March 2009

26 March. After a week and a half of windy weather had kept us on the ground, we started Thursday’s survey in southern Cape Cod Bay. The seas were so flat and glassy that any surface disturbance was visible miles away. By the fourth trackline, we found ourselves in the midst of several groups of right whales. Several of them were resting at the surface, or “logging”, but many of them were in SAGs or “Surface Active Groups.” SAGs of three animals quickly grew in number as individuals from the area approached the groups of rolling and thrashing right whales. It is thought that right whales are attracted to the vocalizations that other whales make while involved in a SAG.

While this is the time of year where we normally start to see more feeding, we didn’t see as much today as we expected. As the habitat team confirmed, their primary food source has not reached high levels yet this spring. We did, however, see a few animals feeding intermittently, their mouths wide open. One animal even rolled over to feed on its side, just as it surfaced!

An incoming rain shower forced us to land before we could complete our northernmost tracklines, but we’re hoping for another good stretch of weather in the near future to see if new individuals are making their way into the Bay.

26 March. Taking advantage of mostly clear skies, forecasted light winds and pleasant temperatures, the Habitat Team set out this morning for another regular sampling cruise on the tail end of a period of uncooperative weather (gale winds and mixed seas resulting in canceled cruises). Our last cruise (March 15) we had an epic day, witnessing 20+ surface skim-feeding right whales and a rich prey resource in the southern section of the bay. Today’s research question followed: would there still be those high numbers of aggregated whales, and would they be surface-feeding, suggesting higher zooplankton concentrations in the top meter of the water column?

Smaller aggregations and a more diffuse distribution of right whales, even in the southern quadrant of the bay was the observed pattern; only 1-2 possible skim feeders were seen. Most whales sighted were single, exhibited straight-line travel and/or periodic fluking dives, suggesting (that if feeding) the targeted prey patches were well below the surface. The Aerial Survey team did document several surface-active groups (SAG) with only a few possible indications of sub-surface feeding. Two more interesting behaviors documented were: first, around midday, where one individual was seen resting unmoving at the surface (logging) and second, much later an individual plowing its head through a fairly obvious surface diatom slick, evidenced by a foamy line of demarcation near the interface of two distinct water masses (see picture below).

The beginning of the cruise was focused towards photo-documentation of individuals and their behaviors, but as no obvious pattern in either distribution or feeding behavior emerged, we returned to the primary cruise objective to measure and quantify the physical parameters and zooplankton characteristics in surface and water columns bay-wide at our nine regular stations.

Zooplankton densities appear well below threshold for a feeding response, with the highest density encountered in the middle section (8M) of the bay, and predominantly Pseudocalanus spp. Analyses for taxonomic richness and abundance require further lab work, but appears at the moment that appearance of the late-season Calanus finmarchicus has yet to occur and may be a determining factor whether large aggregations of feeding whales will likely form again, or whether the whales will continue their thinning out and/or exit the bay in the coming weeks.

Eleven harbor seals, one fin whale and an unidentified (likely fin or minke) large whale sighting and an increase in bird numbers overall (gannets, scoters, cormorants, gulls, red-breasted mergansers) was also documented.

17 March. Tuesday was another calm day in Cape Cod Bay, and taking off from Chatham airport, we headed towards Provincetown to begin our survey on our northernmost tracklines. Our first sighting was just north of Race Point Light in Provincetown. Anyone walking down the beach with a pair of binoculars would have been able to see the splashing and commotion caused by three right whales rolling around at the surface, often slapping their black, paddle-like flippers down on the water.

As we continued to head south, we continued to find right whales evenly distributed throughout the bay. Many of them were in social aggregations or “SAGs”, while others were slowly traveling in groups of two or three. We came across three feeding right whales over the course of our survey; however, they were not in the same area. One was feeding right along a visible slick line. A slick occurs when two currents converge and is often visible as a line along the water. The convergence of currents can sometimes cause plankton to aggregate along such slicks, so it is not uncommon to see whales feeding along these lines.

Today’s survey left us with a lot of questions. There were unusually large numbers of right whales distributed throughout the bay in a seemingly random pattern. Are the whales getting ready to leave, or are they waiting for their food resources to reach higher levels before they start feeding at the scale that they did last April? We will have to wait for our next good weather day to find out!

15 March. With a second consecutive day of ideal weather, the aerial team flew our Cape Cod Bay survey area today. Having spotted over 30 whales earlier in the week, we were very excited to see how many more had made their way into the bay. And more there were, as we had over 75 sightings of right whales for the day. A new record! To coincide with the R/V Shearwater’s cruise plan, we flew from south to north, and due to the incredible number of whales we spotted, we were only able to complete 9 of our 16 survey lines. While the majority of the whales were concentrated in the southern and central portions of the bay, we did continue to have sightings as we moved north until we were forced to land at 1830 due to sunset, so everyone is very curious as to just how many more whales may be in the area. Some interesting sightings included a large congregation of 15-20 right whales west of Wellfleet, most of whom were skim and subsurface feeding. Fortunately, R/V Shearwater was able to come on scene to sample the zooplankton levels in that area to see if the prey source may have influenced the whales’ behaviors. We also spotted EGNO 3530, or Ruffian, a right whale who was very badly injured last year, and we are happy to report he looks much healthier this year.

