Mulloway

24.05.17

Mulloway are a marine fish with excellent prospects for farming in turbid earthen ponds. In their natural habitat, mulloway live and feed at the bottom of lakes and seas in fresh, estuarine and marine waters. Mulloway are found naturally in the coastal waters of subtropical and temperate regions of Asia, Africa and Australia.

Overview

Mulloway are well regarded as a good eating fish with firm white flesh and few bones. The fish may be cooked whole or as cutlets or fillets, with the fillets holding together well when raw and cooked. It is suitable for a large variety of recipes.

Wild mulloway have been commercially harvested and recreationally fished in significant quantities since at least the 1940s. In New South Wales (NSW), commercial catch records show a steady and substantial decline from 380 tonnes during 1973–74 to 37 tonnes during 2008–09. Mulloway are now regarded as overfished.

Aquaculture is an increasingly important means of meeting the world’s demand for protein and consumers’ desire for marine fish to be produced in an environmentally sustainable way. Fish species similar to and related to mulloway are becoming the basis of significant aquaculture industries in many regions of the world, including the United States of America, China, Greece, Italy and Spain.

The mulloway endemic to Australian waters, Argyrosomus japonicas, is considered a good species for aquaculture. They grow quickly, accept artificial food, are highly fecund with good food conversion ratios, tolerate a wide range of salinity and temperature, tolerate low oxygen levels, are not cannibalistic and can be grown at high stocking densities.

To date, they have been farmed mainly in coastal sea cages, however turbid earthen ponds are proving to be a very successful system for commercial production, especially when growers may already have the infrastructure established for prawns or other fish.

While earthen pond production systems are yielding excellent results and market prospects are good, farmed production faces the challenges of any emerging industry; access to low cost fingerlings for grow out and the need to refine feedstock formulations and feeding regimes for greater efficiency and product quality control.

Facts and figures

  • Mulloway are a temperate fish, native to Australian waters and several other regions of the world
  • Mulloway is the aboriginal name for the fish, meaning ‘the greatest one’ – in Australia the species may also be called jewfish, butterfish and kingfish
  • Wild fish spawn at sea and then juveniles settle in turbid waters of estuarine nursery areas until they reach a length of 46cm which takes three to four years
  • A 10kg wild fish is likely to be about six to seven years of age
  • In the wild, 30kg fish are common and they are thought to live for about 30 years
  • Farmed fish present a sustainable alternative to wild-caught mulloway
  • In earthen (prawn) ponds, fish can reach market size (1kg+) in under two years, with high survival rates, good growth and minimal disease
  • Fish in earthen ponds have high production rates, approaching 14t/ha but may be as high as 20t/ha
  • The production of mulloway in earthen ponds is a very new industry and production techniques are still being refined

Production status

In 2010–11, 644 tonnes of mulloway were produced in aquaculture systems in Australia.

Sea cage production accounted for 572 tonnes produced in South Australia and 72 tonnes in New South Wales. Sea cage production has stalled in recent years despite a potentially large market for cultured marine fish. In South Australia, mulloway are not achieving suitable growth rates in sea cages; and in New South Wales, commercial interest in reinvesting in sea cage production is currently low due to a limited number of suitable sites, difficulty of the current approval processes and access to development capital.

The mulloway produced in New South Wales were produced in earthen ponds. This form of aquaculture is a new industry, and proving to be a successful alternative enterprise for prawn farmers whose businesses are struggling against low-priced imports of prawns from Asia.

In northern New South Wales, research work since 2008 has shown that prawn farms can be easily and successfully converted to mulloway farms. In terms of production systems, much higher growth rates of mulloway are being achieved in earthen ponds compared with sea cages.

The volume of mulloway sourced from wild-catch fishing is declining as natural populations are overfished and new and more strict fishing rules are applied to commercial (and recreational) fishing in estuaries and the ocean.

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Map of current and potential growing regions

Uses

Mulloway is a well-regarded eating fish with firm white flesh and few bones. The flesh has an attractive appearance — pale colour when raw, changing to white when cooked — and is tasty and flaky. Mulloway may be prepared as a whole fish, cutlets or fillets, with fillets holding together well when raw and cooked.

The firm texture of mulloway makes it suitable for a large variety of recipes. Small mulloway may be roasted or barbequed whole, but sometimes small fish are regarded as ‘soapy’ to taste. Medium-sized fish remain moist when grilled or fried. Larger fish can be dry and are better suited to soups, curries and other wet dishes. The traditional use of wild mulloway was as a cutlet from a large fish.

Recent Australian research has shown mulloway meat is an excellent source of long chain omega-3 fatty acids and also contains high levels of the monounsaturated omega-9 fatty acid and oleic acid providing important health benefits for consumers.

