Fish Health Better Management Practices for Murray Cod farming. (Version 1.0)
Brett Ingram, Geoff Gooley, Tracey Bradley, Huiking Ho, Shari Cohen
August 2012
Fisheries Victoria Technical Report Series 76
Murray Cod Fish Health BMP
If you would like to receive this Printed by DPI Queenscliff, Victoria information/publication in an Published by the Department of Primary accessible format (such as large Industries. print or audio) please call the Copies are available from the website: Customer Service Centre on: www.dpi.vic.gov.au/fishing 136 186, TTY: 1800 122 969, General disclaimer This publication may be of assistance to you but or email the State of Victoria and its employees do not [email protected] guarantee that the publication is without flaw of any kind or is wholly appropriate for your Copyright © The State of Victoria, Department of particular purposes and therefore disclaims all Primary Industries, 2012. liability for any error, loss or other consequence which may arise from you relying on any This publication is copyright. No part may be information in this publication reproduced by any process except in accordance with the provisions of the Copyright Act 1968. The information contained in this publication is for general information only. The State of Preferred way to cite: Victoria does not expressly or impliedly Ingram B, Gooley G, Bradley T, Ho H, Cohen S guarantee that the proposed chemical treatments (2012). Fish health better management practices contained within this publication will be wholly for Murray cod farming. Version 1.0. Fisheries appropriate for your situation. The proposed Victoria Technical Report No. 76. Department of chemical treatments are drawn from a range of Primary Industries, Queenscliff, Victoria, sources, including common farming practices Australia. 60 pp. and are not intended to be a substitute for ISSN 1835‐4785 professional veterinary advice. The appropriateness of the proposed chemical ISBN 978‐1‐74326‐262‐7 (Print) treatments will depend on the circumstances in Author Contact Details: which they are intended to be used. It is Brett Ingram recommended that you seek professional Fisheries Research Branch, Fisheries Victoria veterinary advice before adopting and PO Box 114, Queenscliff Victoria 3225 implementing any chemical treatment options for managing fish health in Murray Cod. Authorised by the Victorian Government, 2a Bellarine Hwy, Queenscliff, Victoria 3225
Murray Cod Fish Health BMP ii
Executive Summary
The Murray cod aquaculture industry has been developing slowly across the eastern states of
Australia in recent years. This iconic, threatened fish has excellent aquaculture prospects and small quantities are already sold into domestic markets. The production of fingerlings for stock enhancement purposes has been established commercially since the 1980s. More recently a range of different culture techniques have been established for growout including cages in ponds and free ranging in pond systems. These systems are particularly well suited to horticultural enterprises with large water holdings as a means of adding value to a valuable water resource. Previous work has established that, like all aquaculture species, there are a range of health conditions affecting Murray cod that can result in loss of income in culture systems. Anecdotally it appears that parasites in particular pose a threat to the healthy production of Murray cod in open systems. However more work needs to be undertaken in the documentation and rigorous identification of these disease threats. The purpose of this “Better Management Practices” manual is to provide farmers with a practical and evolving resource that can assist them in addressing the myriad of health problems that can affect Murray cod, including disease agents and environmental factors. This manual is supported by a series of Standard Operating Procedures and Appendices that cover a diverse range of subjects. Where this BMP does provide information on available chemical treatments for common parasites, diseases and conditions that affect the health of Murray cod in aquaculture, those treatments are drawn from a range of sources, including common farming practices, and are not intended to be a substitute for professional veterinary advice. It is recommended that professional veterinary advice is sought before adopting and implementing any chemical treatment options for managing fish health in Murray cod.
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Table of Contents
Executive Summary...... iii
Introduction...... 1 Fish health and aquaculture ...... 1 Murray cod aquaculture ...... 1 Better management practices...... 2 Standard Operating Procedures...... 2 Objectives of this BMP...... 2
Murray cod aquaculture industry ...... 4 Industry overview...... 4 Hatchery Phase...... 4 Nursery Phase ...... 5 Grow‐out Phase...... 5 Markets...... 5 Murray cod industry health survey...... 5
Common health problems in farmed Murray cod...... 7 Infectious diseases and parasites...... 7 Sources of infectious diseases and parasites ...... 7 Protozoan parasites...... 7 1. Chilodonella ...... 7 2. Ichthyophthirius multifiliis, (Ich or whitespot) ...... 9 3. Trichodina...... 9 4. Tetrahymena...... 9 5. Ichthyobodo necator (Costia necatrix) ...... 9 Other protozoan parasites ...... 9 Copepod parasites ...... 12 1. Lernaea spp (anchor worm)...... 12 2. Ergasilid copepods ...... 12 Fungi ...... 13 1. Aphanomyces invadans ...... 13 2. Saprolegniosis...... 13 Viruses ...... 15 1. Megalocytivirus...... 15 Bacteria...... 15 1. Aeromonas species ...... 15
Murray Cod Fish Health BMP (Version 1.0, revision date 30 Nov 2011) v
1. Vibrio...... 16 2. Edwardsiella tarda ...... 16 Other bacteria ...... 16 Non‐infectious diseases and syndromic conditions...... 16 Nutritional diseases ...... 16 Chronic ulcerative dermatopathy...... 16
Drug and chemical management...... 18
Other fish health issues ...... 19 Stress and fish health ...... 19 Predation, aggression and cannibalism ...... 19 Predation...... 20
Water quality and environmental factors related to fish diseases...... 21 Dissolved gases ...... 23 Low Dissolved Oxygen ...... 23 Gas Supersaturation – Gas Bubble Disease ...... 23 Chlorine/chloramine poisoning ...... 24 Hydrogen sulphide poisoning...... 24 Metabolic Waste Products ...... 25 Ammonia poisoning ...... 25 Nitrite poisoning (Brown blood disease)...... 26 Other important water quality parameters...... 26 pH...... 26 Temperature...... 26 Salinity ...... 26 Heavy metals ...... 26 Water‐borne contaminants and other problems...... 27
Acknowledgements ...... 28
References ...... 29
STANDARD OPERATING PROCEDURES ...... 30
SOP 1 – Fish health management...... 30 Incorporating biosecurity and fish quarantine ...... 30 Water supply treatment...... 30 Dealing with fish health issues...... 30 Identifying the problem ...... 30
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Managing new stock and quarantine procedures...... 31 Hygiene...... 31 Humane slaughter and destruction of stock...... 33 Disposal of mortalities...... 33
SOP 2 ‐ Monitoring fish health...... 35
SOP 3 – Submission of fish samples for disease diagnosis...... 38 Submission of water samples for analysis...... 39
SOP 4 ‐ Husbandry of captive fish...... 41 Minimise stress ...... 41 Stocking density ...... 41 Size variation...... 41 Transferring fish between farms and culture units ...... 41 Nutrition and feeding ...... 42 Maintenance of water quality...... 43
SOP 5 – Use of Chemicals...... 44 Drug and chemical management ...... 44 State ‘Control of Use’ Legislation ...... 44 Anti‐microbials (anti‐biotics) ...... 44 Salt...... 44 Formalin ...... 44 Treatment in tanks...... 45 Treatment in static ponds...... 45 Treatment in cages...... 45 Training and Supervision ...... 45 Fish sedation and anaethesia...... 45 Anaesthetics...... 45 Materials and Equipment...... 46 Procedure...... 46
Appendix 1 ‐ Useful published resources and internet sites...... 48 General aquaculture...... 48 Murray cod aquaculture ...... 48 Fish health...... 49
Appendix 2 – Parasites, diseases and health problems reported from farmed Murray cod...... 51
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Appendix 3 – Notifiable and reportable fish diseases ...... 54 Notifiable and reportable fish diseases ...... 54
Appendix 4 – Calculation of unionised ammonia...... 55
Appendix 5 – Water quality guidelines for the protection of cultured freshwater fish ...... 56
Appendix 6 – Useful contacts...... 58
Appendix 7 ‐ Useful Conversions ...... 60
Appendix 8 – Glossary ...... 61
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List of Tables Table 1. Reported health problems in farmed Murray cod (further details are presented in Appendix 2) . 8 Table 2. Acceptable water quality ranges for freshwater aquaculture, and water quality recorded from Murray cod aquaculture farms ...... 22 Table 3. Parameters to monitor and frequency of monitoring ...... 37 Table 4. Method of submission for diagnostic procedures ...... 39 Table 5. Stocking densities...... 42
List of Figures Figure 1. The Disease Triad. Interaction between the environment and management, the host (fish) and the pathogen...... 1 Figure 2. Production phases of the Murray cod aquaculture industry ...... 4 Figure 3. Chilodonella hexasticha. on gill tissue (circled) and live (insert)...... 10 Figure 4. Ichthyophthirius multifiliis. (a) Murray cod infested with “whitespot” (b) Live trophonts on fin of juvenile Murray cod (c) Trophonts showing characteristic horseshoe‐shaped macronucleus (Ma)... 10 Figure 5. Trichodina. (a) Live (arrow) on fin of Murray cod (b) Live...... 11 Figure 6. Ichthyobodo (arrows) on gill tissue ...... 11 Figure 7. Lemaea (arrow) on the pelvic fin of a Murray cod...... 12 Figure 8. Dermoergasilus intermedius attached to gill filament ...... 13 Figure 9. Murray cod infected with Epizootic Ulcerative Syndrome (EUS)...... 14 Figure 10. Saprolegnia fungal hyphae ...... 14 Figure 11. Murray cod afflicted by chronic ulcerative dermatopathy (CUD) ...... 16 Figure 12. External and internal factors that affect the health of fish in aquaculture ...... 21 Figure 13. Gas bubble disease. Bubbles of gas between the fin rays of a Murray cod ...... 24 Figure 14. Nitrogen pathway in an aquaculture system ...... 25 Figure 15. Decision support flowchart for identification and management of major health problems in a Murray cod aquaculture facility ...... 32 Figure 16. Microscopes. (a) Binocular dissecting microscope. (b) Binocular compound microscope...... 36
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Introduction
There are numerous articles, general text books Fish health and aquaculture and websites (Appendix 1) that deal with fish Disease events are a well documented diseases in aquaculture. However, there are a significant constraint to profitable aquaculture limited number of Australian publications that enterprises. A variety of factors can cause heavy focus on the health issues of Murray cod. There losses in aquaculture facilities including have also been a number of published articles on pathogens such as viruses, bacteria and specific diseases, parasites and syndromes of parasites; and environmental factors such as Murray cod (Appendix 2). water quality and poor husbandry practices. Often these factors are linked to form the disease Murray cod aquaculture triad in which factors associated with the Murray cod, Australia’s largest indigenous environment and management (husbandry), the freshwater fish, is an iconic species with host (fish), and the pathogen interact to cause significant commercial, recreational, disease and fish losses (Figure 1). For example, conservation and cultural value. Over‐fishing, a decline in water quality associated with poor habitat loss and modification within the cod’s husbandry practices may lead to an increase in natural range in the Murray‐Darling Basin the incidence of bacterial infections. Not only (MDB) have seen numbers reduced since the can disease outbreaks inflict heavy mortalities early 1900s. Since the 1980s, more than 13 on stock, but fish in poor health have million hatchery‐reared juveniles have been considerably lower growth rates which increases released into the wild to enhance recreational the time and costs to grow them to a marketable fisheries and for conservation purposes. Murray size. Some diseases can disfigure or render the cod has excellent aquaculture prospects and fish unsightly, which reduces their small quantities are already being sold into marketability. domestic and international markets.
HOST PATHOGEN
DISEASE
ENVIRONMENT &
MANAGEMENT
Figure 1. The Disease Triad. Interaction between the environment and management, the host (fish) and the pathogen.
Murray Cod Fish Health BMP 1
Although the production of fingerlings for stock disease risk, improved yields and product enhancement purposes is well‐established with quality. Overall BMPs contribute towards fingerlings being commercially available since sustainability and economic viability of farms. early 1980s, grow‐out of Murray cod for human BMPs ensure that adoption of standardised consumption under aquaculture conditions has management guidelines is relatively easy to only recently been undertaken. The industry achieve without increased costs. The word currently employs a range of fish holding and “better” also implies that BMPs are always culture facilities and husbandry techniques evolving as culture practices progress. The including: BMPs therefore need to be revised periodically • earthen ponds for to document and facilitate continuous o holding broodfish improvements and to capture farmer o growing of fry and fingerlings innovations and learnings. o grow‐out under ambient conditions Adoption of BMPs are known to bring about • cages and raceways in dams benefits in other aquaculture sectors, such as: • plastic and fibreglass tanks for • Reducing and/or a minimising disease occurrence o intensive grow‐out • Improving growth performance o purging under environment controlled conditions. • Decreasing cost of farming (e.g. reduced feed and chemical costs) Farming Murray cod occurs predominantly in • Improving pond and effluent water quality, eastern states (Queensland, New South Wales and consequently minimise impacts on the and Victoria) with annual production ranging local environment from 86 to 112 tonnes per annum over the last 5 years. There are also anecdotal reports of • Improving quality and marketability of the Murray cod farming occurring overseas, produce especially in China. • Facilitating long term industry sustainability overall. Better management practices The term “better management practices” (BMPs) Standard Operating Procedures is used in several ways in the aquaculture sector. Standard operating procedures (SOPs) aim to It can refer to the best‐known way to undertake provide simple informative guidelines and any farm activity at a given time. In this sense, it checklists to facilitate practical husbandry and often refers to the practice or practices of only management applications on a consistent and one or a very few producers. A second way the routine basis. SOPs are developed using term BMPs has been used is to describe a few, information sourced from a combination of often different, practices that increase efficiency existing literature, anecdotal information and/or and productivity and/or reduce or mitigate in situ learnings from iterative experiences, negative environmental impacts. Finally, BMPs applied observations and empirical trials. SOPs may be required by government or other typically change over time, in content, style and agencies to encourage a minimally acceptable scope, as a result of continuous improvement level of performance with regard to a specific and the emergence of new information and on‐farm activity. In this sense, the term is used technologies from commercial and scientific in opposition to unacceptable practices. sources. Application of SOPs cannot compensate for non‐compliance with BMPs or BMPs refer to a set of standardised management fundamentally inadequate system design and guidelines that are developed, based on existing operation, and therefore need to be considered practices and associated risks, as determined in in the context of a broader understanding of fish consultation with farming practitioners and health management under commercial relevant industry stakeholders. Where aquaculture conditions. appropriate, new innovations are also routinely incorporated into BMPs to facilitate continuous improvement. Adoption of BMPs by farmers is Objectives of this BMP expected to lead to an improvement in the Minimising stress from disease outbreaks and effectiveness and efficiency in farming practices, therapeutic treatments to maximise not only including improved water quality, reduced survival but also long term growth is critical to
Murray Cod Fish Health BMP
2
the Murray cod aquaculture industry. Disease induced checks to growth and associated mortalities at key physiological development stages have profound impacts on future production. In order to ensure sustainable production of the Murray cod farming industry, and to be competitive within the Australian and global aquaculture/seafood market place, it is imperative that farmers be familiar with the common diseases and conditions that affect the health and well‐being of their stock; and to employ sound health management strategies, which aim to reduce the incidence and severity of these diseases and conditions and to maintain the biosecurity of their facilities. The objectives of this BMP are to provide information and standard operating procedures (SOPs) to fish farmers on: a) Common parasites, diseases and conditions that affect the health of Murray cod in aquaculture b) Strategies to manage and maintain the health and well‐being of Murray cod in aquaculture facilities. Above all, these guidelines aim to promote the concept that prevention is far better than treatment.
Murray Cod Fish Health BMP 3
Murray cod aquaculture industry
earthen ponds, which are typically stocked at Industry overview relatively low densities (<350 kg/ha). Ponds are The Murray cod aquaculture industry can be usually static or have limited water flow to flush broken into several phases of production based the ponds when required and replace water that loosely around the size/age of fish being farmed is lost through evaporation and seepage. (Figure 2). These are: Broodstock may also be held in tanks (2,000– • Hatchery phase: broodstock spawning and 5,000 L) at densities up to 50 kg/m3. These tanks, larval rearing which may be part of a recirculating aquaculture system (RAS), are provided with a constant flow • Nursery phase: fry rearing, weaning and of water and are aerated or oxygenated. The over‐wintering of fish water temperature may also be controlled. • Grow‐out phases: grow‐out of fish to market Broodstock may be held for up to 5 years before size. being replaced with new stock. Some farm operations may focus solely on one Spawning occurs once each year in spring‐ phase of production, while others may summer (September‐December) and is undertake several phases of production at the predominantly triggered by increasing one facility. daylength and water temperatures. Induced Hatchery Phase spawning techniques using injections of hormones followed by hand stripping of The hatchery phase focuses on breeding fish to gametes have been developed for Murray cod, produce larvae for rearing. In most cases, though most hatcheries currently rely on Murray cod broodstock (> 2kg) are held in broodstock spawning unassisted in ponds.
