STANDARDIZED CATCH RATES IN BIOMASS FOR THE SWORDFISH (Xiphias gladius) CAUGHT BY THE SPANISH LONGLINE FLEET IN THE INDIAN OCEAN FOR THE PERIOD 1993-2007.

Preliminary standardized catch rates in biomass were obtained using General Linear Modeling (GLM) procedures from sets carried out by the Spanish surface longline fleet targeting swordfish in the Indian Ocean over two independent periods, 1993-2000 and 2001-2007. The factors used for modeling were year, area, semester/quarter, gear and ratio between swordfish and blue shark catches. The models explained 24% and 51% of the CPUE variability for the first and the second period, respectively. As in the case of the Atlantic and Pacific swordfish, an important part of the CPUE variability was attributed to the ratio between the two most prevalent species in the catch. Other significant, although less important factors, were also identified. The different sensitivity trials have shown similar trends over time. The conclusions on the standardized CPUE suggest a ‘learning’ and erratic trend over the first period of activity of the Spanish fleet and a decreasing trend during the second period.