Application of zero-inflated models to the catch rates of white marlin (Tetrapturus albidus) based on data from the spanish surface longline fishery targeting swordfish in the Atlantic Ocean

Abstract

Zero-Inflated-Models were applied to 3,500 fishing trips and 22,184 records of landings of white marlin (Tetrapturus albidus) obtained by the Spanish surface longline fishery targeting swordfish during the 1993-2000 and 1988-2010 periods, respectively. The data confirm the low prevalence of this species in the catch of this fishery, with zero catch returns amounting to 80% and 95% for each data set, respectively. The explanatory variables in the final model were based on likelihood ratio tests between nested models and AIC scores. In spite of some data limitations, the results show that it was possible to obtain standardized catch rate indices for both data sets, although there was a considerable year-on-year variability in some cases, as well as several limitations on some of the modelled explanatory variables. In addition, this paper presents the annual values for the standardized indices and discusses the potential effects that the Recovery Plan for this species and the current legislation may have been having on catch rates in recent years.