Morphological and meristic evaluation of the population structure of Anguilla marmorata across its range.

The population structure of the giant mottled eel Anguilla marmorata was evaluated using statistical analysis of 21 morphological characters among 13 representative localities across the Indo-Pacific region and as far north as Japan. There were no clear differences in 15 proportional and six vertebral characters using principal component analysis. The total number of vertebrae (N(V)) of A. marmorata at these localities had the widest variation among the morphological and meristic characters examined. A statistical analysis of the N(V) of 1238 specimens from 14 localities that included previously published data found significant differences among Micronesia, French Polynesia and other localities, and between localities in the North Pacific and South Pacific regions. Few differences were detected between specimens from the Indian Ocean and the North Pacific or South Pacific regions. The differences in N(V) among some regions and the population genetic studies of this species indicate that there are at least four populations of A. marmorata (North Pacific, Micronesia, Indian Ocean and South Pacific), which appear to include metapopulation structures in the Indian Ocean and South Pacific. This population structure is consistent with the ocean current patterns in each region and the evolution of migration loops of each spawning population.