Abstract
As marine predators experience increasing anthropogenic pressures, there is an urgent need to understand their distribution and their drivers to inform spatial conservation planning. We used an ensemble modelling approach to investigate the spatio-temporal distribution of southern Australian bottlenose dolphins (Tursiops cf. australis) in relation to a variety of ecogeographical and anthropogenic variables in Coffin Bay, Thorny Passage Marine Park, South Australia. Further, we evaluated the overlap between current spatial management measures and important dolphin habitat. Dolphins showed no distinct seasonal shifts in distribution patterns. Models of the entire study area indicate that zones of high probability of dolphin occurrence were located mainly within the inner area of Coffin Bay. In the inner area, zones with high probability of dolphin occurrence were associated with shallow waters (2–4 m and 7–10 m) and located within 1,000 m from land and 2,500 m from oyster farms. The multi-modal response curve of depth in the models likely shows how the different dolphin communities in Coffin Bay occupy different embayments characterized by distinct depth patterns. The majority of areas of high (>0.6) probability of dolphin occurrence are outside sanctuary zones where multiple human activities are allowed. The inner area of Coffin Bay is an important area of year-round habitat suitability for dolphins. Our results can inform future spatial conservation decisions and improve protection of important dolphin habitat.
Highlights
In the marine environment, coastal ecosystems are the most heavily impacted by human activities[9]
We used an ensemble modelling approach to determine the spatio-temporal distribution patterns of SABD in Coffin Bay, a heterogeneous ecosystem located within a multiple use marine park in South Australia (SA)
Ensemble modelling provided a robust approach for evaluating the importance of ecogeographical and anthropogenic factors influencing dolphin distribution patterns, and identifying important areas of dolphin occurrence
Summary
Coastal ecosystems are the most heavily impacted by human activities[9]. Studies in Gulf Saint Vincent, SA, showed that the distribution patterns of SABD are influenced by a variety of ecogeographic variables, likely linked to prey distribution and availability, such as bare sand habitat in the Port River estuary and Barker Inlet[35], and water depth, benthic habitat type and slope along Adelaide’s metropolitan coast[36] Both studies identified priority areas for dolphin conservation along SA’s coast and highlighted the need for future studies to evaluate the influence of human activities (e.g. vessel traffic, fishing, and ports) on dolphin distribution. Despite the importance of Coffin Bay for SABD, the current lack of information about their distribution patterns in relation to environmental conditions and human activities hampers the identification of important habitats and the potential impacts of these threats. Understanding how aquaculture and vessel traffic may affect dolphins’ distribution patterns is crucial for improving future decision-making regarding the zoning of multiple-use MPAs in SA
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