Predator density and dissolved oxygen affect body condition of <Emphasis Type="Italic">Stenonema tripunctatum</Emphasis> (Ephemeroptera,Heptageniidae) from intermittent streams

The effects of population density, fish density, and dissolved oxygen on body condition of late-instar nymphs of Stenonema tripunctatum (Ephemeroptera, Heptageniidae) were investigated using nymphs sampled from isolated, upland stream pools over summer in central Arkansas, USA. All three factors exhibited high variation among pools. Body condition was negatively related to fish density, and positively related to dissolved oxygen (when included in the model). High fish densities may be related to low body condition because they cause reduced foraging or force earlier emergence at small body sizes. These results emphasize the combined effects of biotic and abiotic factors on body condition in mayflies, and support earlier findings that population density is a less-important factor.