Shallow coastal areas on the Swedish west coast are generally considered highly productive and important nursery grounds for both invertebrates and fish. Several commercial important coastal fish species utilize the abundant food resources in the shallow bays during their juvenile life history stages. In my research, trophic relationships are characterized among a guild of epibenthic fish and crustaceans in some shallow embayments along the Swedish west coast. I focus principally on the influence of physical factors (temperature, salinity, exposure, sediment type, oxygen level and habitat structure) on predator-prey dynamics which are quantified in a multi-level approach involving laboratory experiments and field sampling. My intention is to study biotic regulation of populations within the limits set by naturally occurring abiotic factors in coastal areas. The general hypothesis is that habitat structure (sediment and vegetation) in a coastal area has a decisive importance for community structure and function. The structure of the habitat influence the carrying capacity of the area and set the limits within which population size may fluctuate. Population dynamic, production and consumption of epibenthic fauna and fish has been estimated quantitatively in some shallow soft bottom bays, and energy flow models have been constructed for both a sandy habitat and an eelgrass bed. Interactions between habitat structure (sediment and vegetation) and the structure of epibenthic fauna has been evaluated in several types on coastal environments in the Skagerrak and the Kattegat. For example, changes in macrovegetation in shallow coastal areas and its effects on recruitment and population structure of associated crustaceans and fish has been investigated. Distribution of filamentous algae has been assessed by aerial photo documentation, and interactions between vegetation and fauna has been studied in laboratory experiments and field investigations. Structure of fish assemblages has been related to vegetation type in both rocky and soft bottom communities. In shallow sandy bays recruitment mechanisms in flatfish has been studied. Further, the structuring role of hypoxia on demersal fish communities has been investigated in SE Kattegat and York River, Chesapeake Bay, including studies of species structure, biomass, growth, migrations and food selection.