Update on standardized catch rates for mako shark (Isurus oxyrinchus) in the 2006-2019 Mexican Pacific longline fishery based upon a shark scientific observer program

Citation
Gonzalez-Ania LV, Fernandez-Mendez JI, Castillo-Geniz JL, et al (2021) Update on standardized catch rates for mako shark (Isurus oxyrinchus) in the 2006-2019 Mexican Pacific longline fishery based upon a shark scientific observer program. In: ISC 2021 1st Shark Working Group Workshop. ISC/21/SHARKWG-1/07, Online
Abstract

Abundance indices for mako shark (Isurus oxyrinchus) in the northwest Mexican Pacific for the period 2006-2019 were estimated using data obtained through a pelagic longline observer program, updating similar analyses made in 2014 and 2017. 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 from mainland coast and time-area factors. Standardized catch rates were estimated by applying two generalized linear models (GLMs). The first model (using a quasi-binomial likelihood and a complementary log-log link function) estimates the probability of a positive observation and the second one estimates the mean response for non-zero observations, using a lognormal error distribution. The importance of factors included in the models is discussed. The results of this analysis point at the abundance index trends being close to stability in the analyzed period.