HATCHERY PHASE NURSERY PHASE GROWOUT PHASE
Broodstock Cages or RAS tanks holding facilities Stockers raceways in (6-8 mths) (75-150g) (ponds & tanks) irrigation dams (up to 5 years) Fingerlings (6-15 mths) (0.5-2.5g) Gametes Weaning Hatchery RAS tanks tanks Market-size fish incubators (3-12 mths) (0.6-2.5 kg) (7-28 days) (5-10 days)
Fingerlings Market-size fish Larvae (0.5-2.5g) Grow-out & MARKET Hatchery Earthen fry Fry finishing ponds CHAIN tanks (12-20mm) ponds (6-15 mths) (10-35 days) (20-45 days)
Fingerlings for stock enhancement (0.5-2.5g)
RECREATIONAL FISHERIES
Figure 2. Production phases of the Murray cod aquaculture industry
Murray Cod Fish Health BMP (Version 1.0, revision date 30 Nov 2011) 4
The eggs of Murray cod, which are demersal (at a temperature of 25 °C), with survival rates in (dwell near the bottom of the water) and excess of 80% and stocking densities at 80–100 adhesive, are laid on hard surfaces. Murray cod kg/m3. held in ponds spawn in specially constructed Increasingly, however, fish are being transferred spawning structures. Spawnings, once detected, to floating cages or raceways situated in outdoor are harvested from the ponds and transferred to (open‐water) ponds and dams. Murray cod are the hatchery. The eggs are incubated in tanks also being on‐grown in Partitioned Aquaculture (50–1,000 L) provided with a constant flow of Systems (PAS). At the onset of spring, fish water maintained at a constant temperature (18– (stockers) (>75 g) are moved to outdoor facilities 22 °C), and aerated. At water temperatures of for the grow‐out to a market size under 20–22 °C, eggs commence hatching 5–7 days extensive or semi‐intensive ambient conditions. after fertilisation and continue to hatch for 3–4 Fish that are held at moderate densities (20–75 days. kg/m3), reach initial market size (600 g) after Hatched larvae are 5–8 mm in length, and approximately five months while larger fish (1–3 commence feeding about 10 days after hatching kg) reach market size in 12–24 months. Grading is completed. In the hatchery, the larvae reared of fish occurs regularly to reduce size variation in flow‐through tanks and initially fed on brine and cannibalism. shrimp (Artemia). Some farmers are utilising earthen ponds in Nursery Phase their grow‐out operations. Murray cod may be Production of fry and fingerlings for stock stocked directly into earthen ponds from either enhancement programs and for grow‐out in cages or RAS at various stages through‐out the aquaculture operations rely to a large extent on grow‐out stage. Fish are stocked at a size of 25– the extensive rearing of fish in fertilised earthen 500 g (2–2.5 t/ha). Some grading and culling (by ponds. Fish are stocked at low densities (<35 selective netting) is undertaken during this fish/m2) and there is no supplementary feeding. period. Instead, naturally occurring aquatic organisms Markets are the sole source of food for fish. Ponds are Currently, fingerlings are usually available only harvested 5–7 weeks following stocking when during production season, mostly between fish are at least 0.5 g in weight. Harvested December and May. Prices of fingerlings range fingerlings are either released to the wild to from about $0.45–0.60 per fingerling for lots of enhance recreational fisheries, or transferred to >10,000, and up to $1.60 per fingerling for small tanks for weaning onto an artificial diet and on‐ consignments. Annual production varies across growing. Some hatchery operators are all culture systems from 2.5 to 55 tonne per year, undertaking the weaning of fingerlings prior to not including some hatcheries. The price range sale, but some nursery and grow‐out operators for fish varies from $13 per kg to $35 per kg prefer to purchase non‐weaned fish and (mixed wholesale and retail) and the costs of undertake the weaning process themselves. production also varies markedly from $9 per kg Weaned fish are typically reared over‐winter in to $15per kg. Fish are being sold at a size from indoor tanks that are part of a RAS. These 600 g to about 2 kg. Most fish are sold either systems enable environmental control and can live, fresh on ice (whole or gilled and gutted), or be maintained at elevated temperatures (20– as fresh chilled fillets. Product is being sold 25 °C) which provides for continued growth of through fish markets, wholesalers, distributors, fish over the cooler months. RAS used for the and restaurants, as well as direct to consumers. culture of Murray cod vary considerably in design, configuration and size. Stocking Murray cod industry health densities employed are highly variable. In aerated systems, densities rarely exceed about 80 survey kg/m3, whereas in systems that use liquid In early 2011, a national census of farms was oxygen densities are usually between 60 and 200 conducted with 20 surveys being completed in kg/m3. total. A range of different farm types contributed to the census: cages or free range in Grow‐out Phase ponds, partitioned and recirculating aquaculture In intensive tank culture, trials indicate systems and “other” types. Many of the farms potentially excellent growth rates with 2 g fish had different agricultural enterprises on their reaching a plate size of 600 g within 12 months farms. Generally, seed supply came from a
Murray Cod Fish Health BMP 5
range of sources across farm types and was pre‐ treated prior to stocking in most cases (though not all). Most farms used purchased feed from two suppliers only and figures for feed as a percentage of body weight or FCR was often not known. Treatment of inflowing water varied with farm type as did measurement and frequency of measurement of water quality parameters. In RAS systems there was (as would be expected) a higher level of testing and manipulation of water quality. The majority of health problems and large mortality events were experienced on the non‐ RAS farms with up to 70% of stock. On these farms, most mortalities occurred in the first 2 weeks post stocking. The frequency of checking fish health and means of recording varied across farms and systems. The majority of farmers had microscopes and checked fish health regularly through wet preparations. A survey of farmers suggests that there can be some inaccuracy in the diagnosis reached by farmers. Results also suggest that ectoparasites cause the most health concerns in open systems, especially Chilodonella. A range of treatments such as salt, formalin and peroxide were used for these infestations. The ability to quarantine sick fish was usually absent in these open systems.
Murray Cod Fish Health BMP 6
Common health problems in farmed Murray cod
Ichthyophthirius multifiliis (white‐spot), and the Infectious diseases and parasites flagellated protozoan Ichthyobodo, are the most A number of diseases and parasites have been the common and problematic pathogens that recorded from farmed Murray cod. These affect Murray cod farming. include one viral, four bacterial, three fungal, 11 protozoan, one trematode, two copepod and 1. Chilodonella two mite species. However, only a small Background: Chilodonella is a ciliated protozoan number of these commonly and frequently (Figure 3) It is one of the most serious disease cause health problems and mortalities in problems in Murray cod farming, having caused aquaculture facilities. The most common mass mortalities of larvae, juveniles and parasites and diseases that affect the health of broodfish in both tanks and open‐water farming Murray cod in aquaculture facilities will be systems (ponds and cages). described below. A more detailed description of Gross signs: Infected fish cease feeding, become these diseases and parasites may be found in a listless and show signs of breathing difficulty range of fish health publications (see Appendix including flaring of opercula and swimming 2 and 3). with the head upwards. Some infected fish may Sources of infectious diseases and “flash”. The skin becomes pale and may exhibit a white cloudiness. The gills of heavily infested parasites fish are clogged with mucus and the filaments The two major sources of infectious diseases and may appear swollen and fused together. parasites in aquaculture facilities are the incoming water supply (particularly for pond Diagnosis: Chilodonella are distinguished from systems) and new fish stock from other facilities. other ciliated parasites by the typical gliding movement, the flattened and slightly distorted Many of the parasites that affect Murray cod can oval shaped body ‐ the bottom surface is flat survive for short periods of time off the host and while the upper surface is slightly domed or in the environment. For example, the ciliate vaulted. The gills and body surface, including Ichthyophthirius multifiliis and the copepod fins of larvae, juveniles, sub‐adults and adults Dermoergasilus intermedius have free‐living can be infected by Chilodonella. stages in their lifecycles. Common and problematic parasites of Murray cod, such as Treatment: In cage systems fish can become re‐ Chilodonella, Trichodina, Ichthyophthirius infected with Chilodonella very quickly and multifiliis, Ichthyobodo necator and Lernaea have treatments may need to be applied often (every abroad host range, infecting numerous species 5–7 days) to manage the parasite. Farmers have of fish. successfully used formalin, salt and potassium permanganate to treat Chilodonella. Protozoan parasites Protozoans, particularly the ciliated ectoparasites Chilodonella, Trichodina and
Murray Cod Fish Health BMP 7
Table 1. Reported health problems in farmed Murray cod (further details are presented in Appendix 2)
Parasite, disease, syndrome and condition Comments
Viruses Megalocytivirus Internal organs of juveniles,
Bacteria Aeromonas spp. Body surface & gills Vibrio spp. Body surface, gills & kidney Edwardsiella tarda Kidney of sub‐adults
Fungi Saprolegnia and Achlya Body surface & gills of all life stages Aphanomyces (Epizootic ulcerative Body surface Juveniles & sub‐adults syndrome)
Protozoa Chilodonella piscicola Gills of larvae, juveniles & adults Chilodonella hexasticha Body surface & gills of larvae, juveniles & adults Cryptosporidium molnari Stomach of juveniles & sub‐adults Goussia lomi Intestine of juveniles Ichthyobodo necator Body surface & gills of larvae, juveniles & adults Ichthyophthirius multifiliis Body surface & gills of larvae, juveniles & adults Myxosoma Gills of juveniles & adults Sessile peritrichs Body surface & gills of juveniles & sub‐ adults Tetrahymena Body surface & gills of larvae, juveniles and sub‐adults Trichodina Body surface & gills of larvae, juveniles & adults Gill amoeba Gills
Metazoa Clinostomum complanatum Body cavity & eye of juveniles Dermoergasilus intermedius Gills Lernaea sp. Body surface of juveniles & adults Histiostoma papillata Body surface & gills of juveniles Hydrozetes sp. Body surface of juveniles Other Fatty liver syndrome Liver of juveniles & sub‐adults conditions Chronic ulcerative dermatopathy Body surface of juveniles & adults Blue‐sac syndrome Eggs and larvae Gas bubble disease Larvae, juveniles & adults Enteritis Guts Cannibalism & aggression Juveniles, sub‐adults & adults
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2. Ichthyophthirius multifiliis, (Ich or 4. Tetrahymena whitespot) Background: Tetrahymena is a free‐living ciliated Background: Ichthyophthirius multifiliis is a large protozoan that occasionally parasitise fish. ciliated protozoan that has a complex lifecycle, Murray cod have been reported to be which includes both free‐living and parasitic susceptible to infestations of Tetrahymena (Matt stages. White spot is a common and serious Landos, pers comm.) with outbreaks resulting in disease of many fish species including Murray mass mortalities. cod. All life stages (except eggs) of Murray cod Gross signs: Affected fish show emaciation, are susceptible to infection by this parasite and lethargy, skin lesions, erosions, swelling, and mass mortalities can occur if not detected. white patches Gross signs : Affected fish may be lethargic and Diagnosis: Microscopic examination of live suffer reduced appetite and exhibit flashing. fish/wet preps will reveal the ovoid bodies of Skin lesions may appear as mild haemorrhages Tetrahymena with the appearance of a spiralling early on but when parasites burrow under the football (rather than gliding motion as seen in skin, white spots will appear in advanced cases Chilodonella) measuring 0.5–1 mm diameter on the body surface, fins and gills. (Figure 4). 5. Ichthyobodo necator (Costia necatrix) Background: Ichthyobodo necator (Figrue 6) is a Diagnosis : Microscopic examination of skin and small flagellated protozoan (10–15 μm in length) gill tissue will demonstrate the parasite with a which infects the gills and body surface of distinctive “horse–shoe” shaped macronucleus. larvae, juveniles, sub‐adults and adults. Treatment : Because the trophonts are beneath Gross signs :– Fish cease feeding and become the surface of the skin, many treatments are listless. Infected fish may “flash” and swim ineffective. Instead, control relies on killing the erratically. Heavily infested fish experience free‐living stages. Treatments with formalin, salt difficulty breathing and the body surface may and copper sulphate have been applied develop a bluish‐white cloudy layer. The gills of successfully. heavily infested fish become clogged with 3. Trichodina mucus and the filaments may appear swollen. Background: Trichodina is a ciliated protozoan Diagnosis: Because of its small size, a compound that is distinguished from other parasites by its microscope (> x200 magnification) is required to typical circular shape and active spinning action. observe this parasite. Larvae, juveniles, sub‐adults and adults can be infected. Trichodinosis does not usually cause Other protozoan parasites mortalities in larger. Infection is often associated Other protozoan parasites that occasionally with poor water quality. infest Murray cod include sporozoans, myxozoans, microsporidians and amoebae. Gross signs: Trichodinosis can cause emaciation, lethargy, flashing and skin blotchiness and erosions. Heavily infected fish may have a greyish coat due to excessive mucous production. The gills of heavily infected fish become clogged with mucus and the filaments may appear swollen. Fins of heavily infected juvenile fish become tattered. Mortalities are more likely to occur in larvae, fry and fingerlings. Diagnosis: The body of Trichodina is disc‐shaped and the posterior end, which is fringed with a ciliary band, possesses an adhesive disc containing hook‐like structures (Figure 5). Classically, this parasite is seen spinning under the microscope (Mexican hat).
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Figure 3. Chilodonella hexasticha. on gill tissue (circled) and live (insert)
(a)
(b) (c) Ma
Figure 4. Ichthyophthirius multifiliis. (a) Murray cod infested with “whitespot” (b) Live trophonts on fin of juvenile Murray cod (c) Trophonts showing characteristic horseshoe‐shaped macronucleus (Ma).
Murray Cod Fish Health BMP 10
(a) (b)
Figure 5. Trichodina. (a) Live (arrow) on fin of Murray cod (b) Live
Figure 6. Ichthyobodo (arrows) on gill tissue
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Treatment : Reducing the incidence of Lernaea on Copepod parasites farmed fish can be achieved by improving 1. Lernaea spp (anchor worm) husbandry and management practices in Background: Lernaea are large (up to 22 mm) particular, filtration of inlet water to prevent the crustacean parasites that infest the skin and gills introduction of free swimming stages of the of freshwater fish. Larval and male Lernaea are parasite, and quarantine of all new stock. non‐parasitic whereas the female, following 2. Ergasilid copepods fertilisation, will burrow into the skin of the host Background: Ergasilid copepod ectoparasites to become a parasite. The head and mouthparts have been responsible for massive losses of become modified to form an anchor shape. farmed fish around the world. Mature females Lernaea have not been reported from Murray cod are parasitic whereas immature stages and reared in intensive recirculating aquaculture males are free‐living. Ergasilids attach to their systems, but are often seen on Murray cod host by wrapping their modified second broodfish and other fish grown in outdoor antennae around the filaments of the gills. earthen ponds and cages. Light infestations of Lernaea may not be life threatening unless Gross signs/diagnosis: Attachment and feeding penetration by the parasite is near a vital organ. of the parasite causes severe damage to gill Heavy infestations may lead to debilitation and tissue. Heavy infestations may result in infection by bacteria and fungi. secondary infections by fungi and bacteria, respiratory difficulties and ultimately death. Gross signs/diagnosis: Anchor worm can be Although the ergasilid Dermoergasilus easily seen with the naked eye as a small, red intermedius (Figure 8) has been reported from pustule formed at the site of penetration with a Murray cod, to date there have been no reported large greenish pair of egg sacs on the posterior severe outbreaks of this parasite on fish farms in end of the body, which can be seen protruding Australia. from the host (Figure 7).
Figure 7. Lemaea (arrow) on the pelvic fin of a Murray cod.
