An exploratory analysis of the environmental factors that influence the distribution of Balaenoptera bonaerensis and Megaptera novaeangliae, 43°E – 107°E, and a reassessment of the conservation measures in Eastern Antarctica.
Understanding how environmental variables, both oceanographic and biological, control and influence the distribution of species is central to developing an understanding of both species’ ecology and the functioning of the ecosystem. The Southern Ocean ecoregion provides the largest feeding grounds f...
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| Format: | Thesis |
| Language: | English |
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Apollo - University of Cambridge Repository
2016
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| Online Access: | https://dx.doi.org/10.17863/cam.8761 https://www.repository.cam.ac.uk/handle/1810/263419 |
| Summary: | Understanding how environmental variables, both oceanographic and biological, control and influence the distribution of species is central to developing an understanding of both species’ ecology and the functioning of the ecosystem. The Southern Ocean ecoregion provides the largest feeding grounds for cetaceans anywhere on the planet, and thus needs to be protected. The understanding of the relationships between species and their environments is key to the successful implementation of ecologically significant, scientifically valid and economically viable conservation measures to safeguard this vital habitat. The geographic remoteness and hostile conditions of the Southern Ocean make obtaining data on the species and environmental conditions of this region both dangerous and economically demanding. This is especially applicable to cetaceans as shipborne surveys are still the most reliable and widely available platform from which to study and to collect in situ biological variables pertaining to these species. However, the collection of in situ samples leads to sporadic data coverage, which when incorporated into modelling efforts may not produce ecologically meaningful results. This study will address whether the sole use of physical oceanographic variables is a valid technique for predictive species distribution modelling. This study will also target a gap in the distributional understanding of Balaenoptera bonaerensis and Megaptera novaeangliae in Eastern Antarctica, which currently limits the ability to scientifically inform any top down conservation-orientated management of this region. In doing so, both presence-only and presence-absence techniques will be applied and compared to determine the relationship and significance of these environmental variables to both species. Once this has been established, distributional models will then be used to reassess the proposed marine protected areas that are being negotiated for Eastern Antarctica. This study revealed that the distribution of Balaenoptera bonaerensis and Megaptera novaeangliae can be accurately modelled on physical oceanographic variables alone, with Balaenoptera bonaerensis predicted to be coastally distributed around Eastern Antarctica, whilst Megaptera novaeangliae were shown to be distributed further offshore, forming an approximate arc-shaped band at 55°S. Both species displayed minimal spatial overlaps, consistent with previous observations, and typical of interspecific niche partitioning. When the predicted distributions of these cetaceans were examined in the context of the proposed conservation measures, it was evident that the proposals were seemingly not targeting the spatial and temporal extent required to provide significant protection applicable to cetacean species. Additionally, an examination of these proposed conservation measures over recent years has revealed that there is a diminishing commitment to conservation and a lack of motivation towards facilitating an ecosystem-wide recovery in Eastern Antarctica. This study proposes an overhaul to the negotiation process and a switch to a top down, spatially extensive conservation effort in Eastern Antarctica. |
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