Dolphins in Western Australia’s Kimberley are heavily reliant on their specific habitats and “quite vulnerable” to human activity, researchers have said.
The researchers published the findings of a four-year study which provides the first estimates of the abundance of three shallow, inshore species of dolphin — the Australian snubfin, the Australian humpback and the Indo-Pacific bottlenose dolphin.
The Murdoch University team travelled to five remote locations in the Kimberley to collect data, counting dolphins and mapping the sightings.
They focused mostly on the West Kimberley, visiting Roebuck Bay, Beagle Bay, Cygnet Bay and Cone Bay, but also took in the Inner Cambridge Gulf in the region’s east.
“The motivation for this research was that these animals, from what we know elsewhere in Australia, tend to occur in quite small populations that really depend on the near-shore environment,” lead researcher Alexander Brown said.
ABC TV News story by reporter Natalie Jones
“So that makes them quite vulnerable to human activity that occurs in these habitats.
“Particularly in the Kimberley region, we really had no idea of how many of these species were out there and what key areas there might be.”
The researchers found there was a high degree of population variance between the sites.
“We could go just 100 kilometres up the coast and we’d see quite a change in the dominance of a species over another,” Mr Brown said.
He found that snubfin dolphins were most abundant at Roebuck Bay, and bottlenose dolphins were most abundant at Beagle Bay on the west side of the Dampier Peninsula.
Boosting dolphin conservation
Mr Brown said the team thought each species favoured some habitats over others, and said there may also be some competition between species.
“Without this abundance of data it makes it very difficult to assess the conservation status of the species, to determine if they should qualify as threatened species or otherwise, and it’s very difficult to determine appropriate conservation and management measures,” he said.
Snubfin and humpback dolphins are unique to the waters off northern Australia and Southern New Guinea, but little is known about the species in the tropical north.
The research comes as the State and Federal Governments plan and gazette several marine parks across the Kimberley coast.
Mr Brown — a Murdoch University Cetacean Research Unit (MUCRU) PhD student who partnered with Lars Bejder, Kenneth Pollock and Simon Allen on the study — said his team’s work could help manage those areas.
Snubfin dolphins swimming off the Kimberley coast.
|Snubfin dolphins (Jenny Smith, MUCRU)|
He also warned the three species of dolphin would be particularly vulnerable to any new development.
“If any coastal development or potentially threatening activity is likely to take place, site-specific surveys need to be conducted in order to ascertain if the area’s of particular importance for any one or all three of these species,” he said.
“We also really recommend building upon these abundance estimates in the future by establishing more long-term monitoring programs, in order to determine if populations are stable, increasing or in decline.”
Existing threats to dolphins remain largely unknown, as the study surveyed just six per cent of the Kimberley’s coastline.
The MUCRU research was funded by the Federal Government’s Australian Marine Mammal Centre, WWF Australia and the Western Australian Marine Science Institution’s Kimberley Marine Research Program.
The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley.