Rural Industries Research & Development Corporation

The New Rural Industries
A handbook for Farmers and Investors

Prawns

Introduction

Australian prawn (= shrimp) production has been established over the past ten years along 2000 km of the eastern coastline (from the Clarence River, NSW to Mossman, North Queensland) and in the Northern Territory. Australia has a number of species to choose from, relatively unpolluted coastal waters, a low incidence of disease, and tight environmental regulations—all of which point to the potential for a sustainable industry.

The growth of the industry has been steady in spite of some early cases of poor site and species selection and some recent setbacks with disease and postlarval supply for one species (the black tiger prawn, Penaeus monodon). These setbacks have been offset by the rapid growth of the kuruma prawn (P. japonicus) sector. Recently two other species (the banana prawn P. merguiensis and the brown tiger prawn P. esculentus ) have been tested to help the industry diversify and to meet postlarval shortfalls.

Strict environmental controls and coastal zone management practices prevent the kind of more rapid development seen in SE Asia, but also ensure that the environmental degradation and disease issues that have caused some spectacular crashes in these Asian industries will not be repeated in Australia. Environmental management and the rapid uptake of scientific advances in prawn production technology and disease control will ensure that Australian farmers have a small but competitive and sustainable portion of the world's prawn aquaculture.

Australian prawn farmers generally have agricultural backgrounds but increasingly farms employ key production staff, such as farm and hatchery managers, with tertiary training in intensive animal production or aquaculture.

Marketing issues

Currently Australia grows two species of prawns: the black tiger prawn, Penaeus monodon, and the Japanese king or kuruma prawn, P. japonicus. The black tiger prawn is mostly sold on local Brisbane, Sydney and Melbourne markets, either fresh, frozen or cooked. The kuruma prawn is grown exclusively for live shipment to the markets of Japan, principally Tokyo and Osaka.

Most growers develop their own processing facilities and distribute their own product. The industry could be better served by having co-operative regional processing plants, or by integrating with the capture-industry processors. Average processing and marketing costs range between $1.39 and $2.50/kg.

Most farmers are harvesting, processing and shipping direct to markets, without elaborate chains of agents and middlemen. Shortage of space for this perishable commodity in jet cargoes has been a limiting factor at times in the industry's development, especially at key production times. Access to international airports is critical for site location and marketing.

Key statistics

Queensland's production and value statistics are used to describe the trends in the Australian industry. In 1995, Queensland had 20 farms, NSW 6, Northern Territory 1. Statistics for 1994 are the most recent compiled by the United Nations Food and Agriculture Organization for the global summaries.

Prices of course vary widely because of market demand, exchange rates, and the form and quality of the product. However, as a guide, black tiger prawns sold (ex farm-gate) for
$11.00-15.50/kg (average $13.41) in 1995-96 on Australian markets, while kuruma prawns sold (landed live in Tokyo) for $50 to 150/kg. The average price for kuruma prawns dropped from $84.50 in 1994-95 to $70.70 in 1995-96 because of the strengthening Australian dollar against the yen.

Production requirements

The black tiger prawn is the most popular and widespread species in cultivation from northern NSW to north Queensland and into the Northern Territory. There is also a proposal for a large farm on Exmouth Gulf in Western Australia. In the southern part of its range, temperatures restrict the growing season to one crop per season, while in the north there is potentially a nine- month growing season (at temperatures above 23°C). However, because of shortages of postlarvae and some viral diseases, the number of crops in north Queensland farms has dropped from 1.17 to 1.04 crops per pond per year.

The kuruma prawn production is currently restricted to southern Queensland and northern NSW (Fig. 1). Recent research has shown that pond temperatures above 32°C are sub-optimal and at 36°C are lethal to P. japonicus.

Australian prawn farms are restricted to the coastal zone, virtually all drawing their intake water from tidal creeks and estuaries. Early farms were built in mangroves, but acid sulfate soils have proven unsuitable. Modern farms are behind the mangrove fringe on salt flats or converted cane farms. Unfortunately, most hatcheries are located in similar locations. Water quality and salinity requirements for raising larvae are higher than for adults; poor water quality and attendant diseases have led to intermittent failures in larval and postlarval production.

A recent study by CSIRO, using Geographic Information System (GIS) technology, has shown that less than 4% of available land in the Logan River area of southeast Queensland is optimal for prawn farming when soil type, vegetation, slope and elevation, proximity to water and urban areas are taken into account. GIS offers a powerful tool for site selection by prospective farmers and coastal zone managers to aid the development of coastal aquaculture.

Varieties/breeds

The black tiger prawn (P. monodon) is by far the most popular species grown in Australia and southeast Asia. Its very rapid growth rates and its low requirement for protein make it an attractive species for aquaculture. Ironically, in the wild, in most parts of its Indo-Pacific range, it is rare to uncommon, leading to chronic and at times, acute shortages of spawning stock and postlarvae. There is intensive world-wide research to domesticate this species to alleviate the reliance on scarce wild broodstock and take advantage of selective breeding.

The kuruma prawn (P. japonicus), while less commonly produced, is fast catching P. monodon in value. It too has a very wide range in the wild, but spawners only occur predictably in a few locations off central Queensland. This species has recently been domesticated and selective breeding trials have begun in southeast Queensland.

Recently two other species (the banana prawn P. merguiensis and the brown tiger prawn P. esculentus ) have been tested to help meet postlarval shortfalls and allow the industry greater scope for diversification in growing areas and markets.

Fish husbandry

Site selection is probably the most important element in getting started. Physical location (soil, slope, access to salt and freshwater, tidal range, rainfall and runoff) are all very important. All too often in the past, the growing requirements, especially temperature and salinity optima, of the species have not been carefully examined. Noting subtle differences in optima, not just lethal ranges, can mean the difference between one and two crops per year, or finding which species is best suited to a particular location.