15 March. The habitat team set out for its eighth cruise of the season (SW375) on 15 March 2009 with optimal sea and visibility conditions. Approximately 34-39 right whales and 19 harbor seals were sighted by the R/V Shearwater. The purpose of the cruise was to document the vertical distribution of the controlling zooplankton resource along the eastern and southern margin of Cape Cod Bay. A prey patch dominated by Pseudocalanus ssp. was located in the southern portion of the bay. Vertical sampling revealed that Pseudocalanus ssp. was concentrated in the upper 5 meters of the water column (surface layer). Approximately 21 skim feeding whales were observed in the vicinity of the prey patch. Skimming is a feeding behavior employed by right whales whereby the whales will plough through a dense layer of zooplankton with open mouths, trapping their almost microscopic prey in their baleen plates. Right whales will usually begin feeding once they have a minimum density or caloric value of organisms per cubic meter (3,750 org/m3 or 690 cal/m3 approximately).

14 March. With a weekend of good weather ahead of us, we decided to fly Saturday’s survey east of Cape Cod to see if we could find any right whales on their way to the feeding ground. We started our survey north east of Race Point Light in Provincetown, but didn’t see any marine life until we got closer to the Nauset area. Humpback whales and fin whales, inclined to feed on small schooling fish, seemed to have found a large patch of food and were feeding voraciously. Three humpbacks blew rings of bubbles to corral and trap fish, while the fin whales lunged through their prey at top speed. We watched as one fin whale rolled on its side and hyper-extended its jaw to take in an enormous mouthful, the pleats on the underside of its body expanding to accommodate such a large gulp. Within this feeding frenzy, we also came across three right whales. Right whales have much finer baleen than the humpbacks and fin whales, and as a result they are well-equipped to feed on a smaller prey items. Therefore, we were not surprised that they were not feeding side-by-side with the other whale species. Instead, they were slowly traveling northward, perhaps towards the more productive feeding area in Cape Cod Bay. One of the whales was EGNO 3294, a right whale who was entangled in fishing gear earlier this year, but is now free of the gear.

10 March. After more than a week of windy weather, we were thrilled to wake up to flat-calm seas on Tuesday morning. We started our survey along our southernmost tracklines and almost immediately came across a large aggregation of right whales—approximately 14 within a one-mile radius! We flew in circles, trying to get a clear photograph of each individual, and noticed that some of them had their mouths wide open, revealing rows of baleen. The baleen in a whale’s mouth is used to filter and capture the nearly-microscopic planktonic organisms upon which the right whales feed. We radioed the R/V Shearwater so that they could take a sample of the food resource near the feeding whales, and continued on with our survey.

As we headed north, we continued to see right whales dispersed across the southern portion of the bay. Many were alone or in small groups of two or three, while others engaged in SAGs or “Surface Active Groups.” We watched one whale roll over on its back, revealing a bright white belly. Often, a SAG will start when male right whales converge around a “focal female.” Sure enough, as this animal continued to roll over, we watched other right whales in the area traveling quickly towards it. Photo analysis will reveal the demographic composition of the group, and it will be interesting to see which individuals are engaged in this particular behavior.

After landing to refuel, we re-started our survey right where we left off near Wellfleet. During the first leg of the survey we had counted at least 30 whales, and we were ready for more! While we found several more whales in the middle of the bay, we had significantly less activity on our Northern tracklines, with only a few sightings of fin whales and one humpback. Last year at this time, we were seeing an average of 12 whales per survey. Compared to Tuesday’s total of 38, we are curious to see what will happen as spring approaches!

10 March. The Habitat Studies team headed out from Provincetown harbor this morning to monitor right whale prey resources in Cape Cod Bay after a nearly two week hiatus due to poor cruising conditions. Leaving the dock just before 0945, we had excellent sighting conditions and a good weather forecast in our favor. Starting in the northeastern section of the bay, we collected zooplankton samples at each of our regular 9 stations (both with plankton tow nets for zooplankton resource evaluation, and a CTD for physical characteristics), moving in a clockwise direction around the bay. Since it has been several weeks since a bay-wide survey has been completed, we were interested to discover what the distribution and abundance of calanoid copepod resources might be, and what it suggests regarding the abundance and distribution of whales in the bay.

Zooplankton densities in the water column were greater than in the surface waters; the 19 whales encountered today displayed more social behavior than seen in previous cruises, though the long diving behavior typical of this season’s previous cruises was also observed. A surface active group (SAG) involving three to four individual right whales was encountered about midday, and the splashing and rolling of bodies at the surface as the boat neared allowed our observation team to get a series of photo ID shots.

Zooplankton samples from the southern quadrants of the bay contained the strongest zooplankton resource, causing a trend in right whale aggregation toward the southern part of the bay. At this time, the zooplankton resource remains dominated by Pseudocalanus spp. and appears to be at or above the density threshold attractive to feeding right whales. Whether this prey resource persists, is grazed down, or avected out of the bay, remains open for further investigation. The habitat team is also awaiting the arrival of Calanus finmarchicus, the most calorically rich calenoid copepod found in the bay, and a favorite food of right whales.