whole_FindlayJamesDavid2005_thesis.pdf (28.92 MB)
Physiological responses of bluethroat wrasse, Notolabrus tetricus, horseshoe leatherjacket, Meuschenia hippocrepis and greenback flounder, Rhombosolea tapirina, to low temperature transport
thesisposted on 2023-05-26, 22:00 authored by Findlay, JD
The study reviewed the techniques used in the global trade of live fish. Based on this review and field and laboratory experiments, methods were identified to improve the survival of bluethroat wrasse, Notolabrus tetricus, horseshoe leatherjacket, Meuschenia hippocrepis and greenback flounder, Rhombosolea tapirina, during capture, holding and transport. Investigation of the physiological responses of fish exposed to lowered temperatures was a central theme including description of cold thermal tolerance and the effects of lowered temperature on oxygen consumption. The Critical Thermal Minima and Incipient Lethal Temperature were determined for bluethroat wrasse and greenback flounder. Greenback flounder exhibited remarkable thermal tolerance with a TL 50(24hr) of 2.3¬¨‚àûC (acclimation temperature 15 ¬¨‚àûC). A flow-through respirometer was used to measure oxygen consumption. Bluethroat wrasse exhibited 20% greater oxygen consumption than greenback flounder under normoxic conditions. In both species, a reduction in temperature of 10¬¨‚àûC more than halved the oxygen consumption as predicted by typical biological Q1o values. Greenback flounder maintained or increased oxygen consumption during graded hypoxia (i.e. a non-conformer) and exhibited a critical oxygen tension of less than 25% oxygen in air-saturated seawater. Oxygen consumption of bluethroat wrasse decreased during graded hypoxia (i.e. a conformer) but no significant increase in blood lactate concentration was observed. Lowered temperatures induced and maintained coma in horseshoe leatherjackets and bluethroat wrasse, however mean coma-inducing temperatures were generally <0.5¬¨‚àûC higher than the TL50. The induction of coma in bluethroat wrasse did not significantly reduce oxygen consumption beyond the level predicted by temperature alone and did not result in a significant increase in blood lactate. The risk of exceeding thermal tolerance when applying coma-inducing temperatures needs to be carefully assessed before use. Feeding history had a marked impact on thermal tolerance. Greenback flounder deprived of food for 72hr exhibited greater than 90% survival when exposed to temperatures of 3¬¨‚àûC whereas fish deprived of food for only 24hr exhibited less than 10% survival at the same low temperature. The magnitude of specific dynamic action (SDA) in greenback flounder was 1.88 times higher than the routine rate of oxygen consumption and total duration was 52hr at 15¬¨‚àûC. Oxygen extraction by bluethroat wrasse was significantly reduced during lowered temperature and hypoxia. The ventilation rate and ventilation stroke volume of bluethroat wrasse generally decreased with lowered temperature and afferent oxygen tension. The study demonstrated that food deprivation and temperature reduction are powerful tools to improve the survival of fish during transport.
Rights statementCopyright 2005 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (Ph.D.)--University of Tasmania, 2005. Includes bibliographical references