More importantly, a careful examination of markets must be undertaken. Here again the species choice, size and form (live, fresh, frozen, cooked) of the product can dictate the location, production strategy and infra-structure needs (e.g. proximity to hatcheries, processing plants, domestic or international airports).

In Australia all prawn production is done in earthen ponds, close to tidal sources of seawater. The pond bottoms have a clay base for retaining seawater. Site elevation and tidal range have to be considered, to minimise pumping costs and maximise the options for water exchange.

The key to good culture and husbandry practices is being able to maintain water quality close to the species' growth optima. Often, sites are compromised by intermittent or prolonged periods of low salinity because of poor tidal exchange or rainy season flooding. Stocking densities, food quality and feeding regimes will also influence growth rates and effluent quality. Farms are beginning to experiment with closed system (partial to full recycling) culture methods to maintain water quality and isolate the farm from the vagaries of external water supplies, as well as to comply with increasingly stringent discharge requirements. Effluent treatment, using marine plants and animals as alternative crops, is also being explored in open and closed systems.

Several manuals on production techniques are available and advice is available from extension officers in all States.

Depending on location (and consequent temperature regime) and market strategy, crops of both species can be brought to harvest in 5 to 9 months from stocking postlarvae. Southern locations only get one crop per year, northern farms are in production year-round, but do not yet get two crops per year. Potentially, species rotation would allow double cropping.

Pest and disease control

All animals grown intensively, under artificially high densities, are prone to disease. Prawn aquaculture is no exception with bacterial, viral and parasitic diseases affecting all life history stages and production phases from hatchery to grow-out. Most bacterial and parasitic diseases are easily identified and treated with better hygiene and limited use of therapeutants.

A more insidious and serious threat to the industry is viral disease. The industries in Ecuador, China and southeast Asia have had some catastrophic collapses caused by environmental degradation and/or attendant viral diseases. The relationship between environmental factors and the outbreaks of the causative agents is not well understood.

Australia has only recently been affected by some viral diseases, especially among black tiger prawns in north Queensland. These diseases are new to science, not well characterised and their etiology and epidemiology are poorly understood. Remedial action with pond dry-outs, liming and chlorination seems to be effective, but does not guarantee against re-occurrence. More research into the environmental conditions that predispose prawns to disease (environmental stresses), and the development of diagnostic tools to identify the causative agents and trace their epidemiology are necessary.

The long-term aim is a suite of techniques including diagnostics, vaccines and/or selectively bred strains that are resistant to a variety of viral pathogens. In the meantime, better husbandry practices including ensuring high water-quality standards, lower stocking densities, and the screening of spawners and postlarvae will minimise the occurrence and spread of these viral diseases.

Harvesting and postharvest handling

Harvesting and postharvest treatments are dictated by the species and marketing strategy. Typically black tiger prawns are harvested en-masse with a drain harvest, chilled or cooked on site and shipped to domestic markets. More selective harvests by prawn size or in smaller quantities are undertaken to meet market requirements. Seasonal demands and peaks in prices (e.g. Christmas holiday periods) are often production targets. Alternatively, a steady supply of a certain size of prawn may satisfy other specialist markets such as wholesalers and restaurants.

The kuruma prawn is grown exclusively for the live trade to Japan. Smaller quantities are harvested several nights per week to coincide with market demands and/or air-cargo space and schedules. The animals are chilled and packed in moist sawdust to keep them torpid during transport and timed to emerge actively from the shipping containers. Details about the techniques can be obtained from QDPI. The price paid in Tokyo is based on survival rates, physical appearance and level of activity. Here too prices vary widely according to supply and demand, seasonal spikes at festival times and the quality of the product. Australia is gaining a reputation for high-quality kuruma prawns but cannot yet get the premium price paid for Japanese product, because of either a real need for further quality improvement or of cultural distinctions.

Economics of production processing

Costs of production. Most growers' costs of production, excluding processing and marketing costs, depreciation and financing range between $7.50 and $9.00/kg, depending on the scale of the operation. The average production cost per kg is $8.27 (Table 1).

Profitability (analysis by Paul Thomas, Shrimptec P/L)

Assumptions:

a) Average production/ha/year 5000 kg

b) Average cost of production/kg
$8.27

c) Average processing/marketing costs/kg $2.12

d) Average sale price $14.50

The gross profit/ha on an average production would be $31,150 (42.9%), with a net profit of $20,000/ha/year or 27.5% excluding depreciation and borrowing costs.

Capital costs. To develop a farm fully with all appropriate equipment, ponds, buildings, including processing facilities will cost anywhere between $20,000 and $60,000/ha (pond), not including land costs. These costs vary with site selection and depend on proximity to local infrastructure, site topography, vegetation and seawater access. The major cost will be the installation of an electricity network through the farm. It is difficult to say what is the optimum sized operation, but family-operated farms of
10-20 ha can be very profitable, with corporate operations looking for operations greater than 50 ha to become economical.

The cost of applying for an environmental licence is between $5000 for small (< 5 ha) to $60,000+ for large farms (> 50 ha). Once approval has been given, the annual environmental licence costs (Qld current costs) are up to $3000/year for farms greater than 20 ha.

Key contacts

Key references

Bardach, J. E. (Ed.) 1997 Sustainable Aquaculture John Wiley and Sons, NY, USA

FAO 1996 Aquaculture Production Statistics 1985-1994 FAO Fisheries Circular No 815 Revision 8 (FIDI/C815, Rev 8)

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