Relative Abundance, Diet and Feeding Behaviour of Fishes in Lawis Stream Buruun Iligan City

Abstract

Species composition, relative abundance and feeding behaviour of fishes were determined at different elevations of Lawis stream (124° 0.67' E; & • 11.26'N) in Buruun, Iligan City. Visual census at three stations with riffle and pool areas showed six species of fish: Therapon cancellatus (Theraponidae), Kuhlia sp. (Kuhlidae), Boroda expatria (Eleotridae), Ryacichthys aspro (Rhyacichthyidae), Sicyopteros extranous and S. cyanopterus (Gohüdae). The cylindrical shaped S. extranous was the most abundant in pool areas while the dorsoventrally flattened R. aspro dominated the riffle areas. Relative abundance of fish decreased with elevation. Gut content analysis indicated a hroad diet in fish species examined, but in general diet includes a mixture of insect larvae, amorphous bodies, Macrobrachium sp. larvae and bryophytes. Boroda expatria showed an exclusive molluscan (Bursa echinata) diet. Daytime observation showed that both juveniles of S. cyanopterus and S. extranous exhibited similar sucking behaviour on hard rock surfaces, but the latter species also showed the straining behaviour. The feeding strike movement in these juveniles was ahsent in adult S. extranous which showed the straining behaviour: