2 results

Evaluation of anti-foulants on over-catch, other forms of biofouling and mud worm in Sydney Rock Oysters

Project number: 1998-314
Project Status:
Completed
Budget expenditure: $294,781.00
Principal Investigator: Rocky de Nys
Organisation: UNSW Sydney
Project start/end date: 7 Oct 1998 - 25 Mar 2003
Contact:
FRDC
TAGS
Biofouling
Aquaculture
SPECIES
Native Oyster

Need

Over the past 20 years oyster production in NSW has steadily declined by more than 40%. Two major problems exacerbating the industry's continuing decline are:

1) escalating costs of production associated with slow growth and high mortality rates suffered by Sydney Rock Oysters due especially to QX disease and winter mortality and mud worm infestation .
2) severe overcatch and other biofouling problems generated by both Sydney rock oysters (SRO's) and Pacific oysters(PO’s).

The problem of combating overcatch and fouling is compounded by the protracted 3 to 4 year turn-off times for Sydney rock oysters. These problems are currently being addressed by periodic manual cleaning and hot water dips in conjunction with the use of elevated intertidal growing heights. The latter exposes overcatch oysters and other biofouling organisms and mudworms, to lethal levels of heat stress and desiccation. The hidden costs of elevated growing height is reduced feeding and growth rates.
Direct costs of combating overcatch and other forms of biofouling has been estimated as high as 30% of total operating costs. These have contributed considerably to the progressive decline of many formerly productive leases. This has been of major concern to both government and community based conservation groups. Derelect leases in Port Stephens alone total almost 900ha and will cost an estimated $8million dollars to clean up and rehabilitate.

Development of a cost effective antifoulant coating technique has the potential to significantly arrest the decline of the oyster industry in NSW, and to reduce costs of production inTasmania and South Australia. In a recent postal survey of farming practises and attitudes of NSW oyster farmers to such a development (conducted by the Aquaculture CRC), approximately half of the respondents expressed a high level of enthusiasm and support for this project proposal which has also gained highest priority ranking from ORAC (NSW Oyster Industry Research Advisory Committee) and ACFR(Advisory Council on Fisheries Research) the NSW state FRAB.

Objectives

1. To evaluate the effectiveness and commercial practicality of one application per overcatch season on antifoulant coatings in providing intertidal tray cultured oysters protection from overcatch of both Sydney Rock and Pacific Oyster spat and from other common forms of biofouling commonly encountered in Port Stephens.
2. To assess and improve the cost effectiveness and commercial practicability of these treaments: a) in relation to other forms of farming single seed oysters within Port Stephens (especially intertidal basket and subtidal raft farming) and b) to enable a lowering of usual growing height of oysters thereby accelerating their growth without jeopardising survival or market quality.
3. To determine whether benefits attached to objectives 1 and 2 can be achieved when extended to a representative array of commercial oyster farming areas and techniques used throughout the rest of NSW
4. To assess whether successful types of antifoulant coating techniques pose signficant risks to the environment, to the oysters themselves or to consumers.

Final report

ISBN: 0-7334-2006-0
Author: Rocky de Nys
Final Report • 2003-03-13 • 2.14 MB
1998-314-DLD.pdf

Identification of environmental factors, with particular reference to acid sulfate soil runoff, causing production losses in Sydney rock oysters

Project number: 1996-285
Project Status:
Completed
Budget expenditure: $185,191.50
Principal Investigator: Jesmond Sammut
Organisation: UNSW Sydney
Project start/end date: 31 Dec 1996 - 22 Dec 2004
Contact:
FRDC
TAGS
Pollution
Oceanography
Mortality
Environmental Impact
Disease
SPECIES
Native Oyster

Need

This research proposal developed from discussions with NSW and Queensland oyster growers who consider estuarine acidification is a cause of declining oyster health and productivity. A recently completed study of estuarine acidification and its role in fish kills, habitat degradation and outbreaks of EUS in estuarine fish, showed that the occurrence and duration of acidification events may be a potential threat to sessile organisms such as oysters (Sammut et al., 1996; 1996b; Callinan et al., 1996;1996b). The former study indicates that such associations between acidified water and poor oyster health are plausible. The proposed study is needed to test for putative associations between acidified water and oyster health and productivity problems. It will also generate other data that will be used to identify risk factors for QX disease. If an association between QX disease outbreaks and exposure to acidified water is confirmed, or other water quality variables are identified as causative factors, then appropriate water quality management can be developed. At present, attempts to manage acid sulfate soil drainage in NSW fail to recognise the water quality needs of oyster producers. Data from this study can be used to design acid sulfate soil management strategies to avoid secondary impacts on oyster health and maximise productivity.

Objectives

1. To identify associations between water quality conditions (with particular reference to acidified water and toxic metals), other environmental factors and reduced growth rates and disease outbreaks/mortalisties in oysters at selected sites on the Hastings and Tweed Rivers.
2. To identify specific environment and management related risk factors for reduced growth rates at selected sites.
3. To identify environmental and management risk factors for specific diseases with particular reference to QX on the Tweed River.
4. To effectively communicate the findings of this study to the oyster industry and relevant agencies

Final report

ISBN: 0 7334 2086 9
Author: Jesmond Sammut
Final Report • 2017-09-29 • 5.50 MB
1996-285-DLD.pdf

Summary

The study has confirmed that estuarine acidification, associated with drainage of acid sulfate soils, reduces growth rates and survival in Sydney rock oysters leading to significant production losses. The work has also demonstrated that acidification is not a factor in outbreaks of QX disease. The findings have raised greater awareness of the environmental and economic impacts of estuarine acidification, and have influenced environmental decision making at local and state government levels. The oyster industry is now recognised as an important stakeholder in the management of acid sulfate soils and their impacts. Reactive and proactive strategies to manage acidification now consider the impacts on the oyster industry whereas prior to the study the industry concerns and needs were largely ignored. The industry is now represented on key management and advisory committees responsible for management of acid sulfate soils.  The research has enabled oyster farmers to minimise stock losses through improved risk and stock management in parts of the estuary impacted by acidification. The study has provided a basis for more accurate diagnosis of acid-related oyster mortalities and important baseline information for environmental impact assessment in coastal development.

Keywords: acid sulfate soils, estuarine acidification, Sydney rock oyster, oyster mortalities, aluminium, iron, low pH.

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