Metropolitan dolphins need more protection

Adelaide’s bottlenose dolphin habitats – in particular their favoured summer feeding grounds such as Hallett Cove and their shallow near-shore playgrounds in autumn – need more protection, Flinders University researchers say.

Flinders researcher Nikki Zanardo recording dolphin numbers and behaviour in metropolitan waters of Adelaide.

The latest research by the Flinders Cetacean Ecology, Behaviour and Evolution Lab (CEBEL) delves further into the distribution and behaviour of the metropolitan coastal bottlenose dolphin population, providing valuable new conservation guidelines to inform future management decision-making.

A long-term conservation plan for the 100-200 bottlenose dolphins which seasonally use and reside in Adelaide’s coastal waters needs to be drawn up and involve ongoing support from the community – in particular boaties, fishers and tour operators, says School of Biological Sciences researcher Nikki Zanardo.

“Increased human activities, in fishing, boating, tourism and coastal zone developments, is putting ever more pressure on these dolphins which seasonally inhabit the near-shore metropolitan areas,” says Ms Zanardo.

“Such disturbances over the long term may cause a decline in the dolphin population, or displacement from this important habitat.

“Pressure on fish stocks, too, will influence the prey available to dolphins in these core feeding areas.”

“To support these coastal marine mammals, and aid their future survival, there needs to be more signage and management such as access and speed restrictions in these critical habitats.”

The highly urbanised Adelaide metropolitan coastline, which is used year-round for fishing and other recreations, is a very important habitat for southern Australian bottlenose dolphins (Tursiops sp.).

Apart from the groups resident in the Port River and further south of the Noarlunga Reef, the dolphins using the main metro coastline favour shallow near-shore areas and temperate reefs in summer, shallow near-shore areas in autumn and the deep waters further offshore in winter.

For example, summer dolphin numbers clearly showed Hallett Cove to be a summer feeding hotspot.

Ms Zanardo, with Flinders scientists Dr Guido J. Parra, Associate Professor Luciana Möller and Cecilia Passadore, have published their latest study “Ensemble modelling of southern Australian bottlenose dolphin Tursiops sp. Distribution reveals important habitats and their potential ecological function” (April 2017) in Marine Ecology Progress Series (April 2017, Volume 569, page 253).

Dr Parra says the comprehensive CEBEL studies were identifying important areas for the conservation of southern Australian bottlenose dolphins along Adelaide’s metropolitan coast.

“What’s more, the methods we used in this study can be applied to other marine species, and help identify important habitats and the potential ecological function they provide to these species,” he says.

Associate Professor Möller says interaction with humans emerged as another pressure on the urban dolphin populations.

“It is especially important that we continue to monitor dolphin numbers and changes in their habitats to ensure not only the long-term presence of this urban dolphin population but also the overall health of Adelaide’s coastal environments,” she says.

Current management strategies for dolphins along the Adelaide metropolitan coast are limited to vessel and swimmer approach distances.

The CEBEL researchers previously conducted boat-based surveys and used photo-identification data to obtain abundance estimates of dolphins along Adelaide, which ranged from 95 individuals in winter 2013 to 239 in summer 2014.

Bottlenose dolphins, which have low reproduction rates and can live up to 50 years, are subject to a number of man-made threats, including water pollution from industry and wastewater treatment plants and habitat loss.

More environmental impact assessments, protected area design, and conservation and research investment should underpin management intervention, the Flinders experts say.

The Adelaide Dolphin Sanctuary is raising awareness about the importance of the Port River and environments for bottlenose dolphins, but more can be done.

“We now have some baseline information to assess any future disease outbreaks and other threats,” says Ms Zanardo, who is also working with the Adelaide Dolphin Sanctuary team.

As these dolphins appear to spend considerable time outside the study area, in Gulf St Vincent and beyond, future research and concerted conservation and management efforts also need to conserve these adjacent habitat, Ms Zanardo says.

The field work was conducted with permits from the Department of Environment, Water and Natural Resources (DEWNR), Primary Industries and Regions SA (PIRSA) and with ethics approval from the Flinders University Animal Welfare Committee.

The Flinders dolphin research is supported by Flinders University, Equity Trustees, the Nature Foundation of SA, Field Naturalists Society SA, Biological Society of SA and many volunteers.

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