Complexity of small-scale fisheries on the coast of Paraná is compounded by a great diversity of aquatic habitats, a variety of mostly open-access fishing practices, cultural origins of fishermen, their migratory movements, levels of market insertion, and uses of other natural resources. Amidst such complexity, six fishing production systems were described in a previous work. This work explores the hypothesis that they are related through an evolutionary history of differentiation. By conceiving production systems as new levels of integration between natural and social systems, the theory of nature/society interactions provides a comprehensive, interdisciplinary framework to explore relationships between natural, economic and social processes, hence to investigate environment and development issues. Data on demography, fishing practices and techniques, production marketing and other revenue sources, and geographical and environmental variables, were obtained in 1997 from various primary and secondary sources, including interviews in 22 fishing communities. An evolutionary model is developed to describe patterns of differentiation and factors of change of those systems. Present systems have common roots in the XVIII century, when agriculture and fisheries had both important roles in the economy. In the XX century, agriculture is abandoned, and system differentiation is mostly driven by market forces, demographic dynamics, particularly immigration, and technical innovation, including invention of new gear. While some systems show increased technology and market participation, others fail to cope with change, and seem to be bound to extinction. Management and research do not recognize such different realities, failing to address environment and development issues.