Production Requirements

Growing regions

Theoretically, mulloway could be farmed in all regions where they occur naturally, which is the coastline of the southern half of Australia, from Rockhampton in Queensland around to North West Cape in Western Australia. While their natural distribution is widespread, warmer climates are suited to farming because of the faster growth rates achievable in warm conditions.

Production in earthen ponds has been successful and continues to be investigated in the estuarine areas of the northern rivers region of New South Wales.

Sea cage production in shallow bays/gulfs are operated in New South Wales (Sydney) and South Australia, however the suitability of this system for mulloway is being reconsidered by current operators, as the clear water environment of the sea cage does not match the turbid water conditions that young mulloway seek in their natural environment.

They have been evaluated as a potential species for inland saline aquaculture in New South Wales, South Australia and Western Australia. Despite the growth advantages of farming on land, compared to sea cages, many constraints to inland saline aquaculture exist, including remoteness, the harsh and volatile environment, and variations in the chemistry of inland water.

Climate

Mulloway is a temperate marine fish, suited to temperate and subtropical climates.

Housing

The preferred environment for fish that are less than 2kg in size is turbid estuarine waters rather than clear oceanic water conditions. Recent Australian research has shown that mulloway perform extremely well and are a hardy species in earthen ponds that were previously used for prawn farming. Land-based production methods are also gaining popularity primarily due to the intense scrutiny of sea-cage operations including real or perceived concerns with fish escape, genetic pollution and disease transfer.

Feed requirements

Farmed mulloway in northern New South Wales are fed pellets formulated for other marine fish such as farmed barramundi. The size of the farmed industry is not yet sufficient for stockfeed companies to develop a specific diet for mulloway. While barramundi pellets generally provide adequate nutrition, in certain conditions, product quality (fat accumulation) has been a problem.

Research has been undertaken to investigate feeding strategies and rates to improve grow-out feed management practices for mulloway. Feed is greater than 50% of the total operating costs of a mulloway farming business, so a better understanding of optimal feeding times, frequencies and rates will help eliminate wastage, reduce costs and have better control over product quality.

Breeds and breeding

Throughout the world, there are 50 genera and 210 species of mulloway. In the temperate waters of Australia there are two genera and two species, with the species Argyrosomus japonicas showing good potential for commercial production.

Sourcing stock

Mulloway fingerlings are sourced from a limited number of hatcheries (possibly only three in Australia). Producers prefer not to purchase fingerlings from interstate hatcheries because of concerns about genetic pollution and disease transfer, therefore the options for purchasing fingerlings at competitive rates is very limited.

Stock purchase represents 15% of total production costs, so business viability would be improved if the cost of stock could be reduced. The research into feed requirements also looked at ways to improve mulloway fingerling production on farm, by adapting existing prawn hatchery facilities for fish hatchery.

Health care, pests and diseases

Research into mulloway production as an alternative to prawn production included grow-out trials, which showed mulloway to be extremely hardy and have very few problems with parasites or diseases. Such is the suitability to land-based production that antibiotics and other chemicals have not been needed in existing commercial enterprises to maintain health or promote economical growth rates.

Managing pond phytoplankton blooms is critical in optimising production, and there is a critical need to evaluate new, alternative and safe methods of control.

Fish are cold-blooded, therefore water temperature affects all aspects of their biology including appetite, digestion and growth. During the summer months, pond water temperatures can rise above the natural upper temperature range recorded for mulloway, reducing feed conversion ratios and growth. This has important implications for the optimal location of farms, however there is some potential to minimise the impact of heat stress on growth using dietary strategies.

Infrastructure Requirements

The infrastructure associated with earthen-pond prawn farms has all the capital facilities required for mulloway production (or other temperate marine fish) in place. No major change in pond design is required and additionally, established farms have their own hatcheries to produce stock and current licences to operate in the estuarine environment.

Starting afresh, a fish producer would require buildings for hatcheries, a series of earthen ponds fully integrated with the hatchery, mechanical aeration to oxygenate pond water, icemakers and packing sheds.

Processing & Selling

For freshness and quality, fish must be harvested and delivered to the customer within 48 hours. To reduce stress at harvest time, anaesthetic (AQUI-S) is added to the pond water before harvest. The anaesthetic has a zero withholding period, approved for use in food fish by the Australian Pesticides and Veterinary Medicines Authority, and for some growers, it is the only chemical used in the production process.

Harvested fish are packed onto ice in polystyrene containers and the fish are delivered to restaurants, retailers or wholesalers as whole fish.

