Port Phillip Bay's Smiling Ambassadors

by Troy Muir

Port Phillip Bay is a 2,000 square kilometre estuarine area that meets Bass Strait near the south eastern corner of Australia. It is the gateway to the busy commercial ports of Melbourne and Geelong, supports major commercial and recreational fishing activities, and has over three million Victorians living on its shores. Despite all these pressures, Port Phillip Bay sustains a dynamic ecosystem that boasts a marine diversity greater than that of the entire Japanese archipelago.

Of the thousands of species found in Port Phillip Bay, including the Australian fur seal and the Australasian diving gannet that has an impressive two metre wing span, as well as visitors such as the southern right and humpback whales, it is the resident population of wild bottlenose dolphins that have become symbolic of the Bay's robust vitality.

During the summer months, the dolphins congregate in the southern end of the Bay. The stable weather conditions and prolific fish stocks make for an ideal area for 'nursery' groups to rear their young. Nursery groups primarily consist of female dolphins and their collective offspring. Young males stay with the group for between three and five years before they venture off to form alliances with other males. Females, however, may stay on indefinitely. They often act as 'nurse maids' for their mothers or other pregnant dolphins within the pod, assisting through delivery and caressing the newborn to the surface for its first breath. Later, they act as baby-sitters while the mothers feed, ensuring that they are able to sustain their calves with the nutrient rich milk that they rely upon for their first 18 months of life.

The dolphins tend to remain close to Port Phillip Bay's entrance between November and May, although they are still found less frequently and in smaller numbers in the area throughout the year. The Dolphin Research Institute (DRI) has been studying Port Phillip Bay's bottlenose dolphins since the late 1980s and has been using dorsal fin identification and random transit bearings to estimate the size and social organisation of the resident population.

The DRI believe, from the data collected to date, that anywhere between 150 and 200 animals inhabit the Bay. Occasionally, collectives of this size have been seen feeding and socialising within an area of a few hundred metres, but more often they are found as either solitary animals, small male alliances or nursery groups that frequently meet up with one another throughout the course of the day. Up to 40 dolphins may mill around for a few minutes and then move off in separate directions just as quickly as they came together.

From the Sorrento Pier, which is only 90 minutes from Melbourne, people are offered the opportunity to interact with these beautiful animals in their own environment. While most encounters with people are to the detriment of dolphins, whether the victims of fishing operations or pollution, they still actively seek out our company and many of us are inspired by being lucky enough to share theirs. Each summer season, over 10,000 people go out on organised tours to view and swim with Port Phillip Bay's dolphins.

The peak time is through the January school holidays, although dolphin numbers and weather conditions tend to remain relatively consistent from November through until April. In 1997, dolphin swim operators in Victoria were encouraged to become licensed. A permit system was devised from an existing code of conduct created two years earlier by the government, research institutions and the industry which imposes upon the holder conditions aimed at ensuring the dolphins have a choice of whether or not to interact with boats and swimmers. Those without a permit must not intentionally approach closer than 150 metres, although if the dolphins come to them they are not required to move away.

Australia has particularly stringent laws pertaining to killing, injuring or deliberately interfering with whales and dolphins. Penalties include fines of up to $100,000 and jail terms. Presently, there is a national initiative to create uniform federal guidelines to manage the emerging cetacea (whales, dolphins and porpoises) related tourism industry.