Impact of dipole mode and El-Nino events on catches of yellowfin tuna (Thunnus albacares) in the Eastern Indian Ocean off west Java

The impact of Indian Ocean Dipole Mode (IOD) and El Niño-Southern Oscillation (ENSO) events on catches of yellowfin tuna (Thunnus albacares) (YFT) in the Eastern Indian Ocean (EIO) off Java was analyzed through the use of remotely sensed environmental data (sea surface temperature/ SST and chlorophyll-a concentration/ SSC) and yellowfin tuna catch data. Analyses were conducted for the period of 2003–2012, which included the strong positive dipole mode event in association with weak ENSO in 2006. Yellowfin tuna catch data were based from the report of Palabuhanratu fishing port and remotely sensed environmental data were based from MODIS-Aqua_NOAA. IOD has a significant effect on the catch composition and proportion of YFT. In the strong positive dipole mode event in 2006 and weak ENSO events in 2011 and 2012 the catch of YFT was higher than normal period. An increasing Catch Per Unit Effort (CPUE) of YFT started from May-June and reached the peak on September-October was noted, this might be due to upwelling evident before the increasing trend observed. High increase of YFT-CPUE occurred during strong positive dipole mode event (2006) and a weak ENSO events (2011 and 2012) might be related to the increase of abundance and distribution of chlorophyll-a and phytoplankton in those period. In contrast, YFT- CPUE was very low at the La-Nina event in 2005 while this species was still dominant in the catch composition compared to other tuna species.