Since 1998, the Division Marine Fisheries and our partners at the Provincetown Center for Coastal Studies have been monitoring right whales in Cape Cod Bay. Starting in 2007, the number of whales sighted each season took a big leap – with annual averages double what was seen in previous years. However nothing could prepare us for the bonanza of 2011.
The aerial team documented 312 individual right whales in Cape Cod Bay and adjacent areas – that’s 65 percent of the known population! It’s also astounding that 77 of those whales were “new” to the Bay, having never been seen there in all our years of study. Massachusetts was the place to be in 2011.
Why? Well, the easy answer is…food. But what influences the food supply? There’s a lot of variability in the distribution and abundance of right whales and their food in Cape Cod Bay. Some years the food supply is strong and the Bay is filled with whales, while other times, food supplies are low and we have few whale sightings. The main star in this feeding frenzy is a small crustacean called Calanus finmarchicus, an oily delight much loved by right whales. (I’ve tasted it and it’s pretty good).
However, the abundant supply of Calanus isn’t created in the Bay. It’s renewed every year from sources in the Gulf of Maine via the Western Maine Coastal Current, a counterclockwise gyre of water that funnels right whale food into the Bay each season. This chain reaction – current, food, whales – is highly influenced by the direction of the wind.
In Massachusetts during the spring, the prevailing surface winds are usually out of the northwest, which helps the coastal current surge food into Cape Cod Bay. However, in some years a southwestern wind will dominate and that dampens the ability of the current to bring abundant Calanus supplies to the right whales’ door. A southwest wind pushes the current away from the Bay, diminishing the food supply, and thus making it less attractive to right whales. Researchers have found a significant correlation between the coastal current, wind direction, Calanus supplies and the presence of right whales in Cape Cod Bay.
This year was one for the record books, with the most individual right whales sighted in a single day off the Massachusetts coast, 123, and 312 over the course of the whole season. But will the winds of change blow in 2012, dampening the allure of the Bay? Or will we continue to see extraordinary numbers of right whales flocking to our waters to gorge on their favorite prey? Our partners at the Center for Coastal Studies will begin their aerial surveys again in mid-January. Stay tuned for updates about the 2012 season!