Fuzzy logic analyses for the spawner-recruitment relationship of bigeye tuna (Thunnus obesus) in the Indian Ocean incorporating the environmental regime shift

One of the essential problems discovered in the SR model analyses is that the time series of the SR data frequently followed the trajectories of the loops or the spirals instead of the original SR model curve. Such phenomena implied that the SR data made only apparent fitness to the SR model in many cases because the SR data could not actually satisfy the assumptions behind (the density-dependent process under the same environmental conditions). In our study, such loop was also observed in the original SR data, but after separated into two regimes, the loops were almost disappeared in each regime. This concluded that the bigeye tuna SR data in the Indian Ocean followed the density-dependent process in each homogenous environment (cool or warm regime) and the Fuzzy logic incorporating these two regimes was considered to the most appropriate method.