Fishery biology deals with worldwide fisheries, value-chains and ecological research. We focus on traditional methods to investigate exploited organisms, such as determination of population parameters and field work for direct estimation of fish density. The concept of a fishery model is introduced, and we adapt this theory to widely diverse species, fisheries and level of information available. This helps us making simple quantitative predictions of the suitability of different exploitation regimes. Harvest technology deals with a general description of the most common fishing methods and a brief description of the vessel technology used in different parts of the world. We deal with fish behavior, operation methods, basics on the selective fisheries, fish detection and density estimation with hydro-acoustics during ecosystem surveys. New developments in the pursuit of energy efficient and environmentally adequate gear, by-catch reduction, and user-friendly technology, are addressed. These developments include also capture-based aquaculture. We give, in addition, a brief introduction to the monitoring, control and enforcement of technical measures in regulated capture fisheries.