Dataset

Ecosystem modelling

Australian Ocean Data Network
School of Biological Sciences and Biotechnology (BSB), Murdoch University
Viewed: [[ro.stat.viewed]] Cited: [[ro.stat.cited]] Accessed: [[ro.stat.accessed]]
ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rfr_id=info%3Asid%2FANDS&rft_id=https://catalogue.aodn.org.au:443/geonetwork/srv/en/metadata.show?uuid=516811d7-cc35-207a-e0440003ba8c79dd&rft.title=Ecosystem modelling&rft.identifier=https://catalogue.aodn.org.au:443/geonetwork/srv/en/metadata.show?uuid=516811d7-cc35-207a-e0440003ba8c79dd&rft.publisher=Australian Ocean Data Network&rft.description=The seagrass ecosystem of Shark Bay is characterised by top-down control through tiger sharks. Adult tiger sharks migrate to shallow habitats in Shark Bay during the austral summer. During such times of high tiger shark abundance, the megafauna of the ecosystem leave the seagrass meadows. Despite the fact that only some species of the megafauna are major components of the adult tiger sharks diet, the majority of these species and individuals are impacted by the presence of tiger sharks and leave the feeding grounds in the seagrass beds in summer. This control system has the potential to become imbalanced if, in common with other populations of this species worldwide, there is a decrease in the abundance of adult tiger sharks in the Shark Bay population. Targeting of tiger sharks by fishers in the waters of Northern Australia and Indonesia has increased steadily during the last years, which might impact the tiger shark stock in Shark Bay. Using qualitative modelling, model analyses indicate a strong top-down control of tiger sharks. By implementing a direct and behaviour-induced impact, tiger sharks affect the use of the seagrass habitat by the megafauna and thus impose alternating predation pressure on different prey groups within the seagrass habitat in Shark Bay. Tiger sharks are clearly affected by the Northern Shark Fishery, but the activities of recreational fishermen within Shark Bay reduce the prey availability for juvenile tiger sharks, which might negatively affect the whole tiger shark population and thus may impact the dynamics of this seagrass ecosystem. Recognizing the ecological importance of this species and the potential impact that further decrease of the population is likely to have on the ecosystem, it is important that appropriate management action is taken to maintain the abundance of the tiger shark population in Shark Bay.Original record compiled for the Western Australian Marine Science Institution (WAMSI), Project 3.8, 2008. Originally sourced from several databases compiled by WA DEC Marine Science Branch of projects relevant to the marine parks of WA. Variable metadata information was available.&rft.creator=School of Biological Sciences and Biotechnology (BSB), Murdoch University &rft.date=2017&rft.coverage=northlimit=-24; southlimit=-26; westlimit=112.5; eastLimit=115&rft.coverage=northlimit=-24; southlimit=-26; westlimit=112.5; eastLimit=115&rft_rights=No Restrictions&rft_subject=biota&rft_subject=environment&rft_subject=oceans&rft_subject=Marine Features (Australia) | Shark Bay, WA&rft_subject=Tiger Sharks&rft_subject=Top-down Control&rft_subject=Modelling&rft_subject=Ecosystem Model&rft_subject=Loop Analysis&rft_subject=Recreational Fishing&rft_subject=Seagrass&rft_subject=TROPHIC DYNAMICS&rft_subject=EARTH SCIENCE&rft_subject=BIOSPHERE&rft_subject=ECOLOGICAL DYNAMICS&rft_subject=ECOSYSTEM FUNCTIONS&rft.type=dataset&rft.language=English Access the data

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The seagrass ecosystem of Shark Bay is characterised by top-down control through tiger sharks. Adult tiger sharks migrate to shallow habitats in Shark Bay during the austral summer. During such times of high tiger shark abundance, the megafauna of the ecosystem leave the seagrass meadows. Despite the fact that only some species of the megafauna are major components of the adult tiger sharks diet, the majority of these species and individuals are impacted by the presence of tiger sharks and leave the feeding grounds in the seagrass beds in summer. This control system has the potential to become imbalanced if, in common with other populations of this species worldwide, there is a decrease in the abundance of adult tiger sharks in the Shark Bay population. Targeting of tiger sharks by fishers in the waters of Northern Australia and Indonesia has increased steadily during the last years, which might impact the tiger shark stock in Shark Bay.

Using qualitative modelling, model analyses indicate a strong top-down control of tiger sharks. By implementing a direct and behaviour-induced impact, tiger sharks affect the use of the seagrass habitat by the megafauna and thus impose alternating predation pressure on different prey groups within the seagrass habitat in Shark Bay.

Tiger sharks are clearly affected by the Northern Shark Fishery, but the activities of recreational fishermen within Shark Bay reduce the prey availability for juvenile tiger sharks, which might negatively affect the whole tiger shark population and thus may impact the dynamics of this seagrass ecosystem.

Recognizing the ecological importance of this species and the potential impact that further decrease of the population is likely to have on the ecosystem, it is important that appropriate management action is taken to maintain the abundance of the tiger shark population in Shark Bay.

Notes

Sarah Fretzer
Norm Hall (PhD supervisor)

Lineage

Original record compiled for the Western Australian Marine Science Institution (WAMSI), Project 3.8, 2008. Originally sourced from several databases compiled by WA DEC Marine Science Branch of projects relevant to the marine parks of WA. Variable metadata information was available.

Modified: 200806

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115,-24 115,-26 112.5,-26 112.5,-24 115,-24

113.75,-25

text: northlimit=-24; southlimit=-26; westlimit=112.5; eastLimit=115

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