The Effect of Hypoxia and Anaemia on the Swimming Performance of Rainbow Trout (<i>Salmo Gairdneri</i>)

Abstract

ABSTRACT A series of increasing water-velocity tests in a water tunnel has been used to investigate the maximum swimming performance of two groups of rainbow trout, one acclimated to high temperature (21–23 °C) and the other to low temperature (8–10 °C). At temperatures close to their acclimation temperatures there was no significant difference between the maximum swimming speeds of the two groups of trout. .Exposure to an environmental oxygen tension of half the air-saturation value resulted in a 43 % reduction in maximum swimming performance at low temperature and a 30% reduction at high temperature compared with normal animals. Reduction in haematocrit to one-half or one-third normal resulted in a 34% reduction in maximum swimming speed at low temperature and a 40% reduction at high temperature compared with control animals (blank injected). The results are discussed in terms of whether fish can be assumed to be in a steady state at all velocities below the critical velocity and whether it is possible to attribute the differences in performance, during anaemia and hypoxia, to increased metabolic cost of the cardiac and branchial pumps.