SECTION 6 THE SHARK BAY DRAFT AQUACULTURE PLAN
6.3 S PECIES SUITABLE FOR A QUACULTURE IN S HARK B AY
6.3.4 Marine Invertebrates
quite good, since they would be sold at an early age and for a comparatively high value per unit weight. As culture technologies are developed, the same or similar species are likely to be produced in South-east Asian countries, which have an established marketing network and other competitive advantages, such as competitive labour costs.
The commercial viability of aquaculture enterprises growing aquarium fish in Shark Bay will be governed largely by the extent to which local competitive advantages can be exploited, and the relative costs and availability of cultured and wild-caught fish in global export markets.
6.3.3.6 Tuna Species
Southern bluefin tuna and yellowfin tuna occur naturally in all oceanic waters off the Western Australian coast.6 These species may be ideally suited for aquaculture in Shark Bay, particularly in the northern areas subject to more oceanic conditions and remote from the more environmentally sensitive locations.
At present, in Australia, tuna aquaculture is limited to the grow-out or fattening of wild-caught juvenile fish in sea cages located off the coast of the Eyre Peninsula, near Port Lincoln. The aquaculture of southern bluefin and yellowfin tuna off the western coastline of Western Australian is considered feasible from a technical perspective, by growing out wild-caught juveniles as well as hatchery-reared seed stocks.
Preliminary research in several countries has indicated the viability of tuna aquaculture using hatchery- reared seed produced from captive broodstock. Their very high market value, particularly for southern bluefin tuna, makes the commercial aquaculture of these species feasible in difficult, remote locations.
From a physiological perspective, there is no reason the tunas cannot be cultured in warmer waters than previously considered suitable; indeed, warmer waters could have significant positive effects on critical production efficiency factors such as growth rate and FCRs. The potential commercial viability of the aquaculture of southern bluefin and yellowfin tuna in Shark Bay is considered promising, despite the failure of a previous attempt to fatten wild-caught yellowfin tuna in cages in the same area.
6.3.4.1 Artemia
Artemia or brine shrimp are produced in arid tropical and subtropical environments and used world- wide as a live food in marine and fresh water aquaculture hatcheries. Per unit weight, artemia may be considered a high-value aquaculture product. Market prices vary according to supplies, which may vary from year-to-year.
The product from this species would principally be desiccated cysts for use in hatcheries, but could also include limited quantities of biomass for sale to the aquarium trade. The culture technology for artemia is well known, however, as a rule, aquaculture operations producing the species do not have any operational inputs and hence costs. Instead, they depend on the natural productivity of salt lakes and harvest of the desiccated cysts seasonally. The production efficiency of this method is high.
The commercial viability of artemia aquaculture in Shark Bay is considered good, subject to suitable production and harvesting areas being available. In particular, opportunities exist for artemia production to be integrated with existing salt mining operations in Shark Bay.
Artemia are not native to Western Australia but are already established at the salt works in Shark Bay.
Given that Artemia are already widely distributed around the State (and will continue to be distributed on water birds and the like) and have been here for some time, they are considered to be more or less
‘naturalised’.
Parartemia spp. are native brine shrimp similar to artemia that may have some potential for aquaculture. Research to explore the potential of the species is at an early stage, but the genus is characterised by several features that require careful consideration if their commercial culture is to be contemplated.
The negative buoyancy of their cysts may constitute a significant disadvantage in relation to the cost of production, since harvesting methods would need to be more elaborate, and hence more expensive, than those traditionally used for artemia. Proposals to produce the species in intensive systems more conducive to harvesting would again need to consider the cost of production.7
6.3.4.2 Edible Oysters
Western rock oysters - the same species as the highly-regarded Sydney rock oyster - occur naturally in Shark Bay and are known for their excellent quality, due in part to limited fresh-water input and good sea-water quality. Oysters bearing the name Shark Bay would probably be well received in the market place and may receive premium prices, due to the region’s pristine environment.
The culture technology for many edible oyster species is well known and the western rock oyster has previously been produced in commercial hatcheries located near Carnarvon and Albany. Subject to the availability of suitable sites and conditions, the production efficiency is high.
However, despite the evident advantages, the commercial prospects for western rock oyster aquaculture in Shark Bay are not considered good, due principally to the limited number of available intertidal or nearshore sites for rack or longline production. Further, it is anticipated that the limited number of offshore sites would be devoted to the production of blacklip pearl oysters, since pearl production is likely to be more profitable and the blacklip oyster more suited to low nutrient conditions.
7 By way of comparison, artemia cysts are positively buoyant and tend to accumulate at the downwind shores of drying salt lakes.
Enterprises that consistently and profitably produce artemia are characterised by natural productivity in salt lakes and are those for which the only cost is the cost of harvesting, processing and packaging.
6.3.4.3 Roe’s Abalone
Most abalone species, including Roe’s abalone, may be considered to have good market prospects.
Shark Bay is included in the natural distribution of the species, albeit approaching its northern extreme.
The culture technology for Roe’s abalone is still being developed, but is similar to that currently used to successfully grow other abalone species and may be considered ready for commercial development at a pilot scale. The production efficiency and commercial viability are relatively unknown, particularly intensive, onshore production systems.
Roe’s abalone have limited tolerance for salinity variations, particularly for salinities greater than that of sea water, so are not likely to be commercially viable in most areas of Shark Bay. Their aquaculture may be technically feasible in areas with access to oceanic-quality water; but these areas are very limited or remote and, consequently, expensive to develop and operate. It is likely that aquaculturists wishing to grow Roe’s abalone would seek alternate, more suitable sites south of Shark Bay.
It has been suggested that tropical abalone (Haliotis asinina) could grow in Shark Bay. Similar seawater quality restrictions, as described for Roe’s abalone would apply, given Shark Bay is at the southern extreme of the species’ distribution. Any aquaculturist contemplating the production of tropical abalone would almost certainly seek a site north of Exmouth and preferably in the Pilbara or Kimberley regions.
6.3.4.4 Western Rock Lobster
Western rock lobster is Australia’s most valuable single-species wild fishery that has a consistently high market demand and price. Rock lobsters are not currently produced by means of aquaculture and it will probably be some time before technology is developed for the closed-cycle production of the species. However, given the high value of the species, there are strong prospects for the grow-out of wild-caught pueruli.8
A Fisheries and Research Development Corporation-funded research project aimed at establishing post pueruli grow-out data for western rock lobster has recently begun. Results from this project will enable the economic potential for this form of aquaculture to be assessed. Issues in respect of access to wild stocks of larval, juvenile and adult rock lobsters are yet to be finalised.
6.3.4.5 Saucer Scallop
Saucer scallops are an important wild fishery species in Shark Bay, with annual catches ranging from around 1,000 tonnes to 20,000 tonnes (live weight). However, catches are highly variable due to the high level of variability in recruitment success, primarily as a result of environmental influences on larval survival.
8 The puerulus is a post-larval development stage in the early life history of rock lobster that can be caught in large numbers off the Western Australian coast using purpose-built collectors.
At times of good recruitment success, scallops are found in beds of very high density (around one scallop per square metre). Scallops appear to grow and survive well at these high densities, suggesting that there may be scope for ocean ranching (bottom culture) of hatchery-supplied spat. Hanging culture (suspending scallops in baskets in the water column) has not been shown to be useful for this species because of its fragile shell.
Growth of the species is rapid (9-10 months to harvestable size), which, combined with its ability to tolerate high densities, make it an attractive aquaculture species, provided that techniques of bottom culture can be developed for the species.