This article provides a survey of the economic literature on investment behaviour and capacity adjustment in fisheries. An overview of the existing theoretical and the empirical work is provided, and areas that require more work are pointed out. The survey shows that while a large body of theoretical work has been developed on the issue of capital adjustment in fisheries, relatively less attention has been granted to the theory of investment, where this becomes a separate decision to the decision about capital levels: i.e., where capital is quasi-malleable. In addition, empirical studies have been fairly limited, and more work is still needed to analyse and further investigate these issues in practical situations. There is particularly a need for more empirical studies of investment behaviour and drivers of investment behaviour at the firm level based on adequate economic data.