Bigeye Tuna Cath Relative to Sea Surface Height Anomaly during El Nino and Indian Ocean Dipole Event in Eastern Indian Ocean

Abstract

The study is aimed at understanding the variability of sea surface height anomaly (SSHA) of Eastern tropical Indian Ocean (EIO) and assessing its impact on bigeye tuna catchability. A nine-year (1993-2001) time series of SSHA data set are used in this investigation. A six year daily tuna fish catch data (1997-1999, and 2004-2006) and aeight-years (1993-2000) monthly average of tuna hook rate is derived from a tuna fishing company “Perikanan Samodra Besar” (PSB) Corp. Ltd. logbooks of 15-20 fishing vessels operated in EIO. Daily and an eight-year of monthly mean SSHA derived from data base of Colorado Center of Astrodynamics Research and NASA-POET-JPL respectively. The Spectrum analysis of SSHA and HR anomaly shows there are two dominant signals are representation of the annual and inter-annual variability. Significant interannual variability of SSHA is influenced El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole mode (IOD). During ENSO and IOD event, SSHA negative in IOD corresponding to shallow thermocline depth and enhanching upwelling strength. The Monte Carlo analysis shows that the relationship between of the highest hook rate and negative SSHA is significant especially in latitude of 13oS, where tuna fishing ground concentrated. The depth of thermocline become shallower and enhanching upwelling might have contributed to increase the bigeye tuna catchibility by providing suitable ambient temperature and feeding ground.