Indonesian waters has high level of eel biodiversity, which is recognized as the origin of the world eels. Poso Lake is one of the most abundant eel habitat, located in central part of Sulawesi Island. Like most of eels populations worldwide, the population in this lake has been declining and the causes are still uncertain. Very few studies had been undertaken regarding the eel population including the population in Poso Lake environment. As a response to an urgent need for research on the population biology of Poso Lake eel, the present study was conducted to provide base line information on silver eels or mature eels which captured during their on set spawning migration out of Poso Lake. A total of 100 eels which have silver eel characters were collected from weirs along the out let of Poso Lake over the study period. The sizes of eels captured ranged from 48,9 – 136,8 cm with mean 78,3 cm in total length, and 265 - 7025 g with mean 1289 g in body weight. Among them only 63 eels had gonadosomatic index (GSI) > 1%, had been determined as A. celebesensis (41) and A. marmorata (22), and they were all female. GSI values of A. celebesensis were significantly higher than A. marmorata. There were no apparent differences in the condition factor of the two eels species.