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Figure 8. Dermoergasilus intermedius attached to gill filament
species from EUS. Red spot is spread with Fungi contaminated water and fish. Fungal infections are commonly encountered in Gross signs: The initial signs of red spot are area Murray cod farming, with most infections being of pale skin which progress to red lesions and caused by oomycete fungi (water moulds). ulcers (Figure 9). Whilst other diseases can cause These water moulds typically infect fish that are ulceration, red spot is known for ulcers physically injured, stressed or infected with extending deeply into the muscle areas. Fish will another disease. All life stages can be infected start dying and infection and mortalities may with fungi. Murray cod eggs are particularly spread very rapidly through the pond. prone to attack. Fungi are rarely considered to be the primary disease pathogen, but are more Diagnosis: Histological sectioning of lesions, often a secondary pathogen that colonises isolation of Aphanomyces and a PCR test may be damaged tissues infected by bacteria or required for diagnosis. parasites. Treatment: Once fish are infected there is no 1. Aphanomyces invadans known treatment of EUS. Treating the water fish Background: This fungi is the cause of Epizootic are held in with formalin or salt may reduce the Ucerative Syndrome (EUS), otherwise known as infectious stage of the fungus. Moving fish to an “red spot” disease. Red spot disease has uninfected pond may assist controlling the occurred in different species of fish in fresh and disease. estuarine environments across Australia and has been isolated in Murray cod in Victoria and 2. Saprolegniosis Queensland. In NSW, red spot occurs commonly Background: Saprolegnia spp are amongst the most important fungal infections of wild and with acid water runoff and is often seen after heavy rains. Optimal temperature for growth of cultured fish. There have been limited reports of Saprolegniosis in Murray cod but this may be a Aphanomyces appears to be between 20 °C and 30 feature of a lack of submissions coming into °C. On a Murray cod farm in northern Victoria EUS caused over 90% mortalities in fingerlings laboratories rather than an absence of the which were also co‐infected with Chilodonella disease. Winter saprolegniosis has been identified as a new disease of silver perch and white spot. One hundred percent mortality ° has been reported in juvenile fish in other affecting larger fish and at temperatures <16 C. Transmission of saprolegniosis occurs directly in the water via motile zoospores and most
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infections are generally believed to come from Diagnosis: Saprolegnia spp can be diagnosed by inanimate sources such as fungi sporulating on observation of cotton proliferative growths on dead organic matter. These fungi can also infect skin and gills. There are other pathogens that up to 100% of fish eggs rendering them non‐ cause such lesions (e.g. Flavobacterium) but an viable. experienced pathologist should be able to differentiate. Fish need to be examined live to be Gross signs: Early in the infection, there may be able to make a definitive diagnosis. Under a pale focal areas in the skin. Growths may occur microscope fungal hyphae between 10 – 30 on the skin and gills which although primarily microns can be seen (Figure 10). white, will take on the colour of surrounding organic material. These patches may grow to Treatment: As for red spot diseases, treatment is look like “cotton wool” and occur on the gills in very difficult for infected fish. advanced cases.
Figure 9. Murray cod infected with Epizootic Ulcerative Syndrome (EUS)
Figure 10. Saprolegnia fungal hyphae
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surface, ulcers on the body surface and erosion Viruses of fins. Internal symptoms include 1. Megalocytivirus haemorrhages on the visceral organs. Background: Megalocytivirus is a highly Diagnosis of a bacterial infection requires the infectious iridovirus that was observed from the skills of a specialist and if suspected, a qualified spleen and kidneys and gills of juvenile Murray veterinarian should be consulted. Identification cod held in a RAS farm in 2003. This infection of causative organisms can be obtained by resulted in 90% mortality in fingerlings (40–60 taking a swab and submitting to a laboratory. mm) and 25% mortality in larger fish (100–150 This can be done by a farmer who has had mm). A review of imported ornamental fish in adequate training so that accurate and Sydney pet shops has also isolated very similar meaningful results are obtained. viruses. This virus is very closely related to Epizootic Haematopoietic Necrosis Virus 1. Aeromonas species (EHNV), a cause of mass fish deaths in a range Background: Aeromonal bacteria are ubiquitous of species in south eastern Australia. organisms found in freshwater ponds and the muddy sediment. A range of Aeromonas species Gross signs: Mortality may be the first sign occur as natural inhabitants of the noted in affected stock and was the main finding gastrointestinal tract of both freshwater and in the 2003 outbreak on a Victorian Murray cod marine fish. farm. Furunculosis is an important exotic disease that Diagnosis: Affected fish should be submitted to does not occur in Australia. It is caused by the a laboratory for pathology and virus isolation bacterium Aeromonas salmonicida. An atypical and may be subjected to PCR tests. form of this disease has been reported to occur Treatment: There is no known treatment for this in Australian native fish: however, not in virus. Murray cod. This bacterium causes skin ulceration and has been reported to cause Bacteria mortalities in other species such as silver perch. Numerous bacterial organisms have been recorded across all fish species; however, many Gross signs: Aeromonal bacteria have been occur as secondary infections. These bacteria isolated from silver perch and many other may be normal inhabitants of the aquatic species and have been identified as the cause of environment, but only cause disease following skin lesions “Summer spots” which may start as stress‐induced factors such as parasitic areas of depigmentation but then progress to infestation, changing environmental conditions ulcers. In these cases, mortalities are generally (temperature, pollution etc.) and poor not a problem but skin lesions may render the husbandry techniques. Therefore, when fish unmarketable. considered alone, bacterial diseases should not Other Aeromonas species such as A. hydrophila cause a problem in healthy fish with good have been reported to cause a range of quality water. syndromes including haemorrhagic septicaemia There are only a small number of bacteria that in fish (Woo and Bruno 2010). Aeromonas species have been reported in Murray cod: however, has also been identified internationally (again this may be a feature of samples not being not in Murray cod specifically) as causing tail rot submitted for identification. The reported disease. In other studies, Aeromonas spp. are bacteria are listed in Table 1 and Appendix 2. identified in studies of surface bacteria for food safety purposes and so may not be involved in All life stages can be infected with bacterial causing disease in fish. diseases. The body area of infection varies with the pathogen but may include gills, the body Diagnosis: Laboratory confirmation of this surface, including fins, internal organs and bacterial pathogen is required. tissues. Signs that fish may be infected with a Treatment: Where a specific Aeromonas spp has bacterial disease vary depending on the bug been isolated antimicrobial treatment may be involved but may include decreased appetite, instituted under veterinary advice. becoming listless and dying (this may be chronic or acute). External symptoms that occur with bacterial infections include discolouration of the skin including parts of the fins and body
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1. Vibrio disease in farmed fish. For example, swollen Vibriosis is more commonly a disease of the yolk‐sac syndrome” (SYSS), which has caused marine genus Vibrio although infrequently Vibrio significant mortalities of the eggs and newly spp have been isolated from freshwater fish. hatched larvae of Murray cod, has been Vibriosis can result in an overall infection in fish attributed to an inbalance in essential and non‐ with the classic signs of haemorrhage of the skin essential amino acids. Feeding high‐energy, and fins, “pop eye” and internally lipid‐rich diets to juvenile and sub‐adult Murray discolouration of the internal organs. There have cod in captivity over extended periods of time been very few reports of Vibrio in Murray cod. can cause loss of appetite, lethargy, excessive fat deposition in body organs, especially within the 2. Edwardsiella tarda body cavity and liver (“fatty liver”), and This organism is ubiquitous in freshwater ultimately death. environments and little is known about its occurrence in Murray cod, which from one Inappropriately stored feeds can become rancid when stored in damp, warm conditions, and report may be an incidental finding. breakdown of fatty acids in feeds containing Other bacteria insufficient amounts of anti‐oxidants can result Cytophaga‐ and Flexibacter‐like bacteria in the production of harmful toxins. Moulds (“myxobacteria”) typically infect the gills, body and fungi growing on the feeds may also surface and fins of fish, especially juveniles. produce toxins. Symptoms associated with These bacteria can also be associated with feeding rancid diets to fish include loss of saddleback”, “fin rot” and “tail rot” diseases, appetite, darkening of the skin, pallor of gills, and acute infections with these bacteria can lead swollen, fatty and pale liver and mortality. to mortalities. Chronic ulcerative dermatopathy Background: Chronic ulcerative dermatopathy Non‐infectious diseases and (CUD) was first identified as a problem on syndromic conditions Murray cod in intensive aquaculture operations Diseases and syndromes that cannot be in the mid to late 1990s. transmitted from one fish to another are Gross signs: CUD is an ulcerative condition that considered non‐infectious. affects the sensory pores and tissue overlaying the lateral line (Figure 11). In extreme cases, the Nutritional diseases eyes and fins are also affected. Few mortalities Nutritional requirements of fish, including appear to occur and fish continue to grow. CUD protein, amino acids, lipids, minerals and is not transmissible between fish. vitamins, vary with species and age of fish. Nutritional deficiencies or imbalances in the diet of fish can reduce growth rates and even cause
Figure 11. Murray cod afflicted by chronic ulcerative dermatopathy (CUD)
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Diagnosis: The causative agent of CUD has yet to be conclusively identified. Viruses, protozoan and metazoan parasites are not implicated. Bacterial pathogens are present but considered to be opportunistic colonisers of infected areas. The causative agents of CUD are thought to be waterborne toxicants, and that some components of the groundwater in which the fish are cultured are responsible. All farms that have experienced CUD were using bore water. Elevated and/or imbalances of certain elements and/or compounds in the bore water, perhaps operating in synergy, may be directly affecting the sensor nervous tissues over the head and body of the fish. Treatment: Replace groundwater with surface water where possible, or preconditioning of groundwater either in a vegetated earthen pond or in the presence of artificial macrophytes for three days.
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Drug and chemical management
Broadly speaking, any product used to treat Off‐label Permits are separated into: animals can be considered a veterinary chemical • Minor use: or medicine. The Australian Pesticides and Issued for uses not listed on the label of Veterinary Medicines Authority (APVMA) a product because the cost of their (http://www.apvma.gov.au) is the national body inclusion would exceed the economical that controls the registration of all agricultural return to its manufacturer or distributor. and veterinary chemicals. There are over 8000 Examples include a product used on a different products in the Australian marketplace specialty animal grown by a few but very few of these are registered for use in producers on a small scale (minor aquatic species. All states in Australia have animal); a product rarely used for legislation controlling the use of chemicals control of a minor disease in a major which ensures these products are used animal (minor use in a major animal); or appropriately and our food products are safe to a variation made to the way in which a consume. registered drug is administrated in Products that have full registration can be used special circumstances. The applicant as directed under label conditions. The must be able to justify to the APVMA manufacturers of veterinary chemicals used in why the product and/or use should be aquaculture in Australia are reluctant to apply considered under minor use permit for full registration as the marketplace for this requirements. Minor use permits are chemical use is limited. This is an issue faced by granted for a specific period and require all small sectors. Where products are not renewal at the end of that period. registered for use in aquatic, food producing • Emergency use: animals then “off‐label” or “minor use permits” An application that must be elevated can be utilised. Once again products must be rapidly to meet an actual emergency registered for this manner of use and will need situation, such as the use of an to be used under the direction of a veterinarian unregistered product to control a registered in the state. contagious disease outbreak for which no registered product exists. There are three options for registering chemicals Verification that the ‘emergency’ is with the APVMA. These are: genuine will be conducted by contacting • Full registration the appropriate State coordinators. Not usually an option in aquaculture Trial Permits may be issued by the because of the lack of data to support an APVMA for small‐scale trials, field trials application and the high costs in obtaining and product evaluation trials. these data, along with the small potential market for the product. • Exemptions In certain instances when a chemical is • Permits considered to be innocuous, it may not be A permit for the use of an unregistered necessary to apply for either registration or chemical product or an unapproved active a permit. In order to apply for an exemption constituent may be issued by the APVMA in a letter must be submitted to the APVMA certain circumstances. Permits are ideal for requesting the exemption, including aquaculture because of the small quantities supporting documentation to justify the of the drugs / chemicals used and the lack of request. detailed information required for registration. Permits are divided into two main types, Off‐label Permits and Trial
Permits.
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Other fish health issues
anti parasitic action. Fish should be routinely Stress and fish health graded to reduce size variation. Hygienic Background: Stress is considered as an conditions and water quality should be environmental externality that reduces the maintained, and stocking densities, feeding rates ability or capacity of a fish to maintain health and water flows managed. and well‐being. More importantly, stress can reduce growth and illicit poor fish health. Predation, aggression and Stressed fish suffer from depressed immune systems and consequently lowered resistance to cannibalism disease or parasite infestation. Background: Murray cod can be aggressive, territorial and predatory in nature, and Stressors in fish farming include: cannibalism can occur in culture systems where • Handling. Capture, netting, grading densities are low and/or the size range of fish is weighing, tagging, injecting great. Other factors have also been shown to • Transport affect the rate and extent of cannibalism, • Territorial behaviour. Aggression by including availability and nutritional dominant fish, competition for food, composition of food, feeding frequency, water competition for refuges, competition for clarity, light intensity and the presence of mates, etc refuges. Increased turbidity may reduce territorial and aggressive behaviour and • Predation pressure cannibalism. Murray cod are less likely to attack • Confinement during culture, handling or and consume siblings that are already dead. transfers, and associated with overstocking Cannibalism can lead to shifts in the size • Chemicals and water quality variation of stock and increase the risk of disease. Stress associated with cannibalism • Temperature changes pressure may reduce growth rates in smaller • Parasitism/disease. fish and lead to increased susceptibility to Some factors may not be stressful by themselves disease. Larger fish may also suffocate while but combinations of several of these factors, attempting to ingest smaller fish. acting in synergy, can have a cumulative affect Gross signs: Bite marks on the body surface, on inducing stress. Therefore, care should be damage to dorsal, anal and caudal fins, loss of taken to minimise the number of stressors acting scales or physical marks on the sides of the upon fish at any one time, such as handling fish body, unexplained loss of fish. The presence of when ammonia concentrations are excessively large fish with grossly expanded abdomens or high. with tails protruding from the mouth. Gross signs: Fish display loss of appetite. Fish Treatment: Grade fish regularly (every 2–4 that have been poorly handled, damaged during weeks), especially in the first few months of transport, or injured by territorial behaviour, grow‐out, to reduce size variation and maintain can often be recognised by having severely densities to reduce stress associated with frayed fins, lost scales, marks or abrasions on the undercrowding or overcrowding. Increasing body and cloudy eyes. stocking densities may reduce the ability of fish Treatment: Reduce/eliminate stressors. Improve to establish territories and thereby reduce the husbandry practices and take an active impacts of territoriality and aggression. Improve approach to managing the health of stock. husbandry practices and take an active Reduce excessive handling of fish. Where approach to managing the health of stock. possible, when handling and transporting fish, Ensure that fish are receiving ample feed to sate use light dosages of anaesthetics and salt to appetite. Feeds should be specifically reduce stress. Not only does salt help to reduce formulated and appropriately sized for the stress, but also promotes the production of species, and feeding frequency/timing optimised mucus and healing, is beneficial to osmo‐ to correspond with peak feeding periods. regulation and has anti bacterial, anti‐fungal and Feeding strategies may be facilitated by using
Murray Cod Fish Health BMP 19
automatic feeding devices. Where possible distribute feed over a large area or have several feeding stations. Remove obvious cannibals and dominant individuals. Maintain optimal stocking densities. Grade fish regularly to reduce size variation. Juveniles may require grading every 3‐4 weeks, but as fish grow the need to grade will reduce. Predation Several species of aquatic semi‐aquatic animals may prey on Murray cod in tanks, ponds and cages. Some predatory aquatic insects, such as dragonfly larvae, beetles and water boatman, may prey on larvae and fry in rearing ponds. Birds that most frequently occur around aquaculture ponds are the wading birds (herons and egrets), diving birds (cormorants and darters) and web‐footed birds (ducks, grebes etc.). Some of these species are considered a pest in aquaculture ponds. The cormorants are notorious fish predators and can eat up to 27% of their body weight per day. Apart from devouring small fish, cormorants also cause injury and stress fish, which may reduce feeding and growth and increase susceptibility to disease. Controlling bird predation can be costly and time consuming. The use of harassment devices such as noise makers and scarecrows to control bird predation are mostly ineffective because the birds eventually become accustomed to them. More often than not, lethal control measures, namely the use of fire‐arms, are used. Although all native birds, including cormorants, are protected by legislation, a permit can be obtained to control pest species. However, the most effective method, though expensive, is to exclude the birds by enclosing ponds in bird‐proof netting. Freshwater turtles and native water‐rat may also feed on fish and occasionally are found around aquaculture facilities. Since all native reptiles, including turtles and water rats, are protected by legislation, offending animals should be relocated rather than destroyed.
