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

This paper illustrates some practical Geographical Information System (GIS) applications for aiding fishery managers and coastal area planners in anal ysing the likely interactions of ports, inshore fleets, and local non-migra tory inshore stocks, and in providing a flexible modelling framework for de cision making on fishery development and zoning issues. The classic geograp hical "friction of distance" approach to generating fields of action around home ports of inshore fleets which largely make day trips to their adjacen t fishing grounds, is compared with a more flexible empirical "Gaussian Eff ort Allocation" (GEAM) modelling approach where peak effort may occur at di fferent distances from port. The latter approach is considered more appropr iate in describing resource depletion with distance. The geographical impli cations 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 geographi cal reference points for inshore fishing fleets are derived. The GEAM frame work allows a range of geographical characteristics to be taken into accoun t in describing the interactions of ports and local fleets with inshore res ources and local fishing grounds, and unlike friction of distance concepts, allows for resource depletion close to port. Two examples are given of fit ting effort "fields" from port-based fleets to observed data, in this case on survey biomass, following the assumption of local effort allocation prop ortional to local catch rate. Procedures are also suggested for collecting prior information on fleet activity to tune the model. The GEAM model is al so suggested as an aid to deciding on the location of marine parks or fishe ry closure areas. (C) 1999 International Council for the Exploration of the Sea.