Monday, December 3, 2012

Reflections on the Summer in the Bay of Fundy

Right whales were hard to find in the Bay of Fundy in the summer of 2012.  Those that were found were often travelling.  Few settled in the Bay for any length of time other than the mother 3390 and her calf.  They were seen for over a month and were the only right whales to remain for any length of time.

Calf of right whale 3390.  The calf opened its mouth and the baleen can be seen hanging down.  Baleen in calves is very light in colour.  Adult baleen colour is much darker.
Why the instability when the Bay of Fundy is a designated critical habitat for North Atlantic right whales?  Right whales come to the Bay of Fundy for many reasons but an important one is the availability of huge patches of zooplankton, primarily copepods.  When in large quantities, these copepods provide enough energy for the whales to add to their blubber layer for winter months when food may be more scarce and they may need to fast, relying on the blubber reserves.

It is important to photo-document young right whales so they can be followed throughout theirs lives. Each right whale has a unique pattern of callosities on its head, rough patches of skin where we have facial hair. This calf's mother, 3390, was not photographed as a calf and we, therefore, do not know when she was born or to whom she is related. 
The copepod patches were sporadic, never seemed to develop into large patches, and also appeared pale in colour, indicating low energy reserves in the copepods.  Why the change from most years when the copepod patches develop in the Grand Manan Basin, the deepest area in the Bay of Fundy?  The 2011-2012 winter was one of very mild temperatures and hardly any snow.  This resulted in very little runoff into the ocean and, therefore, lower nutrient input for phytoplankton.  Warmer winter temperatures and little cold water runoff from snow melt also meant warmer ocean temperatures.  The counter current gyre that sets up each summer in the Grand Manan Basin and accumulates zooplankton, is temperature dependent and may not have occurred where it normally does in 2012.

Right whale stretching after a nap between dives.  This whale was been down to the bottom because of the muddy head.  It is not sure why right whales and also humpback whales rub in the muddy bottom, whether it is for feeding, relieving an itch or as a mud facial!
Warmer water temperatures can result in many changes.  It is a suggestion of why Atlantic herring didn't come inshore, preferring the deeper, colder waters.  There were several sightings of leatherback turtles, the largest sea turtle.  While the occasional sighting is normal in the Bay of Fundy, there did seem to be more this summer, including one that swam up a tidal river.  Unfortunately, the turtle died despite efforts to rescue it when it stranded on the muddy river bank several times.

Small Atlantic herring (brit) leaping out of the water after being pursued by Bluefin Tuna from below and great shearwaters from above.  Herring are a keystone species in the Bay of Fundy, providing food for many species.  They eat copepods as do right whales.
 What do low copepod resources in the Bay of Fundy mean for right whales?  It can affect calving success.  Right whale females need to have a good fat reserve to get pregnant because of the high energy demands of nursing a calf.  This is the reason right whale females take a resting year after weaning their calf so they can adequately recover their blubber reserves.  If the right whales found large patches of zooplankton elsewhere, then calving may not be affected.  In 2010, few right whales were seen in the Bay of Fundy and this past calving season had only seven calves born.  Low resource availability one summer is reflected in calving rates not that year but the following year.

Right whale 3390 and her calf diving in the Bay of Fundy off Grand Manan Island in August 2012.

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