The History of Oyster Farming in Australia

JOHN A. NELL

Introduction and Sydney rock oysters were collected 1981) and natural oyster beds (Malcolm, for consumption by Aborigines along the 1987). As Europeans increased in num­ Oyster production in Australia, in- coastal regions of eastern Australia; some bers, they depleted the natural oyster volves five species, namely the Sydney of the shell deposits in Aboriginal kitchen stocks. Government officials banned the rock oyster, Saccostrea glomerata, middens can be quite substantial, up to burning of oyster shells for lime in NSW formerly known as S. commercialis; 400 m long and 4 m high (Bailey, 1975). in 1868 (Malcolm, 1987), and soon after, Pacific oyster, Crassostrea gigas; flat Middens in northern New South Wales oyster farming began (Roughly, 1925; oyster, Ostrea angasi; and two tropical (NSW) (Bailey, 1975) and southern Smith, 1985). species, the coral rock or milky oyster, Queensland (Catterall and Poiner, 1987) Commercial production of oysters Saccostrea cucullata, and the black-lip consist largely of Sydney rock oysters in Australia began simultaneously with oyster, Striostrea (Parastriostrea) myti- and in central NSW, where flat oysters the farming of the Sydney rock oyster in loides, formerly known as Saccostrea are now rare, they consist of a mix of NSW and southern Queensland around echinata. The Sydney rock, Pacific, and flat and Sydney rock oysters. However in 1870 (Roughley, 1922; Smith, 1985). It flat oysters have been farmed. Before Eu- southern Australia, the middens consist began with the exploitation by dredging ropeans settled in Australia, flat oysters largely of flat oyster shells (Sullivan, of oyster beds (5–20 m deep) and har­ 1984). Obviously, the Aborigines con- vesting of oysters by hand from intertidal John A. Nell is with the Port Stephens Fisheries Centre, NSW Fisheries, Taylors Beach, NSW sumed the species that were abundant beds, and with placement of a range of 2316, Australia [e-mail: John.Nell@fisheries. and easy to collect. Until the 1820’s, catching and growing substrata such as nsw.gov.au]. Views or opinions expressed or most lime for making mortar in NSW sticks, slabs of rock, and shell placed on implied are those of the author and do not neces­ sarily reflect the position of the National Marine was produced from seashells, including intertidal mudflats to exploit natural re­ Fisheries Service, NOAA. those from Aboriginal middens (Pearson, cruitment. As dredge beds were depleted, problems with silt accumulation attract­ ing the invasive mudworm, Polydora sp., which kills oysters, increased. Therefore, ABSTRACT—Aboriginal Australians con- gigas, are produced in Tasmania, South Aus­ the industry progressively adopted stick sumed oysters before settlement by Europeans tralia, and Port Stephens, NSW. Flat oysters as shown by the large number of kitchen mid- currently are farmed only in NSW, and there and tray culture on intertidal racks in dens along Australia’s coast. Flat oysters, is also some small-scale harvesting of tropi- the early 1900’s. To a large extent, this Ostrea angasi, were consumed in southeastern cal species, the coral rock or milky oyster, farming system protects oysters from the Australia, whereas both flat and Sydney rock S. cucullata, and the black-lip oyster, Striostrea mudworm. Dredge bed culture (a most oysters, Saccostrea glomerata, are found in mytiloides, in northern Queensland. Despite effective way of oyster farming) has dis­ kitchen middens in southern New South Wales intra- and interstate rivalries, oyster farm­ (NSW), but only Sydney rock oysters are found ers are gradually realizing that they are all appeared from NSW because of siltation in northern NSW and southern Queensland. part of one industry, and this is reflected by and the mudworm. Oyster fisheries began with the exploitation the establishment of the national Australian In South Australia, an extensive flat of dredge beds, for the use of oyster shell for Shellfish Quality Assurance Program and oyster fishery existed between 1860 and lime production and oyster meat for consump- the transfer of farming technology between tion. These natural oyster beds were nearly states. 1885. About 30 sailing vessels and some all exhausted by the late 1800’s, and they Australia’s oyster harvests have remained 80 fishermen harvested the oysters with have not recovered. Oyster farming, one of relatively stable since Sydney rock oyster dredges at 5–20 m depth (Olsen, 1994). the oldest aquaculture industries in Australia, production peaked in the mid 1970’s at 13 The harvesting depleted the beds, and began as the oyster fisheries declined in the late million dozen. By the end of the 1990’s this only a few vessels remained after 1885. 1800’s. Early attempts at farming flat oysters had stabilized at around 8 million dozen, and in Tasmania, Victoria, and South Australia, Pacific oyster production reached a total of By 1905 the fishery barely existed (Olsen, which started in the 1880’s, were abandoned 6.5 million dozen from Tasmania, South 1994). Similar oyster dredging existed in in the 1890’s. However, a thriving Sydney Australia, and Port Stephens, a total of 14.5 Victoria (Saville-Kent, 1891) and Tasma­ rock oyster industry developed from primitive million dozen oysters for the whole country. nia (Sumner, 1972) around the same time. beginnings in NSW in the 1870’s. This small increase in production during a Sydney rock oysters are farmed in NSW, time of substantial human population growth This was a huge industry; in Tasmania southern Queensland, and at Albany, Western shows a smaller per capita consumption and alone, 1.9 million dozen oysters were Australia (WA). Pacific oysters, Crassostrea a declining use of oysters as a “side-dish.” landed annually between 1860 and 1870

