Modelling energy sequestration and foraging by harbor porpoises in San Francisco Bay
The occupation of an ecosystem by a new top predator could affect the stability of a food web. In San Francisco Bay (SF Bay), there is evidence for a multi-decadal disappearance of harbor porpoises {Phocoena phocoena) that spanned from the 1940's to the early 2000's. Understanding the ener...
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San Francisco State University
2016
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ftcalifstateuniv:oai:scholarworks:hq37vq104 2024-09-30T14:41:23+00:00 Modelling energy sequestration and foraging by harbor porpoises in San Francisco Bay Cara Alyse Gallagher C. Sarah Cohen Ellen Hines Jonathan Stern 2016 http://hdl.handle.net/10211.3/172982 English eng San Francisco State University Science & Engineering Biology: Concentration in Integrative Biology http://hdl.handle.net/10211.3/172982 Copyright by Cara Alyse Gallagher, 2016 AS36 2016 BIOL .G35 Masters Thesis 2016 ftcalifstateuniv 2024-09-10T17:06:15Z The occupation of an ecosystem by a new top predator could affect the stability of a food web. In San Francisco Bay (SF Bay), there is evidence for a multi-decadal disappearance of harbor porpoises {Phocoena phocoena) that spanned from the 1940's to the early 2000's. Understanding the energetic role of this predator in the food web, in addition to the conditions that allowed for occupation of the Bay, is crucial to shedding light on the possible impacts of this species and on the state of the ecosystem. Here two modelling approaches were used in order to assess the energetics of harbor porpoises in SF Bay. The first model presented was an equation-based, velocity-dependent energy budget of harbor porpoises. As harbor porpoises have been shown to reproduce on an annual calving cycle in some regions, the minimum cost of transport was found for each possible reproductive state (non-pregnant, non-lactating (NPL)=1.6 J k g 'W pregnant (P)=1.8 J k g 'W lactating (L)=3.1 J k g 'W 1; and pregnant and lactating (PL)=3.2 J k g 'W 1). The total daily costs, in terms of carbon uptake, were then estimated for a NPL porpoise and a PL porpoise (NPL=341.3 g; PL=756.4 g) and when compared using a one-way ANOVA test, the difference was significant (F=15,797, d /= l, p0.001). The second model presented was an agent-based, ecophysiological model of porpoise foraging in central SF Bay. Energy expenditure was estimated using the swimming speed and the reproductive status of the porpoise agent and energy intake was dependent on foraging success, measured by the capture of anchovy agents in SF Bay. The total daily energetic costs of each reproductive state were found (NPL=8060.4 kJ; P=8776.3 kJ; L= 19269.6 kJ; and PL=19985.6 kJ). The marginal value theorem was used as a test of habitat optimum for harbor porpoises in SF Bay and using the model, it was found that foraging success was more dependent on the number of anchovy schools than the number of anchovies per school. The number of schools that allowed for foraging levels higher ... Master Thesis Phocoena phocoena Scholarworks from California State University |
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Scholarworks from California State University |
op_collection_id |
ftcalifstateuniv |
language |
English |
description |
The occupation of an ecosystem by a new top predator could affect the stability of a food web. In San Francisco Bay (SF Bay), there is evidence for a multi-decadal disappearance of harbor porpoises {Phocoena phocoena) that spanned from the 1940's to the early 2000's. Understanding the energetic role of this predator in the food web, in addition to the conditions that allowed for occupation of the Bay, is crucial to shedding light on the possible impacts of this species and on the state of the ecosystem. Here two modelling approaches were used in order to assess the energetics of harbor porpoises in SF Bay. The first model presented was an equation-based, velocity-dependent energy budget of harbor porpoises. As harbor porpoises have been shown to reproduce on an annual calving cycle in some regions, the minimum cost of transport was found for each possible reproductive state (non-pregnant, non-lactating (NPL)=1.6 J k g 'W pregnant (P)=1.8 J k g 'W lactating (L)=3.1 J k g 'W 1; and pregnant and lactating (PL)=3.2 J k g 'W 1). The total daily costs, in terms of carbon uptake, were then estimated for a NPL porpoise and a PL porpoise (NPL=341.3 g; PL=756.4 g) and when compared using a one-way ANOVA test, the difference was significant (F=15,797, d /= l, p0.001). The second model presented was an agent-based, ecophysiological model of porpoise foraging in central SF Bay. Energy expenditure was estimated using the swimming speed and the reproductive status of the porpoise agent and energy intake was dependent on foraging success, measured by the capture of anchovy agents in SF Bay. The total daily energetic costs of each reproductive state were found (NPL=8060.4 kJ; P=8776.3 kJ; L= 19269.6 kJ; and PL=19985.6 kJ). The marginal value theorem was used as a test of habitat optimum for harbor porpoises in SF Bay and using the model, it was found that foraging success was more dependent on the number of anchovy schools than the number of anchovies per school. The number of schools that allowed for foraging levels higher ... |
author2 |
C. Sarah Cohen Ellen Hines Jonathan Stern |
format |
Master Thesis |
author |
Cara Alyse Gallagher |
spellingShingle |
Cara Alyse Gallagher Modelling energy sequestration and foraging by harbor porpoises in San Francisco Bay |
author_facet |
Cara Alyse Gallagher |
author_sort |
Cara Alyse Gallagher |
title |
Modelling energy sequestration and foraging by harbor porpoises in San Francisco Bay |
title_short |
Modelling energy sequestration and foraging by harbor porpoises in San Francisco Bay |
title_full |
Modelling energy sequestration and foraging by harbor porpoises in San Francisco Bay |
title_fullStr |
Modelling energy sequestration and foraging by harbor porpoises in San Francisco Bay |
title_full_unstemmed |
Modelling energy sequestration and foraging by harbor porpoises in San Francisco Bay |
title_sort |
modelling energy sequestration and foraging by harbor porpoises in san francisco bay |
publisher |
San Francisco State University |
publishDate |
2016 |
url |
http://hdl.handle.net/10211.3/172982 |
genre |
Phocoena phocoena |
genre_facet |
Phocoena phocoena |
op_source |
AS36 2016 BIOL .G35 |
op_relation |
http://hdl.handle.net/10211.3/172982 |
op_rights |
Copyright by Cara Alyse Gallagher, 2016 |
_version_ |
1811643777211695104 |