Food Habits, Functional Digestive Morphology, and Assimilation Efficiency of the Rabbitfish Siganus spinus (Pisces, Siganidae) on Guam

Abstract

Analyses of stomach contents of Siganus spinus showed that algal availability and size and behavior characteristics of the fish determine what kinds of algae are ingested in the field. Sixty-two algal species were tested during multiple choice food preference trials in the laboratory. Elimination trials and observation tests showed a ranked order of algal preference: (1) Enteromorpha compressa, (2) Murrqyella periclados, (3) Chondria repens, (4) Boodlea composita, (5) Cladophoropsis membranacea, (6) Acanthophora spicifera, and (7) Centroceras clavulatum. An: examination of the morphology of the digestive system showed that the fish are well adapted herbivores, especially toward the filamentous algae. The assimilation values for the adults ranged from 6 to 39 percent; those for the juveniles ranged from 9 to 60 percent.