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Trip to the Edge of the Continental Shelf

The Thelma Dale IV pulled out of the marina at Lewes, Delaware, just after 5 a.m. on Saturday, August 27. As we headed towards the open sea, the sky began to lighten on the eastern horizon. The colors and cloud formations between dawn and sunrise were spectacular. It was one of those "you had to be there moments".

Not long after we passed Cape Henlopen, Delaware, a secondyear immature northern gannet flew alongside our boat. While most gannets would be in the Gulf of Saint Lawrence or the coasts of Newfoundland, Labrador, and Iceland at this time of year, occasional individuals remain well south of their breeding range after spending the winter off our coast.

As promised in our last newsletter, members of BRMC participating in this trip got to check Wilson's storm-petrel off their life lists. We didn't just see one or two, but by the end of the day, tallied 581! The Wilson's storm-petrel is a transequatorial migrant, breeding in such places as Tierra del Fuego, the Falklands, and islands off Cape Horn and spending their "winter" as far north as New England.

A group of birds aptly names "shearwaters" were represented by two species. These birds wheel and turn and glide just over the surface of the ocean on stiffly held wings, almost as if they shear the tips of the ocean waves. The first was a Cory's shearwater, of which we tallied a total of 19 for the day. This species is also called the Mediterranean shearwater as it occurs there, as well as in the Atlantic Ocean. The second species was the Audubon's shearwater, which is widespread in tropical oceans. Of the seven Audubon's shearwaters we observed, some could have come from islets off the Caribbean coast of Panama, the West Indies, or even the Galapagos, following the Gulf Stream north to reach us.

We saw other pelagic bird species, but the real show was the marine mammals. The first whale species that we spotted was a pod of about 30 short-finned pilot whales. These whales are found in tropical, subtropical, and warm, temperate waters. Typically a deep-ocean species, they move north from the Caribbean in summer to give birth off the mid-Atlantic coast. Ocean currents crossing the deep canyons along the edge of the continental shelf create upwellings, bringing food and nutrients to the surface. This creates a rich community of marine life-including the squid that are the main food for these species. We were able to get quite close to them.

Another interesting species that appeared soon after was the gray grampus or Risso's dolphin. Adult Risso's dolphins are easily recognizable at sea by the obvious scarring on their bodies. There may be many reasons for this scarring. Aggressive behavior, play, sexual encounters, and even encounters with giant squid. One of the 40 or so individuals that we came across was so scarred he appeared totally white. The dolphins repeatedly came completely out of the water, jumping almost 10 feet high as they swam in front of us.

As the day progressed we had sightings of loggerhead turtles and the giant ocean sunfish or Mola mola. This slow-swiming species can reach up to one ton in weight and over 10 feet in length. We got so close to it, as it swam just below the surface, that we were actually looking down on it through the clear, blue water.

The day was passing quickly and, unfortunately, we had to head back to land. We figured we had seen everything that day that we could. But, wait… what was that in the distance? A tall spout of mist on the distant horizon got everyone excited. We headed in that direction and saw more activity ahead. More spouts, some 15 to 20 feet high appeared. Soon, we closed in on a pod of six fin whales, a species second in size only to the blue whale, the largest living animal on earth. We were close enough now to see the dorsal fin appear just after the blow. We observed them for at least 20 awe-inspiring minutes. Fin whales are found in every ocean of the world and rarely come close to shore. The best chance to see them is on a pelagic trip.

As we returned to the marina we discussed how glad we were to have had such an interesting day-and not one BRMC member got seasick!