A Summary of Right Whale Activity in Cape Cod Bay 2018
Charles “Stormy” Mayo, PhD
Excerpted from the July 2018 Right Whale News, Volume 26, Number 2.
Just when we think we understand what right whales are up to, how they make a living, where they aggregate, and how many there are, they surprise us. These surprises have been obvious during the last decade, and were amplified during the 2018 winter season in Cape Cod Bay (CCB). In 2018, as in every year since 1984, our work at the Center for Coastal Studies (CCS) was concentrated in the heart of winter, the season when right whales feed deep in the Bay, in areas that vary at different time-scales. Supported by the Massachusetts Division of Marine Fisheries and the National Oceanic and Atmospheric Administration (NOAA), in January 2018, we began our aerial survey, although, as in the recent past, shore sightings suggested that right whales were in our waters in numbers as early as late November.
The CCS aerial survey team headed by Amy James (flight coordinator), Brigid McKenna (individual ID manager), and Alison Ogilvie (aerial survey observer) documented 13 right whales in the Bay on the first 2018 flight, on 16 January, and thereafter reported right whales on all CCB flights until 14 May. The maximum number of whales observed in the Bay on one day in 2018 was recorded on 27 April, 137 individuals. While a high number of rare whales (137) in such a small embayment is only the fourth highest total we’ve recorded during the study, in 2016 we documented 198 individuals on a one-day survey confined to the Bay. As of this publication, we have identified 249 individual right whales in the Bay or nearby in 2018, and suspect that a number yet to be matched to the catalog will bring the total to well over 250, more than half of the estimated population.
As in all of the 34 years of the study, according to Christy Hudak (vessel survey manager), the first whales seen in January and February were on long diving patterns, apparently feeding very close to the bottom on dense layers of the copepod Pseudocalanus sp. The early-season deepdiving behavior continued until early March when gradual changes in the distribution of zooplankton brought the feeding whales closer to the surface. From late March through midMay, the observed behavior was dominated by surface or near-surface skimming, first on Pseudocalanus and then later on Calanus hyper-dense patches (sometimes exceeding densities of 106 organisms/m3).
During the first 25 years of our study, the patterns of whale activity in CCB seemed stable over a season spanning late January through late April, when yearly around 25% of the estimated population was foraging along the eastern shore of the bay. Then, in 2010, the numbers of individual whales documented yearly began to increase faster than the numbers estimated alive by the North Atlantic Right Whale Catalog team at New England Aquarium. That rising trend has continued.
Since 2010 the increasing proportion of the North Atlantic population using CCB, the lengthening of the whales’ residency season from three months to more than five, and changes in the areas of aggregation from the eastern side of the Bay to the western, suggest that the whales are responding to a changing environment. Although the activities of the whales, including the period of residency, and the increasing proportion of the population coming to the bay, are likely related to the long season of dense zooplankton patch formation. The underlying biological and physical processes that cause the enrichment of the Bay and the southern Gulf of Maine remain unclear.
Our recent work has identified the individuals of the North Atlantic population that preferentially choose to come to CCB, so in 2018, it was not a surprise that several of the regular yearly visitors to the Bay were again back for a long residency. These included Catalog #3946 (adult female); seen repeatedly throughout the season; #3546/Halo (adult female); #3823 (adult female); #1817/Silt (adult female); #1708 (adult male); and #1711 (adult female).
Although Cape Cod Bay is a regular early-spring nursing area for mother/calf pairs, the troubling lack of calves in 2018 as reported by the Southeast U.S. surveys was, unfortunately, reflected in our observations of no new nursing calves in the Bay.