- Research & Education
- Cape Cod
On June 15, the week began with finwhales and minke whales being finwhales and minke whales. Both species spent much of the day foraging deep in the waters of the nearby North Atlantic, appearing to surface in random directions and after random amounts of time beneath the surface. A number of both types of whales were viewed from the Dolphin Fleet boats today. If you had asked the passengers, they would possibly have told you that the basking shark was the highlight of the day. Basking sharks are the second largest fish currently inhabiting the earth. A large one might be forty feet or more in length, but, here in the waters of the Gulf of Maine, they are more frequently around 18 feet. They have numerous teeth, but due to their prey species and method of feeding, those teeth are largely undeveloped. Feeding on very similar species as the North Atlantic Right Whale, they have a feeding technique that is very similar. Right Whales swim forward with their mouths open, allowing the plankton rich waters to flow into their mouths and filter out between the baleen plates that hang down from either side of their upper jaw. Copepods are collected by the very fine hairs on the inside of their baleen plates. Basking sharks feed in a similar manner, swimming along with their mouths open and allowing the plankton rich waters to pass over their gills. The gills of the fish extract oxygen from the water at the same time as specialized spines, called gill rakers, collect the zooplanters from that water. At some point, just as with the Right Whale, the Basking Shark will close its mouth an swallow so that it can go back to feeding again. Very little is know about how Right Whales and Basking Sharks find dense enough patches of plankton to be worth feeding upon.
By noon on this Father’s Day, June 16, the finback whales had found sufficient schooling fish beneath the surface to get their attention. While the lunges through the schools of fish could not be seen at the surface, their was still evidence of their feeding for those that cared to look for it. The finback whales would surface several times making an arch that, when you connected it with the flukeprints, turned into a circle. Then a quick surfacing for a single breath before a quick dive. When the whale would resurface, it would do so slowly, appearing to just kind of float up to the surface. Big and round, because of the extended rorqual pleats on their undersides, they would slowly move forward. Using the strong mucles between those pleats to collapse the swollen undersides and push the fish and saltwater against the back of their baleen plates, they would begin to separate the fish and seawater. At times, you could see the water pouring out of the corners of the finback whales mouths. Big and round at the fronts of their bodies, but having a normal tail stalk region, makes them look very much like huge tadpoles while they are feeding.
Bright, hazy skies and a gentle breeze madeJune 17 a beautiful day for a trip to the North Atlantic. And though the feeding behavior of the finback whales was every bit as spectacular today, the highlight of the day probably goes to the ten oclock voyage of the Dolphin IX that found the Mute Swan, just because of how rare that sighting is. More common in ponds and rivers, Mute Swans also are known to frequent coastal lagoons and bays. A large bird, they were introduced to New England from Europe. In Pennsylvania, a mating pair of Mute Swans had come to inhabit the pond in the center of my alma mater, becoming unofficial mascots and raising several nestfuls of cygnets during my years there.
As a sidenote, Cygnus, a male humpback whale first sighted in the late seventies, got his name because his nearly sickle shaped dorsal fin had such a graceful and elegant curve that it got compared to the neck of a swan.
The bright, sunny skies and flat seas of June 18 expanded sightings to include other marine mammals like gray seals and harbor seal. It also allowed for the sighting of a single ocean sunfish or Mola mola. A giant of a fish, the sunfish can be as long as ten feet and more than eleven feet tall. Those dimensions do suggest a very round fish. Don’t be fooled though. In the warmer waters of the tropics, sunfish are very strong swimmers. It is only in colder waters that they are considerably more at the mercy of the currents and, as such, huge zooplankters. They have beak-like mouthparts that they use to capture jelly-fish like animals called ctenophores for food. Unlike most types of fish, they swim by rhythmically beating their dorsal and anal fins in unison, as they don’t have much of a tail. This naturalist was very fortunate in that his whalewatch included a sighting of a Great Blue Heron as the Dolphin IX passed the breakwater leading into the inner harbor.
The action on June 19 was down the backside of the Cape. Finback whales spent the day circling around the balls of schooling fish, likely a way to concentrate them closer together so the whales get more fish in each mouthful. Let’s face it, when a finback whale opens its mouth and lunges through a school of fish, as those rorquals expand, the hydrodynamics of that fast, streamlined whale changes abruptly. As it continues to lunge, the front of the whale’s body becomes a huge balloon of water that actively pushes back on the water coming at it. So it requires a huge amount of force to lunge through a school of fish and, also, a huge amount of energy. That expenditure of energy must be compensated for it the whale is to nourish itself and expand the blubber layer it will depend on in times of scarcity. Toward that end, many kinds of whales have developed techniques to concentrate their prey species. Humpback whales, for example, blow spirals of bubbles around the schools of fish to scare them together and pods of Atlantic White-sided Dolphins have been seen to corral herring against the hulls of boats so that they can take turns darting into the school to grab a bite.
When viewing humpback whales, it is fairly common to see them complete their feeding lunges above the surface of the sea. Even with finback whales, it is not uncommon to see a feeding whale roll on its side as it lunges through a school of fish at the surface. But to see a minke whale lunge at the surface of the water is something that a New England whalewatch naturalist sees two or maybe three times in a career. That was the story of June 20.
When a finwhale lunges at the surface, it typically rolls on its side and moves with a huge amount of speed, pushing an immense amount of water. Humpback whales might lunge like that or they might lunge with speed and force straight up from beneath the school of fish. Or, when bubble feeding, they might rise majestically and slowly from the depths. When a minke whale lunges at the surface, it is dorsal fin up and, BAM, it’s all over. No warning from bubble clouds. No last second jump to get clear of the whale’s mouth. Without warning, you are all-of-a-sudden in the mouth of the whale and it is too late.
June 21 should be referred to as Skeg Day. Aware of our presence, but appearing oblivious to it, this finback whale spent a great deal of the afternoon feeding beneath the surface. What that looks like at the surface has already been described earlier this week. But today, there was a point that the animal surfaced facing the boat. There is a finite line on the lower jaw of a finback that marks the abrupt edge of the assymetric pigmentation. A point where brilliant white becomes dark. The passengers of the Dolphin IX saw that line today. And, following along behind it, the huge puffed out rorquals of a whale in feeding mode.