Quantification of annual variations in fishing power due to vessel characteristics:: an application to the bottom-trawlers of South-Brittany targeting anglerfish (Lophius budegassa and Lophius piscatorius)

We present a method based on generalised linear models fitted to CPUE data to quantify the changes in fishing power in a fleet targeting a particular species. Changes in the fleet's fishing power are differentiated from variations in population abundance through the use of an abundance index estimated from the CPUE of an index vessel catching the species as by-catch. Observed inter-vessel differences in efficiency are then explained by vessel characteristics such as gear used, engine power, length of headline and ground rope, availability of GPS and skipper skills. The application of the method to the French bottom-trawlers targeting anglerfish in the Bay of Biscay and in the Celtic Sea during the period 1983-1998 reveals that fishing gear (twin or simple trawls) and engine power are the most important variables for explaining differences in fishing power. (C) 2003 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.