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The trend and variability of climate and oceanic variables were investigated with emphasis on the conditions for the recent years (2016-2018). The ENSO cycle has been mostly in a neutral phase since September 2016, however a La Niña event developed between October 2017 and March 2018. Normal conditions prevailed since then but there is a high probability (65-70%) that an El Niño develops by the end of 2018. The Indian Ocean Dipole was in negative phase in 2017 and turned into a positive phase in 2017. There is a high probability that it returns to a normal phase by December. These cycles were associated to inter-annual changes in SST, thermocline depth and sea surface chlorophyll. However, in 2017, the thermocline pattern did not exhibit the typical situation observed during a positive dipole as the mixed layer remained shallow throughout 2017 and until March 2018 between latitudes 10°N-10°S. These conditions which occurred in the core of the purse seine fishing grounds, could have promoted the vulnerability of schools to the purse seine gear. The recent trend (since 2014) in chlorophyll concentration is characterized by higher productivity which may promote the aggregation of tuna preys and ultimately, a greater abundance of tuna schools. That link between chlorophyll and CPUE on free schools and floating objects associated schools was further investigated. It leads to the conclusion that the chlorophyll concentration is an important factor to incorporate in CPUE standardization, in addition to other physical-derived factors.
