First published in Landings, November, 2013.
In October, news outlets in New Brunswick and Nova Scotia reported a total of five sightings of North Atlantic right whales in the Bay of Fundy this summer. In previous years, summer counts have hovered closer to 100 whales in the Bay of Fundy, with numbers peaking in August and September. The endangered right whales use the Bay to feed and to nurse their young before returning to their calving grounds off the southeastern coast of the United States for the winter months.
This year’s count is the lowest in the 34 years that researchers have been monitoring right whales in the bay, but scientists are not suggesting that these unprecedentedly low numbers signal any similarly drastic drop in the population of the species. Rather, census estimates suggest North Atlantic right whales are doing well. Estimates put the right whale population somewhere over 500 whales, showing a steady increase from a 2000 estimate of just 300 whales.
While it is not yet entirely clear where exactly the whales ventured off to this summer, researchers from the New England Aquarium hypothesize that the drop in whale sightings in the Bay of Fundy may be tied to changes in food availability leading the whales to seek new feeding grounds.
Right whales feast primarily on copepods known as Calanus finmarchicus. These tiny critters are little bundles of fat, providing the energy source right whales need to sustain good health and ensure reproductive capability. The most efficient way for the whales to obtain the tiny copepods in sufficient quantities is by feeding in areas where they can be found in densely-concentrated patches. However, Heather Koopman, research biologist at the Grand Manan Whale and Seabird Research Station and associate professor at the University of North Carolina, reported finding very low abundance of overwintering Calanus finmarchicus this past September at her sampling station near Grand Manan Island. The low density of the copepods coupled with hardly any right whale sightings in the Bay has researchers wondering if the whales headed elsewhere this summer in search of more suitable feeding grounds.
This would not be the first time right whales have shifted their migratory patterns based on food availability. Right whales became similarly scarce in the Great South Channel, the deep channel that stretches between Nantucket and Georges Bank, from 1992 to 1998, apparently in response to food availability, according to the New England Aquarium.
What does a diminished population of the right whales’ preferred food in the Bay of Fundy mean? “The low numbers of Calanus finmarchicus in the Bay of Fundy raise concern, as it is thought that Calanus finmarchicus in the Bay of Fundy are the source of production supplying Calanus finmarchicus in Wilkinson Basin”, Jeffrey Runge, research scientist at the Gulf of Maine Research Institute and University of Maine’s School of Marine Sciences explained. “Low abundances in the Bay of Fundy may ultimately indicate low abundances in the Gulf of Maine. The implications for right whales may be lower calf production and redistribution to places like the waters off Nova Scotia where they can find more prey.”
Moira Brown, a senior scientist with the New England Aquarium and the Canadian Whale Institute, wrote in an email, “Whales feeding elsewhere means that we are not able to monitor the population annually as we have been doing in the Bay of Fundy which means we lose monitoring data on reproduction, scarring rates and health assessment.”
Runge reported that normal, high abundances of overwintering copepods were found in Wilkinson Basin in 2012, but sampling ended due to lack of funding, so there are no 2013 data on the abundance of Calanus finmarchicus. The Wilkinson Basin sampling data are used as a proxy measure for the health of Calanus finmarchicus populations in the entire Gulf of Maine. Researchers recognize that changes to the temperature of seawater as well as altered wind and current patterns can affect formation of the dense copepod patches. Other species that feed on Calanus finmarchicus that could be affected by changes in its distribution include cod, haddock, herring, and mackerel.
So what’s the next strategy for collecting survey data on the whales if they don’t return to the Bay of Fundy? For now, fishermen and others working on the water are being asked to keep their eyes open. “We worked this year on collecting opportunistic sightings from fishermen and fisheries surveillance in Canada. If the Bay of Fundy continues to be rather devoid of right whales next summer we will look further afield based on reports from other eyes on the water,” Brown noted.Category: Science