An updated overview of the swordfish catches by the Portuguese pelagic longline fishery in the Indian Ocean between 1998-2012: catch, effort, CPUE and catch-at-size

The Portuguese longline fishery targeting swordfish in the Indian Ocean started in the late 1990’s, targeting mainly swordfish. A recent effort by Portuguese Marine and Atmosphere Institute (IPMA) has been made aiming the collection of historical catch data on this fishery since the late 1990’s to the present date. This working document reports an updated overview of the Portuguese swordfish fishery, including analyses on the catches, effort, catch-at-size and CPUE trends for the period 1998-2012. The trends in the swordfish catch-at-size were analyzed annually, and compared between months and regions of operation of the fishery. Nominal annual CPUEs were calculated as kg/1000 hooks, and were standardized with Generalized Linear Models (GLMs) using year, quarter, location and swordfish/blue shark ratio as explanatory variables. Three different modeling approaches were used and compared, including tweedie, gamma and lognormal models, and model validation was carried out with a residual analysis. A sensitivity analysis to the influence of the ratio factor in the models was carried out. The results presented in this paper update a previous analysis on the trends of swordfish catches available from the Portuguese longline fishery operating in the Indian Ocean.