Standardized CPUE for juvenile yellowfin, skipjack and bigeye tuna from the european purse seine fleet in the Atlantic Ocean from 1991 to 2006

Abstract : In this document three abundance indices are obtained for the juveniles of tropical tunas (yellowfin (≤30Kg.), skipjack and bigeye of European purse seine fishery in the Atlantic Ocean from 1980 to 2006 using generalized linear models (delta-lognormal model). Catch and effort data come from detailed daily logbooks. Catch rates are modelled using the delta lognormal model. The method estimates a combined CPUE of the three species from aggregated catches, and the proportion of catches for each species, so the final individual abundance indices are calculated multiplying both estimators for each species. Explanatory variables used in the analysis are: year, zone, quarter, harvest capacity, country, and starting date of the vessel. Year and zone are the most explanatory factors of variability in CPUEs and vessel characteristics have a minor explanatory effect in observed catch rates.