In 2005, the right whale surveillance program supported by the Commonwealth of Massachusetts Division of Marine Fisheries (DMF) was conducted in Cape Cod Bay and adjacent waters from 1 January through 15 May by the right whale research team at the Provincetown Center for Coastal Studies (PCCS). The program included bi-weekly aerial surveys and weekly habitat sampling. Two flights were also conducted on 9 and 18 December 2004. Upon completion of each survey, all sightings were reported to the NOAA Fisheries Sighting Advisory System (SAS) and the US Army Corps of Engineers Cape Cod Canal Field Station.
During the 2005 winter and spring season, PCCS observers performed 39 aerial surveys totaling 175 hours of flight time covering Cape Cod Bay and the near-shore of the outer shore of the cape.
Right whales were observed in Cape Cod Bay for 86 days, from 30 January through 26 April. This period of occupation of the bay is only slightly shorter than in 2004 (90 days), although in 2004 zooplankton was substantially more abundant than in 2005 (at least by a factor of two). In 2005, a total of 264 right whale sightings were recorded from all platforms, of which 249 were photographed. Of the photographed sightings, 192 were in Cape Cod Bay representing 45 different individuals, and 57 were in an area east of the Cape, representing another 45 individuals. Although all identification photographs have already been matched to the existing right whale catalogue by two independent experienced researchers, most of the matches are still awaiting final confirmation by the New England Aquarium, and the results outlined in the present report may change slightly once confirmation is obtained.
In 2005, fewer right whales than average visited CCB (45 individuals versus an average from 1998 to 2004 of 60) and their average individual residency time was also shorter (`x=13 days versus a project average of 21 days). This substantially shorter individual residency time was likely related to the low zooplankton density throughout the season. Unlike 2004 when only 1% of the sightings occurred in adjacent waters, a large number of sightings (28%) occurred in adjacent waters in 2005 and a similar number of individual right whales were identified in CCB and in adjacent waters. Ten mother and calf pairs were sighted in CCB and adjacent waters. The residency time of mother and calf pairs was substantially longer than of single females and the residency time of single females was also substantially longer than that of single males. This result was consistent with that of all previous years (1998-2004) suggesting that CCB is an important nursery area and that the habitat is more intensively used by females than by males. Few juveniles were seen in 2005 (n=5) and the adult:juvenile ratio was significantly different than the ratio found in the catalogued right whale population. Twelve right whales, principally mothers with calves, identified in the southeastern US calving grounds were re-identified in CCB and adjacent waters by the PCCS aerial survey team a median of 39 days later, providing some indication of transit time. As in previous years, the number of right whales increased slowly between late January and late March, peaked from late March through late April, and dropped off to zero at the end of April. Gaps in the sighting histories of individually identified whales may indicate that some animals periodically leave the bay for short periods, perhaps traveling to adjacent areas beyond detection by standard aerial surveys.
Most of the whales were sighted in the southern-central part of the Bay, a region that corresponds to the area of highest zooplankton concentration (from oblique tows) during the 45-day period from 1 April to 15 May. Therefore, at the time of peak abundance of both copepod density and right whales, there seemed to be a good overlap between whale and copepod distribution. Large aggregations of whales in the northeast part of the bay (close to Provincetown) that were frequently observed in previous years were not observed in 2005.
Two previously entangled whales were sighted during the 2005 season; an updated assessment is presented on the condition of these two whales each entangled since 2002 (#s 1424 and 2320). Both were also sighted in the bay in 2004.
In 2005, the right whale habitat sampling team was available for Cape Cod Bay field sampling aboard the R/V Shearwater from 1 January through 15 May. Twenty-two habitat sampling cruises were completed between 5 January and 14 May, totaling over 170 hours at sea. The technique developed in 2003, using four parameters of zooplankton richness to predict the occurrence, aggregation, and residency of right whales in Cape Cod Bay, was continued in 2005. Weather permitting eight stations located throughout the Bay were selected and sampled on every cruise to maintain a baseline data set. Data, graphics and written assessments from every cruise were, in most cases, sent out within a 36-48 hours to an e-mail distribution list including interested academic, governmental, scientific, and management agencies and individuals for the purposes of aiding the management of right whales within the Cape Cod Bay Critical Habitat. Additionally, faxes detailing cruise duration, sampling locations and types, opportunistic sightings of fishing gear, and marine mammal sightings were sent to Division of Marine Fisheries state biologists immediately following every cruise. In 2005 the evolving habitat assessment technique repeatedly demonstrated its utility of explaining the movements of right whales, often in a predictive capacity.
A total of 434 zooplankton samples (from surface tows, oblique tows and vertical pump casts) were collected. Data from surface and oblique net tows and vertical pump samples showed 2005 as a year of substantially lower zooplankton densities than many prior years. The usual seasonal progression of dominant taxa (Centropages spp. to Pseudocalanus spp. to Calanus finmarchicus) began earlier in 2005 than in previous years, resulting in a shorter peak period for Centropages spp. February was characterized by very low copepod density and it has been hypothesized that during this time right whales were feeding on juvenile midwater euphausiids of the genus Meganyctiphanes, a "krill" organism, that are poorly sampled using standard zooplankton nets.
The comparative plots offer some insights into the influence of the zooplankton resource on whale distribution. The long-held view that the zooplankton resource in the eastern two thirds of the Critical Habitat is a controlling factor of whale presence in the eastern bay is supported by the comparisons presented. The comparisons also show that the zooplankton sampling methods do not fully capture the controlling influence of the food resource, failing to fully represent the importance of deep layers of plankton that may contribute to the aggregation of whales.
The 2005 right whale habitat monitoring season was also designed as a testing period for the incorporation of an optical plankton counter (OPC) into PCCS's existing zooplankton sampling and assessment program in Cape Cod Bay. The OPC collects high-frequency data on the abundance and size of zooplankton that pass through its sampling channel as the instrument is towed behind a vessel or deployed as a vertical profiler. When used in conjunction with other sensors, such as a Conductivity-Temperature-Depth Probe (CTD), this sampling method yield high-resolution oceanographic and zooplankton data that can aid in predicting when conditions are conducive to right whale presence and foraging.
Many unforeseeable difficulties arose during this trial season, including antiquated and simplistic OPC software, an inherently flawed configuration of instruments, and a trio of platforms with many sensors that were not designed to communicate with one another. However, despite these problems, the OPC/CTD package was deployed vertically on-station during every habitat cruise from 18 March onwards and the results showed the amazing potential of these instruments to detect temporal trends and to make spatial comparisons.
