Catadromous eels undergo stepwise migration from marine to estuarine, then to freshwater habitats. A few species are able to stop their migration and settle in marine habitats, while some can migrate between seawater and freshwater habitats throughout their life. However, it is necessary to know the effects of salinity on the preference and growth performance of tropical freshwater eels found in the Philippines to optimize practices on the culture of these species . In this study, glass eels of Anguilla marmorata, an economically important freshwater eel, were collected from an estuary near Cagayan River, northern Philippines and observed for choice and growth experiments.
Majority of the glass eels were active towards freshwater compartment (0-5‰) and this continues to increase with time from 80% to 92.5%. After 60 days of culture, glass eels reared in freshwater (0‰) and brackish water (17.30 ± 0.01‰) have significantly higher growth performance in terms of total length and weight. On the othe r hand, delayed growth was observed in seawater (31.79±0.01‰) until day 45. Glass eels reared in freshwater, brackish and seawater had comparable survival, indicative of wide salinity tolerance of A. marmorata at glass eel stage. Examining the habitat preference and its influence on growth and survival are essential in improving the culture techniques and understanding the spatial distribution of Anguilla
marmorata glass eels.