Simulating mobile populations in aquatic ecosystems

Many aquatic species of management interest, such as endangered, sport, or commercially valuable fish, move extensively within a hydrosystem as they u se different habitats for spawning, rearing, feeding, and refuge. Engineeri ng tools are presently inadequate to simulate movement by such species as p art of the water resources planning and management. We describe how fixed g rid-cell methods can be coupled with mobile object-oriented modeling method s (called Eulerian-Lagrangian methods) to realistically simulate movement b ehavior of fish in the complex hydraulic and water quality fields of aquati c ecosystems. In the coupled system, the Lagrangian framework is used to si mulate the movement of symbolic fish (that is, an individual fish, schools of fish, or some aggregate of the population), and the Eulerian framework i s used to simulate the physicochemical regimes that influence fish movement behavior. The resulting coupled Eulerian-Lagrangian hybrid modeling method is based on a particle-tracking algorithm supplemented with stimuli-respon se rules, that is, the numerical fish surrogate.