The spatial allocation of fishing intensity by port-based inshore fleets: A GIS application

Abstract

This paper illustrates some practical Geographical Information System (GIS) applications for aiding fishery managers and coastal area planners in analysing the likely interactions of ports, inshore fleets, and local non-migratory inshore stocks, and in providing a flexible modelling framework for decision making on fishery development and zoning issues. The classic geographical 'friction of distance' approach to generating fields of action around home ports of inshore fleets which largely make day trips to their adjacent fishing grounds, is compared with a more flexible empirical 'Gaussian Effort Allocation' (GEAM) modelling approach where peak effort may occur at different distances from port. The latter approach is considered more appropriate in describing resource depletion with distance. The geographical implications of fishing effort and intensity fields are contrasted, and compared with Beverton and Holt's (1957) ideas on the effect of distance from port on the 'limiting effort distribution'. Similar readily-calculated geographical reference points for inshore fishing fleets are derived. The GEAM framework allows a range of geographical characteristics to be taken into account in describing the interactions of ports and local fleets with inshore resources and local fishing grounds, and unlike friction of distance concepts, allows for resource depletion close to port. Two examples are given of fitting effort 'fields' from port-based fleets to observed data, in this case on survey biomass, following the assumption of local effort allocation proportional to local catch rate. Procedures are also suggested for collecting prior information on fleet activity to tune the model. The GEAM model is also suggested as an aid to deciding on the location of marine parks or fishery closure areas.