the blue whale

BLUE WHALE RESEARCH PORTLAND 2004

In February 2004 a team from Deakin University used Pelican to conduct research on the blue whale population near Portland in south western Victoria. The general public had a unique opportunity to participate as volunteers and learn directly from the experts by observing and helping out with the many research tasks. Their participation helped to ensure the continued welfare of this unique population of blue whales

Background:
Blue whales are the largest animals to have ever lived, reaching 30 metres and over 150 tonnes. As a species they were almost exterminated for their oil by commercial whaling during the 20th century. They are still only at about 2% of their original population size, which numbered well over 200,000 in the Southern Hemisphere, and they are showing few signs of recovery from near-extinction.

Blue whales carry out long migrations between summer feeding areas, and wintering areas where breeding occurs. There are only 10-12 known feeding areas worldside. Until recently, the only known feeding areas anywhere near Australia were in Antarctic waters, but in recent years, at least two have been ‘discovered’ in Australian coastal waters. One of these is off Rottnest Island, WA. The other is in the Bonney Upwelling region of western Victoria and south-east South Australia.  

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FEEDING ON KRILL AT THE BONNEY UPWELLING

In recent years, two feeding areas have been ‘discovered’ in Australian coastal waters. One of these the Bonney Upwelling region of western Victoria and south-east South Australia.

The Bonney Upwelling:
The Bonney Upwelling is a seasonal oceanographic feature along the continental shelf between north-west Tasmania and Kangaroo Island, South Australia. Between November and April, strong south-east prevailing winds drive a current northwestwards along the coast, which due to the Earth’s rotation, tends to drift the surface water offshore. This displaced water must be replaced with something, so cold, nutrient-rich bottom water is upwelled onto the shelf. When the nutrients reach the sunlit surface zone, there is an explosion of minute plant life due to photosynthesis. This ‘phytoplankton’ is the basis of the marine food web, and is a primary food of the local species of krill, Nyctiphanes australis.

Krill:
Blue whales feed almost exclusively on krill, crustaceans similar to (but usually smaller than) prawns. Krill often form huge, coordinated, active swarms of many millions, and feed on a variety of plant and animal matter. They occur widely in many areas of the world, but there are few areas where they really concentrate into predictable swarms which are large enough to feed predators on the scale of blue whales. These swarms tend to gather in areas where productivity is highest, but think of this dynamic ecosystem as a boiling pot, with ‘cells’ of productivity bubbling up, then settling down over a scale of hours, with swarms gathering and scattering, as they seek food and avoid predators. A blue whale must somehow locate scattered swarms of krill in a large expanse of ocean, and then actively hunt them, scooping four to six tons of krill a day in powerful feeding lunges. Pleated muscles allow the whale’s throat to expand into a huge water- and prey-filled sac, before the whale filters out the water through its fibrous, hanging baleen plates, leaving the krill trapped inside. One of the really interesting things about Nyctiphanes australis is that it frequently swarms at the surface, so that is where blue whales are often found feeding, in plain view. In other blue whale feeding areas overseas, whales disappear for 15-20 minutes while diving to feed on deep krill swarms.

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FIELD WORK

Since 1998, Pete Gill of Deakin University and Australocetus Research has been studying the ecological links between the winds, the currents, the upwelling, krill, and blue whales, which were first reported here only in late 1995. Using a range of methods including aerial surveys, satellite remote sensing (internet –accessed images of weather, surface temperature and surface chlorophyll concentrations) and yacht-based fieldwork, he has been able to show that blue whales arrive in the area in December, soon after the upwelling starts, and remain until May, when the upwelling season has ended. His work has outlined the approximate limits of the feeding area, although smaller numbers of blue whales are likely to be found both east and west of this area. The work has thrown new light on a range of subjects from the upwelling itself, to the swarming behaviour of krill, the ecology and behaviour of the blue whales, and some of the threats that face them in this region.

Margie Morrice joined the Study in 2001, bringing her own considerable experience to bear on the blue whale research. Pete and Margie plan to continue the work carried out so far, and to expand into new areas of research, in order to provide the information that is essential to successfully manage human activities in this habitat, which is critical to the survival of this Endangered species.

The program of aerial surveys and satellite remote sensing will continue as in past seasons. However, this season the researchers had access to the Pelican for more varied work. it enabled them to carry out research which formed a central part of Margie’s doctoral studies. They used Pelican to carry out surveys in selected parts of the feeding area, and documented the following:

The properties of the ocean, such as temperature at various depths, salinity, etc, which can be related to the dynamics of the upwelling;

• The distribution of krill swarms, both at the surface, and below it;
• Aspects of the biology of the krill e.g. their reproductive state, what they are eating, etc.;
• The distribution of blue whales, in relation to krill swarms, other species, the upwelling etc.;
• The behaviour of blue whales, including their feeding behaviour and their underwater sounds.;
• The continuing process of identification of individual blue whales, by photographing unique pigment patterns on their flanks.;
• The collection of skin samples from blue whales, to add to the understanding of how these whales fit into the global blue whale population structure;
• The continuing documentation of other species of mammals, birds, fish and invertebrates that also use this rich feeding area; and
• Human uses of the area, and the possible threats that they pose to blue whales.
• The researchers hoped to attach satellite trackers to some blue whales near the end of the season, to remotely track their migration away from this summer-autumn feeding area, to unknown tropical breeding areas.This did not occur this season.

Krill
Loggers are deployed at desired depths, and record temperature at set intervals, to give information on 3-dimensional temperature structure of the ocean. This is a simple, useful method for examining extent of upwelling.

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WHAT DID THE WORK INVOLVE?

The work involved field trips of between 1 and 4 days each, moving out from Portland Harbour to areas where blue whales were feeding, and then concentrating the work in these areas. During each research voyage, the boat either ‘heaved to’ at night, drifting near the work area, or will anchored in sheltered bays nearby. At first light, we were off to find the whales. Sometimes they were be in the same place as ‘yesterday’; other times the circus will have moved on, as the krill is eaten or dispersed.

At times we were doing surveys along chosen tracklines, monitoring the properties of the ocean as we went, surveying underwater krill with sonar, and searching for blue whales. At other times, we stopped in areas where whales were feeding, and gathered as much information as we could, while we could.

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HOW CAN I PARTICIPATE?

We know that many people will want to be involved in the research, and whenever possible, we will be glad to use your help. Whale research is not all glamour and excitement (in fact it is not at all glamorous, though it can be very exciting). It often involves discomfort, frustration, weariness, and boredom. We are working with a very powerful and capricious element, the Southern Ocean; and we are working with whales, animals which seem to have an infinite talent for being unpredictable and making life difficult when you want it to be easy for a while. But the rewards are huge: aboard Pelican, you will be out in the blue whales’ world, getting unique insights into their lives, and seeing sights that are rarely seen anywhere.

There are many small jobs which must be done in preparation before whales are encountered. Then, we may sail along for hours, patiently looking for blows of whales, krill swarms, changes in water colour or temperature, or other telltale signs of the ecosystem in action. When we find whales, encounters are often frantic affairs, with a flood of data coming in and being recorded on film, video, voice recorder, hydrophone, sonar, and in nets and other sampling devices. Then, we may move on in search of another ‘hot spot’, before repeating it all again. Or we may search in vain, but even when we are not finding whales we are learning something about the upwelling environment and the other animals that share it. Finally, when the day’s work is over, there is the often tedious task of sorting and cataloguing films, tapes and biological samples, of transcribing voice recordings of the day’s events, and then debriefing and discussing what we have seen and learnt. Then we can relax and have a gin and tonic!

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