Hobart

Seminar Abstract

Tuesday 16 February 2010, 11.30am (Tas time)
CSIRO Auditorium, Hobart

Christine Largouët & Yves-Marie Bozec
Agrocampus Ouest
Laboratoire informatique
Centre de Rennes, France

Modelling a coral-reef food web using timed automata network

Timed automata refer to discrete-event simulation models supplied with clocks and timing constraints. They have been successfully used in a wide range of industrial applications where timing aspects are critical. We are currently exploring their ability to simulate the dynamics of fish stocks according to prey-predator relationships and fishing mortality. A well-documented coral-reef ecosystem (Uvea atoll, New Caledonia) was used as a case-study. The modelled system was designed as a network of fish automata, each one representing a trophic guild and being defined by a finite set of formal biomass states. Some of them were also connected to automata of fishing pressure. For a given fish automaton, biomass changes result from synchronized changes in biomass states of connected prey or predator, or changes in fishing pressure. Timing constraints associated to biomass changes are estimated by using simple biomass dynamics models accounting for fish production and mortality by predation or by fishing. Model-checking techniques are used for determining critical delay times between biomass changes and for verifying the achievability of particular biomass states. As a result, the model allows to investigate the direct and cascading effects of time-based fishing scenarios, such as chronic increasing fishing pressures and various schemes of rotational closures.

Scenario templates to analyse qualitative marine ecosystem

Ecosystem management requires needs scenarios that are commonly used as tools for evaluating future evolution of ecosystems depending on policy or potential climatic changes. We are currently developing discrete-event approaches to qualitatively model ecosystems including a high-level language used to express environmental scenarios. An ecosystem is considered as a timed system made of a set of interacting components, each one having uncertain temporal constraints on its evolution. Timed Automata are then used to describe the system behaviour according to a general framework defining the ecosystem, environmental issues and human pressures. Timed automata are worth using because of their ability to be coupled with efficient checking techniques (model-checking), particularly relevant to analyse large-scale systems. To explore the ecosystem, we define generic patterns, associated to the most usual types of scenarios, and translate them into temporal logic formula (TCTL). The qualitative answer of scenario evolution is then computed thanks to model-checking techniques.

We experimented our approach on a coral-reef marine ecosystem (Uvea atoll, New Caledonia) under various fishing pressures. The model describes the tropho-dynamic interactions between fish trophic-groups as well as interactions with the fishery activities. Results present the use of scenario patterns for several fishery policies.

Seminar recording

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
Clothilde Langlais, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5399
Natalie Kelly, (Biology/Modelling seminars) CSIRO Marine and Atmospheric Research 0438 452 483
Jillian Enraght-Moony, (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5320
Communications Manager, Antarctic Climate and Ecosystems CRC (03) 6226 2265
Margaret Hazelwood, Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2971

Last updated 11/05/10