Inshore migration of the tropical eels Anguilla spp. recruiting to the Poigar River estuary on north Sulawesi Island

To understand ecological and behavioral aspects of inshore migration of tro pical eels, Anguilla spp., we collected 32836 glass eels in the Poigar Rive r estuary on north Sulawesi Island, Indonesia, in monthly collections from 1997 to 1999. The specimens were identified using morphological characters, and 3 species, A. celebesensis, A. marmorata, and A. bicolor pacifica, wer e found each year in fluctuating abundances. A. celebesensis was the most a bundant species and comprised 73.5, 79.5, and 81.9% of all glass eels recru iting to the estuary of the Poigar River in 1997, 1998, and 1999, respectiv ely. This species was relatively abundant in all 3 years with peaks during June in 1997 and 1998, and during September in 1999. A. marmorata was the s econd most abundant species and comprised 23.8, 18.8, and 17.7% of the year ly catches, respectively, and reached peaks in abundance during June in 199 7 and 1998, and during January in 1999. A. bicolor pacifica comprised only 2.7, 1.7, and 0.3% of the yearly catches, respectively, with peak catches i n June in 1997, in January in 1998, and in January and February in 1999. A. celebesensis and A. marmorata were collected almost throughout the year in 1997, 1998, and 1999, suggesting that in contrast to the temperate eels th at recruit during half the year from winter to spring, these tropical eel s pecies recruit to some degree throughout the year. Glass eels clearly were more abundant during new moon sampling events, with a total of 3075, 183, 3 , and 90 glass eels collected in 10 sampling periods during new moon, waxin g moon, full moon, and waning moon, respectively. All glass eels were colle cted at night (18:00 to 05:00 h) when light intensity ranged from 0 to 1.86 lux, and no glass eels were collected during the day (06:00 to 17:00 h) wh en light intensity ranged from 500 to 150000 lux. During new moon, more gla ss eels were collected during flood tide than during ebb tide. These result s suggest that a greater number of glass eels recruited to the Poigar River estuary at night, during new moon and during flood tide.