Fishery indicators for shortfin mako shark (Isurus oxyrinchus) caught by the portuguese pelagic longline fishery in the Indian Ocean: catch, effort, size distribution and standardized CPUEs

This working document provides fishery indicators for the shortfin mako shark captured by the Portuguese pelagic longline fishery in the Indian Ocean, in terms of catches, effort, standardized CPUEs and size distribution. The analysis was based on data collected from fishery observers, skipper's logbooks (self sampling) and official logbooks collected between 1998 and 2016. The mean sizes were compared between years and seasons (quarters). The CPUEs were analyzed for the Indian Ocean and compared between years, and were modeled with tweedie GLM models for the CPUE standardization procedure. In general, there was a large variability in the nominal CPUE trends with the standardized CPUEs relatively similar to the nominal trends. In terms of size distributions there were some spatial trends with larger specimens tending to occur in the central and eastern areas and smaller specimens in the southwest Indian Ocean. The size distribution time series showed slight increases in mean sizes through time.