There is general recognition that many of the world's marine and freshwater fisheries are overexploited, that the ecosystems containing them are degraded, and that many fish stocks are depleted and in need of rebuilding (for a review see the FAO report (Anonymous 2002)). There is also general agreement among scientists, the industry, the public and politicians that the search for sustainable fishing should receive high priority. To keep matters brief, and to avoid crossing the line between environmental science and environmentalism (Mangel 2001b), I do not go into the justification for studying fisheries here (but do provide some in Connections). In this chapter, we will investigate various single species models that provide intuition about the issues of sustainable fisheries. I believe that fishery management is on the verge of multi-species and ecosystem-based approaches (see Connections), but unless one really understands the single species approaches, these will be mysteries (or worse – one will do silly things).

The fishery system

Fisheries are systems that involve biological, economic and social/behavioral components (Figure 6.1). Each of these provides a distinctive perspective on the fishery, its goals, purpose and outputs. Biology and economics combine to produce outputs of the fishery, which are then compared with our expectations of the outputs. When the expectations and output do not match, we use the process of regulation, which may act on any of the biology, economics or sociology. Regulatory decisions constitute policy. Tony Charles (Charles 1992) answers the question “what is the fishery about?”