Advanced course: Ecotroph

13 November 2014, room P41 at ICM-CSIC

This advanced one day course presented the main principles and applications of the EcoTroph model. Participants learned how to parameterize and analyze results from EcoTroph using the EwE plug-in and the analog R package.

Teachers: Mathieu Colléter (UBC, Canada), Didier Gascuel (Agrocampus, France)

EcoTroph (ET) is a modeling approach articulated around the idea that an ecosystem can be represented by its biomass distribution across trophic levels, the biomass trophic spectrum. The ecosystem functioning is viewed as a biomass flow moving from lower to higher trophic levels, due to predation and ontogenetic processes (Gascuel et Pauly, 2009 ; Gascuel et al., 2011). Thus, the ecosystem biomass present at a given trophic level may be estimated from two simple equations, one describing biomass flow, the other their kinetics (which quantifies the velocity of biomass transfers towards top predators).

Such an approach, wherein species as such disappear, may be viewed as the ultimate stage in the use of the trophic level metric for ecosystem modeling. Modeling biomass flows as a quasi-physical process enables to explore aspects of ecosystem functioning that are complementary to EwE analysis. It provides users with simple tools to quantify fishing impacts at an ecosystem scale, and a new way of looking at ecosystems. It also provides tools and indicators to analyze fleets’ interactions at the ecosystem level (Gasche and Gascuel, 2013). Thus, EcoTroph constitutes a useful complement to existing ecosystem model such as Ecopath or Osmose.
EcoTroph can be used either in association with an existing Ecopath model or as a stand-alone application, especially in data-poor environments. It runs either as a plug-in of the EwE software, or as an R-package (Colléter et al., 2013)
This one day advanced course was mainly based on practical applications and case studies analyses, in order to provide users the ability to further develop their own applications. The EwE plug-in and the EcoTroph R package were presented in parallel.


Thursday 13 November
09:00-10:15 The trophic spectrum graphical representation
ET-Transpose: looking at an Ecopath model using EcoTroph
Tutorial: Building biomass and catch trophic spectra, the ET-Main table, forgetting species and looking at exploitation patterns at the ecosystem scale
Some examples of the use of trophic spectra
10:15-10:30 Break
10:30-12:30 Theoretical basis of the EcoTroph model
ET-Diagnosis: using EcoTroph for simulation and global diagnosis
Tutorial: Defining accessibilities, simulation of biomass and catch trophic spectra for increasing or decreasing fishing efforts, the Top-down effect, summary statistics, indicator, and whole-ecosystem diagnosis
12:30-14:00 Break
14:00-15:15 ET-Diagnosis: using EcoTroph to analyze fleets interactions
Tutorial: Isopletes of catch, biomass and mean trophic level as indicators of the effect of each fleet on ecosystem, and as a tools to analyze interactions
15:15-15:30 Break
15:30-17:00 The Catch Trophic Spectrum Analysis (CTSA): a VPA at an ecosystem scale
ET- CTSA: estimating ecosystem biomass from catches and using EcoTroph as a stand-alone approach in data-poor environments
Tutorial: Basic parameters and input data file, CTSA Forward and CTSA backward
ET-Dynamics: using EcoTroph with time series
Tutorial: Input data file, fitting time-series and hindcasting, catch and biomass forecasts

Software needed

  • Please bring a laptop that can operate in Window (i.e. no Mac’s of if you have a Mac please make sure that it has a Windows OS installed and that all the software works on it.
  • Please download the newest version of Ecopath with Ecosim EwE v. 6.4.3 (October 2014) from the Ecopath website and make sure that it works.
  • Please make sure you have Microsoft Office (excel, word, etc.) or equivalent downloaded
  • There will be access to the internet provided in the course room

Recommended reading

  • GASCHE L., GASCUEL D., 2013 – EcoTroph: a simple model to assess fisheries interactions and their impacts on ecosystems. ICES Journal of Marine Sciences, 70: 498–510.
  • COLLETER M., GUITTON J., GASCUEL D., 2013 – An Introduction to the EcoTrophR package: analyzing aquatic ecosystem trophic network. The R Journal, 5(1): 98-107
  • GASCUEL D., PAULY D., 2009 – EcoTroph: modelling marine ecosystem functioning and impact of fishing. Ecological Modelling, 220: 2885-2898.
    GASCUEL D., GUENETTE S., PAULY D., 2011 – The trophic-level based ecosystem modelling approach: Theoretical overview and practical uses. ICES Journal of Marine Sciences, 68: 1403-1416. [doi:10.1093/ icesjms/fsr062]