Role of Hypoxia in Limiting Diel Spring and Summer Distribution of Juvenile Yellow Perch (Perca flavescens) in a Prairie Marsh

Abstract

Comparative field and laboratory data on the distribution-limiting levels of dissolved oxygen (DO) for yearling yellow perch (Perca flavescens) is presented. At Blind Channel, Delta Marsh, Manitoba, diel fluctuations in DO concentrations began by June, approximately 6 wk after ice-off. By early July severe hypoxia (≤ 1.5 ppm DO) first occurred in the cattail habitat close to the substrate at dawn, and by early August severe hypoxia extended throughout the cattail bed. Using wire minnow traps, juvenile perch persisted within the cattails close to the substrate in June. In early July, juvenile perch occupied the submerged macrophyte – open water habitat, away from the cattail and hypoxia. Significant diel changes in horizontal distribution were evident at one site, where fish avoided severe hypoxia in the cattail bed overnight but returned during the day, as there was little alternative cover and when DO levels were not lethal. In situ survival experiments demonstrated decreased survival close to the substrate, in the cattail, and overnight compared with overday, reflecting the distribution of low DO. Survival increased 27% over the control by bubbling oxygen into holding cages. In a two-chambered normoxic/hypoxic tank, perch demonstrated a preference for cover, and avoidance of hypoxia at 1.5–3.0 ppm DO. The habitat choice of juvenile yellow perch in Delta Marsh is a compromise between the cattail, with favorable predator/prey conditions, and hypoxia.