Snubfin dolphins call Roebuck Bay home

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A community of snubfin dolphins has taken up residency in Roebuck Bay, according to a new study investigating the species’ use of the area.

The study, led by Edith Cowan University, confirms the presence of the resident dolphin community in Yawuru Nagulagun (Roebuck Bay) in the northwest of Western Australia and provides the first insights into how they use the area.

Researchers from Edith Cowan University, WA’s Department of Biodiversity, Conservation and Attractions, and Yawuru Native Title Prescribed Body Corporate collaboration combined data from multiple contributors to analyse the dolphins’ behavioural patterns.

Australian snubfin dolphins are a species with a limited distribution, vulnerable conservation status, and high cultural value and understanding how they use this area could help inform future management for their long-term conservation.

The researchers reviewed 11 years of data obtained from researchers, rangers and citizen scientists, including through WAMSI’s Kimberley Marine Research program, to determine the ranging patterns and site fidelity of snubfin dolphins in the region.

The combined dataset was more than four and a half times larger than the single largest study completed previously and produced results that could not have been obtained with the data from any single study alone.

Lead author Alexandra D’Cruz from Edith Cowan University, said the results highlighted the importance of Yawuru Sea Country as a high-quality habitat that offered abundant resources, and shelter from predators.

“These important insights contribute new information for the continued conservation and management of snubfin dolphins at the broader species level, as well as more specifically for the local population,” Ms D’Cruz said.

The findings could improve the potential to detect changes in the population and respond to pressures over decadal timeframes.

“For long-living species such as marine mammals, having sufficient data on ranging patterns and space across a broad timescale which is suitable for population management and conservation can be difficult,” she said.

“This approach could be applied to improve conservation management strategies for other cryptic, data deficient, vulnerable, and long-lived species.”

We would like to thank the Traditional Owners of the land and sea on which this study was based on, the Yawuru people. We would also like to thank those involved with the data collection through WAMSI’s Kimberley Marine Research program.

Traditional knowledge verifies key turtle nesting sites

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New research merging modern marine science with Traditional ecological knowledge has uncovered key nesting sites for turtles in Western Australia.

Western Australia’s remote Kimberley coastline spans multiple Traditional Owner estates and the findings will contribute towards future co-management plans to conserve turtle populations in the northwest, including continued monitoring for marine turtles.

Led by a team from WA’s Department of Biodiversity, Conservation and Attractions (DBCA), the study ranked marine turtle nesting sites in the region and found the islands off the Kimberley coast had higher nesting usage and fewer terrestrial predators.

Researchers used aerial surveys to assess marine turtle nesting distribution and abundance during summer and winter nesting seasons in Indigenous Protected Areas and newly declared Kimberley Marine Parks.

Images of nesting tracks were then quantified in the lab and Traditional ecological knowledge and ground-based surveys verified the harder-to-detect species (olive ridley or hawksbill turtles) with irregular nesting, low track persistence and non-aggregated nesting in the more remote areas.

The three highest density rookeries were found to be winter flatback turtles at Cape Domett, summer green turtles at the Lacepede Islands and summer flatback turtles at Eighty Mile Beach. Nesting by summer green turtles and winter flatback turtles occurred at a lower density in the North Kimberley offshore islands.

Lead researcher Dr Tony Tucker from DBCA said while the higher-density rookeries provided locations for long-term monitoring using repeated aerial or ground surveys, the sparse or infrequently nesting species required insights gleaned by Traditional ecological knowledge.

“Common and conspicuous nesters are easily detected and ranked, but better-informed co-management requires additional ground surveys or surveys timed with the reproductive peaks of rarer species,” Dr Tucker said.

Dean Mathews of the Indigenous Saltwater Advisory Group (ISWAG) and Dr Scott Whiting, leader of the WAMSI Marine Turtle Project agreed.

“Besides the mainland flatbacks, the collective cultural importance of green turtles to Kimberley Indigenous groups logically identifies the Lacepede Islands as an index rookery for summer green turtles,” Mr Matthews said.

Dr Whiting said the study demonstrated the importance of integrating traditional and western approaches to conserve and manage species populations, particularly in northwest Australia.

“Sharing information for the purpose of joint management is crucial for migratory marine megafauna that traverse multiple management jurisdictions,” Dr Whiting said.

“It’s expected these results will underpin future conservation efforts, including continued monitoring for endangered turtles.”

This research was carried out under WAMSI’s Kimberley Marine Research Program.

Recreational fishers report signs of a changing climate

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New research has revealed two out of three recreational fishers perceive climate change to be real and have noticed changes in the types and distributions of fish species over time as they regularly venture out in marine waters.

A team of researchers assessed fisher demographics and fishing behaviour in a boat-based recreational fishery in Western Australia where fishing occurs in both temperate and tropical waters.

Published in ICES Journal of Marine Science, the study found recreational fishers associated changes in species type and distribution with climate change, with more than half attributing climate change to human activity. This recognition was higher amongst metropolitan residents, females and younger respondents.

Lead researcher Karina Ryan from the WA Department of Primary Industries and Regional Development, said recreational fishers were well positioned to notice changes to the marine environment over time.

“Fishers are aware of the potential impacts of climate change on fishing experiences through reduced catches of usual species or interactions with transitional species,” Ms Ryan said.

“Their contributions to long-term citizen science programs can provide information across the spatial and temporal time scales required to observe climate change. Adaptive responses can then be proposed to mitigate the effects of climate change and build resilience for the recreational sector.”

Co-author Dr Jenny Shaw from the Western Australian Marine Science Institution, said the study provided a useful baseline to assist in informing future research as well as policy changes that might be required to address climate change impacts.