The late 20th century has witnessed increasing crises in the world's marine fisheries. A causal analysis of these reveals that a common element are various manifestations of spatial inequity. This most frequently includes the inequity of access rights to the resource, but factors such as variations in resource depletion, spatio-temporal variations in stock recruitment, the imposition of regulatory zoning, destruction of marine ecosystems and the siting of mariculture facilities are other examples. To resolve some of these problems, management practices must be improved. As has been shown in other fields where spatially related problems occur, there is now a promising tool, Geographical Information Systems (GIS), which, combined with other analytical tools and models, could allow for improved spatial management. GIS are basically integrated computer based systems which allow for the input of digital geo-referenced data to produce maps plus other textual, graphical and tabular output. The essential usefulness of GIS however, lies in its ability to manipulate data in a large number of ways and to perform various analytical functions so as to produce output which makes for more efficient decision making.As with many computer based systems, the key to GIS success lies in the acquisition of suitable data. The various means by which both primary and secondary data can be located, gathered, accessed and stored are described.