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Bigeye tuna, Thunnus obesus (Lowe, 1839) is one of the main target species for Indonesian tuna longline fishery in the Eastern Indian Ocean. The tuna longline fishery has begun since 1978 and around 1980, bigeye tuna started as target when deep longline introduced. However, little is known about its abundance, especially in the north eastern area where is the core fishing ground for Indonesian tuna longline fishery. The objective of the study is to provide a preliminary assessment about the abundance indices of bigeye tuna from Indonesian tuna longline fishery. In this paper, four types of Generalized Linear Model (GLM) was used to standardize the catch per unit effort (CPUE) and to estimate the relative abundance indices, i.e. Zero-inflated Negative Binomial (ZINB), Negative Binomial (NB), Tweedie (TW) and Delta-lognormal (DEL).We used two types of data used in this study; the scientific observer data conducted by Research Institute for Tuna Fisheries (RITF) from 2006 to 2018 and national observer program conducted by Directorate General of Capture Fisheries (DGCF) from 2016-2017. On overall, the abundance of bigeye tuna was depleted quite substantially over the years (almost two-fold from the beginning of observation). ZINB failed to give plausible indices due to convergence problems when areas were included. NB, TW and DEL produced similar trends, especially NB and TW produced almost identical trends. DEL produced higher abundance indices between 2006-2012 and lower prediction afterwards compared to previous two models. NB produced the lowest AIC but TW has the lowest BIC values than others, however, it was suggested that abundance indices by NB is likely the most plausible.
