Dr Alastair Harborne
Relevant funding scheme: NERC
Background:
Fisheries are a key ecosystem service provided by coral reefs1, but little is known about the population dynamics of most species. It is well established that juvenile fishes experience high mortality rates, and that predation is an important process contributing to juvenile mortality. Furthermore, predation of recruiting fish is frequently density dependent and this is important for regulating populations2. However, why predation is density dependent has received little attention, despite its importance to prey population dynamics.
Holling3 described three potential relationships between predation rates and prey densities. Type 3 functional responses are particularly important because they can lead to density-dependent responses of prey species, and can stabilise predator-prey models4. Type 3 responses can also be generated by predators ‘switching’ among prey species depending on their relative density (i.e., taking a higher than expected proportion of the abundant species). Reef fish communities have many of the properties characteristic of Type 3 interactions5, but the presence of this important functional response has never been documented.
Aims of the project:
(1) Investigate in aquaria the functional response of a predator to varying prey density in (a) a one prey system and (b) two prey system;
(2) Demonstrate that functional responses seen in aquaria are also exhibited by predators in highly-controlled experiments in marine environments; and
(3) Model the implications of the empirical data on the population dynamics of the prey species.
Key hypotheses that will be tested are:
H1: The functional response of a reef fish predator when exposed to increasing densities of prey can be characterised as Type 3 because of factors such as increased hunting efficiency.
H2: Because of the use of ‘search images’ for prey, reef fish predators exhibit switching behaviour when exposed to varying proportions of different prey, also leading to Type 3 functional responses.
H3: Functional responses of reef fish predators lead to density dependent mortality of prey species, and this stabilises the population dynamics of the interaction.
Programme:
Fieldwork would be based at the Cape Eleuthera Institute (The Bahamas). Research will focus on
three species common in The Bahamas: the predator Cephalopholis fulva and two of its prey species, Chromis cyanea and Thalassoma bifasciatum. Initially, the student will survey patch reefs to establish realistic prey densities for the aquaria experiments and pilot the aquarium trials to quantify, for example, the optimal time period for each trial. The first aquaria experiments will consist of a minimum of three replicate predators in three different tanks being presented with a specific density of one of the prey species, and the density will then be increased in each subsequent trial (e.g., 5, 25, 50, 75, and 100 prey per tank). By repeating the experiment for the other prey species, this will establish the functional response of the predator to each individual prey species. The second series of aquaria experiments will expose the predator to both prey species simultaneously in different proportions (e.g., 25:75, 50:50, and 75:25) and total densities to investigate switching behaviour.
The aquaria experiments will then be repeated in situ on small, caged, isolated patch reefs specifically built from live rock. Finally, the empirical data will be used to parameterise the range of theoretical models developed within this fielde.g.,6 to gain a more generic understanding of predator-prey interactions on reefs.
Strategic relevance of the research:
This project addresses two of the seven science themes in NERC’s Strategy for 2007-2012 (‘Biodiversity’ and ‘Sustainable use of natural resources’). The PhD would complement current population ecology research on parrotfishes within Prof. Mumby’s Marine Spatial Ecology Lab (MSEL), and more generally other work on predator-prey systems within the School. I believe the PhD would lead to a range of questions that would be appropriate for Research Council Standard Grants, including consideration of how predator-prey interactions are affected by decreasing habitat quality driven by factors such as climate change.
Student support:
This would be Harborne’s first post-graduate student, but the student would benefit from integration with other PhD students within MSEL. Dr David Hodgson, co-investigator, has extensive experience of working with predator-prey systems, including empirical modelling. Hodgson is a valued cosupervisor to several Biosciences PhDs, and contributes training in quantitative aspects of ecological research.
1. Moberg, F. & Folke, C. Ecol. Econ. 29, 215-233 (1999). 2. Hixon, M. A. & Webster, M. S. in Coral reef fishes: dynamics and diversity in a complex ecosystem (ed. Sale, P. F.) 303-325 (Academic Press, San Diego, 2002). 3. Holling, C. S. Canad. Entomol. 91, 385-398 (1959). 4. Begon, M. et al. Ecology (Blackwell Sceintific Publications, Boston, 1990). 5. Cornell, H. Am. Nat. 110, 317-320 (1976). 6. Abrams, P. A. & Matsuda, H. Popul. Ecol. 46, 13-25 (2004).
Application details
You should have (or expect to gain) a 1st class or high 2:1 class degree and excellent academic references. Applications only accepted from UK/EU nationals. UK citizens and EU nationals who have been resident in the UK for 3 years prior to the start of the studentship will receive both fees and stipend scholarship, other EU nationals will receive a fees scholarship only.
Applicants should send a covering letter explaining your suitability for this post, along with a CV including contact details of two academic referees to:
Mrs S. Mudge,
Postgraduate Secretary,
School of Biosciences,
University of Exeter,
Geoffrey Pope Building,
Stocker Road,
Exeter EX4 4QD
or by email to BS-PGadmissions@exeter.ac.uk
The closing date for applications is 28th November 2008. We aim to interview short‐listed candidates in the week commencing 12th January 2009
Relevant funding scheme: NERC
Background:
Fisheries are a key ecosystem service provided by coral reefs1, but little is known about the population dynamics of most species. It is well established that juvenile fishes experience high mortality rates, and that predation is an important process contributing to juvenile mortality. Furthermore, predation of recruiting fish is frequently density dependent and this is important for regulating populations2. However, why predation is density dependent has received little attention, despite its importance to prey population dynamics.