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Water quality and environmental factors related to fish diseases
Water is a vital component of any aquaculture geology, soils and the climate. Internally, water venture as it is the medium in which the fish live quality may be influenced by farm management, and grow. Many water quality parameters can fish husbandry (including stocking density and influence fish health both directly and indirectly. feeding) as well as excreted wastes of the fish. Each species has a preferred range of water The physical action of the fish in stirring up quality parameters but there are very little data sediments can also have an impact on some on the tolerance levels of Murray cod or other parameters. native finfish. Outside of the optimal range, fish In a survey of the Murray cod aquaculture will suffer stress, which may lead to disease and industry, 28% of respondents were experiencing even death. There is a high degree of inter‐ water quality problems including problems with relationship between water quality parameters, dissolved oxygen, gas super saturation, build‐up which means that a variation in one parameter of metabolic wastes (ammonia), and toxic can influence the toxicity of others. contaminants. Fish can be affected by water‐borne In the absence of specific water quality contaminants from the external environment as requirements for Murray cod, water quality for well as those arising from their own activities the aquaculture of freshwater fish and a (Figure 12). Potential external sources of water summary of historical water quality data from contaminants include pollution from Murray cod aquaculture operations, may be agriculture, sewage or industrial sources as well used a guide (Table 2). as natural variations in water quality caused by
External Factors Internal Factors
Pollution Farm management • Agriculture • Water exchange • Industry • Cleaning • Sewage • Maintenance
Natural Factors FISH Fish husbandry • Stocking density • Geology HEALTH • Soils • Feed management
Climate Fish activities • Temperature • Excreted wastes • Storms
Figure 12. External and internal factors that affect the health of fish in aquaculture
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Table 2. Acceptable water quality ranges for freshwater aquaculture, and water quality recorded from Murray cod aquaculture farms Suitable Recorded from Murray cod aquaculture farms Parameter concentrations (continuous) Ponds RAS exposure)* 10%‐90% Median 10%‐90% Median Water temperature (oC) 5‐30 12.9‐28.2 21.6 13.2‐26.7 24.8 Dissolved oxygen (mg/L) >5 3.1‐12.0 7.7 3.4‐13.3 6.9 Dissolved oxygen (%sat.) 57‐151 99.2 pH 5.5‐9 6.7‐9.6 7.8 5.1‐8.7 6.4 Total ammonia (as nitrogen) <3.0 0.003‐3.9 0.22 0.004‐34.7 0.6 (TAN) (mg/L) Unionised ammonia (UIA) (mg/L) <0.02 (pH>8.0) <0.01 (pH<8.0) 0.0004‐0.3 0.0037 0.00003‐0.067 0.0019 Total alkalinity (mg/L) 20‐400 2.4‐88.6 24 2.3‐418.0 12.1 Carbon dioxide (mg/L) <10 16.9‐45.6 30.7 Chlorine (mg/L) <0.003 Conductivity (us/cm) <10,000 84‐100 94 211‐4,917 938 Salinity (ppt) 0.054‐0.064 0.06 1.7‐6.7 5 Total hardness (mg/L) 20‐400 Hydrogen sulphide (mg/L) <0.002 Nitrate (mg/L) <100 0‐260 10.1 4.8‐589 200 Nitrite (mg/L) <0.1 0‐3.69 0.014 0.5‐7.12 1.4 Phosphorus (mg/L) No data 0.02‐1.15 0.26 0‐20 0.36 Suspended solids (mg/L) <25 5‐175 33 0.001‐124.2 0.018 Dissolved solids (mg/L) No data 0‐0.02 0.001 45‐1144 299 Turbidity (FAU) <25 5‐809 60 0‐120 10 BOD (5 day) (mg/L) <15 0‐44.2 10 COD (mg/L) <15 Metals Aluminium (mg/L) <0.03 (pH>6.5) <0.01 (pH <6.5) Cadmium (mg/L) <0.003 Calcium (mg/L) 10‐160 Copper (mg/L) <0.005 Iron (mg/L) <0.05 Lead (mg/L) <0.01 Magnesium (mg/L) <15 Manganese (mg/L) <0.01 Mercury (mg/L) <0.001 Zinc (mg/L) <0.01 * summarised from Shepherd and Bromage (1988), Boyd (2000), Boyd and Tucker (1998). Piper et al. (1998) and ANZECC water quality guidelines
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ensure that biological filtration is functioning in Dissolved gases RAS. In the long term, undertake routine (daily) Low Dissolved Oxygen monitoring of DO in ponds (at dawn when DO Background: Environmental hypoxia is a low is at its lowest) and tanks. In ponds, provide concentration of dissolved oxygen (DO) in the supplementary aeration that is automatically water and is perhaps the greatest risk in timed to operate during periods of low DO aquaculture. The sensitivity of fish to low (especially early morning). Install and maintain concentrations of DO varies although a emergency back‐up aeration and oxygenation minimum level of 5 mg/L is considered ideal for systems. Do not overstock tanks and ponds, optimal growth and reproduction. Below this improve feed management and/or increase level, food consumption decreases and growth water exchange. slows. A DO of less than 2 mg/L is very Gas Supersaturation – Gas Bubble stressful and may lead to opportunistic infections (bacteria, fungi, parasites). Low DO Disease levels may be caused by: Background: Gas super saturation may be caused by excessive plant photosynthesis during • Overstocking and overfeeding resulting in daylight hours in ponds with dense algal low DO levels blooms, inflow water saturated with gases as a • Increasing water temperature, which result of heating under pressure, water inflow decreases the solubility of oxygen in water pipes sucking in air (prior to pumps) and • Excessive plant respiration; in ponds where ground water that is super saturated with algal growth is very high, DO levels may be nitrogen and/or carbon dioxide. Most gas depleted during the night, and DO levels emboli are produced by excess nitrogen. may also become depleted after several Oxygen rarely causes gas bubble disease overcast days because it is assimilated metabolically and thus • Use of ground waters that often have low DO less likely to form persistent bubbles. levels and with high iron contents Gross signs: Fish become listless and float to the • Breakdown of the aeration systems surface. Small bubbles can be seen forming in • Presence of decaying organic matter superficial blood vessels typically on the gills and fins (Figure 13) and behind the eyes. • Use of industrial wastewaters containing chemicals that will reduce DO levels. Diagnosis: Measure water with a saturometer (an oxygen meter will give an indication of Gross signs: Fish cease feeding and may “gasp” oxygen super saturation only). Small bubbles at the water surface or gather at water inlets. will immediately form on any object placed in Death occurs with opercula flared and mouth the water. agape. Often large fish die and small fish may survive. Treatment: Eliminate excess gases from the water source by aerating water in a reservoir to Diagnosis: Direct measurement of DO with a allow gases to equilibrate. Install de‐gassing calibrated DO meter. devices on pipelines and systems before the Treatment: Immediately increase aeration, water enters the culture vessels. increase water exchange, stop feeding and reduce stocking density. Supplement aeration with oxygenation via an oxygen cylinder fitted with a diffuser. Monitor ammonia and nitrite to
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Chlorine/chloramine poisoning chemical neutraliser such as sodium Background: Chlorine is commonly used to treat thiosulphate. town water to make it suitable for human consumption. Ammonia is sometimes also Hydrogen sulphide poisoning added to stabilise the chlorine, and reacts Background: Hydrogen sulphide (H2S) forms producing chloramines. Both chlorine and from the reduction of sulphate under anaerobic chloramine are extremely toxic to fish and can conditions. It is more of a problem in brackish cause acute or sub‐acute toxicity. water/marine systems, but can occur in Gross signs: Symptoms of chlorine/chloramine freshwater systems where there is an poisoning include breathing difficulty and accumulation of organic matter. Disturbing death. Gill tissue of affected fish becomes pond sediments can also release this gas from necrotic. Fish exposed to chlorine poisoning the mud. H2S interferes with respiration causing appear to have improved survival if the water is hypoxia. super‐saturated with oxygen for several days Diagnosis: Presence of H2S is often detected by a and the temperature is lowered. characteristic “rotten egg” smell, and can be Diagnosis:A reliable water quality measured by a reliable water quality spectrophotometer‐based test kit can measure spectrophotometer. chlorine. Chlorine can also be detected by smell. Treatment: H2S can be removed from water by Any detectable amount of chlorine or vigorous aeration or use of a degassing device. chloramine is undesirable. Raising pH and lowering temperature also Treatment: Chlorine can be removed from water reduce toxicity. Build‐up of H2S in ponds can be by vigorous aeration, but chloramines are not so avoided by maintaining aerobic conditions with readily removed. Water may also be filtered supplementary aeration. Regular addition of through activated carbon or treated with a fresh water also assists in reducing H2S concentrations.
Figure 13. Gas bubble disease. Bubbles of gas between the fin rays of a Murray cod
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ammonia increases as pH and temperature Metabolic Waste Products increase. Appendix 4 provides a table for The waste products from the fish themselves, calculating unionised ammonia at different pHs particularly nitrogenous wastes, can adversely and temperatures. See Table 2 for water values affect water quality if they are allowed to related to ammonia. accumulate. Protein in food is a source of Gross signs: Acute ammonia toxicity can cause nitrogen and is excreted as ammonia, primarily behavioural abnormalities such as hyper‐ across the gills. Decaying organic matter within excitability and fish often stop feeding. Sub‐ the culture system, such as waste food, faeces, lethal ammonia poisoning decreases growth and dead plants or animals also produces ammonia. disease resistance. Under aerobic conditions, ammonia is oxidised by bacteria to nitrite and then to nitrate (Figure Diagnosis: Chemical measurement of total 14). Nitrate is generally considered non‐toxic to ammonia, pH and temperature using fish, but both ammonia and nitrite are toxic appropriate test kits and meters. Use attached under certain conditions. tables to convert total ammonia to unionised ammonia (NH3) (Appendix 4). Ammonia poisoning Background: Ammonia poisoning is one of the Treatment: ‐ Dilution by addition of fresh water, most common water quality problems in stop feeding, decrease stocking density, reduce aquaculture. Ammonia can cause acute temperature and reduce pH. Some types of mortality, but most often it presents as a sub‐ Zeolite may also be used to strip ammonia from lethal stress. Potential causes of elevated water. Improve husbandry practices and take ammonia levels include overcrowding of fish, an active approach to managing the health of recent medication or other chemicals added, stock. Monitor ammonia concentrations (daily newly established recirculation systems, failure in intensive recirculating systems, less of biological filters, reduced water flow and frequently in ponds), maintain hygienic accumulation of waste feed or other organic conditions, avoid waste accumulation in culture matter. Ammonia is present in water in two system, improve water quality, ensure sufficient forms: unionised ammonia (NH3), which is toxic volume of bio‐filtration media in recirculation to fish; and ionised ammonia (NH4+), which is systems and manage stocking densities, feeding much less toxic. The proportion of unionised rates and water flows.
Removal by water exchange
O2 O2
Uneaten Ammonia Nitrite Nitrate Food NH , NH + - - 3 4 NO2 NO3 Nitrosomonas Nitrobacter Uptake by Dead Plants and plants animals
Figure 14. Nitrogen pathway in an aquaculture system
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Nitrite poisoning (Brown blood Gross symptoms: Highly acidic waters increases disease) mucus production of the gills causing Background: Nitrite is an intermediary product respiratory difficulty and mortality in extreme in the oxidation of ammonia to nitrate by cases. Highly alkaline waters can cause cloudiness of skin and gills, and mortality in bacteria (Figure 14). Many of the circumstances that lead to a build up of ammonia can also lead extreme cases. to nitrite poisoning. Peaks of ammonia and Diagnosis: pH can be directly measured with a nitrite occur in the weeks following the meter – this should be done regularly (daily for commissioning of newly established biological RAS). Normal levels recorded for Murray cod filters. In ponds, nitrite peaks can occur in systems are given in Table 2. Fish affected by pH autumn as the temperature optima of the two extremes often have changes that can be bacteria (Nitrosomonas and Nitrobacter) are detected by histopathology. different leading to nitrite accumulation. Susceptibility to nitrite toxicity varies Treatment: Extreme pH levels can be treated by enormously between species. There are no data dilution with fresh water and/or the addition of on the toxicity of nitrite to Australian native fish. a buffering agent to lower/increase pH. Concentrations of nitrite less than 0.1 mg/L are Managing pH in RAS is a balancing act. If pH is considered suitable for continuous exposure; allowed to become too acidic, fish may become however, higher concentrations in excess of 0.6 stressed and nitrification processes are impaired, mg/L have been recorded from some Murray whereas increasing pH will increase the cod aquaculture operations (Table 2) proportion of ammonia that is toxic to fish. Gross signs: Behavioural changes are similar to Temperature characteristics of hypoxia. In acute to chronic Temperature dramatically affects fish cases, dyspnoea may occur and gills become metabolism and each species has a preferred light tan to brown in colour due to a change in temperature range. All fish are susceptible to blood colouration. rapid changes in temperature, but seem to tolerate a rapid decrease in temperature better Diagnosis: Test for nitrite using a chemical test than the reverse. At the extremes, fish may be kit. stressed to the point where growth and survival Treatment: Dilution by addition of free water. are affected. Temperature stress depends not Nitrite toxicity is reduced by addition of salt only on how low or high the temperature (<50 mg/L salt is usually sufficient) as the becomes, but how quickly it arrives at the chloride ion competitively inhibits nitrite uptake temperature. Water temperature is readily across the gills. measured by thermometer or meter. Under ambient conditions within the natural Other important water quality range in the Murray‐Darling Basin, Murray cod parameters may be exposed to temperatures from less than 10 °C to in excess of 30 °C. At temperatures pH below 16 °C, feeding and growth is reduced and Background: A pH range of 6.5‐9.0 is generally at higher temperatures, fish may stop feeding recommended for freshwater fish. Outside of and become stressed, predisposing them to this range is stressful to fish and levels less than disease. Table 3 gives some recorded 4.0 (acidic) and greater than 11.0 (alkaline) are temperatures for Murray cod culture. usually lethal. Fish acclimatised to low or high pH levels, or fish used to pH fluctuations are Salinity more tolerant of pH changes than fish kept Salinity is a measure of all ions in water and is under more stable conditions. pH can affect the most commonly expressed as parts per toxicity of other chemical parameters. Sources of thousand (ppt). Freshwater generally has less low pH water include groundwater in contact than 0.5 ppt salinity while seawater is 30‐40 ppt. with silicate minerals, and waters draining from Salinity tolerance of fish varies with species and or overlaying acid sulphate soils. The metabolic length of exposure. activity of fish and other aquatic organisms produces acid, which can gradually lower the Heavy metals pH in some systems. Some ground waters may Fish are sensitive to dissolved metals and metals also contain high pH levels. Both meters and are most toxic in low alkalinity waters in which test strips are used to measure pH levels. high concentrations of metals remain dissolved.
Murray Cod Fish Health BMP 26
Metal contamination may occur from the Water‐borne contaminants and other following sources: problems • Leaching from lead, copper or galvanised Organic compounds such as PCBs, detergents (containing zinc) plumbing fittings and hydrocarbons, pesticides, herbicides and • Groundwater (especially soft, acid water) molluscicides can be extremely toxic to fish and that may have high concentrations of metals may reach aquaculture water supplies by • Rainfall run‐off from soils that are poorly accidental spillage or contamination and runoff buffered or are contaminated (e.g. mine from agricultural and industrial lands. Clinical wastes). symptoms vary with the type of compound but tend to include distress, respiratory failure, Symptoms of metal poisoning vary and depend avoidance behaviour and death. on the metal and fish species. Most heavy metals primarily affect the gills. Standard water quality test kits used in aquaculture are usually not sensitive enough to detect metal concentrations that affect fish. Water and fish tissue samples must be submitted to a laboratory specialising in this type of analysis.
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Acknowledgements
The authors wish to acknowledge the funding support of the Fisheries Research and
Development Corporation and Fisheries Victoria (Department of Primary Industries) through the Aquaculture Futures Initiative for this project. Significant in‐kind contributions, in the form of farm access and information, from Murray cod farmers in Queensland, NSW and Victoria is also gratefully acknowledged. Information on legal and regulatory matters associated with use of chemical in aquaculture was provided legal staff within DPI Victoria.
Murray Cod Fish Health BMP 28
References
Gooley, G.J., Bailey, M.L., Abery, N.W. and . Ingram, B.I. (In prep.). Standard Operating Procedures for Pilot‐Scale, Open‐Water Cage Culture of Murray cod in North‐Western Victoria: Part 1‐ Fish Health Management. Fisheries Victoria Internal report.
Ingram, B.A., Gavine, F. and Lawson, P. (2004). Diseases and health management in intensive Murray cod aquaculture. In: Development of Intensive Commercial Aquaculture Production Technology for Murray cod. Final Report to the Fisheries Research and Development Corporation (Project No. 1999/328). (Ingram, B.A. and De Silva, S.S. eds.), pp. 129‐146. Primary Industries Research Victoria, DPI, Alexandra, Victoria, Australia.
Mohan, C.V. and De Silva, S.S. (2010). Better management practices (BMPs)‐gateway to ensuring sustainability of small scale aquaculture and meeting modern day market challenges and opportunities. . Aquaculture Asia 15: 9‐14.
Read, P., Landos, M., Rowland, S. and Mifsud, C. (2007). Diagnosis, Treatment and Prevention of Diseases of the Australian Freshwater Fish Silver Perch (Bidyanus bidyanus). NSW Department of Primary Industries. 81 pp.
