| Summary: | A method has been developed for the continuous automated monitoring
of cardiac output in adult rainbow trout. Average cardiac output measured under
control conditions and varied environmental conditions of hypoxia and post-hypoxia
was significantly higher (P≤ 0.05) in male than female trout. The cardiac
output of trout in spawning condition was significantly higher (P≤ 0.05) than that
of trout not in spawning condition. Measurements of pulsatile cardiac output
were made simultaneously with trout ventilation, and revealed ventilatory
interactions with blood flow that varied depending on environmental oxygen
condition.
The method for monitoring gill blood flow was used with methods for
automated measurement of gill water flow, oxygen uptake, and chemical flux in
vivo. An experimental protocol was developed in which environmental oxygen
was varied to obtain maximum increases in water flow over the gills without
blood flow changes, and subsequent attainment of maximum increases in blood
flow through the gills with decreasing water flow. The protocol was used as a
probe to study variations in chemical flux with varied blood or water flow.
The changes in gill flux of butanol (Log octanol/water partition coefficient
(P) = 0.88) measured during control, hypoxia, and post-hypoxia correlated with
observed changes in blood flow. A 70% increase in butanol flux was noted with
a 50% increase in cardiac output, but there was no increase in butanol flux with
a 100% increase in ventilation volume. Changes observed in the gill flux of
decanol (Log P = 4.57) measured under varied environmental oxygen conditions
correlated with observed changes in ventilation volume. A 100% increase in
decanol flux was noted with a 160% increase in ventilation volume. The observed
blood flow limitations to uptake of the low Log P butanol, and the water flow
limitations to uptake of the high Log P decanol helped to verify assumptions
made in recently proposed flow-limited models for prediction of chemical flux
across fish gills. === Graduation date: 1991
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