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Collaboratory Research Projects
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All of the following projects are the result of collaboration between DRI and Monash University Science Faculty www.sci.monash.edu.au >
Two Monash PhD students are currently completing their studies in association with DRI on the Port Phillip, Western Port and Gippsland Lakes dolphins and their marine habitats. In addition we have recently had five Monash Honours students complete their projects with DRI, each study achieving first-class Honours.
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Our Dolphins are Unique
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Bottlenose dolphins are found world-wide in coastal and offshore, tropical and temperate waters. Currently there are two recognised species of bottlenose dolphin, the common bottlenose (Tursiops truncatus) and the Indo-Pacific bottlenose (Tursiops aduncus). In southern Australia we have two distinct 'types' that look physically different. The 'inshore' dolphins in the Port Phillip and Westernport Bays and the Gippsland Lakes are smaller and have a grey colour pattern, whilst 'offshore' dolphins are larger and have a darker colouration. It was not known what species of dolphin we had residing in our 'inshore' regions.
In order to manage and conserve dolphin populations one of the important factors is to know what species they are.
The aim of this study, undertaken by Kate Charlton-Robb a PhD student at Monash University together with the Dolphin Research Institute, was to genetically determine which species of dolphin live in Victoria's coastal regions. This project uses multiple regions along the dolphins DNA and can be compared to other dolphins found world-wide. Samples were collected from dolphins across coastal Victoria and it was shown that there were two distinct genetic types. Those found 'offshore' were the common bottlenose dolphin, however the dolphins living in Port Phillip and Westernport Bays and Gippsland Lakes were not genetically 'bottlenose'. These inshore dolphins formed a distinct cluster that was not in the bottlenose lineage. The use of multiple genetic markers strongly support that the dolphin in these regions are a distinct new species.
Current research is examining not only the species status of these dolphins but the level of genetic diversity, population structure and level of reproductive isolation of this new species. In addition to the genetic analyses, skull morphology has been used to assess morphological differences of this new species for formal species classification.
Kate Charlton-Robb has recently received the John G. Shedd Aquarium Award for the Best Student Presentation at the 18th Biennial conference of the Biology of Marine Mammals for the Society of Marine Mammalogy. The conference was held recently in Quebec, Canada.
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Contaminants in our Water - How do the affect our Dolphins?
Contaminants and pollutants can enter our waterways in a number of ways. No matter how they end up in our water it is inevitable that they will also affect our marine life.
There are certain contaminants that can magnify in concentration through food chains. If organisms low in the food chain become contaminated and are then eaten by animals higher on the food chain, contaminates will accumulate in these 'higher food chain' animals this process is known as bioaccumulation.
Dolphins are part of these 'higher food chain' animals and if the concentration of contaminants reaches certain levels in their systems there can be serious health implications.
Recently researchers from DRI and Monash University have been conducting studies to identify contaminants that may be of concern to bottlenose dolphins (Tursiops sp.) in inland coastal Victorian waters.
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Understanding Dolphin Movements
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In order to affectively protect and conserve the dolphins that live in Port Phillip Bay we must understand what parts of the Bay they inhabit.
Port Phillip, Victoria is home to a small, unique population of bottlenose dolphins (Tursiops sp.) which currently share the bay with a recently 'discovered' short-beaked common dolphin (Delphinius delphis) pod.
As part of our current research program, researchers at DRI and Monash University have been investigating the distribution of dolphins between Mornington and Observatory Point.
One particular study was conducted during winter where environmental variables such as sea surface temperature, depth, and presence of gannets, fur seals and penguins as well as fish density were recorded.
It was found that common dolphins preferred areas from Mornington to Mt Marta whilst the bottlenose dolphins were mush more widespread throughout the entire study area and were randomly distributed. However the environmental variables measured did not seem to have any impact on dolphin distribution.
Overall it was suggested that dolphins may move seasonally in Port Phillip.
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What do our dolphins eat?
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In addition to understanding where dolphins live, understanding what food they eat is also important to be able to manage the populations. Variation in the type of prey available in different environments may impact on the diet of the local dolphin populations. However, learning what the diet of dolphins is difficult as they feed underwater and can't be monitored constantly to determine the full extent of their diet. Due to these limitations, a new technique of called stable isotope analysis is able to be completed on the tissues of the dolphins to give an indication of the differences that may exist between different dolphin species, populations, and sexes.
