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Abstract

Stock losses in the range 50-90% were recorded at experimental and pilot
scale sea-based abalone farms in southern Tasmania in the mid-1990's.
These were associated with spionid polychaete "mud worm" infestation,
especially Boccardia knoxi. The overall aim of the multi faceted research
presented here was to minimise the effects of spionid infestation. Studies of
reproductive biology indicated initial infestation with B. knoxi could be
delayed by placement of stock after the spring planktotrophic dispersal
phase. This would also reduce infestation by a second species Polydora
hoplura. Fieldwork during 1998-2001 indicated that large settlements of
spionids might be relatively uncommon. Testing of 16 chemical/drug agents
and freshwater bathing as a treatment for mud worm infestation failed to
yield a useful candidate. Agents lacked penetration into shell burrows or
were harmful to abalone at levels sufficient to kill spionids in situ. Air
exposure of abalone for 2-4 hours at humidity less than approximately 63%
was highly effective as a spionid treatment, especially in the first 6 months
post infestation. Assessment of risk factors associated with spionid
settlement found that elevated levels of spirorbid polychaetes enhanced
mud worm colonisation. Stock size, rearing vessel design and position in the
water column also led to differential spionid settlement outcomes. Spionid
infestation was associated with a reduction in: growth, % flesh weight,,
protein and carbohydrate reserves and with an increased respiration rate.
Major histological changes were elevated levels of brown pigment in the
right kidney and digestive gland consistent with mobilisation and consumption of energy reserves. The ranges in levels of sodium, potassium,
calcium, magnesium, chloride, copper, glucose and protein in haemolymph
were established for apparently healthy abalone and spionid infested
animals.

Item Type:	Thesis - PhD
Authors/Creators:	Lleonart, Mark
Keywords:	Abalone culture, Abalones, Spionidae
Copyright Holders:	The Author
Copyright Information:	Copyright 2002 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).
Additional Information:	Thesis (Ph.D. )--University of Tasmania, 2002. Includes bibliographical references
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