The need for a broader understanding of the actual status of whale stocks in the Southern Hemisphere led the International Whaling Commission (IWC) to coordinate multilateral studies of different species in their feeding and breeding sites. The humpback was one of the most depleted whale species from commercial whaling. Uncontrolled hunting drove the species to the edge of extinction. Only some years after the whaling moratorium did humpback populations start to show gradual signs of recovery. The species is still considered Vulnerable and won research priority as one of the objectives of the Commission. The aim of the global evaluation of their stocks includes understanding how many populations of humpbacks exist, where the populations concentrate, and in what abundance. The effective management and conservation of any species depends upon the understanding of and the answering to these questions, as well as the knowledge of the role of the species in its ecosystem.
With the goal of collaborating with the IWC, the Brazilian Antarctic Whales Project (Projeto Baleias Antárticas) engaged the broader Brazilian Antarctic Program (PROANTAR), which includes several projects on Earth, Atmospheric and Life Sciences, according to the aims and the policy of the Antarctic Treaty. Our participation in the PROANTAR commenced during the 1994/95 austral summer (mostly to evaluate the logistical viability to study cetaceans in such a remote area) and continued in the last two summers. The objectives of our whale project are: 1) to photo-identify humpbacks around the South Shetland Islands and Antarctic Peninsula; 2) to biopsy humpbacks from the same areas for DNA analysis; 3) to estimate cetacean density in these areas; 4) to record every cetacean sighted while the ship is navigating.
During the 1997/98 summer season, we were able to report about 700 cetacean sightings, to photo-identify and take tissue samples from humpbacks and to estimate whale density (mostly humpbacks) in the Gerlache Strait and around King George Islands (where Brazil and many other countries have their Antarctic stations). A comparison among the photos taken in three different occasions in the Gerlache produced at least one match, suggesting that some individuals may remain in the area for a relatively long period during the feeding season if food is available. Further comparisons among several different years may show us if some whales present some degree of fidelity to their feeding ground.
Gerlache is a wonderful narrow corridor of calm water gently flowing between the high snow-covered mountains of the Antarctic Peninsula and some neighboring islands. Local fauna is very diverse and includes many species of penguins and petrels, gulls, seals and Antarctic fur seal, whales (mainly humpbacks, minkes, orcas, and occasionally southern right whales and beaked whales), besides those ever submerged zooplankton, benthos and fish.
Interesting feeding behavior could also be observed in the Gerlache. While groups of humpbacks were swallowing patches of krill, large flocks of Antarctic fulmar flew over the humpbacks' heads to opportunistically feed on scattered escaping krill. Also, a lonely orca was seen slapping a seal out of water and a pod of eighteen orcas were seen swimming around a frightened group of six humpbacks.
Although our field work for the 1998/99 summer season is still in its midway, we could already individually identify many humpbacks. Skin samples were also collected from 65 for DNA analysis. We also recorded eight cetacean species in Antarctic and sub-Antarctic waters: fin whale, Balaenoptera physalus, sei whale, B. borealis, minke whale, B. acutorostrata, humpback whale, Megaptera novaeangliae, sperm whale, Physeter macrocephalus, orca, Orcinus orca, hourglass dolphin, Lagenorhynchus cruciger and, surprisingly a mother-calf pair of southern right whales, Eubalaena australis; also Peale's dolphins, Lagenorhynchus australis, inside the channels of the Tierra del Fuego, in Argentina and Chile.
When the ship was navigating we had the opportunity of watching wonderful moments of natural whale shows. A group of five fin whales kept about an hour bow-riding and "horsing" ahead of the ship. In a single and unforgettable day, the same day we enjoyed the fin whales, another four species were seen, including a pod of orcas and the unexpected mother and calf right whales. Marvelous breachings of huge adults as well as of fragile humpback calves were frequently appreciated. When the ship was standing by (mainly in Gerlache) waiting the end of our zodiac-based photo-id work, groups of curious humpbacks friendly approach and "spy-hop" the ship for up to a couple of hours. Such exciting moments were greatly appreciated by the whole crew and by us from the zodiac. It was really amazing!
Our proposal for the coming year includes an integrated study of predator-prey interactions in Antarctica. In this sense, we intend to run acoustic and whale surveys in the Area 48 (around South Shetlands and Antarctic Peninsula) in order to understand more clearly predator (whale) and prey (krill) interactions. Environmental data must also be obtained at regular intervals during the cruises. Observations of krill behavior in areas with and without whales can be developed from these data. Trends on predator density and distribution may be evaluated according to the density and distribution patterns of their prey.
We are proud to be engaged in the PROANTAR and to have the singular opportunity to contribute to the progress of the science and to the conservation of invaluable components of the natural heritage, the whales and the Antarctic ecosystem. Hopefully our effort could be of some help.
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