In Japan, warm ‘Black Current’ runs parallel with and south of the main islands, bringing with it huge range of migratory
fish, including many varieties of tropic fish (Saiki, 1982). Migration is a strategy to exploit seasonal environments, and
migratory species occur disproportionately at higher latitudes and their habitats display marked seasonality, thus their
availability fluctuates greatly (Robinson et al., 2008). In fact, few congeneric species were captured in this study, and high
interspecific genetic distances were observed due to the scarcity of pairwise comparisons between species of close phylogenetic
relationships (Table 2).