Ontogenetic microhabitat shifts in Sacramento pikeminnow, <Emphasis Type="Italic">Ptychocheilus grandis</Emphasis>: reducing intraspecific predation

The Sacramento pikeminnow (Ptychocheilus grandis) is a piscivore that will prey on its own young in streams. Microhabitat use by two size classes of juvenile pikeminnow in stream pools with and without adults present was examined in the South Yuba River, California. Juvenile pikeminnow were generally found in shallower and slower conditions than adult pikeminnow, but shifted to even slower and shallower conditions with more cover in the presence of large adults. Microhabitats selected were related to fish size, suggesting that intraspecific predation was the dominant factor affecting local distribution. Patterns of microhabitat use were consistent with ecological segregation of species and size classes observed in other California streams with more diverse fish faunas.