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The environmental impacts of land based abolone aquaculture


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Ho, J 2006 , 'The environmental impacts of land based abolone aquaculture', PhD thesis, University of Tasmania.

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This study of land based abalone farming was conducted to investigate the
industry's environmental impact and long-term sustainability. There is a paucity of
information surrounding the environmental impacts of land based abalone farming
despite the increase in the growth of the industry. Information which forms the basis of
abalone farm environmental management and monitoring was developed as part of this
project. This information is likely to provide a great deal of perspective to all existing and
planned Australian abalone farms.
Three preliminary experiments were conducted to determine how nutrients were
being produced within the abalone farm and how they were varying on a diurnal scale.
Production ofnutrients is clearly related to the formulated feed, however two possible
means of nutrient production were deemed likely. Firstly from the formulated feed
leaching or secondly from the degradation of the waste produced on farm. Finally a
experiment was conducted to determine the pattern in nutrients exiting the abalone farm's
effluent pipe.
The nutrient stability of a commercially available formulated feed was assessed.
This is of importance as on most Australian abalone farms there is usually a delay
between the time the formulated feed enters the abalone culture tanks, and the time of
consumption by the abalone. This leads us to believe that there may be nutrients from the
formulated feed. The formulated feed leaching appears to be significant in terms of
phosphorus (30% of total P content), whilst it appears to be relatively insignificant in terms of all other measured components. This research indicates that there may be a need
for further research into the binding of phosphorus in Adams and Amos formulated feed.
An examination of the tank waste was conducted to examine if the waste within
the abalone culture tanks was a major source of dissolved nutrients that are produced as
the waste degrades. Results show that approximately 50% of the C,N,P and organics of
the formulated feed was collected in the abalone culture tank waste. Further the
settlement pond waste contained approximately 30% of the C,N,P and organics of the
formulated feed. This equates to approximately 40- 50% of the abalone tank waste
nutrients (i.e. particulate waste) being degraded and remineralised as dissolved nutrients.
The temporal variation in nutrient export for a single farm was characterised on a
diurnal basis. Maximum concentrations of ammonium and phosphate were recorded at
approximately sunrise at the farm outflow on the day of sampling. Therefore the time of
day that water sampling takes place is important in the accurate assessment of
environmental impact and may explain some of the variability in current monitoring
program data sets.
Results indicate that of the nutrients measured from a 20 tonne abalone farm,
dissolved nitrogen and phosphorus were predominantly exported with exports of, up to,
1000g and 280g per day respectively. The source of these nutrients is the formulated
feed. Daily feed rate can predict dissolved nitrogen and phosphate loads exported from
the farm (P<0.05, r2 = 0.98 and 0.42 for Nand P, respectively). The relationship between
daily feed rate and nutrient export was found to hold at three abalone farms around
Tasmania (P<0.05, r2 = 0.71 for Nand r2 = 0.62 for P). These relationships can assist in
the environmental management of the abalone industry and provide a consistent basis to judge the impact of abalone farming relative to other sources of nutrient inputs into our
coastal environment.
This study showed a 10-50 fold increase in biomass of nutrient scavenging
seaweeds in the intertidal region in the vicinity of the abalone farm's discharge point.
This was relative to both control sites and the discharge site prior to the commencement
ofthe effluent discharge. Despite this the farm associated seaweed proliferation is
unlikely to occur beyond 50 metres from point of discharge (i.e. at the end-of-pipe).
Grazing and particulate feeding intertidal faunal communities were highly variable in
time and space making it impossible to detect any effects of the farm's discharge. In the
subtidal zone, there was no evidence of an impact on the macroalgal canopy assemblages
within 50m of the end-of-pipe.
The importance of solid separation devices was also highlighted in this study.
Output ofparticulates from farms without Solid Separation Devices (SSD's) is likely to
be significantly greater than farms with SSD's (i.e. approximately 30-50% of feed input
is lost as particulate waste). Relative to farm inflow waters, Abalone Farms Australia
(AFA) did not increase particulate loads into the marine environment (measured by
weight); however, even with farms with SSD's, the composition of the particulates in the
discharge is likely to change. For example, AFA the discharged particulates had a
slightly greater (i.e. 3% greater) organic content relative to intake particulates.
This study also showed that effluent nitrogen loads may be reduced by an average
of 34% by a novel seaweed raft system held within the tanks. The seaweed raft system
not only provided shade but most importantly a nutritious source of supplemental feed for
the abalone. The present study intensively examined a single farm, and extensively examined a
number of farms to gain a perspective on the environmental impact of the Tasmanian
abalone industry relative to other industries that discharge nutrients into the marine
environment. The study found that the entire Tasmanian abalone industry as at 2005 was
likely to have little more impact than a small town of 600 people's sewage treatment
plant (based on total nitrogen discharge). Additionally detailed characterization of
abalone farm effluent and the subsequent environmental impacts of that effluent was
determined to be negligible for AFA at current production rates (i.e. 20 tonnes of abalone

Item Type: Thesis - PhD
Authors/Creators:Ho, J
Keywords: Abalone culture
Copyright Holders: The Author
Copyright Information:

Copyright 2006 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:

No access or viewing until 23 May 2008. Thesis (PhD)--University of Tasmania, 2006. Includes bibliographical references

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