In order to better understand the feeding ecology of Victorian dolphin populations, researchers from DRI and Monash University completed stable isotope analysis on dolphin teeth. The results showed that the offshore species (Tursiops truncatus) and the inshore species (Tursiops sp. undescribed) are likely to feed on different prey items. The stable isotope analysis also suggested that the Port Phillip Bay population may feed on prey higher up the food chain than the Gippsland Lakes population. Within the inshore species, large sex based differences in stable isotope signatures were also observed suggesting that males and females may consume different prey.
Comparisons of the dolphin stable isotope signatures to potential prey items and the base of the food chain suggest that the males in Port Phillip Bay may be relying more on offshore prey items and phytoplankton based food chains where as the females may rely more on food chains based on seagrass. These findings are important as seagrass levels in Port Phillip Bay are believed to be declining and continued decline may create greater competition between males and females for access to food.
Further research is needed to determine exactly what the dolphins are feeding on and the interaction of these populations with the local food chains.
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Impacts of Boat Traffic on Acoustic BehaviourPort Phillip Bay is subject to high levels of boat traffic. A major shipping port is situated at Port Melbourne, in the northern part of the Bay but there is also a significant amount of traffic associated with recreation, fishing, diving and other marine-based industries.
This high usage by watercraft may present a number of problems for dolphins. As part of recent research DRI researchers have investigated the impact of boat traffic on the acoustic behaviour of bottlenose (Tursiops sp.) and short beaked common dolphins (Delphinus delphis) in Port Phillip Bay and Gippsland Lakes.
Dolphins use their highly developed senses especially vocal and hearing to communicate and synchronise with each other. It is thought that the presence of watercraft may potentially mask the sound of these whistles and disrupt the dolphins' behaviour.
This study recorded and analysed the whistles and behaviours of the two species of dolphins at both sites before, during and after experimental boat approaches. Analysis revealed an increase in whistling rate for both species of dolphins and at both locations during travelling and feeding behaviour.
Results from this study demonstrate an apparent impact of boats on acoustic communication in dolphins. However further research is needed to fully address the implications and thus future management practices.
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Swimming with Wild Dolphins - What are the Impacts?
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Commercial vessels have been conducting tours with wild dolphins in Port Phillip Bay since the early 1990's. This industry has rapidly expanded during the last decade. There are now five commercial vessels conducting swim tours in the southern part of the Bay. There are also many other commercial vessels that engage in dolphin watching on an opportunistic basis. When you include the impact of all of the various recreational vessels, particularly over the summer months, you are looking at a significant pressure on the dolphin population.
In 1996, the Institute began a long-term study into the impacts of these tours on the dolphins. Primarily we are interested in measuring factors such as how much time per day the dolphins spend interacting with boats, how they respond to boats, and the long-term impacts resulting from these human/dolphin interactions.
All of the information obtained from both our long-term studies and our investigations into the impacts of dolphin tours is made available to the relevant management authorities to assist in the sustainable management of the dolphin population.
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Impacts of Boat Traffic
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Port Phillip Bay is subject to traffic from a number of different vectors. A major shipping port is situated at Port Melbourne, in the northern part of the Bay.
There are also thriving fishing, diving and other marine-based industries. There is also a significant amount of traffic associated with recreational vessels that utilise the Bay for various activities. Over the summer months, recreational vessels are present in large numbers in the southern part of Port Phillip Bay, especially on warm days. This appears to be the peak time for dolphin sightings and is also the peak season for commercial dolphin watching vessels. This large concentration of vessels in this part of the Bay can be problematic for the dolphins who may become "harassed" due to the large amount of boat traffic, both recreational and commercial who may be attempting to interact with them.
Dolphins are a protected species under the Wildlife Act 1975. A set of regulations has been developed to regulate boat traffic around all cetaceans in Victorian coastal waters, including Port Phillip Bay. These regulations apply to ALL vessels (with the exception of some commercial dolphin tours that operate under separate conditions of permit). Institute researchers spend a lot of time educating the community about these regulations, including explaining and handing out copies of the regulations to other boats.
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