Discrimination and Distribution of Two Tropical Short-Finned Eels (Anguilla bicolor bicolor and Anguilla bicolor pacifica) in the Indonesian Waters

Abstract

A total of 272 glass eel specimens of the two tropical short-finned eels (Anguilla bicolor bicolor and Anguilla bicolor pacifica) were collected around Indonesian waters from 2004 to 2007. Field sampling was conducted in 11 estuaries (Krueng Aceh, Air Kertaun, Cibaliung, Citanduy, Pacitan, Palu, Dumoga, Poigar, Bone Bolango, Akelamo, and Pami River) that spread out from western to eastern Indonesian archipelagos. Objectives of the study were to understand subspecies discrimination and distribution as well as population study of the tropical short-finned eel species (Anguilla bicolor) in the Indonesian waters based on morphological analyses of body measurements and vertebrae counts. Although morphological key characters of ano-dorsal length as a percentage of total length (-2.13 ~ 3.92) and number of ano-dorsal vertebrae (-3 ~ 4) overlap between subspecies, specimens were assigned to one of two subspecies based on their reported range of distribution from the western Sumatera Island to the southern Jawa Island (A. bicolor bicolor) and from the western Sulawesi Island to the western Papua Island (A. bicolor pacifica). Cluster analyses based on Euclidean distance separated the tropical short-finned eel species into two major clades. The first clade consisted of subscpecies of A. bicolor bicolor from Cibaliung, Air Kertaun, and Pacitan River estuaries. The second clade consisted of subspecies of A. bicolor pacifica from Palu, Dumoga, Poigar, Bone Bolango, and Akelamo River estuaries. Interestingly, A. bicolor bicolor from Citanduy River estuary (Jawa Island) nested in the second clade. The results suggested that a single tropical short-finned eel species, A. bicolor, inhabit in the Indonesian Waters. However the species was ecologically and biologically separated into two clade of subspecies, i.e. a Western Indonesian Clade of A. bicolor bicolor derived from Indian Ocean and an Eastern Indonesian Clade of A. bicolor pacifica derived from Pacific Ocean.