An updated model of the krill-predator dynamics of the Antarctic ecosystem
The objective of this thesis is to update the Mori-Butterworth (2006) model of the krill-predator dynamics of the Antarctic ecosystem. Their analysis aimed to determine whether predator-prey interactions alone could broadly explain the observed population trends of the species considered in their mo...
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Marine Resource Assessment and Management Group
2017
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ftunivcapetownir:oai:open.uct.ac.za:11427/25490 2024-09-15T17:48:31+00:00 An updated model of the krill-predator dynamics of the Antarctic ecosystem Moosa, Naseera Künzi, Hans-Peter A Butterworth, Doug S 2017 application/pdf http://hdl.handle.net/11427/25490 eng eng Marine Resource Assessment and Management Group Faculty of Science University of Cape Town http://hdl.handle.net/11427/25490 Marine Resource Assessment and Management Master Thesis Masters MSc 2017 ftunivcapetownir 2024-06-25T03:44:05Z The objective of this thesis is to update the Mori-Butterworth (2006) model of the krill-predator dynamics of the Antarctic ecosystem. Their analysis aimed to determine whether predator-prey interactions alone could broadly explain the observed population trends of the species considered in their model. In this thesis, the Antarctic ecosystem is outlined brie y and details are given of the main krill-eating predators including whales, seals, fish and penguins, together with an historical record of the human harvesting in the region. The abundances and per capita krill consumption of the krill-predators are calculated and used to determine the main krill-predators to be used in the updated model developed. These predators are found to be the blue, fin, humpback and minke whales and crabeater and Antarctic fur seals. The three main ship surveys (IDCR/SOWER, JARPA and JSV) used to estimate whale abundance, and the abundance estimation method itself (called distance sampling), are summarised. Updated estimates of abundance and trends are listed for the main krill-predators. Updated estimates for the biological parameters needed for the ecosystem model are also reported, and include some differences in approaches to those adopted for the Mori-Butterworth model. The background to the hypothesis of a krill-surplus during the mid-20th century is discussed as well as the effects of environmental change in the context of possible causes of the population changes of the main krill-feeding predators over the last century. Key features of the results of the updated model are the inclusion of a depensatory effect for Antarctic fur seals in the krill and predator dynamics, and the imposition of bounds on Ka (the carrying capacity of krill in Region a, in the absence of its predators); these lead to a better fit overall. A particular difference in results compared to those from the Mori-Butterworth model is more oscillatory behaviour in the trajectories for krill and some of its main predators. This likely results from the ... Master Thesis Antarc* Antarctic Antarctic Fur Seals University of Cape Town: OpenUCT |
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Open Polar |
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University of Cape Town: OpenUCT |
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ftunivcapetownir |
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English |
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Marine Resource Assessment and Management |
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Marine Resource Assessment and Management Moosa, Naseera An updated model of the krill-predator dynamics of the Antarctic ecosystem |
topic_facet |
Marine Resource Assessment and Management |
description |
The objective of this thesis is to update the Mori-Butterworth (2006) model of the krill-predator dynamics of the Antarctic ecosystem. Their analysis aimed to determine whether predator-prey interactions alone could broadly explain the observed population trends of the species considered in their model. In this thesis, the Antarctic ecosystem is outlined brie y and details are given of the main krill-eating predators including whales, seals, fish and penguins, together with an historical record of the human harvesting in the region. The abundances and per capita krill consumption of the krill-predators are calculated and used to determine the main krill-predators to be used in the updated model developed. These predators are found to be the blue, fin, humpback and minke whales and crabeater and Antarctic fur seals. The three main ship surveys (IDCR/SOWER, JARPA and JSV) used to estimate whale abundance, and the abundance estimation method itself (called distance sampling), are summarised. Updated estimates of abundance and trends are listed for the main krill-predators. Updated estimates for the biological parameters needed for the ecosystem model are also reported, and include some differences in approaches to those adopted for the Mori-Butterworth model. The background to the hypothesis of a krill-surplus during the mid-20th century is discussed as well as the effects of environmental change in the context of possible causes of the population changes of the main krill-feeding predators over the last century. Key features of the results of the updated model are the inclusion of a depensatory effect for Antarctic fur seals in the krill and predator dynamics, and the imposition of bounds on Ka (the carrying capacity of krill in Region a, in the absence of its predators); these lead to a better fit overall. A particular difference in results compared to those from the Mori-Butterworth model is more oscillatory behaviour in the trajectories for krill and some of its main predators. This likely results from the ... |
author2 |
Künzi, Hans-Peter A Butterworth, Doug S |
format |
Master Thesis |
author |
Moosa, Naseera |
author_facet |
Moosa, Naseera |
author_sort |
Moosa, Naseera |
title |
An updated model of the krill-predator dynamics of the Antarctic ecosystem |
title_short |
An updated model of the krill-predator dynamics of the Antarctic ecosystem |
title_full |
An updated model of the krill-predator dynamics of the Antarctic ecosystem |
title_fullStr |
An updated model of the krill-predator dynamics of the Antarctic ecosystem |
title_full_unstemmed |
An updated model of the krill-predator dynamics of the Antarctic ecosystem |
title_sort |
updated model of the krill-predator dynamics of the antarctic ecosystem |
publisher |
Marine Resource Assessment and Management Group |
publishDate |
2017 |
url |
http://hdl.handle.net/11427/25490 |
genre |
Antarc* Antarctic Antarctic Fur Seals |
genre_facet |
Antarc* Antarctic Antarctic Fur Seals |
op_relation |
http://hdl.handle.net/11427/25490 |
_version_ |
1810289805784776704 |