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DRIs Core Long-term Research
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Long Term Population Studies
Dolphin Research Institute has been conducting population studies on the dolphin population in southern Port Phillip since the early 1990's. Port Phillip is a large embayment of approximately 1,950 square kilometres located in southern Victoria, Australia. The bay is comparatively shallow with around half being less than 14 metres deep. A narrow entrance in the south provides the only access to the open sea, in this case Bass Strait. Approximately 3 million people live around Port Phillip, and Victoria's capital city, Melbourne, is situated at the northern end. Due to the sheer size of the bay, the Institute's research programs have mainly focussed on southern Port Phillip, in an area approximately 100 square kilometres in size. These programs aim to understand more about the dolphin population that inhabits this area. Investigations are targeted towards collecting a range of information, including:
- How many dolphins there are.
- Where the dolphins move around Victorian waters.
- How often they can be found, ie. are they resident to certain areas?
- Learning how dolphin numbers change through time.
- Which habitats they utilise and for what purpose (eg feeding, breeding).
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Identifying Individual Dolphins
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In order to learn more about the dolphin population, it is important that we can identify individuals. To assist with this, we use a dorsal fin identification technique which utilises marks and notches as well as the shape of the dorsal fin. Identification of individual dolphins allows us to learn much about the dolphin population. Through repeated sightings, coupled with behavioural data, we can ascertain how dolphins utilise their habitat. It can also help us understand how many dolphins may be resident to a particular area.
Identification techniques allow us to estimate population sizes and changes. We can learn much about social dynamics and group associations using this technique. So far, we have identified approximately 90 individual dolphins that are regularly sighted in southern Port Phillip.
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Understanding Dolphin Movements
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Photo-identification also allows us to learn more about how the dolphins utilise their habitat. Although most of our research is focussed in southern Port Phillip, surveys have been conducted throughout other areas of the bay to collect photographs of dolphins. These revealed that the same dolphins are moving around the whole bay. Future research will be expanding on these surveys to determine if there are other areas aside from the south that the dolphins frequent. Easily identifiable dolphins, such as Bent Fin, have also been reported by Community Dolphin Watch sighters in Western Port. Although we receive regular sightings from this bay, there does not appear to be a population of the same size as in Port Phillip. Research will be expanded to Western Port over the next year to try and confirm this. Another area that the Institute is expanding research to is the Gippsland Lakes. Located in eastern Victoria, three main lakes form a series of coastal lagoons over an area of 340 square kilometres. Several rivers terminate at the lakes and a permanent entrance to the Tasman Sea was created in the late 1800's. The lakes, which are highly valued as an internationally recognised wetland, are the next major boating destination after Port Phillip. The Institute began photo-identification studies in 2003 after receiving many reports, from the local community, of dolphins in the lakes and even up the rivers. It appears that a population of dolphins is regularly utilising the lakes, but to what extent is yet to be determined, as is the size of the population.
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Behaviour
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In order to understand a population of dolphins, it is necessary to identify and quantify dolphin behaviour. Over the years, the Institute has identified a number of behavioural categories which have assisted us in understanding the dolphin population. Coupled with other studies, behavioural studies help us to learn how dolphins utilise their habitat. By examining the range of behaviours associated with particular habitats, we can better understand how dolphins utilise each habitat or area of the Bay. Behavioural observations are present, in one from or another, in all of our current studies.
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