| The objective of this study is to carry out the CPUE standardizations and preliminary stock assessments for striped marlin and blue marlin in the Indian Ocean. Standardized CPUEs of striped marlin reveals substantial decline since 1980. Standardized CPUE of blue marlin deceased since mid-1980s, revealed increasing trends during 1990s but they gradually decreased for recent years. Based on the results of stock assessments, the stock status of striped marlin might be very pessimistic, current (2011) fishing mortality might be higher than MSY level and current biomass might be lower than MSY level. The stock status of blue marlin might be relatively optimistic. However, different CPUE series might result in significantly diverse assessment results and thus current assessment results are very uncertain. In addition, this study also carried out CPUE standardization for southern bluefin tuna. The CPUE standardization is performed based on the sub-area effect of either CCSBT statistical areas or Taiwanese SBT fishing ground. Standardized CPUEs generally reveal quite different trends for different area. It is apparent that the CCSBT statistical areas are not appropriate for Taiwanese SBT fleet since the main fishing grounds are separated into several parts by CCSBT statistical areas. It would be helpful to redefine CCSBT statistical areas for Taiwanese SBT fishery according to the temporal and spatial analysis of its fishing characters.