Coupling the population dynamics and ecosystem function of grazing fishes
Lead Research Organisation:
UNIVERSITY OF EXETER
Department Name: Biosciences
Abstract
Societies are ethically and legally charged with the sustainable management of biodiversity. Most conservation strategies either focus on a particularly important species and assume that the conservation measures also protect other components of the ecosystem or attempt to protect many species by setting aside some of their habitat in reserves. The latter approach assumes that many species can complete their life cycle in the area preserved. An alternative paradigm, albeit one that has been difficult to realize, is that managers focus on the key processes driving the ecosystem. If the ecosystem processes remain intact, then many components of biodiversity should be sustainable. To date, there have been few demonstrations of this approach even though it is explicitly embodied by an 'Ecosystem-based approach to management' to which most governments are now legally obliged to undertake. A process-based approach to conservation will only work if two conditions are met. Firstly, that biodiversity is profoundly influenced by a limited number of processes and secondly that these processes are subject to management intervention. Coral reefs of the Western Atlantic provide an exceptionally compelling case for this approach. The ability of corals to recover from disturbance is highly dependent on the abundance of their seaweed competitor. In turn, the availability of seaweed is determined by grazing parrotfish. Inadequate levels of grazing allow seaweed to bloom and prevents corals from building the complex reef habitat on which much biodiversity depends. This project builds on the success of an earlier NERC grant and enables us to manage a key ecosystem process (parrotfish grazing) explicitly. We recently modelled the importance of grazing in coral reef dynamics. The model allowed corals to compete with seaweeds and the ecosystem was subjected to severe external impacts including hurricanes. Parrotfish grazing was found to exert an overwhelming positive impact on the dynamics of corals. However, whilst we now appreciate the importance of maintaining grazing, we lack the science to achieve it. This project fills this gap by modelling the population dynamics of parrotfish and the impact of exploitation on their communities. The models have two uses. Firstly, they will allow us to test novel ecological hypotheses about exploited communities. Secondly, we will couple the model of parrotfish population dynamics with our existing models of parrotfish grazing and the impact of grazing on coral reef dynamics. Thus, our coupled models allow us to develop the theory of ecosystem-based management because we can answer the question, 'How should parrotfish communities be managed sustainably so that extractive activities do not reduce grazing beyond the level required by the ecosystem?'. Outcomes of this project will have wide interest because we will significantly develop the science behind 'ecosystem-based management' and, by coupling complex ecological models, provide fresh insight into the analysis of complex systems (which lies at the intersection of biology and mathematics).
Organisations
Publications
Arnold S
(2010)
Running the gauntlet: inhibitory effects of algal turfs on the processes of coral recruitment
in Marine Ecology Progress Series
Beger M
(2010)
Conservation planning for connectivity across marine, freshwater, and terrestrial realms
in Biological Conservation
EDWARDS H
(2011)
How much time can herbivore protection buy for coral reefs under realistic regimes of hurricanes and coral bleaching? CORAL AND CLIMATE CHANGE
in Global Change Biology
Harborne A
(2008)
Reserve effects and natural variation in coral reef communities
in Journal of Applied Ecology
Hoegh-Guldberg O
(2007)
Coral reefs under rapid climate change and ocean acidification.
in Science (New York, N.Y.)
Hughes TP
(2010)
Rising to the challenge of sustaining coral reef resilience.
in Trends in ecology & evolution
Mumby P
(2008)
The impact of ecosystem connectivity on coral reef resilience
in Journal of Applied Ecology
Mumby P
(2012)
Fishing down a Caribbean food web relaxes trophic cascades
in Marine Ecology Progress Series
Mumby P
(2009)
Herbivory versus corallivory: are parrotfish good or bad for Caribbean coral reefs?
in Coral Reefs
Description | These were reported previously and included talking to US fisheries about policy |
Exploitation Route | To formulate fisheries policies |
Sectors | Environment Government Democracy and Justice |
Description | They were reported in previous annual reports. |
First Year Of Impact | 2013 |
Sector | Environment |
Impact Types | Policy & public services |