Holling3 described three potential relationships between predation rates and prey densities. Type 3 functional responses are particularly important because they can lead to density-dependent responses of prey species, and can stabilise predator-prey models4. Type 3 responses can also be generated by predators ‘switching’ among prey species depending on their relative density (i.e., taking a higher than expected proportion of the abundant species). Reef fish communities have many of the properties characteristic of Type 3 interactions5, but the presence of this important functional response has never been documented.
Aims of the project:
(1) Investigate in aquaria the functional response of a predator to varying prey density in (a) a one prey system and (b) two prey system;
(2) Demonstrate that functional responses seen in aquaria are also exhibited by predators in highly-controlled experiments in marine environments; and
(3) Model the implications of the empirical data on the population dynamics of the prey species.
Key hypotheses that will be tested are:
H1: The functional response of a reef fish predator when exposed to increasing densities of prey can be characterised as Type 3 because of factors such as increased hunting efficiency.
H2: Because of the use of ‘search images’ for prey, reef fish predators exhibit switching behaviour when exposed to varying proportions of different prey, also leading to Type 3 functional responses.
H3: Functional responses of reef fish predators lead to density dependent mortality of prey species, and this stabilises the population dynamics of the interaction.
Programme:
Fieldwork would be based at the Cape Eleuthera Institute (The Bahamas). Research will focus on
three species common in The Bahamas: the predator Cephalopholis fulva and two of its prey species, Chromis cyanea and Thalassoma bifasciatum. Initially, the student will survey patch reefs to establish realistic prey densities for the aquaria experiments and pilot the aquarium trials to quantify, for example, the optimal time period for each trial. The first aquaria experiments will consist of a minimum of three replicate predators in three different tanks being presented with a specific density of one of the prey species, and the density will then be increased in each subsequent trial (e.g., 5, 25, 50, 75, and 100 prey per tank). By repeating the experiment for the other prey species, this will establish the functional response of the predator to each individual prey species. The second series of aquaria experiments will expose the predator to both prey species simultaneously in different proportions (e.g., 25:75, 50:50, and 75:25) and total densities to investigate switching behaviour.
The aquaria experiments will then be repeated in situ on small, caged, isolated patch reefs specifically built from live rock. Finally, the empirical data will be used to parameterise the range of theoretical models developed within this fielde.g.,6 to gain a more generic understanding of predator-prey interactions on reefs.
Strategic relevance of the research:
This project addresses two of the seven science themes in NERC’s Strategy for 2007-2012 (‘Biodiversity’ and ‘Sustainable use of natural resources’). The PhD would complement current population ecology research on parrotfishes within Prof. Mumby’s Marine Spatial Ecology Lab (MSEL), and more generally other work on predator-prey systems within the School. I believe the PhD would lead to a range of questions that would be appropriate for Research Council Standard Grants, including consideration of how predator-prey interactions are affected by decreasing habitat quality driven by factors such as climate change.
Student support:
This would be Harborne’s first post-graduate student, but the student would benefit from integration with other PhD students within MSEL. Dr David Hodgson, co-investigator, has extensive experience of working with predator-prey systems, including empirical modelling. Hodgson is a valued cosupervisor to several Biosciences PhDs, and contributes training in quantitative aspects of ecological research.
1. Moberg, F. & Folke, C. Ecol. Econ. 29, 215-233 (1999). 2. Hixon, M. A. & Webster, M. S. in Coral reef fishes: dynamics and diversity in a complex ecosystem (ed. Sale, P. F.) 303-325 (Academic Press, San Diego, 2002). 3. Holling, C. S. Canad. Entomol. 91, 385-398 (1959). 4. Begon, M. et al. Ecology (Blackwell Sceintific Publications, Boston, 1990). 5. Cornell, H. Am. Nat. 110, 317-320 (1976). 6. Abrams, P. A. & Matsuda, H. Popul. Ecol. 46, 13-25 (2004).
Application details
You should have (or expect to gain) a 1st class or high 2:1 class degree and excellent academic references. Applications only accepted from UK/EU nationals. UK citizens and EU nationals who have been resident in the UK for 3 years prior to the start of the studentship will receive both fees and stipend scholarship, other EU nationals will receive a fees scholarship only.
Applicants should send a covering letter explaining your suitability for this post, along with a CV including contact details of two academic referees to:
Mrs S. Mudge,
Postgraduate Secretary,
School of Biosciences,
University of Exeter,
Geoffrey Pope Building,
Stocker Road,
Exeter EX4 4QD
or by email to BS-PGadmissions@exeter.ac.uk
The closing date for applications is 28th November 2008. We aim to interview short‐listed candidates in the week commencing 12th January 2009