Woo and Bruno 2010
Murray Cod Fish Health BMP 29
STANDARD OPERATING PROCEDURES
SOP 1 – Fish health management
present in the water supply. Treatment options Incorporating biosecurity and may include combinations of the following fish quarantine depending on culture system: The principal objective of fish health • Mechanical screening (sand filters, carbon management strategies in intensive aquaculture filters, screen filters) to remove particulate operations is to maintain the health and well‐ matter being of stock, while optimising fish production. • Chemical treatment (chlorination followed Key actions, which are critical to achieving this by de‐chlorination and/or aging) to eliminate objective are: pathogens • Take an active approach to managing the • Ozonisation to eliminate pathogens health of stock • UV sterilisation to eliminate pathogens • Maintain hygienic conditions • Elimination of fish from the water source • Sterilise inlet water (where possible). • Guard against poor water quality Bore water is generally considered to be • Monitor water quality regularly pathogen‐free; however, since water quality • Seek health certification for new stock varies widely from one source to another, • Quarantine all new stock groundwater requires thorough testing before use in aquaculture. Concentrations of some • Minimise unnecessary stress parameters (e.g. iron, hardness, conductivity • Monitor health of stock regularly and dissolved oxygen) may render the water • Feed fish an appropriate diet (composition, unsuitable for fish culture. Some form of pre‐ size, amount etc.). treatment may be required before it is suitable for fish. Water supply treatment Domestic waters provide a clean, hygienic A major source of pathogens to intensive alternative water source. However, the presence aquaculture facilities is the water supply. Both of high levels of chlorine compounds (used by the quantity and quality of water used in councils to disinfect water for human aquaculture are critical to the well‐being of fish consumption) necessitates the need to “age” or under culture. A regular and abundant water de‐chlorinate the water before use. supply is essential for any aquaculture operations. A number of water sources are Dealing with fish health issues currently being used for Murray cod farming including, surface waters (streams, rivers, lakes Identifying the problem and dams), groundwater (bore water) and Monitoring is an important part of early identification and management of disease domestic/urban waters. Ideally these waters should be regular and reliable, free of problems. A decision support flowchart has pathogens, and free of pollutants (organic, been prepared to assist farmers in the identification of common health problems in industrial and urban. Regardless of the water source, some form of pre‐treatment will be intensive aquaculture systems (Figure 15). required before it is used in the culture system. Changes in behaviour may be the first sign that fish are being stressed. These changes may Untreated surface waters pose the greatest risk of pathogen contamination, especially if fish are include:
Murray Cod Fish Health BMP 30
• Reduced or cessation of feeding quarantine facility that is separate from the rest • Lethargy of the facility. The quarantine system should be physically isolated from the other facilities • Floating near the water surface and/or (separate room, building or pond). Water used swimming with the head upwards in the quarantine system must be totally • “Flashing” or erratic swimming separated and must not be allowed to mix with • Increased or laboured respiration (as the water of other culture systems within the indicated by “gasping”, flaring of opercula facility. Equipment used in the quarantine area or rapid opercula movement). should not be used in other areas of the facility. For RAS minimise traffic through the quarantine Physical changes may become apparent, such as area and disinfectant footbaths should also be abnormal growths, lesions or discolouration on used at the entry/exist of the quarantine area. the body surface, loss of some scales and New stock should be quarantined for at least 2 cloudiness of eyes. Fins may become tattered or weeks before introducing to the production eroded. The gills may become clogged with facility. During the quarantine period, fish mucus and the filaments may appear swollen or should be checked regularly for signs of disease, fused together. and should be given prophylactic treatments, Water quality should always be checked to such as salt and formalin baths, to eliminate determine if key parameters, especially, DO, external parasites which have previously been ammonia, nitrite, pH and temperature, have not identified as a major health problem for farmed departed from optimal or normal conditions. Murray cod. Finally, the water quality conditions within the quarantine system may be Visible examination of fresh wet preparations of different to that within the production system. skin, mucus and gill tissue under a dissecting Therefore, gradually acclimatise new stock to microscope or compound microscope may be production system water conditions during the sufficient to detect the presence of common quarantine period. parasitic infections (some fungi, protozoans and metazoans). However, identification of many New stock should appear healthy at the time of pathogens, especially viruses and bacteria, delivery. The presence of fish that appear weak, requires the skill of a specialist using specialised underfed or unhealthy is a clear sign that health analytical techniques. More detailed problems may arise. Always purchase new descriptions of the symptoms and diagnosis of stock from a reliable supplier, and always seek fish diseases are found in fish health/disease health certification. As an added measure of texts. security, samples of fish can be sent to a fish health specialist for disease screening. Immediate action in response to a health problem will assist in reducing the severity of the incident. Where possible eliminate the Hygiene probable causative agent and reduce stress. A comprehensive cleaning and sanitising Water quality problems may be alleviated by program should be established to maintain dilution or flushing with fresh water. Infected hygienic conditions within the facility. This fish should be isolated from other stock within program should include the treatment of all the facility. All equipment exposed to equipment that may be exposed to pathogens, infected/contaminated fish and water should be including tanks, nets, buckets, meters, and disinfected. Treatment of infected fish with a floors. Sharing of equipment between different therapeutic drug or chemical may ultimately be systems of the facility should be prohibited. necessary. Uneaten and spilled food and sick or dead fish should be immediately removed from culture Managing new stock and systems. Cleaning of the floors to prevent the build‐up of debris, including spilt feed, must be quarantine procedures a regular activity. There are numerous cleaning An important source of pathogens is new fish and sanitising chemical compounds and agents. stocks that are brought onto the farm. To ensure However, there is limited information on the that contagious diseases are not introduced performance/efficacy of these products, which though restocking of aquaculture production facilities, all new stock, regardless of the source, should be quarantined. All aquaculture facilities, regardless of size, must have a
Murray Cod Fish Health BMP 31 DECISION SUPPORT PATHWAY FOR MURRAY COD HEALTH
Problem Routine monitoring solved
ABNORMAL / SICK / DYING FISH
ENVIRONMENT Water quantity Yes Check system/pumps No
Dissolved gases Check aeration/oxygenation Water quality Yes Check degassing of CO (O , CO ) 2 2 2 Increase aeration/oxygenation No
Ammonia & nitrite Check biofilter, feeds & feeding rates Yes (TAN, NO , NH3) Dilute/flush water 2 No
pH Yes Dilute/flush (add buffer)
No Temperature Yes Check heating system No Check inlet water supply. Other parameters Yes Dilute/flush or No (additives, contaminants) isolate water supply Observations FISH (behaviour, No. fish & tanks/units affected)
Gross examination Physical damage (body surface, gills & Yes Grade fish, protect fish, reduce stress (cannibalism/predation) internal organs) Monitor,& re-assess record
No Check water supply & eliminate Gas bubbles present Yes sources of gas supersaturation
No Isolate affected fish No Disease/parasites present Yes Apply appropriate approved therapeutic treatment
Nutrition Use correct feed (size, composition & Yes OTHER (quality/quantity) amount), & store appropriately No
Other factors ? Yes correct, rectify, eleiminate
Problem No Isolate affected fish & reduce stress not solved Seek help
Consult colleagues, other farmers & specialists
Submit water & fish samples for Re-assess analysis by specialists
Figure 15. Decision support flowchart for identification and management of major health problems in a Murray cod aquaculture facility
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make it difficult to establish a quality control larger species. AQUI‐S is a type of anaesthetic program. Care should be taken in the use of that is produced from clove oil. Using AQUI‐S these products, as they may be hazardous to with aerated or oxygenated water at the humans, fish and the beneficial microorganisms prescribed dose rate results in the fish becoming within the systems (especially the biological heavily sedated. The fish can then be killed filter). Some commonly used sanitisers include quickly during processing. One advantage of chlorine solutions, iodine solutions, quaternary this technique is that it allows specific sized fish ammonium solutions, ultraviolet radiation, to be targeted and smaller ones can be graded chlorine dioxide, phenols, alcohols and out and returned to recover in a tank or pond. aldehydes (e.g. Formaldehyde). Hygiene Care must be taken not to under or overdose the management should also extend to staff. stock. In early trials, electrical stunning resulted Management practices may include provision of in broken vertebrae and haemorrhaging in many anti‐bacterial soaps for washing hands, use of fish. Subsequent experiments varying the footbaths and disinfection of footwear and frequency and current duration overcame these restricted visitation of people from other fish problems. farms. Whatever the type of humane slaughter technique adopted by the farmer, there will be Humane slaughter and costs incurred. The technique used must meet destruction of stock humane standards, but it must also be practical Coinciding with growing public concerns about and economically viable. Not all of the the slaughter of finfish, the Victorian Prevention of mentioned techniques are practical for handling Cruelty to Animals Act (1986) was amended in large volumes of relatively small fish, which is a 1995 to include the humane killing of fish and situation at many aquaculture operations. In crustaceans. On an international scale, the order to address the issue of animal welfare subject of humane slaughter of finfish has been during slaughter different aquaculture sectors researched extensively. One report reviews a are starting to incorporate humane slaughter project carried out in the UK that brought techniques into their industry Codes of Practice. together animal welfare groups, retailers, research groups and aquaculture stakeholders to Disposal of mortalities investigate the issue. It is important to note that Fish carcasses may represent a potential source the type of slaughter method and degree of of certain fish pathogens, especially viruses and stress on the fish during harvest can have a bacteria. Fish mortalities occur during significant effect on product quality. production, and regardless of the reasons for the mortality, carcasses require prompt removal Measured welfare found that none of the most from culture units and careful, effective popular methods, death in air, death on ice or disposal. Transportation of mortalities from site carbon dioxide, resulted in humane slaughter. generates potential risks of infection spread, and In order to achieve effective welfare it was should only be undertaken with direction from determined that either a rapid kill was required appropriate authorities if no on‐site alternative or stress minimised if the kill was not can be found. Current practice involving pit immediate. The four possible options that disposal on site is poorly defined, with no achieved humane slaughter were percussive direction on position, depth construction or stunning, pithing, AQUI‐S (registered limitations on materials to be placed there. Pit anaesthetic) and electrical stunning. disposal, if not carefully administered, may Percussive stunning is inflicting a fast, firm blow represent a potential source of reinfection for to the head, using a club such as a wooden stock. dowel or a mechanical bolt gun. While being a If pit disposal is to be used, the pit must be in a very effective method of humane killing of large clearly marked area, and be lined with a non‐ fish, the quality of the final product will depend permeable barrier to prevent leakage to the on operator experience and fatigue. Pithing is a surrounding soil and groundwater table. technique that sees a sharp spike inserted into Recommended linings include 2‐5 mm high the brain; this interrupts nervous activity, density polyethylene (HDPE) or clay compacted reduces muscle twitching and slows rigour to a standard of 1x10‐9 m/s with a minimum mortis, giving rise to higher quality flesh. This thickness of 0.3 m. Pits should be situated at method is effective only when under‐taken by least 100 m away from surface waters experienced operators and is more suited to
Murray Cod Fish Health BMP 33
(waterways, drainage lines etc.) and a minimum watertable depth of 2.0 m. Lime should be added to the carcasses being disposed of and final burial should involve a top dressing of soil placed over the carcasses.
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SOP 2 ‐ Monitoring fish health
Monitoring fish health is an essential part of the appearance of the fish should be made. These role of the Murray cod farmer. This often include: incorporates a regular regime of sampling fish. • Body shape hollow gutted, swelling Maintaining a history of events associated with • Skin coloration changes, each holding facility (tank or pond) or batch of blotchiness, “saddleback”, fish greatly facilitates disease diagnosis and presence of sores, necrosis, long‐term management. These records should ulcers, spots, bleeding, loss of include daily mortalities, health checks, water scales, changes in texture quality and treatments. Information can be recorded on paper and then transferred to • Eyes swollen, cloudiness computer for ease of organisation. Many farmers • Fins tattered, frayed, eroded use simple excel spreadsheets or electronic • Gills pale, swollen, filaments fused recording systems developed over time. There together, filaments are a range of commercially developed software clubbed/swollen, filaments products available for collecting information on eroded, excess mucus, farms. presence of debris. The type of information that should be recorded Dissecting instruments used in examining and and frequency of collection is summarised in dissecting fish include blunt and fine‐pointed Table 3. Sampling should be frequent enough to forceps, blunt and pointed probes, dissecting ensure diseases are detected in time to reduce scissors preferably with pointed tips, scalpels their impact on fish health and survival. In fry and a range of scalpel blades. Also a notepad rearing ponds sampling should be undertaken and pencil will be required to take notes. at least weekly whereas in tanks daily checks Various sized petri dishes or shallow plastic should be undertaken. Since some species of trays are useful for holding fish for examination. external parasites, such as Trichodina, will leave Tissue samples biopsied from fish, such as gill their host shortly after death, it is important to tissue, can also be observed under a dissecting examine fish, live or moribund, as soon as microscope in a petri dish, but for higher possible after collection. magnifications, tissue samples and mucus Prior to sampling fish, where possible monitor scrapings should be mounted on microscope the behaviour of the fish. These observations, slides for examination with a compound which will assist in diagnosis, may include: microscope. A camera is useful for photographing the gross appearance of fish. • Loss of appetite • Listlessness Often it is better to make observations on living animals because preservation can distort soft‐ • Gulping at the water surface bodied organisms. Observations of motion and • “Flashing” or “rubbing” morphology of live animals assists • Flaring of gill covers (opercula) identification. • Swimming action ‐ loss of balance, position Small whole fish can be examined directly under in water column, swimming with head up, a dissecting microscope (see below). However, swimming with head down, spiraling, etc. for larger fish, samples of fish skin mucus, fins • Number of fish affected and number of and gill tissue will need to be removed from the mortalities. fish. A sample of mucus is collected by scraping the side of the fish with the back of a scalpel. Prior to undertaking any biopsy or autopsy The sample collected, skin cells, mucus and procedures, care should be taken in ensuring scales, can then be transferred to a drop of that fish are handled in such a manor to reduce freshwater on a microscope slide. A coverslip stress and or that slaughter is done humanely. may then be gently lowered onto the drop of Once a fish has been removed and examined water. Samples of gill tissue can be treated the with the naked eye, observations of the physical same way. Whole gill arches can be removed from small euthanised fish whereas individual
Murray Cod Fish Health BMP 35
gill filaments can be snipped off a gill arch from microscope (Figure 16a) is used for viewing larger sedated fish with a pair of scissors with specimens at low magnifications of between 5x minimal trauma. However, it is useful to and 60x. Combinations of lighting from beneath examine the tissue with a dissecting microscope and above the specimen greatly improve before adding a cover slip. viewing with a dissecting microscope. This type of microscope is suitable for most protozoan and After dissection, all equipment should be metazoan parasites. However, for some disinfected to reduce the risk of spreading protozoans, such as Ichthyobodo, and bacterial infectious pathogens. cells, a compound microscope (Figure 16b), Many of the pathogens of Murray cod are too which has magnifications of between 40x and small to be seen clearly by the naked eye and so 1000x, is necessary. Compound microscopes special instruments and equipment are usually with built‐in illuminators and binocular needed to locate and observe them in detail for eyepieces are more convenient than those with a identification purposes. Light microscopes separate light source or fitted with a single provide the magnifications necessary to observe eyepiece. It is important to follow the guidelines and identify parasites. Light microscopes are supplied with these microscopes to ensure that broadly separated into two types, dissecting settings and adjustments are correct to optimise microscopes and compound microscopes, based viewing. on their magnifying ability. The dissecting
(a) (b)
Figure 16. Microscopes. (a) Binocular dissecting microscope. (b) Binocular compound microscope.
