February 2009

02 February. Light winds and warmer-than-average temperatures made Monday another beautiful day for flying. As we flew North along our easternmost trackline off the back side of Cape Cod, we passed several Minke whales, distinguishable by the small white dots on their pectoral flippers. Nearing Race Point, tall spouts in the distance caught our attention, but when we flew over for a closer look, we found four fin whales surrounded by a pod of Atlantic white-sided dolphins.

Finally, near Wellfleet, our observer spotted the distinct, V-shaped blow of a right whale. As we turned to circle over the animal, we found that there were, in fact, two animals within a few body lengths of one another. They dove quickly, raising their wide, black flukes, and were not spotted again until approximately 12 minutes later, when they stayed at the surface long enough for us to take a series of photographs. During the bout of bad weather this week, we will be busy in the lab scrutinizing these photographs, trying to identify these individuals based on the unique callosity patterns on their heads.

10 February. While the primary objective of the right whale aerial survey is to monitor animals in Cape Cod Bay, we are also interested in the right whales making use of adjacent waters. For the first time this year, we flew a series of tracklines east of Cape Cod to see if anything was going on out there. The southeastern portion of this survey area covers a small section of the Great South Channel, another known right whale habitat. As we approached this area, we immediately noticed a great deal of splashing in the distance. As we got closer, we knew we were approached a group of right whales when we saw a black, paddle-shaped flipper smack the surface of the water. We had come across a SAG!

A SAG, or “surface active group” describes a group of right whales in close physical contact with one another. Animals engaged in a SAG might roll on their backs, touch each other with their flippers, and swim belly-to-belly. For obvious reasons, SAGs are thought to play a role in mating. However, because they occur throughout the year, many scientists believe that they have other social functions as well. While the number of animals in a SAG can vary quite a bit, this particular aggregation was comprised of only four animals.

Typical commotion of a SAG: One animal is belly-up as others approach.

As if we hadn’t had enough excitement for one day, we soon came across at least eight feeding right whales! Right whales typically don’t feed in Cape Cod Bay until late March and early April, but the Great South Channel is known for its rich planktonic resource as well. Nearby, several fin whales were spotted feeding as well. The survey team will be up again the next day, this time, covering Cape Cod Bay.

11 February. A second consecutive day of good weather allowed us to survey inside of Cape Cod Bay. We began our survey with a few fin whales on our track line east of Cape Cod. On our third track line, just west of Herring Cove, we spotted some white water, and whales rolling at the surface. We had come across a SAG (Surface Active Group) of four right whales! Characteristics of a SAG include rolling and physical contact. These aggregations can sometimes include upwards of 40 individual animals. Usually a SAG has one focal female who calls the males to her. When they arrive she rolls over on to her back and the males compete to be the closest to her, and when she rolls to take a breath the males that are the closest get the opportunity to try and mate with her.

We had continued south on a few more track lines when we broke track again to find three more right whales. Two were traveling together, and the third we only briefly saw by itself, with mud covering it’s head and body. Mud on the head and body can be an indication of an animal feeding on the ocean floor.

Once we were back up in the air, after having to land to refuel, we came across two more right whales who were traveling at a moderate pace. At this point we had to, unfortunately, cut our survey a little bit short due to impending fog. Nevertheless, it was a great day on the water with the most sightings in the bay so far this season!

11 February. The Habitat team set out for its fourth cruise of the season, enjoying optimal sea state and wind conditions, and approximately 10-km visibility. Several marine mammals were observed, including three harbor seals, one harbor porpoise and four North Atlantic right whales.

Surface and water column sampling occurred at all regular stations. Preliminary estimates suggest low zooplankton abundance at all stations with the exception of those in the southeastern part of the bay where densities approach a feeding threshold. Vertical-pump sampling (sampling at discrete depths) was conducted in proximity to where three right whales where seen diving and captured a likely mid-water concentration of copepods between 23 and 27 m depth.

Harbor porpoises, Phocoena phocoena, residents of cold temperate and subarctic waters of the Northern hemisphere, occur in small group sizes (2-5 individuals). Abundance estimates for harbor porpoises in the western Atlantic is approximately 75,500. Adult porpoises are typically between 4 ft and weigh 125-145lb and feed on a variety of fish and cephalopods. Although harbor porpoises are commercially exploited in some regions near Greenland, their greatest threat is incidental catches in fishing gear.

16 February. We began our survey in the southern portion of Cape Cod Bay, and as we flew west out of Chatham to begin our tracklines, we became slightly concerned with the sea state. The sea state, or Beaufort scale, is measured numerically on a scale of 0-12, with zero indicating flat calm seas with little to no wind. As the numbers of the scale increase, so do waves and wind. For example, a Beaufort of 12 would entail hurricane-force winds and giant swells nearly 50 feet high. In order to best spot whales at the surface, we typically fly surveys in sea state 5 or less. When flying a survey at anything above that, every wave can look deceptively similar to a whale. Our sea state averaged 4 throughout this survey, but nonetheless, we were able to spot and identify right whales, as we encountered a SAG, or “surface active group” of at least 4 individuals midway through our 3rd trackline, north of Barnstable Harbor. In addition to the right whales, we also spotted a humpback whale in close proximity to the group. As we continued north, the rest of the aerial survey proved to be fairly uneventful.

