First published in Landings, June, 2017
An unprecedented number of endangered North Atlantic right whales showed up in Cape Cod Bay this winter and spring. Aerial surveys conducted by the Center for Coastal Studies in Massachusetts indicated that at times 200 of the 526 estimated existing whales could be found in the Bay, a “remarkable concentration,” according to Charles “Stormy” Mayo, director of right whale habitat studies at the Center.
Yet at the same time researchers noted that the number of right whale calves born over the winter was extremely low. Just five young right whales have been seen, continuing a low birth rate that began in 2010. In an average year the number would be closer to 14. Whale scientists have declared that the recovery of the population that began in the 1990s has effectively stalled.
But why? The population of North Atlantic right whales grew by 2.8% per year from 1990 to 2010, reaching more than 500 animals. Some heralded the slow but steady increase as a success story, to the relief of lobstermen throughout the region who had made significant changes to the way they fish in order to reduce the possibility of gear entanglements.
Whale researchers keep track of right whales through photo identification. Right whales have unique growths on their bodies called callosities. Aerial surveys allow researchers to identify individuals by those callosities. “For the past four or five years we’ve been looking in the areas that they traditionally are found and not seeing them,” said David Gouveia, Marine Mammal and Sea Turtle Program Coordinator at NOAA GARFO in Gloucester. “Are they dead or have they moved elsewhere?” what’s going on with North Atlantic right whales?
Right whales give birth in the warm waters off Georgia and Florida in the winter months. The females don’t eat until they return to the rich waters of the Gulf of Maine in the early spring. That’s when they can chow down on a good meal of zooplankton, specifically lipid-rich Calanus finmarchicus. Calanus finmarchicus builds up its reserves of lipids ( fats) by consuming the abundant phytoplankton that bloom each year, then settles in the deep waters of the basin to overwinter, safe from predators.
“Calanus finmarchicus is a subarctic species found throughout the North Atlantic. It is the foundation of the Gulf food web,” said Jeffrey Runge, professor in the School of Marine Sciences at the University of Maine and based at the Gulf of Maine Research Institute in Portland. “The seed stock of Calanus finmarchicus here is largely supplied from Canada and then amplified by local production here in the Gulf of Maine.” The copepods have the ability to move up and down in the ocean but travel over time with the dominant currents, in this case the Nova Scotian/Labrador current. “When and where the right whales are likely to be is based on where the Calanus are,” Runge added.
Runge and colleagues have monitored zooplankton populations on Wilkinson Basin for 15 years. Each month they visit the area to conduct net tows, moving the seafloor to the surface, to learn what sorts of zooplankton are present. “Since 2010 we’ve seen the abundance of lipid-rich, older-stage Calanus drop by 30%,” Runge said. “This corresponds to the Atlantic Zone Monitoring Program by Canada’s Department of Fisheries and Oceans, which shows abundance down in Canadian waters since 2010.”
Yet the whales are flocking to Cape Cod Bay, likely in pursuit of food. “The timing of biological events is changing. The winter/early spring [phytoplankton] bloom is happening earlier. The overwintering copepods are reproducing earlier which could explain why so many whales are in Cape Cod Bay in the spring,” Runge said
They may be getting a long-awaited meal in Cape Cod Bay, but that doesn’t mean those right whales are in the peak of health. “They are a little on the skinny side,” commented Mayo. “They are not looking that great.” Many of the whales bear scars from entanglement in fishing gear or strikes by vessels. Mayo admits that he is amazed by the numbers of animals in the Bay this spring. “We are stumbling around trying to figure out what’s what,” he said. He compared the situation in Cape Cod Bay to a street of many restaurants. “If all of a sudden you see everyone going to one restaurant, you can say that there’s either really good food there or all the other restaurants have closed. I’m inclined to think that if there’s food in other places, the whales wouldn’t come to the Bay,” he said.
Right whales may be heading off in directions that researchers are unaware of. In April this year, a female right whale turned up in Cape Cod Bay with a new calf. The last time she had been seen was off Iceland fourteen years ago. Perhaps the right whales are choosing to visit areas where their preferred food can be found in the dense quantities they need. “Whales are more adaptable than many marine creatures, including lobster,” Mayo said. If the Calanus finmarchicus populations are failing in the Gulf of Maine, it seems likely that the whales will go to where they are not failing. “There are lots of pieces of the jigsaw puzzle and some of those pieces are missing,” he said.
Everyone seems to agree that large-scale changes are happening in the Gulf of Maine ecosystem but what, specifically, those changes mean is less clear. “We don’t have enough science to do management at the scale we need. When you think you have one question answered, ten more pop up. It’s a continual puzzle,” Gouveia said. “But under federal law we must use the best science available to recover and conserve the species [right whales]. It’s a real challenge.Category: Management, Programs