Analyse et estimation des puissance de pêche

-An analysis of the fishing power concepts leads to a distinction between local fishing power (at a given location). and overall fishing power. Overall fishing power takes into account the ability to detect and quickly exploit rich areas. In order to estimate local fishing power it is necessary t o compare the catches of different ships operating in neighbouring areas. Such a comparison performed on two ships will give an estimate of their relative fishing powers. The closer the two ships are, the more reliable will be the estimate. A weighting function must be used, and this function is related to the spatial heterogeneity of the fish density. Such a function is provided by the variogram as defined by Matheron (1965).-Overall fishing powers can be estimated using Robson's method (1966) where no division into spatial blocks is made: the fact that a ship is in a rich or a poor area must be related to the strategic component of its overall fishing power. A comparison between local and overall fishing powers may give a good insight of the strategic activity of the fishing fleet. The North East Atlantic albacore (Thunnus alalunga) surface fishery, more precisely its French component, has been studied as an example. The variograms have been estimated and appear to give a significant description of the spatial heterogeneity of the fish density. Individual loca