A methodological approach to identify fishing grounds: A case study on Greek trawlers

Identification of fishing grounds is crucial for a good understanding of fisheries practices and for proposing effective management measures. A methodology to map fishing grounds and analyze their spatial patterns was developed. The proposed approach combines VMS (Vessel Monitoring System) data, used for estimation of fishing effort, and catch data, used for modelling species presence. The methodology is based on the assessment of the probability of species presence using generalized additive models, the estimation of a presence threshold for binary classification of presence/absence, the spatial overlay between the probability of species presence and fishing effort to identify fishing grounds, and finally the analysis of spatial patterns to identify hot (clusters of high fishing effort and high probability of presence) and cold (clusters of low fishing effort and low probability of presence) spots. The methodology was applied in Greek waters to identify bottom trawl fishing grounds. Survey and commercial fishing data, collected from 1985 to 2008, were analysed. Fifteen demersal species were studied; all considered important target-species for bottom trawlers in the Mediterranean. The main fishing grounds in Greek waters for the fifteen studied species, as well as aggregated hot and cold spots, were identified and analyzed.