With changing climatic and environmental conditions, it has become vital to understand the impact of these changes on tuna resources. This work aimed to investigate whether the stock dynamics of yellowfin tuna ( Thunnus albacares), albacore tuna ( Thunnus alalunga) and Bigeye tuna ( Thunnus obesus) in the South Pacific Region can be explained significantly only by the environmental factors of sea surface temperature (SST) and Atlantic Multidecadal Oscillation AMO. Monthly variables of SST and AMO were used as candidates independent variables in Generalised Linear Model and Generalized Additive Model to reproduce the natural logarithm of standardized CPUE of tuna from 1972 to 2019. Although models with single variable resulted in significant fitness, models with two variables had a better fit in comparison to models with single variable for all tuna stocks. Possibilities of two significantly different patterns in the trajectory of three tuna and environmental conditions used in models were observed. Environmental conditions play a highly significant role in structuring tuna stock trajectory in the South pacific and need to be included in tuna management/harvest plans.