16 February. With a weather forecast unfavorable for most of the week, the Habitat team cruised today in hopes that seas and wind conditions would remain workable. Winds were generally 10-15 knots from the north and seas were 2-3 feet. Although not the near-ideal conditions we enjoyed last cruise, we did spot whales from a fair distance away (1-2 miles), and completed two special stations (A, B) plankton tow surveys proximate to whales. Vertical pump sampling was not conducted due to sea state conditions.

Approximately nine different sighting events (~8-12 whales) combined with challenging sampling conditions resulted in time constraints that permitted sampling our regular weekly monitoring stations in the eastern section of the Bay only. No whales were observed actively feeding, but many exhibited moderate to long dives and fluking behaviors indicative of possible mid-water column feeding. Two events had loosely associated whales (2-3 indiv.) rolling and generally spending some time at the surface, though these were not considered SAGs (Surface Active Groups).

Overall zooplankton abundance appeared below threshold, although diatom mats (phytoplankton) and prey-rich (zooplankton) samples near whales suggest that conditions might be developing (albeit patchily) for increased prey densities more characteristic of spring in the coming few weeks.

25 February. After a stretch of windy weather, we were excited to get back into the air on Wednesday. Despite the calm seas, we had no species sightings for the first few hours of our flight. Finally, just west of Wood End Light in Provincetown, we came across a single right whale, followed by four more closer to the beach. The first whale was embarking on long dives, suggestive of bottom feeding and foraging, while the whales near the beach were in a SAG or “surface active group.”

We soon came across another cluster of right whales southwest of Provincetown. After flying in circles around them, trying to get clear photographs, it became apparent that one of them was entangled. We recognized this as individual #1140, also known as “Wart.” “Wart” is a mature female who had her last calf in 2005. Her age is unknown, but she was first seen in 1981. Her entanglement was first documented in Cape Cod Bay last winter, and although some of the line was removed by the disentanglement team last spring, there is still some remaining.

We promptly called the Provincetown Center for Coastal Studies Disentanglement Hotline, and the team arrived on the scene quickly. The habitat team on R/V Shearwater stood by while we landed to refuel, and when we returned, we helped the disentanglement team on R/V Ibis to re-sight the whale, as there were many other right whales around and the entanglement is hard to see from the water. While the team wasn’t able to remove any gear from the animal yesterday, the photographs from both the plane and the boat will be used to assess Wart’s health, and to help the team figure out the best strategy for disentangling this animal in the future.

A healthy population of calving females is critical to the survival of this dwindling species, so we are especially interested in this particular entanglement case and we hope to see “Wart” again on upcoming surveys so we can continue to monitor her status.

25 February. With excellent sea conditions and low air temperatures, the Habitat Studies team left on its sixth survey cruise of the season at 1100 hours today. The day’s cruise plan (including this later-morning departure) was ambitious: to sample not only our regular monitoring stations (tows, CTD, and water quality samples) but to document the diel vertical migration (DVM) of a calanoid prey resource. Diel vertical migration is a common zooplankton behavior in which organisms reside in surface or near-surface waters at night and at deeper depths during the day in response to light levels. The implications for right whale feeding behavior suggest that with prey concentrated nearer the surface at night, right whale behavior may shift from longer duration dives to shallow swimming and skim feeding at or near the surface, thereby exposing the whales to an increased risk of being struck by passing ships or entangled in near-surface fishing gear. Because of the obvious challenges and risks imposed by night time studies, few have been conducted in Cape Cod Bay. Using night vision equipment, we hope to conduct several sampling events dedicated to DVM/nocturnal right whale behavior documentation this season.

Regular monitoring was interrupted (and eventually discontinued) at approximately 1300 when we received a sighting report of an entangled whale by the Aerial team. We responded on scene to provide logistical support until the Disentanglement team could arrive. Further sightings of deep-diving right whales (12 to 18 total) and our efforts to couple observed feeding behaviors with intensity and duration prey resource (as well as DVM) afforded us a good opportunity to conduct three vertical pumping events, across daylight and into nighttime hours, in proximity to feeding whales.

Over 70 samples were collected, and will be worked up in the lab in the coming few days. Although a full bay survey was not completed this cruise, we predict aggregations of right whales may persist in the southern quadrants of CC Bay over the next few weeks, where enriched resources are expected to persist near the lower portions of the water column. We look ahead to the analyses and sharing of the findings of the DVM studies, and towards the possibility of getting at what right whales (and their prey) are doing after dark in Cape Cod Bay!