Mulloway in northern New South Wales are harvested at a size of 1.8kg, which meets the market’s expectations of mulloway. Through the commercial wild capture industry, large mulloway have an established market profile and attract a premium.

Markets & Marketing

Globally, aquaculture is expected to play a crucial role in compensating for declining ‘wild’ capture fisheries and in meeting increased consumer demand for high quality protein. Significant large-scale aquaculture of marine fish in Australia is currently limited to production of southern bluefin tuna (South Australia), Atlantic salmon (Tasmania) and barramundi (predominantly Queensland, New South Wales and Northern Territory). Sea cage production of yellowtail kingfish has increased in South Australia, replacing some existing mulloway production.

In general, due to reductions in wild catch and consumer preference for marine fish rather than freshwater fish, there is a potentially large market for cultured marine fish. However, this depends on sufficient venture capital being attracted to market development and sites with favourable water access and temperatures being found.

In the market place, mulloway would compete against better known farmed fish products (such as salmon, barramundi, trout, and kingfish). Analysts predict that the domestic market for mulloway can be expanded to the current output of freshwater trout or barramundi, at around 2,000 tonnes per year, if marketing of mulloway is actively managed and promoted, and the product is based on large fish (greater than 1.5kg) rather than small fish.

The mulloway that has been produced in northern New South Wales, in ponds previously used to grow prawns, has been extremely well received in the market place by retailers and restaurants, and increasingly by wholesalers. Mulloway has been appearing at many of the top restaurants in Sydney, and chefs and patrons are attracted to farmed mulloway as a sustainable food choice (compared with wild fishing) and its ‘clean and green’ production system.

Risks & Regulations

Risks/Challenges

The main challenge for mulloway producers is the very new stage of development of the industry. Entrants into the industry will be reliant on one or two existing businesses for advice and mentoring. However, the pioneering efforts of existing businesses are being rewarded with success, and the industry is keen to encourage others so that it can develop critical mass.

Producers are challenged by a lack of knowledge about diets, feeding protocols and the effects of environmental parameters, such as temperature and salinity, on feed intake. Current diets and feeding strategies for large mulloway are not optimal. Food conversion ratios are well above the industry standard for marine fish, resulting in financial losses through food wastage and poor growth.

Producers have difficulty finding reliable suppliers of low-cost, high-quality fingerlings, which are also essential for a viable industry to develop. At present there are few suppliers and little competition.

The eastern coastline of Australia, in particular, is undergoing rapid change as a result of continued pressure to allocate areas for residential development, parks, reserves, recreation and wilderness areas. These pressures have meant the establishment of marine aquaculture sites on the coastline will continue to become more difficult.

Regulatory considerations

An aquaculture farm must obtain a licence to operate in an estuarine environment, and develop an Environmental Management Plan as part of the licensing process to ensure environmental sustainability. State and local governments have specific requirements for development and licensing of aquaculture farms (some documents relating to this are listed in Other resources such as the NSW Land Based Sustainable Aquaculture Strategy)

National and state level regulations are in place to protect estuaries, coastal areas and groundwater systems from contamination by sewerage, agricultural pesticides, fertilisers and urban runoff. Untreated pond effluent cannot be discharged into adjacent waterways. All new aquaculture farms in Australia, or expansions of existing farms, require effluent treatment systems.

Publications

Publications/information

Optimising Mulloway Farming Through Better Feed and Hatchery Practices RIRDC publication (2015)

Emerging animal and plant industries: Their value to Australia RIRDC report (2014)

Re-invigorating NSW Prawn Farms through Culture of Mulloway RIRDC 11-178  RIRDC (2011)

Hatchery Manual for the Production of Australian Bass, Mulloway and Yellow Kingfish New South Wales Department of Industry and Innovation (March 2011)

NSW Land Based Sustainable Aquaculture Strategy

Other resources

Fisheries Research and Development Corporation

NSW Aquaculture Industry Directory 2016

National Seafood Industry Alliance

Site assessment survey for marine aquaculture facilities on the NSW coastline NSW Department of Primary Industries website (2003)

Planning for aquaculture in Queensland Fisheries Queensland (2011)

Policy and Legislation for Aquaculturey SA Department of Primary Industries and Regions SA

Australian Pesticides and Veterinary Medicines Authority

Industry Bodies

There is currently no specific industry body for the land-based mulloway industry, however, there are the following bodies for aquaculture:

National Aquaculture Council Inc. – The NAC is widely recognised as the peak industry body of the Australian aquaculture industry.

NSW Aquaculture Association Inc

Image Gallery

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Aerial perspective of mulloway ponds, Palmers Island, NSW

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Harvesting mulloway with nets

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Chilled mulloway ready for sale

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Preparing mulloway for transfer to retailers