A BRIEF OVERVIEW OF THE SWORDFISH CATCHES BY THE PORTUGUESE PELAGIC LONGLINE FISHERY IN THE INDIAN OCEAN: CATCH, EFFORT, CPUE AND CATCH-AT-SIZE

SUMMARY The Portuguese longline fishery targeting swordfish in the Indian Ocean started in the late 1990’s. This fishery targets mainly swordfish, but also bycatches pelagic sharks such as blue shark and shortfin mako. 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 overview of the Portuguese swordfish fishery, including analyses on the catches, effort, catch-at-size and CPUE trends. 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. The results presented in this working document provide the first preliminary trends and analysis on swordfish catches available for the Portuguese longline fishery operating in the Indian Ocean.