Update on standardized catch rates for blue shark (Prionace glauca) in the 2006-2020 Mexican Pacific longline fishery based upon a shark scientific observer program

Abundance indices for blue shark (Prionace glauca) in the northwest Mexican Pacific for the period 2006-2020 were estimated using data obtained through a pelagic longline observer program. Individual longline set catch per unit effort data, collected by scientific observers, were analyzed to assess effects of environmental factors such as sea surface temperature, distance to the nearest point on the coast and time-area factors. Standardized catch rates were estimated by applying generalized linear models (GLM). Sea surface temperature, mean SST anomalies, distance to the coast, year, area fished, quarter and fraction of night hours in the fishing set were all significant factors included in the model. The results of this analysis show a relatively stable trend with a sharp descent in the last year of the time series in the standardized abundance index in the period considered. This trend could be explained in terms of recent oceanographic events and possible recent changes in fishing strategy of the fleets involved.