Whales of the Perth and Bremer Canyons

The talk was given by Gemma Sharp, a member of a WA family which has been involved in western waters since pearling in the Kimberley in 1985. The company now runs whale watching tours throughout the year from Bremer Bay, Augusta and Fremantle. Species seen on the different tours are Orcas (so-called Killer Whales), Pygmy Blue, Humpback and Southern Right Whales and also various species of dolphins and sea birds. The operators have accumulated a lot of knowledge of the creatures in our waters.

Orcas are found in the Bremer canyon: they can be up to 10 metres long and 10 tonnes in weight, are usually in a pod of 6 to 20 individuals, live up to possibly 100 years and communicate individually (i.e. they appear to have ‘names’ for each other!) They have teeth and their food includes the 3-13 metre long Giant Squid which can injure the Orcas with the barbs in their tentacles. However the blubber of whales is quick-healing and produces its own antibiotics. In answer to an audience question, we learnt that observations have shown that Great White Sharks do not choose to share waters with Orcas—the sharks make themselves scarce if Orcas show up. Orcas are very curious and seem to enjoy investigating the boat.

The Pygmy Blue Whale, one of the largest mammals on earth (up to 27m and 90 tonnes) and one of three Blue Whale subspecies, is a baleen whale feeding on krill the size of a fingernail. Its summer feeding ground (March – May) is in the Perth Canyon west of Rottnest, where there is an upwelling of nutrient-rich water and the whales dive down to feed, resurfacing every 12-15 minutes to breathe. The whales then migrate to the Banda Sea in Indonesia. Many other marine species also enjoy this Perth Canyon seasonal bonanza.

Some club members went with Whale Watch WA to Perth Canyon on April 28 of this year and were fortunate enough to see this 22m individual, which repeatedly displayed its tail on its sounding dives and also the beautiful aquamarine colour that gives the animals their common name, i.e. Pygmy Blue Whale.

The Humpback Whales appear off Augusta in May where mating occurs, then the females migrate up to the warmer waters of the Kimberley to calve and are often seen along the coast. Other species in our waters include Sperm, Beaked and Pilot Whales, and several types of dolphins.

In conservation terms, the Blue Whales are rated as Endangered and the Humpback as Vulnerable. Some threats of concern include ship-strike and entanglement with fishing lines/cray pot lines. There is a need to understand migration patterns so that these areas can be avoided by shipping. Tracking is being used for this. The reproduction rates are not high—the Humpback has a calf only every 2-3 years. Whales rely on sound and magnetic fields to investigate their environment and the sound of ships can be a problem. The Royal Australian Navy has been made aware of the importance of the Perth Canyon, since they use it for naval exercises in deep water near the coast. Overall there is a need for research on whales, especially their migration patterns and feeding. Will climate change affect them?

The presentation was accompanied by an exceptional video display taken on the tours. There are also pictures of our meeting on the Whale Watch TV page. Many of our club members have enjoyed their tours.

You can see many pictures of each trip on their website at Daily Report

Margaret Larke