Final Activity Report Summary - TROPHMOD (Coupling trophodynamic models to improve Ecosystem Approach to marine Fisheries)
According to the project, Prof. Didier Gascuel was hosted within the UBC Fisheries Centre (Vancouver) from August 2006 to August 2007. During that period, as a visiting professor, he beneficiated from the experience of worldwide well known Canadian colleagues, working in the field of ecosystem modelling. He worked on two approaches: one regarding the implementation of models applied to African marine ecosystems; and the other devoted to the theoretical analysis of ecosystem functioning, based on the representation of virtual ecosystems. This work was completed during the return phase of the project, from September 2007 to February 2008, leading to the publication or submission of 7 peer reviewed papers. Reports, conference papers, and oral seminars add to this dissemination work. At the same time, the EcoTroph model was implemented as a sub-routine of the EwE software and a new scientific program was set up in partnership with the UBC Fisheries Centre, Agrocampus Rennes and others French or European institutes.
Major scientific achievements of the TROPHMOD project are the following:
1. Preliminarily to ecosystem modelling, catch and abundance time series have been estimated in Mauritania and Guinea; these analyses notably showed that the decline of demersal resources in these two countries was caused by a strong overexploitation that affected the various groups successively. West African ecosystems presented a very fast evolution and thus are of major ecological interest for understanding of the ecosystem response to an increasing fishing pressure.
2. At the same time, a new version of the trophic level-based model, from now on named EcoTroph, was developed. EwE (Ecopath with Ecosim), developed by the UBC Fisheries Centre since the beginning of the nineties, is worldwide considered as a standard tools for ecosystem modelling. EcoTroph is based on a more theoretical approach, closer to physical representation of trophic flows in an ecosystem.
3. Ecopath, Ecosim and EcoTroph models have been built for the Guinean case study, leading to a comparison between models, their capabilities and complementarities. This was the first application to a real case study of the EcoTroph model, previously developed in a theoretical context. Results notably showed that increasing fishing pressures induce significant modifications in the trophic functioning of ecosystems, leading to a loss in their functional biodiversity. EcoTroph model was also used for prevision and forecast considering various scenarios of fishing.
4. The EcoTroph model was also applied to a virtual ecosystem, showing the generic impact of fishing at the ecosystem scale. The model illustrates complex patterns such as cascade effects, earlier overexploitation of top predators, and 'fishing down the food web'. It provides diagnostic tools regarding generic relationships between catch or ecosystem biomass and fishing effort at the ecosystem scale.
5. A generic model of trophic flow kinetics in marine ecosystems was proposed as a key step in building a theoretical approach for ecosystem functioning. Indeed, EcoTroph model shows that the trophic flow kinetics is a key characteristic of ecosystems' dynamics, partly determining their response to human disturbances such as fishing pressure. An empirical model that expresses the flow kinetics as a generic function of the trophic level and the mean water temperature was proposed.
6. The EcoTroph model has been implemented as an additional sub-routine of the EwE software, which is worldwide, disseminated. First seminars on EcoTroph capabilities and practical use were organised in Vancouver, Rennes and Sètes (France). The user's guide of the program should be released in the coming weeks.
7. A new program of scientific collaborations and research activities was set up for the 2008 - 2011 period. It includes joint Master and PhD theses, and a Canadian scientist will be host in Rennes for an eight months period. The objective is to improve dissemination of ecosystem modelling, by building various models in Europe and Africa, developing comparative studies between ecosystems and implementing a worldwide approach of marine ecosystem modelling.
Major scientific achievements of the TROPHMOD project are the following:
1. Preliminarily to ecosystem modelling, catch and abundance time series have been estimated in Mauritania and Guinea; these analyses notably showed that the decline of demersal resources in these two countries was caused by a strong overexploitation that affected the various groups successively. West African ecosystems presented a very fast evolution and thus are of major ecological interest for understanding of the ecosystem response to an increasing fishing pressure.
2. At the same time, a new version of the trophic level-based model, from now on named EcoTroph, was developed. EwE (Ecopath with Ecosim), developed by the UBC Fisheries Centre since the beginning of the nineties, is worldwide considered as a standard tools for ecosystem modelling. EcoTroph is based on a more theoretical approach, closer to physical representation of trophic flows in an ecosystem.
3. Ecopath, Ecosim and EcoTroph models have been built for the Guinean case study, leading to a comparison between models, their capabilities and complementarities. This was the first application to a real case study of the EcoTroph model, previously developed in a theoretical context. Results notably showed that increasing fishing pressures induce significant modifications in the trophic functioning of ecosystems, leading to a loss in their functional biodiversity. EcoTroph model was also used for prevision and forecast considering various scenarios of fishing.
4. The EcoTroph model was also applied to a virtual ecosystem, showing the generic impact of fishing at the ecosystem scale. The model illustrates complex patterns such as cascade effects, earlier overexploitation of top predators, and 'fishing down the food web'. It provides diagnostic tools regarding generic relationships between catch or ecosystem biomass and fishing effort at the ecosystem scale.
5. A generic model of trophic flow kinetics in marine ecosystems was proposed as a key step in building a theoretical approach for ecosystem functioning. Indeed, EcoTroph model shows that the trophic flow kinetics is a key characteristic of ecosystems' dynamics, partly determining their response to human disturbances such as fishing pressure. An empirical model that expresses the flow kinetics as a generic function of the trophic level and the mean water temperature was proposed.
6. The EcoTroph model has been implemented as an additional sub-routine of the EwE software, which is worldwide, disseminated. First seminars on EcoTroph capabilities and practical use were organised in Vancouver, Rennes and Sètes (France). The user's guide of the program should be released in the coming weeks.
7. A new program of scientific collaborations and research activities was set up for the 2008 - 2011 period. It includes joint Master and PhD theses, and a Canadian scientist will be host in Rennes for an eight months period. The objective is to improve dissemination of ecosystem modelling, by building various models in Europe and Africa, developing comparative studies between ecosystems and implementing a worldwide approach of marine ecosystem modelling.