Foods of Age-0 Rio Grande Silvery Minnows (Hybognathus amarus) Reared in Hatchery Ponds

We examined contents of alimentary canal from pond-reared Rio Grande silvery minnows (Hybognathus amarus; n = 183) to determine frequency of occurrence for foods consumed among small (9–20 mm), medium (21–35 mm), and large fish (36–75 mm). Among 183 fish, 19% (n = 34) of alimentary canals were empty. Of those with food items (n = 149), insects were the most common and were present in 66% of fish, followed by formulated feed (60%), diatoms (40%), cladocerans (36%), rotifers (35%), filamentous algae (32%), bryozoan statoblasts (19%), copepods (11%), protozoa (9%), plant material (9%), ostracods (6%), detritus (5%), and sand (4%). Among size groups, small and medium fish consumed a greater variety of foods than large fish. Information on contents of alimentary canal of pond-reared Rio Grande silvery minnows will aid in refining culture techniques for this federally listed endangered species.