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Table 3. Parameters to monitor and frequency of monitoring Parameter Frequency of sampling Comments General (all data sheets) Pond/tank number Every sample period Date and time Every sample period
Primary water quality parameters Temperature Daily May fluctuate diurnally Dissolved oxygen 1‐2 daily (RAS) Marked diurnal fluctuations can occur in 1‐3 weekly (ponds) ponds pH 1‐2 daily (RAS) Marked diurnal fluctuations can occur in 1‐3 weekly (ponds) ponds Ammonia Daily (RAS) Amount of ammonia in toxic form Weekly (ponds) influenced by temperature and pH Nitrite Daily (RAS) Weekly (ponds) Nitrate Daily (RAS) Weekly (ponds) Other water quality parameters Alkalinity Weekly (ponds) Where water source is low in alkalinity Phosphorus or phosphate Weekly (ponds) Secchi disk depth Daily to weekly (ponds) Indicator of plankton density Turbidity As required Suspended solids As required Salinity As required Fish Sample collection 1‐2 weekly Behaviour Each sampling Feeding activity, swimming behaviour etc. Appearance Each sampling Skin, eyes, fins, gills, colouration, markings, fin condition, shape of body etc. No. fish affected Each sampling No. of moribund fish, No. of dead fish, etc. No. fish sampled Each sampling Length of fish Each sampling Weight of fish Each sampling Parasite species observed Each sampling If cannot be identified, photograph and/or draw and describe size, appearance and behaviour. Location of parasites Each sampling body surface, gills, fins, internal organs on/in fish No. of parasites present Each sampling No. observed per field of view Action taken Each sampling What action was taken following inspection of fish (ie, treatments applied et.) Additional useful information Tank/pond volume, date filled, date stocked Source/Species/strain of fish stocked Length, weight and age at stocking, and Number fish stocked Feeding information (Feed type and feed rate etc) Chemicals added (type, amount and reason for addition)
Murray Cod Fish Health BMP 37
SOP 3 – Submission of fish samples for disease diagnosis
Laboratory services are often used in order to All specimens should be clearly labelled and gain a diagnosis where there are sick or dead submitted with the appropriate paperwork that fish. The general rule of thumb is the fresher the will detail: sample, the more likely a diagnosis can be ‐ Name, address and contact details of person reached. Preferably fish can be sent live in requesting the examination sufficient water in a secure container with ‐ Description of contents of the consignment oxygen added. If fish are freshly dead they can including species, numbers, and method of be sent on ice. Fish that have been dead for as preservation. little as 24 hours are unlikely to yield a diagnosis. Preferably a number of specimens ‐ A description of observations made should be submitted including moribund fish ‐ Nature of tests to be undertaken. and fish exhibiting different stages of the disease. Parasites are more easily isolated and Accurate diagnosis of a disease is largely identified when living. Despite fish arriving at a dependant on the quality of the specimens submitted for examination, and the laboratory in perfect condition, a diagnosis may still not be made. Most laboratories will charge accompanying documentation describing the for any work done unless prior arrangements event. The type of examination and tests that can be undertaken will also depend on the way have been made. Diagnostic work in fish can easily run to many hundreds of dollars so it is specimens are submitted. Live, freshly killed on preferable to submit good samples and have ice specimens should reach the laboratory within 24 hours of dispatch. discussions with your advisor or the laboratory prior to dispatch to discuss what testing will be Live specimens are preferred as they allow for done and an approximate cost. Some tests more flexibility in diagnosis options by the undertaken by the specialists may need prior specialist. Place the fish in a strong plastic bag notice. (or two). Ensure that sufficient packaging At this stage it is useful to have made some procedures are used that the fish will survive the transport period (24 hours). Consideration preliminary observations on the disease situation which can be discussed with the should be given to time in transit, number fish, specialist including: and volume of water and air/oxygen. • Species of fish and number of fish affected No more than half the volume of the container • Symptoms observed (fish behaviour, signs of should be water to ensure there is a sufficient disease etc) amount of air/oxygen above the water to maintain dissolved oxygen levels. Bags should • Prevailing environmental conditions (water be sealed to prevent air and water leakage and quality etc) containers should be insulated to reduce • Previous treatments undertaken. temperature changes. Often dead specimens are less useful because the rapid post‐mortem invasion of bacteria and degeneration of tissues reduce the usefulness of sample for virology, bacteriology and pathology. Some external parasites may quickly leave the fish soon after death. Dead fish should be placed in clean sealed plastic bags and placed in an esky containing crushed ice. Ensure that water leakage cannot occur.
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Table 4. Method of submission for diagnostic procedures
Diagnosis procedure Method of submission Live Freshly Frozen Preserved in killed on ice a fixative Gross examination YES YES YES YES Toxicology YES YES YES Parasitology YES YES Limited Limited Bacteriology YES YES Virology YES YES
Pathology YES YES YES
Send frozen samples as a last resort. The ability Fixative for preserving samples: to detect viruses, bacteria and parasites in these • 10% neutral buffered formalin in saline: samples is greatly reduced or impossible in • 100ml concentrated formalin (40% w/v many cases. Further, subsequent thawing of formaldehyde) samples causes cellular disruption which makes histopathology ineffective. Samples should be • 900 ml tap/distilled water sealed in clean plastic bags and snap frozen. • 4g NaOH2 PO4 H2O (if available) These samples can then be sent in an insulated container with crushed ice. Ensure that samples • 6g Na2 HPO4 (if available). will reach their destination before thawing occurs, and that leakage cannot occur. Submission of water samples for Samples may also be submitted in a preservative analysis such as formalin (see below). Formalin is a Specific recommendations for sample collection dangerous substance and care should be taken vary with the type of substance being measured when used. To ensure rapid preservation of and with how quickly the sample can be internal organs, slit open the body cavity of submitted for analysis. The laboratory should larger fish before placing into the preservative. be contacted prior to submitting the samples as Care should be taken to avoid damage to many have specific requirements on the type of internal organs. Ensure that excess preserving container to be used (some require that you use solution is used. The biomass of fish being their bottles) and methods of preservation and preserved should take up less than 15% of the shipment. Ideally, a clean polyethylene bottle volume of the preserving agent. It is prudent to should be used to collect the sample (except if preserve some fish even if live samples are being pesticide contamination is suspected when glass submitted as this is insurance against loss due to bottles are best). In urgent situations, a still delays in transport resulting in death and/or mineral water bottle may be used (if this is deterioration of live fish or samples sent on ice. acceptable to the laboratory). The water bottle Preservative containers must be leakproof and should be rinsed at least three times with the ideally made of non‐brittle plastic to avoid water to be sampled before filling to the top and breakage during transit. As a precaution seal sealing with a lid. The sample should then be the containers in bottles in plastic bags and chilled, frozen or preserved on the advice of the ensure adequate package is used to prevent laboratory, and submitted for analysis as soon as damage. possible.
Murray Cod Fish Health BMP 39
Sample volumes, storage and fixation for key water quality parameters Min. Preferred Short term storage (up Parameters sample vol. sampling Long term storage to 48 hrs) (mL) container Polyethylene or Filter and refrigerate Filter, and freeze (‐ Ammonia 25 borosilicate glass (4˚C) 20oC) Polyethylene or Filter and refrigerate Filter, add HgCl2 and Nitrite 50 borosilicate glass (4˚C) freeze Polyethylene or Filter and refrigerate Filter, acidify (pH<2) Nitrate 50 borosilicate glass (4˚C) and freeze Dissolved reactive Polyethylene or Filter and refrigerate Filter, add HgCl2 and 25 phosphorus borosilicate glass (4˚C) freeze Polyethylene or Filter and refrigerate Filter, acidify (pH<2) Heavy metals 50 borosilicate glass (4˚C) and freeze Polyethylene or Filter and refrigerate Filter and refrigerate Alkalinity 100 borosilicate glass (4˚C) (4˚C) Polyethylene or Filter, acidify (pH<2) Hardness 25 Refrigerate (4˚C) borosilicate glass and freeze amber glass Acidify (ph<2) and Pesticides 1000 Refrigerate (4˚C) bottles refrigerate Polyethylene or Acidify and refrigerate COD 1000 Freeze borosilicate glass (4˚C) Polyethylene or BOD 1000 Refrigerate (4˚C) borosilicate glass pH N/A, analyse immediately on‐site Dissolved oxygen N/A, analyse immediately on‐site Temperature N/A, analyse immediately on‐site Total dissolved Polyethylene or 5000 Refrigerate (4˚C) solids TDS borosilicate glass Polyethylene or Suspended solids 5000 Refrigerate (4˚C) borosilicate glass Polyethylene or Filter, and freeze Chlorophylls 1000 Refrigerate (4˚C) borosilicate glass residue (‐20oC)
Key references Federation (WEF). http://www.standardmethods.org/ Australia/New Zealand Standard (1998). Water quality—Sampling Part 1: Guidance on the design of Stirling, H.P. ed. (1999). Chemical and Biological sampling programs, sampling techniques and the Methods of Water Analysis for Aquaculturists, preservation and handling of samples (AS/NZ Pisces Press Ltd, Stirling. 119 pp. 5667.1:1998). Standards Australia and Standards
New Zealand (http://infostore.saiglobal.com/store/Details.aspx ?ProductID=387165). Standard Methods for the Examination of Water and Wastewater, is a joint publication of the American Public Health Association (APHA), the American Water Works Association (AWWA), and the Water Environment
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SOP 4 ‐ Husbandry of captive fish
This SOP aims to provide basic guidelines for handling, noise, confinement, abrasion, maintenance of fish in captivity. Management increased density, light intensity, and rapid of farm facilities should aim to maintain fish in changes or reductions in water quality good health. (particularly temperature), oxygen, pH and ammonia levels. The ability of fish to cope with Minimise stress the stress of transport will depend on the fish’s state of health, species, age, sex, stocking Stress is essentially a state resulting from density, period without food, the duration of the environmental conditions that threaten survival, trip, the mode of transport, and water quality. impair feeding, growth, reproduction or other During transport, stress can be minimized by aspects of the normal performance, physiology and activity of an animal. In fish, the adrenergic • The appropriate size, design and system and the hypothalamic‐pituitary‐ construction of transport containers interregnal axis mediate hormonal actions • Maintenance of good water quality, stimulated by abnormal deviations in their appropriate for the fish being transported environment (stressors). • Limiting exposure to extremes of, or rapid variation in, environmental conditions Stocking density including temperature, water quality, noise, High densities of fish in tanks, ponds or cages visual disturbance (light), and vibration can lead to increased stress in fish (independent • Administering anaesthetics/sedatives, if of any affects on water quality). In some appropriate, prior to handling. The addition circumstances, however, normal territorial or of NaCl (5 g/l) to the transport water can antagonistic behaviours among fish may become held to reduce stress and osmoregulatory suppressed under conditions of high stocking dysfunction as well as control some densities, leading to lower stress levels. parasites Stocking densities should be adjusted to • The regular inspection and monitoring of minimise stress levels. conditions in the transport vessels. These can be accomplished by careful planning Size variation of stocking densities, times of loading and Grade fish to reduce size variation and maintain transport, withholding of food prior to densities (see table 5) to reduce stress associated transport, the use of well‐insulated, clean and with under‐crowding and over‐crowding. well‐maintained transport containers, effective Increasing stocking densities may reduce the aeration systems including the pure oxygen, and ability of fish to establish territories and thereby the use of wet loading and unloading methods reduce the impacts of territoriality and where possible. Staff should be trained in the aggression. Where possible, remove obvious maintenance and use of all equipment cannibals and dominant individuals. Predation associated with the transport, and be familiar and aggression towards other fish may also be with the tolerances of the species being reduced by feeding sate appetite. transported. For longer trips, transport facilities Juveniles (fry and fingerlings) may require should include the capability to monitor critical grading as frequently as once every 2 weeks. water quality parameters to detect adverse As fish grow the need to grade will reduced trends before fish health is compromised. When from once every 1‐3 months for yearlings transferring fish from transport equipment to (stockers) to once every 3‐6 months for fish holding facilities, investigators and researchers approaching market size. need to ensure that water quality (ph, ammonia etc) and temperature are the same. Transferring fish between farms and culture units Fish are particularly susceptible to stress during transport because of the potential effects of
Murray Cod Fish Health BMP 41
Table 5. Stocking densities
Fish Density size age (g)
Periodic or no Constant aeration Oxygen‐injected water (tanks in RAS only) aeration (ponds & cages in ponds)
<5 Ponds <35 fish/m2 2‐10 kg/m3 5‐50 kg/m3 Tanks
5‐100 ‐‐‐ 20‐80 kg/m3 30‐150 kg/m3
>100 10‐50 kg/m3 (cages & 20‐80 kg/m3 (cages & 30‐150 kg/m3 tanks) tanks) 0.6‐1.2 kg/m2 (ponds) 0.6‐1.2 kg/m2 (ponds)
Data presented above is tentative and requires validation.
Where ever possible: Nutrition and feeding • Use feeds that are specifically formulated for Diets used in aquaculture range from live prey Murray cod. As a guide, the following diet to artificial, manufactured pellets. Early life formulation was developed for grow‐out of stages of Murray cod, larvae and fry, are initially Murray cod reared on live food. In the hatchery, larvae are offered newly hatched Artemia nauplii at the Grow‐out onset of feeding, while in fry rearing ponds, De Silva et al. 2004 juvenile Murray cod fry and fingerlings prey on zooplankton, especially copepods and Moisture (%) 6.9 cladocerans, and aquatic insects, especially Protein (%) 49.1 chironomids. Murray cod fingerlings, once Lipid (%) 16.1 harvested from fry rearing ponds, are weaned onto artificial diets. Ash (%) 10.4 Energy (kJ/g) 20.9 Food suitable for the Murray cod should be provided to maintain good health and growth. • Use appropriate feed rates for age and Sufficient feed should be provided to sate all fish conditions under which Murray cod are in the culture unit. Food should be of high being reared quality and free from contamination. Diets • Store feed appropriately to avoid should be complete and balanced and food contamination, and rancidity. All fresh and items provided in quantities necessary for dry feeds should be kept in suitable storage growth and the maintenance of healthy body areas (temperature, humidity and vermin condition. proof) to ensure nutritional value is Currently, there are no commercially available sustained. Coolrooms, fridges and freezers artificial diets specifically formulated for should maintain the appropriate Murray cod. Farmers are therefore using temperature for products used for food for commercial extruded salmonid (rainbow trout fish in captivity. Commercial feeds should or Atlantic salmon) and/or barramundi diets for be stored according to manufacturer’s various stages of production of Murray cod. instructions. Both floating and sinking pellets are being used. Feed rates vary depending on size of fish and culture water temperature. Food conversion ratios of between 1.2 and 1.5 are being attained.
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Maintenance of water quality Water is a vital component for fish. Holding facilities should provide water of adequate quality and quantity. Water quality parameters that most commonly cause fish health problems include: • Dissolved gases particularly dissolved oxygen. Other gases that may be important include carbon dioxide; chlorine; hydrogen sulphide; methane and nitrogen • Metabolic waste products particularly ammonia and nitrite • Other important parameters pH, temperature, heavy metals, water hardness, osmolarity and salinity • Water‐borne contaminants and other problems toxic organic compounds, biocides, noxious algae, weather. Appendix 5 summarises the water quality guidelines for the protection of cultured freshwater fish.
