Standardized catch per unit effort (CPUE) of shortfin mako (Isurus oxyrinchus) for the Moroccan longline fishery

Shortfin mako shark Isurus oxyrinchus is harvested as bycatch by the Moroccan longliners targeting swordfish Xiphias gladius in the south of Moroccan waters. The average catch of shortfin mako reached 680 tons during the period 2012-2016. A time series of standardized catch per unit effort (CPUE) for shortfin mako was estimated by first analyzing the fleet dynamic and identification of fishing tactics using multi-table method, and then using two statistical models, including Generalized Linear Models (GLM) and Boosted Regression Trees model (BRT) with main effects and two-way interactions. BRT with two-way interactions was selected as the best model to estimate CPUE with less RMSE and high PDE. The standardized CPUE analysis indicates a declining trend since the early years and slight increase and stability in the last three years of the time series.