  Capital accumulation has been a major issue in fisheries economics over the
last two decades, whereby the interaction of the fish and capital stocks were
of particular interest. Because bio-economic systems are intrinsically complex,
previous efforts in this field have relied on a variety of simplifying
assumptions. The model presented here relaxes some of these simplifications.
Problems of tractability are surmounted by using the methodology of qualitative
differential equations (QDE). The theory of QDEs takes into account that
scientific knowledge about particular fisheries is usually limited, and
facilitates an analysis of the global dynamics of systems with more than two
ordinary differential equations. The model is able to trace the evolution of
capital and fish stock in good agreement with observed patterns, and shows that
over-capitalization is unavoidable in unregulated fisheries.