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SOP 5 – Use of Chemicals
drugs must be done under the supervision of a Drug and chemical management qualified veterinarian, and should be confined Aquaculturists should only use chemicals and to emergency situations only. In extreme drugs that are either registered for use by the bacterial disease outbreaks, it may be necessary Australian Pesticides and Veterinary Medicines to destroy infected stock and eliminate the Authority (APVMA) responsible pathogens by sterilisation of ponds, (http://www.apvma.gov.au), covered by a tanks and equipment. APVMA Minor Use Permit or are exempt from Use of antibiotics to treat diseases should be registration. Often, use of registered chemicals, undertaken with extreme caution as bacteria and chemicals covered by minor use permits have the ability to develop and transfer drug should be used under the direction of a resistance. The occurrence of multiple antibiotic registered veterinarian. resistances by bacterial fish pathogens is Chemicals, therapeutics and medicines should becoming more evident in farmed fish, be stored in dry facilities to avoid degradation of especially in areas where antibiotics are widely the substances or their packaging. Stores should and indiscriminately used. Fortunately, as the be secured to stop access by foraging animals fish farming industry has grown, effective and unauthorised personnel. vaccines are being developed for some bacterial pathogens and fish species, and are becoming More background on chemical use was covered more readily available to replace the use of in the BMP on page 18. antibiotics for control of bacterial diseases. In open pond Murray cod systems, consideration must be given to the effects of Salt chemical treatments used to treat fish diseases Salt (sodium chloride, NaCl) is effective in on the subsequent use of that water. Murray controlling some external bacterial, fungal and cod may be farmed in water, such as on‐farm ectoparasitic diseases in freshwater fish. irrigation dams, that is subsequently used for Treatment concentrations range from 3–10 g/L crop irrigation and stock watering purposes. for 30–60 minutes depending on species and Factors to consider include: age. Salt increases production of mucus and is • The chemical being used thought to promote the healing of damaged skin • Concentration of the chemical and gill tissues. Salt also helps to reduce stress • The chemical breakdown rate as it acts as a mild sedative and may benefit osmo‐regulation. Iodised table salt should not • Time between chemical treatment and use of be used. Due to the relatively large quantities of water for other purposes. salt that are required to treat fish diseases, its use is confined to intensive systems. Salt is State ‘Control of Use’ Legislation generally safe and easy to use; however, it is not Chemicals and drugs used in aquaculture are registered for use as a therapeutic in aquaculture covered by the relevant state legislation. by the APVMA. Contacts for all states are provided in Appendix 5 should more information be required. The Formalin APVMA website and state department of Formalin (37% by weight formaldehyde) is used agriculture websites provide detailed extensively throughout the aquaculture industry information on using chemicals. as a treatment of certain diseases in aquaculture, especially external bacterial, fungal, protozoan Anti‐microbials (anti‐biotics) and metazoan diseases. Formalin is registered Bacterial diseases are commonly treated with under a minor use permit for native finfish. antimicrobial agents (antibiotics). Currently, High concentrations are used to treat fungal however, there are no antimicrobial agents infections on eggs. Since formalin is a known registered for use on aquaculture fish in carcinogen and formaldehyde is a noxious gas, Australia. Regardless, use of these restricted this chemical should be handled with caution
Murray Cod Fish Health BMP 44
and used according to the supplier’s Treatment in static ponds instructions. To treat fish in a static pond, the chemical/ drug Treating ponds with formalin can cause a is made up into a concentrated solution. The substantial decline in both dissolved oxygen dose rate for the static pond is calculated (each 5 mg/L formalin removes 1 mg/L according to volume of the pond being treated, dissolved oxygen) and pH within 36‐42 h of species and size of fish being treated. The treatment, which may stress the fish being appropriate amount of the drug is then diluted treated. Continuous aeration should be into 100 L of water which is held in a treatment undertaken for a least three days following tank mounted on a trailer. treatment. DO, ph, and ammonia should be monitored for at least three days after treatment. Treatment commences when the concentrated Formalin toxicity increases with increasing solution is applied to the pond. This is done using a pump and spray bar. The treatment is temperature but is not affected by pH. Sometimes a white/cloudy precipitate, known as applied as the trailer is driven around the paraformaldehyde, develops in formalin that perimeter of the pond. has been stored for long periods or been To ensure the treatment is mixed into the static exposed to cold temperatures. pond, aeration devices are activated (e.g. paddle Paraformaldehyde is highly toxic to fish and wheels). The operation of the aeration devices should not be used in treatments. To remove also ensures an adequate oxygen supply to the paraformaldehyde, decant the clear formalin fihs during the treatemtn period. into another container and discard the remaining precipitate. Once the treatment phase has elapsed, a sample fish should be selected to determine Treatment in tanks effectiveness of the treatment. When treating animals in tanks, the water must The trailer mounted treatment tank should be be well aerated and well oxygenated and flushed with clean water for at least 30 minutes sufficient water must be available so that the to remove all traces of chemicals/drugs. tank can be filled with clean aerated water when As most chemical are hazardous all operators the treatment has ended. must abide by the safety instructions detailed in Water flow to the tanks must be stopped during the relevant MSD sheets. the treatment phase. Once the water flow has stopped the chemical/ drug is added to the Treatment in cages water at the required dose rate. Date rates are Procedure yet to be finalised. calculated according to the volume of water in the treatment tank and the species and size of Training and Supervision fish being treated. The treatment commences when the chemical is added to the tank. The described procedures are reliable, manageable and routinely applied by trained During the treatment phase, both fish health and staff. However a high level of training, expertise water quality must be monitored. The and practice is required to cover all aspects of monitoring required will depend on the nature the procedures, disease identification, of the chemical, but will usually consist of determining the appropriate treatment protocols monitoring dissolved oxygen and salinity (if a and calculating dose rates. Trained staff under salt is applied). Monitoring of fish health should supervision may undertake most components of be continuous during the treatment phase and the task. In some cases, treatments may need to treated fish should not be left unattended. be undertaken or overseen by a registered Once the treatment period has elapsed, the veterinarian. treatment tanks should be flushed with clean, fresh water. A sample fish should be selected Fish sedation and anaethesia and observed to determine the effectiveness of Anaesthetics the treatment Two chemicals have been registered for use as As most chemical are hazardous all operators anaesthetics in aquaculture, Aqui‐S and must abide by the safety instructions detailed in benzocaine (http://www.apvmqa.gov.au/). Dose the relevant MSD sheets, rates for both chemicals depend on the size of fish and level of sedation required. Use of these
Murray Cod Fish Health BMP 45
chemicals should follow the instructions Procedure provided by the supplier. These drugs are administered through the water and are taken 1) Induction of Anaesthesia up across the gills. Exposure time should be To minimise stress and potential injury, fish to minimised where possible to avoid death from be anaesthetised are held in aerated holding over exposure. tanks or fish bins at normal stocking rates. Fish should not be fed immediately prior to It is important to handle fish as gently as possible to preserve the surface mucous coating anaesthesia. and the integrity of the integument, and to The fish are quickly netted and transferred to prevent any damage that may occur, for the fish bin or bucket containing the correct example, to the eyes. At times, fish need to be working concentration of anaesthetic. (both handled for such as, harvesting, measurement benzocaine and MS222 have induction times of 1 (size and weight), transferring between culture to 3 minutes and a recovery time of 3–15 units on farm, transport to other farms and minutes). Fish may initially show signs of breeding. Handling of fish is always stressful, hyperactivity as a response to the drug. and may lead to lowered immune function and subsequent increased risk of infectious disease. Dose rates for anaesthetic agents should reflect Thus, for certain procedures, especially with recommended treatments provided by the larger fish, sedation or anaesthesia is required to suppliers (i.e. information booklets). General minimise this stress and physical damage. recommendations for dose rates are not appropriate, as there is a wide range according Only use chemicals and drugs that are to species, and even within species dose rates registered through the APVMA, and/or vary with water temperature. For example, rates approved for use by a registered veterinarian of 0.04–0.120 g.L‐1 for Eugenol (Aqui‐S) and (by prescription), who takes responsibility for 0.05–0.2 g.L‐1 for MS‐222 are suggested. any problems or issues that may arise from the prescribed use. 2) Monitoring Oxygen levels need to be maintained during Materials and Equipment anaesthetic procedures. In large tanks or fish Ensure that when using chemicals and drugs the pens, this may be achieved by aeration or appropriate operator protection equipment, bubbling pure oxygen from a gas cylinder such as protective overalls, gloves and face directly into the treatment water. Fish condition mask, is used (as specified in MSD sheets for the needs to be monitored closely while under anaesthetic agent being used). anaesthesia, for example, opercula movement should be regular, flaring of opercula may Fish handling and associated equipment. Fish indicate over exposure and immediate steps bin or bucket (suitable volume for size of fish), should be taken to recover the animal. Fish net, Oxygenation/aeration, Clean water (at same water temperature as with source of fish). Fish are to be handled as quickly and as efficiently as possible. Anaesthetic agent: Measuring equipment for anaesthetic agent (e.g. measuring cylinder, 3) Recovery graduated pipette or syringe). Fish are removed from anaesthetic treatment Post‐Operative Recovery. Fish bin or tank and placed in clean, well aerated water. Fish are containing clean aerated/oxygenated water, or monitored until they have returned to a normal flow‐through holding tank. Aeration state and reflexes return. Initial recovery should equipment, including gas cylinder containing be quick (i.e. a few seconds to a few minutes). oxygen or air blower (depending on number of Full recovery may take several minutes or fish and length of time under sedation) and longer depending on species and drug used. In diffusers (i.e. airstones). some cases, assisting with the “swimming” of fish to increase ventilation of the gills may facilitate recovery from deep anaesthesia.
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Stages of anaesthesia in fish. Stage Plane Description Physiological and Behavioural Signs I 1 Light sedation Responsive to stimuli but motion reduced, ventilation decreased 2 Deep sedation As above, some analgesia, only receptive to gross stimulation II 1 Light anaesthesia Partial loss of equilibrium. Good analgesia 2 Deeper anaesthesia Total loss of muscle tone, total loss of equilibrium, ventilation almost absent III Surgical anaesthesia As above: total loss of reaction to even massive stimulation IV Medullary collapse Ventilation ceases, cardiac arrest, eventual death. Overdose.
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Appendix 1 ‐ Useful published resources and internet sites
Ho, H.K., Rourke, M.L., Bravington, W., General aquaculture McPartlan, H. and Ingram, B.A. (2008). Genetic Boyd, C. (2000). Water Quality: an introduction. and reproduction technologies for enhanced Kluwer Academic Publishers, Dordecht, the aquaculture and fisheries management of Netherlands. Murray cod. Aquaculture Asia 13 (1 (Jan‐Mar)): 15‐21. Boyd, C. and Tucker, C.S. (1998). Pond aquaculture water quality management. Kluwer Ingram, B.A. and De Silva, S.S. eds. (2004). Academic Publishers, Dordecht, the Development of Intensive Commercial Aquaculture Netherlands. Production Technology for Murray cod. Final Report to the Fisheries Research and Brune, D.E. and Tomasso, J.R. (Eds.) (1991). Development Corporation (Project No. Aquaculture and Water Quality. The World 1999/328). Primary Industries Research Victoria, Aquaculture Society, Baton Rouge. 606 pp. DPI, Alexandra, Victoria, Australia. 202 pp. De Silva, S.S. and Anderson, T.A. (1995). Fish Ingram, B.A., De Silva, S.S. and Gooley, G.J. Nutrition in Aquaculture. Chapman and Hall, (2005). The Australian Murray cod ‐ A new Melbourne. 319 pp. candidate for intensive production systems. Goddard, S. (1996). Feed Management in Intensive World Aquaculture 36 (3): 37‐43 and 69. Aquaculture. Chapman and Hall, New York. Ingram, B.A., Gavine, F. and Lawson, P. (2005). 194 pp. Fish Health Management Guidelines for Farmed Piper, R.G., McElwain, I.B., Orme, L.E., Murray Cod. Fisheries Victoria, Technical Report McCraren, J.P., Fowler, L.G. and Leonard, J.R. Series No. 32, Alexandra, VIC. 56 pp. (1998). Fish Hatchery Management. US Ingram, B.A., McPartlan, H., Ho, H.K., Rourke, Department of the Interior, Fish and Wildlife M. and Bravington, W. (2007). Final Report for Service, Washington, D.C. 517 pp. Project 05194: High Value Aquaculture in Shepherd, J. and Bromage, N. eds. (1988). Sustainable Rural Landscapes. Our Rural Intensive Fish Farming, BSP Professional Books, Landscape. Sustainable Development Through Oxford. 404 pp. Innovation. Department of Primary Industries, Melbourne. 27 pp.
Rowland, S.J. (2005). Overview of the history, World Aquaculture Society: fishery, biology and aquaculture of Murray cod https://www.was.org/main/Default.asp (Maccullochella peelii peelii). In: Management of Network of Aquaculture Centres Asia‐Pacific: Murray cod in the Murray‐Darling Basin. http://www.enaca.org/ Statement, recommendations and supporting papers (Workshop held in Canberra, 3‐4 June 2004) (Lintermans, M. and Phillips, B. eds.), pp. 38‐61. Murray‐Darling Basin Commission, Murray cod aquaculture Canberra. Gooley, G.J., Bailey, M., Abery, N.W., Bretherton, M.J. and Gavine, F. (2007). Final Report for Project 05190: Multi Water‐Use in Murray cod aquaculture research in Victoria. Agricultural Landscapes. Our Rural Landscape. http://www.dpi.vic.gov.au/fisheries/aquaculture Sustainable Development Through Innovation. /murray‐cod‐aquaculture‐research Department of Primary Industries, Melbourne.
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Fish health purpose, and how to administer them. Interactive Disease Diagnostic Center designed Austin, B. and Austin, D.A. (1993). Bacterial Fish to help determine the illness affecting fish. Pathogens. Disease in Farmed and Wild Fish. Ellis http://www.fish‐disease.com/fish‐disease.htm Horwood Ltd., New York. 384 pp. Microscope Diagnosis of common parasite Eiras, J., Segner, H. and Wahli, T. eds. (2008). infections of fish. Fish Diseases (Vol. 1 & 2). Science Publishers. http://www.ntlabs.co.uk/microscope_diagnosis. 1340 pp. htm Iwama, G.K., Pickering, A.D., Sumpter, J.P. and Aquatic Disease. A Veterinary Medical Primer. Schreck, C.B. (Eds.) (1997). Fish Stress and Health http://www.athiel.com/Lib10/drj4.htm in Aquaculture. Society for Experimental Biology Seminar Series 62. Cambridge University Press, A broad range of fish health topics. Cambridge. 278 pp. http://www.koivet.com/ Leatherland, J.F. and Woo, P.T.K. eds. (1998). Freshwater Fish Parasites Fish Diseases and Disorders. Volume 2. Non‐ http://www.aces.edu/dept/fisheries/education/ra infectious Disorders, CAB International, New s/publications/Update/Introduction%20to%20Fr York. 400 pp. eshwater%20Fish%20Parasites.pdf MacMillan, J.R. (1991). Biological factors Fish Necropsy Document: impinging upon control of external protozoan http://fishdata.siu.edu/vet/necropsy.pdf fish parasites. Annual Review of Fish Diseases: 119‐ Water Calculations: 131. http://www.indianafishfarming.com/images/stor Noga, E.J. (2000). Fish Disease Diagnosis and ies/Workshops/WaterQuality/File%203A%20Cal Treatment. Iowa State University, Ames, Iowa. culating%20Area%20Volume.pdf 367 pp. Water Quality: Paperna, I. (1991). Diseases caused by parasites http://www.indianafishfarming.com/images/stor in the aquaculture of warm water fish. Annual ies/Workshops/WaterQuality/File%203B%20Wat Review of Fish Diseases: 155‐194. er%20Quality.pdf Read, P., Landos, M., Rowland, S. and Mifsud, Oxygen in Water: C. (2007). Diagnosis, Treatment and Prevention http://www.indianafishfarming.com/images/stor of Diseases of the Australian Freshwater Fish ies/Workshops/WaterQuality/File%203C%20Dis Silver Perch (Bidyanus bidyanus). NSW solved%20Oxygen.pdf Department of Primary Industries. 81 pp. Aquaculture (USA based but still lots of good Schlotfield, H.‐J. and Alderman, D.J. (1995). info): What Should I do? A Practical Guide for the http://www.indianafishfarming.com/index.php? Fresh Water Fish Farmer. Supplement to Bulletin option=com_content&view=frontpage&Itemid=1 of the European Association of Fish Pathologists Understanding Water Reports: 15(4): 60 pp. http://www.chemone.com/default/copper%20sul Woo, P.T.K. ed. (2006). Fish Diseases and fate%20phosphate%20issue.pdf Disorders. Volume 1. Protozoan and Metazoan
Infections, CAB International, New York. 800 pp. Federal Government Woo, P.T.K. and Bruno, D.W. eds. (2010). Fish Aquaplan. Australiaʹs National Strategic Plan for Diseases and Disorders. Volume 3. Viral, Aquatic Animal Health 1998‐2003. National Office Bacterial and Fungal Infections, CAB of Animal and Plant Health, Agriculture, International, New York. 1000 pp. Fisheries and Forestry ‐ Australia, Canberra. 33 pp. www.affa.gov.au. FINS: The Fish Information Service. Fish Disease Diagnosis. Australian Pesticides and Veterinary Medicines http://fins.actwin.com/disease/chart1.php Authority (APVMA). Lists information on drugs and chemicals registered for use in Fish‐Disease.com. Information on nearly 70 aquaculture in Australia. different diseases and over 200 different http://www.apvma.gov.au/ Medications, their active ingredients, their
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Australian and New Zealand Guidelines for State Government Fresh and Marine Water Quality. Water quality Fisheries Victoria, Department of Primary guidelines for the protection of cultured fish, Industries. http://www.dpi.vic.gov.au/fisheries molluscs and crustaceans. http://www.mincos.gov.au/publications/australi Primary Industries and Fisheries, Queensland. an_and_new_zealand_guidelines_for_fresh_and http://www.dpi.qld.gov.au _marine_water_quality Primary Industries, NSW. Disease Watch. latest information on training http://www.dpi.nsw.gov.au/fisheries and awareness resources for aquatic animal disease emergencies. http://www.disease‐ watch.com
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Appendix 2 – Parasites, diseases and health problems reported from farmed Murray cod
Parasite, disease, syndrome Culture system Fish size Body tissue References affected Viruses Megalocytivirus (Hypertrophy iridovirus) RAS Juveniles Internal organs Lancaster et al. (2003), Go et al. (2006), Go & Whittington (2006) Bacteria Aeromonas schubertii Body surface & gills DPI, Attwood (M. Forsyth) Aeromonas sobria (HG7 {7}) Body surface & gills DPI, Attwood (M. Forsyth) Vibrio spp. Body surface, gills DPI, Attwood (M. Forsyth) & kidney Edwardsiella tarda Tanks (RAS) Sub‐adults kidney Matt Landos (pers comm.) Fungi Saprolegnia, & Achlya (Oomycete fungi) Tanks (RAS) All life stages Body surface & gills Rowland and Ingram (1991)
Epizootic ulcerative syndrome (EUS) Cages Juveniles & sub‐ (Aphanomyces) adults Murray
Cod
Fish
Health 51
52 Murray Parasite, disease, syndrome Culture system Fish size Body tissue References
affected Protozoa
Cod Chilodonella piscicola (= C. cyprini) Tanks Larvae, juveniles & Gills Ashburner and Ehl (1973)
Fish adults Chilodonella hexasticha Tanks (RAS), ponds Larvae, juveniles & Body surface & gills Rowland & Ingram (1991)
Health & cages adults Cryptosporidium molnari Juveniles & sub‐ Stomach Baragahare et al. (2011)
adults Goussia lomi Tanks Juveniles Mucosa of intestine Molnar & Rohde (1988), Philbey & Ingram (1991)
Ichthyobodo necator (= Costia necatrix) Tanks (RAS) & Larvae, juveniles & Body surface & gills Rowland & Ingram (1991) ponds adults Ichthyophthirius multifiliis (white spot) Tanks (RAS) & Larvae, juveniles & Body surface & gills Rowland & Ingram (1991) ponds adults
Parasite, disease, syndrome Culture system Fish size Body tissue References affected Myxosoma Ponds Juveniles & adults Gills Ashburner (1978) Sessile peritrichs Tanks (RAS) Juveniles & sub‐ Body surface & gills Halliday & Collins (2002), Ingram et al. (2005), Matt (including Ambiphrya & Epistylus) adults Landos (pers comm.) Tetrahymena Tanks (RAS) Larva, juveniles & Body surface & gills Rowland & Ingram (1991), Matt Landos (pers comm.) sub‐adults Trichodina Tanks ponds & Larvae, juveniles & Body surface & gills Rowland & Ingram (1991) cages adults Gill amoeba Tanks (RAS) Gills Matt Landos (pers comm.) Metazoa Clinostomum complanatum ponds Juveniles Body cavity & eye Anon (2001) Dermoergasilus intermedius Ponds & cages Gills Kabata (1992), Ingram & Philbey (1999) M. Lancaster (pers comm.)
