A new study confirms what marine mammal researchers have suspected for a while: right whales use nearly the entire eastern seaboard during the winter, and they move around a lot more than was previously thought. How long they spend in some areas of their range has also changed in recent years.
(From Phys.org) — The findings, published in Nature Scientific Reports, were based on passive acoustic monitoring. Using bottom-mounted listening devices deployed along the coast, researchers can record whale calls 24/7 and obtain new insights into how whales use all habitats.
“This study demonstrates that passive acoustic monitoring is a useful tool in understanding and tracking shifts in the movements of large whales over long periods of time,” said Genevieve Davis, an acoustician at the Northeast Fisheries Science Center’s Woods Hole Laboratory in Massachusetts and lead author of the study. “This kind of information is impossible to access in any other way because of weather and day light constraints for visual surveys.”
Analysis of data collected by passive acoustic monitoring between 2004 and 2014 by 19 organizations throughout the western North Atlantic Ocean revealed North Atlantic right whales have increased time spent in the Mid-Atlantic region since 2010 and decreased their presence in the northern Gulf of Maine. They were also less likely to be found in the waters off Cape Hatteras, North Carolina in summer and fall, and are widely distributed across most regions throughout the winter months.
“Right whales are the least abundant but most intensively studied species, yet we don’t know a lot about them in terms of their movements and migration patterns,” Davis said. “They seem to be visiting the Bay of Fundy less frequently than they used to, now appearing along the East Coast year-round where they were once only seen for a few weeks passing through, and more of them are gathering as a population in Cape Cod Bay in recent years.”
More than 35,600 days of data from 324 listening devices deployed from Florida to Canada were processed for the study using an automated classification and detection system. The data confirmed the nearly year-round presence of North Atlantic right whales along the entire East Coast, particularly north of Cape Hatteras. In the past researchers assumed the majority of the population migrated between calving grounds off northern Florida and Georgia in winter months and northern feeding grounds off New England and Canada in summer months, but the data reveal that not all of the population has an annual migration.
North Atlantic right whales were detected from Jacksonville, Florida to Nova Scotia from late October through early April. The only exception was on the Scotian Shelf, where no whales were detected from December through February. Fewer detections were recorded during the summer months in southern areas, indicating the known movement of breeding individuals towards northern feeding grounds.
Right whales were also detected near Iceland and Greenland from July through October, and whales have been sighted more frequently further north as far as the Gulf of St. Lawrence. Individual right whales have also made trips to European waters, including a 131-day round trip from U.S. waters to an old whaling ground off northern Norway.
Read the full story here: https://phys.org/news/2017-11-shifting-presence-north-atlantic-whales.html#jCp