic mortalities (ship strikes and fishing gear entanglement),” Meyer-Gutbrod wrote.
The team of researchers also found that the Gulf of Maine is warmer not just from the top, as previous studies had shown, but the bottom as well. Meyer-Gutbrod said this is likely due to an increase in the relative contribution of warm, salty Gulf Stream water coming in through the deep channels at the entrance to the Gulf of Maine.
In 2017, 17 right whales died — 12 in Canadian waters and five in the U.S. due to entanglements and ship strikes. Between 2017 and 2020 the population saw a roughly 7 percent loss. The population now hovers around 360 whales in the world.
Both the U.S. and Canada have since implemented measures to help protect the whales. The day before the study was released, the National Ocean and Atmospheric Administration announced new rules for the lobster industry to cut down on the number of vertical lines in the water. Lobstermen have said they go too far, and conservationists say they don’t go far enough to prevent the species demise. NOAA also is looking at potential changes to other fisheries.
Meyer-Gutbrod said this study should send a signal that climate change is making things less predictable and both researchers and regulators need to become more flexible.
“Scientists and managers will need to shift their thinking and be more proactive about preparing for and identifying species distribution shifts,” she said. “This is especially important for species that are heavily managed and rely on protective policies to mitigate human impacts.”