Ecopath introduction

Introduction to ecosystem modelling: Foundations with Ecopath

Welcome to what may be your first step into the world of ecosystem modeling! This introductory session will equip you with the foundational understanding and practical skills to begin constructing and interpreting ecosystem models, focusing on the widely-used Ecopath with Ecosim (EwE) software. We'll begin with a brief overview of the course and an introduction of participants – please be ready to share a bit about yourself and your motivations for taking this course. We will then dive directly into the core concepts of ecosystem modeling with EwE.

In preparation for the first class, you are expected to download and install the latest version of the EwE software, available at www.ecopath.org. Please also prepare by reading the materials  listed below, and look through the presentations and tutorial (or even better, try working on the tutorial).  The readings will introduce the principles of energy flow and the metrics used to describe and evaluate ecosystem models.

The session will help consolidate your understanding of energy flows, trophic interactions, and model parameterization, preparing you for more advanced exercises.

Learning outcomes

By the end of this session, participants will be able to:

1. Explain the fundamental principles of mass-balance modeling, including the conceptualization and quantification of energy flows within ecosystems. 

2. Define and interpret key ecological parameters (e.g., biomass (B), production-to-biomass ratio (P/B), consumption-to-biomass ratio (Q/B), Ecotrophic Efficiency (EE)) and describe their role in constructing and balancing an Ecopath model. 

3. Construct and parameterize a basic Ecopath model, such as for Anchovy Bay, by inputting ecological data and achieving mass balance. 

4. Navigate the Ecopath with Ecosim (EwE) software interface and utilize its basic functions for initial model development. 

5. Articulate the critical role of clearly defined research or policy questions in guiding the design and application of ecosystem models. 

6. Critically evaluate the assumptions and limitations inherent in simple mass-balance models. 

Resources and preparation

To prepare for the Week 1 session, you need to focus on key chapters, install the EwE software,  and study a practical tutorial that will build your foundational understanding of ecosystem dynamces.  Here's a listing

1. Software Installation

• Download and install the EwE software, available at www.ecopath.org.

2. Essential Readings

These short chapters will introduce the principles of energy flow, key metrics for ecosystem evaluation, and the critical importance of a well-defined research question:

• Your research question.  Understand why models should be driven by clear policy or research questions.  

• Modelling predator-prey systems.  A historical overview

• Defining the ecosystem.  General aspects of delineating the area and components for your models. (Feel free to skip the 'Open systems' section for now).

• The energy balance of a box.  Overview of mass balance, the two Master Equations of Ecopath, and descriptions of key input parameters.

• Biomasses, energy and units

• Production/biomass  

• Consumption/biomass  

• Ecotrophic efficiency 

• Fish 501 - #03 The Ecopath model - Data requirements and mass-balance. YouTube video 

Presentations

Please look through lectures before class.

• 00: About.  A brief introduction to the course.

• 01: Introduction to Ecopath with Ecosim. 

Tutorials

Please look through tutorials before class.

• Construct an ecosystem model of Anchovy Bay.

This hands-on exercise will guide you through parameterizing and balancing a simple ecosystem model, applying the concepts from your readings.  A recording of this tutorial is also available on the Ecopath YouTube channel.