This course is intended to provide graduate students of marine sciences an introduction to general ecosystem theory and mathematical concepts about and quantitative representation of trophic relationships between organisms/populations/communities within marine food webs along with the command of a widely-adopted marine ecosystem modelling tool Ecopath with Ecosim (Christensen et al.,2005). The topics of interest include, but not limited to foraging arena theory, ecological network analysis, ecological indicators, and quantification of ecosystem maturity/health.