Lernaea sp. Ponds & cages Juveniles & adults Body surface Ashburner (1978), Rowland and Ingram (1991) Histiostoma papillata Tanks (RAS) Juveniles Body surface & gills Halliday and Collins (2002) Hydrozetes sp. Tanks (RAS) Juveniles Body surface D. Walters (pers comm.) in Halliday & Collins (2002)
Other conditions Fatty liver syndrome Tanks (RAS) Juveniles & sub‐ Liver Ingram et al. (2005) adults Chronic ulcerative dermatopathy (CUD) Tanks (RAS) Juveniles & adults Body surface Humphrey et al. (2000), Trott (2000), Baily (2003), Baily et al. (2005), Schultz et al. (2008), Schultz et al. (2011) Blue‐sac syndrome Tanks Eggs and larvae Eggs and larvae Gunasekera et al. (1998) Murray
Gas bubble disease Tanks Larvae, juveniles & Gills, eyes and fins Ingram et al. (2005)
adults Cod Enteritis Tanks (RAS) Guts Matt Landos (pers comm.)
Fish Cannibalism & aggression Tanks (RAS), ponds Juveniles, sub‐adults Ingram et al. (2005)
& cages & adults Health 53
Appendix 3 – Notifiable and reportable fish diseases
Within Australia, lists of notifiable or reportable provided in Appendix 5. Where a registered fish diseases are defined by each state (see table veterinarian is notified by a farmer of a below). In Victoria notifiable diseases for notifiable disease, in most cases the duty of aquatic animals are listed under the Livestock responsibility for notification to government Disease Control Act 1995. The simple message falls to the veterinarian. from notifiable disease legislation across all In summary, this means that the state states is that if a farmer suspects a notifiable government must be notified of an outbreak of disease they must notify the relevant state body. any disease as listed below. Contacts for Victoria, NSW and QLD are Notifiable and reportable fish diseases Disease Department of NSW QLD VICTORIA Agriculture, Fisheries & Forestry (DAFF) Epizootic haematopoietic necrosis (EHN) virus1* Reportable Declared Notifiable EHN – European catfish virus / European sheatfish Reportable Declared Notifiable virus Infectious haematopoietic necrosis Reportable Declared Notifiable Spring viraemia of carp Reportable Declared Notifiable Viral haemorrhagic septicaemia Reportable Declared Notifiable Channel catfish virus diseases Reportable Declared Notifiable Viral encephalopathy and retinopathy1 Reportable Declared Notifiable Infectious pancreatic necrosis Reportable Declared Notifiable Infectious salmon anaemia Reportable Declared Notifiable Epizootic ulcerative syndrome (EUS) (Aphanomyces Reportable Declared Notifiable invaderis)1 Bacterial kidney disease (Renibacterium Reportable Declared Notifiable salmoninarum) Enteric septicaemia of catfish (Edwardsiella ictaluri)1 Reportable Declared Notifiable Piscirickettsiosis (Piscirickettsia salmonis) Reportable Declared Notifiable Gyrodactylosis (Gyrodactylus salaris) Reportable Declared Notifiable Red sea bream iridoviral disease Reportable Declared Notifiable Furunculosis (Aeromonas salmonicida subsp. Reportable Declared Notifiable salmonicida) Aeromonas salmonicida (atypical strains) (GUD)1* Reportable Declared Notifiable Whirling disease (Myxobolus cerebralis) Reportable Declared Notifiable Enteric redmouth diesease (Yersinia ruckeri – Reportable Declared Notifiable Hagerman strain) Koi herpesvirus disease Reportable Declared Notifiable Grouper iridoviral disease Reportable Declared Notifiable ISKNV‐like viruses Reportable Koi mass mortality Notifiable DAFF: http://www.daff.gov.au/animal‐plant‐health/aquatic/reporting Victoria: http://www.dpi.vic.gov.au/agriculture/pests‐diseases‐and‐weeds/animal‐diseases/notifiable‐diseases2/list NSW: Fisheries Management Act 1994 No 38 (Version 1 Nov 2011) 1. Recorded from Australia but restricted to some areas. * Murray cod experimentally infected in laboratory trials only
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Appendix 4 – Calculation of unionised ammonia
The following table (after Emerson et al. 1975) is used to calculate the amount of ammonia in freshwater that is in the toxic unionised form. When water temperature is 28 °C and pH is 7.2, from the table below the percentage of total ammonia nitrogen (TAN) present in the unionised form is 1.10%. Therefore, if the concentration of TAN was 5.0 mg/L, then the amount of unionised ammonia present is: 5.0 x 1.10% = 0.055 mg/L
pH Temperature (oC) 12 14 16 18 20 22 24 26 28 30 5.6 0.009 0.010 0.012 0.014 0.016 0.018 0.021 0.02 0.03 0.03 5.8 0.014 0.016 0.019 0.022 0.03 0.03 0.03 0.04 0.04 0.05 6 0.022 0.03 0.03 0.03 0.04 0.05 0.05 0.06 0.07 0.08 6.2 0.03 0.04 0.05 0.05 0.06 0.07 0.08 0.10 0.11 0.13 6.4 0.05 0.06 0.07 0.09 0.10 0.12 0.13 0.15 0.18 0.20 6.6 0.09 0.10 0.12 0.14 0.16 0.18 0.21 0.24 0.28 0.32 6.8 0.14 0.16 0.19 0.22 0.25 0.29 0.33 0.38 0.44 0.51 7 0.22 0.25 0.29 0.34 0.40 0.46 0.53 0.61 0.70 0.80 7.2 0.34 0.40 0.47 0.54 0.63 0.72 0.83 0.96 1.10 1.26 7.4 0.54 0.63 0.74 0.85 0.99 1.14 1.31 1.51 1.73 1.98 7.6 0.86 1.00 1.16 1.35 1.56 1.80 2.07 2.37 2.72 3.11 7.8 1.36 1.58 1.83 2.12 2.45 2.82 3.24 3.71 4.24 4.84 8 2.13 2.48 2.87 3.31 3.82 4.39 5.03 5.75 6.56 7.46 8.2 3.34 3.87 4.47 5.15 5.92 6.79 7.75 8.82 10.01 11.32 8.4 5.18 5.99 6.91 7.93 9.07 10.34 11.75 13.30 14.99 16.83 8.6 7.98 9.18 10.52 12.01 13.65 15.46 17.43 19.55 21.84 24.28 8.8 12.08 13.80 15.71 17.78 20.04 22.47 25.06 27.81 30.70 33.70 9 17.88 20.24 22.80 25.53 28.43 31.48 34.64 37.91 41.25 44.62 9.2 25.65 28.69 31.88 35.21 38.63 42.13 45.66 49.18 52.67 56.08 9.4 35.35 38.93 42.59 46.27 49.94 53.57 57.11 60.53 63.81 66.93 9.6 46.43 50.26 54.04 57.71 61.26 64.65 67.85 70.85 73.65 76.23 9.8 57.87 61.56 65.07 68.39 71.48 74.35 76.98 79.39 81.58 83.56 10 68.52 71.74 74.70 77.42 79.89 82.12 84.13 85.93 87.53 88.96
Emerson, K., Russo, R.C., Lund, R.E. and Thurston, R.V. (1975). Aqueous ammonia equilibrium calculations: effect of pH and temperature. Journal of the Fisheries Research Board of Canada 32: 2379‐ 2383.
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Appendix 5 – Water quality guidelines for the protection of cultured freshwater fish
Information presented in the table below is a summary of recommended water quality guidelines for the culture of freshwater fish, from Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Chapter 4. Primary Industries (http://www.mincos.gov.au/publications/australian_and_new_zealand_guidelines_for_fresh_and_marine _water_quality ). Note that these values presented do not apply equally to all situations, locations and species.
Category Parameter Guideline for continuous exposure (mg/L) unless specified
Physico‐chemical Alkalinity >20 indicators Biochemical oxygen demand (BOD) <15 Chemical oxygen demand (COD) <40 Carbon dioxide <10 Colour and appearance of water 30‐40 Dissolved oxygen >5 Gas supersaturation <100% pH 5.0‐9.0 Suspended solids (and turbidity) <40 Temperature <2.0oC change over 1 hour Total hardness (CaCO3) 20‐100 Salinity (total dissolved solids) <3000
Inorganic chemicals Aluminium <0.03 (pH>6.5), <0.01 (pH <6.5) (heavy metals and others) Ammonia (un‐ionised) <0.3 warm freshwater Ammonia (TAN) <1.0 Arsenic <0.05 Cadmium <0.0002‐0.0018 Chlorine <0.003 Chromium <0.02 Copper <0.005 Cyanide <0.005 Hydrogen sulfide <0.001 Iron <0.01 Lead <0.001 Magnesium <15 Manganese <0.01 Mercury <0.001 Nickel <0.1 Nitrate (NO3‐) <50 Nitrite (NO2) <0.1 Phosphates <0.1 Selenium <0.01 Silver <0.003
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Category Parameter Guideline for continuous exposure (mg/L) unless specified
Inorganic chemicals Tributyltin <0.000026 (heavy metals and others) Vanadium <0.1 Zinc <0.005
Organic chemicals Detergents and surfactants <0.28 (LAS) (nonpesticides) <0.65 (AES) <0.14 (AE) Methane <65 Oils and greases (including <0.3 (petroleum) petrochemicals) Phenols <0.0006‐0.0017 Polychlorinated bi phenyls (PCBs) <0.002
Pesticides 2,4‐dichlorophenol <4.0 Aldrin <0.01 Azinphos‐methyl <0.01 Chlordane <0.01 Chlorpyrifos <0.001 DDT <0.0015 Demton <0.01 Dieldrin <0.005 Diquat <0.5 Endosulfan <0.003 Endrin <0.002 Gunthion (see also Azinphos‐methyl) <0.01 Hexachlorobenzole <0.00001 Heptachlor <0.005 Lindane <0.01 Malathion <0.1 Methoxychlor <0.03 Mirex <0.001 Parathion <0.04 Pyrethrin <0.001 Pyrethrum <0.01 Rotenone <10 Simazine <10 Toxaphene (9478) <0.002 Trichchlorphon <0.001
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Appendix 6 – Useful contacts
State Government Victoria Department of Primary Industries Fisheries Victoria GPO 4440 Melbourne. VIC. 3000. Ph: (03) 9658 4376. Web: http://www.dpi.vic.gov.au/fishing
Biosecurity Victoria Aquatic Animal Health 475 Mickleham Rd Attwood. VIC. 3049. Ph: (03) 9217 4171. Fax: (03) 9217 4322.
Chemical Standards Box 3100 Bendigo Victoria 3554
Ph 03 5430 4559 Fax 03 5430 4454
NSW Department of Industry and Investment Elizabeth Macarthur Agricultural Institute Private Bag 4008 Narellan NSW 2567 Ph: 02 4640 6333, Fax: 02 4640 6300
QLD Department of Employment, Economic Development and Innovation Biosecurity Sciences Laboratory (BSL) Health and Food Sciences Precinct 39 Kessels Road, Coopers Plains Qld 4108 Phone: 07 3276 6062 (submission enquiries) Fax: 07 3216 6620
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Chemicals and drugs APVMA APVMA, PO Box 6182, Kingston, ACT, 2604, Australia Ph: 02 6210 4701 http://www.apvma.gov.au
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Appendix 7 ‐ Useful Conversions
Area 1 A (acre) = 0.405 ha (Hectare) 1 ha = 10,000 m2 (square meters)
Volumes 1 cm3 (cubic centimetre) = 1.0 mL (millilitre) 1,000 mL = 1 L (litre) 1,000,000 L = 1 ML (megalitre) 1 gal (gallon) = 4.545 L (litre) 1 A‐ft (acre‐foot) = 1,233.5 m3
Weight 1,000 ug (micrograms) = 1 mg (milligram) 1,000 mg = 1 g (gram) 1,000 g = 1 kg (kilogram) 1,000 kg = 1 tonne
Conversions 1 ppm (parts per million) = 1 mg/L (milligram per litre) 1 ppm = 1 L in 1,000,000 L 1 ppm = 1 mL in 1,000 L 1ppt (parts per thousand) = 1 g/L (gram per litre) 1 ppt = 0.1% 1 ppt = 1,000 ppm 1% = 10 ppt 1% = 10 g/L 1 mg/L = 1 g in 1,000 L
Salinity conversions 1 dS/m (deci Siemens per meter) = 1 mS/cm (milli Siemens per cm) = 1,000 μS/cm (micro Siemens per cm) 1,000 μS/cm = 640 ppm = 0.64 ppt (approximate conversion, subject to salt composition)
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Appendix 8 – Glossary
Abiotic Non‐living. Hypoxia State where insufficient oxygen is available for Anaerobic requiring the absence of oxygen utilisation by tissues. (eg. anaerobic bacteria) Lesion An alteration to the normal Bacterivore Bacteria‐eating. structure of cells, tissues or Biocides Substances that are capable of organs. killing living organisms. Metazoan Multicellular organisms. Biopsy Excision and diagnostic study Necrosis Death of a particular part of a of tissue from a living body. tissue or organ. Biotic Pertaining to life or living Obligate With no choice. An obligate organisms. parasite depends on its host Cilia Minute, fine, hair‐like to live. outgrowths Opercula External covering of gills. Commensal An organism living with Osmo‐regulation Regulation of the osmotic another and sharing food, both pressure in the body by species as a rule benefiting by controlling the amount of the association, or one water and/or salts in the benefiting and the other not body. being harmed. Posterior Pertaining to, or situated Contractile Capable of contracting. toward, the rear end. Cosmopolitan World‐wide in distribution Protozoan Microscopic organism; Cyst Protective, spore‐like cell; an usually single celled but may enclosed membrane consist of a group of similar surrounding an organism or cells. group of organisms. Septicaemia Invasion and persistence of Denticles Small tooth‐like processes. pathogenic bacteria in the bloodstream. Dyspnoea difficult or laboured breathing. Ubiquitous Being everywhere. Facultative Ability to live either a parasitic or non‐parasitic life. Ulcer Break in the skin or surface membrane, with Filter‐feeding Feeding on small organisms by disintegration and necrosis of straining them out of the tissue. surrounding medium. μm micrometres, 0.001 mm. Flagella Long, whip‐like projections. Visceral organs Organs within the body Haemorrhagic Characterised by discharge of cavity. blood. Hyphae Thread‐like filaments of a fungus.
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