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A physiological investigation into methods of improving the post-capture survival of both the southern rock lobster, Jasus edwardsii, and the western rock lobster, Panulirus cygnus

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Crear, BJ (1998) A physiological investigation into methods of improving the post-capture survival of both the southern rock lobster, Jasus edwardsii, and the western rock lobster, Panulirus cygnus. PhD thesis, University of Tasmania.

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Abstract

The southern and western rock lobsters (Jasus edwardsii and Panulirus
cygnus, respectively) form the basis of two of the major seafood export industries
in Australia; between them earning over $500 M export dollars yearly. Although a
major portion of the catch is exported as 'whole-cooked' or 'tailed' products, an
increasing share of the catch is exported live. The majority of lobsters arrive at the
processing sheds as live lobsters. However, a lack of basic physiological
information has impeded advances in the design and management of transport and
holding systems, often resulting in a deterioration of the physiological condition
of some lobsters. Such physiological deterioration may result in the final product
choice for the processors being limited, leading to a reduced value of the catch.
The aim of this study was to develop an understanding of the physiology of
lobsters, especially in relation to factors the lobsters may be subjected to during
post-capture handling practices. This information could be used to redefine postcapture
handling practices and holding system design and management.
Standard oxygen consumption of both species increased in response to
increases in temperature and body weight. Activity had the greatest effect on
oxygen consumption rates, causing an approximate 3-fold increase above standard
rates. The increase in oxygen consumption due to activity decreased at
temperatures approaching the upper and lower extremes of each species. After a
period of activity and emersion oxygen consumption remained elevated for up to 8
hours. A marked diurnal rhythm was evident, with a 48% and 87% (J. edwardsii
and P. cygnus, respectively) increase in oxygen consumption at night. This was
largely related to increased activity at night. Feeding resulted in a substantial
(greater than 2-fold in P. cygnus) and sustained (up to 48 hours) increase in
oxygen consumption. Both species were essentially oxygen regulators, able to
maintain standard rates of oxygen consumption down to around 30% water
oxygen saturation. Below that oxygen level the lobsters became oxygen
conformers. Activity resulted in an approximate doubling of the water oxygen
level at which lobsters acted as oxygen conformers.
The total ammonia nitrogen (TAN) excretion rates of both species
increased with increases in temperature and body weight. Activity had minor influence on the TAN excretion rate. A diurnal rhythm was evident in J. edwardsii
but not in P. cygnus. Feeding had a large affect on the TAN excretion rate, with an
approximate 6-fold increase occurring in each species. The excretion rates
remained high for over 24 hours post-prandial.
The effect of the dissolved oxygen level on recovery of P. cygnus from a
period of activity/emersion was investigated. Based on the rate of recovery of
various physiological parameters (oxygen consumption, haemolymph ammonia,
lactate, glucose, and pH), the maintenance of water oxygen levels close to 100%
saturation is recommended. Water oxygen levels less than 60% saturation slowed
the rate of recovery. All lobsters recovering in water with oxygen levels less than
20% saturation died.
Carrying P. cygnus out of water imposes physiological disturbances to the
lobsters. The severity of the disturbances increased when the relative humidity
was lower and when wind was present. Spraying water over the lobsters prevents
some of the physiological consequences of emersion, such as decreases in pH and
haemolymph ammonia buildup, however it does not prevent haemolymph lactate
increases. Therefore, lobsters still rely on anaerobic metabolism when emersed in
sprays. There was no evidence that failure of lobsters to recover from a period of
emersion was caused by gill damage.
A half hour period of emersion/handling at 23°C caused large
physiological disturbances of P. cygnus. Halving the emersion/handling time did
not decrease the extent of the physiological disturbances. Slow-chilling the
lobsters to 11°C prior to emersion/handling, was an effective means of decreasing
the physiological disturbances associated with emersion.
This study has developed our understanding of the physiological responses
of the southern and western rock lobsters to factors affecting them during postcapture
processes, and will allow the design and management of rock lobster
holding facilities to be based on a sound scientific basis. It also represents a major
contribution to knowledge on respiration and nitrogen metabolism of large
decapod crustaceans.

Item Type: Thesis (PhD)
Keywords: Lobsters, Lobster fisheries, Lobster culture
Copyright Holders: The Author
Copyright Information:

Copyright 1998 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, 1998. Includes bibliographical references

Date Deposited: 09 Dec 2014 00:04
Last Modified: 05 Apr 2016 00:14
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