14 Marine Fisheries Review Figure 1.—Oyster growing areas in Australia.

(Royal Commission of the Fisheries of in Western Australia, and tropical species, fully compared. The Sydney rock oyster Tasmania, 1883). the coral rock or milky oyster and the does best in intertidal estuarine habitats In the late 1800’s, the flat oyster fish­ black-lip oyster, in northern Queensland such as rocks, mangroves, and man-made eries in Victoria, Tasmania, and South also now occurs (Fig. 2). structures, but it also occurs subtidally on Australia were fished out and attempts natural dredge beds. in the early 1900’s to culture these oys­ Sydney Rock Oysters Oyster cultivation began in NSW ters failed (Sumner, 1980a). Sydney rock A continuous distribution of Sydney around 1870 when oyster farmers began oyster farming in NSW (Roughley, 1925) rock oysters exists from the Victoria/ to set out sticks, stones, and shells to and southern Queensland (Smith, 1981/ NSW border (lat. 37°S) on the east catch and grow oysters in the intertidal 82) began in the 1870’s. The Sydney coast through temperate NSW, subtropi­ zone (Roughley, 1922). Around 1888, rock oyster industry had a slow start cal Queensland, across the tropical north spat from the New Zealand rock oyster, and attempts to culture on the dredge and along the west coast as far south as S. glomerata, (which is the same species beds were unsuccessful. In their place, Shark Bay in Western Australia (lat. as the Sydney rock oyster (Anderson farmers developed the intertidal stick 25°S) (Slack-Smith1). The Sydney rock and Adlard, 1994)), were imported into and tray culture system (Nell, 1993) to oysters along the NSW coast do not differ NSW to replenish depleted oyster stocks avoid problems with the mudworm and genetically from each other (Buroker et (Roughley, 1922). The mudworm, Poly­ developed a thriving industry. Pacific al., 1979). The genetics of the oysters in dora sp., appeared in NSW concurrently oyster farming began in Tasmania in the Shark Bay on the west coast and those with the introduction of New Zealand 1960’s (Wilson, 1970), in South Australia farmed on the east coast in NSW and oysters, and farmers developed intertidal in the 1970’s (Olsen, 1994), and in Port southern Queensland have not been farming methods using sticks (Fig. 3) and Stephens, NSW, in 1991 (Nell, 1993) trays (Roughley, 1922) to provide some (Fig. 1). Some experimental farming of 1Slack-Smith, S. Western Australian Museum, protection against mudworm infestation. flat oysters in NSW, Sydney rock oysters Perth, W. Personal commun., 2001. This was the dominant growing system

63(3) 15 Figure 2.—From left to right, at the top, Sydney rock (66–86 mm shell height), coral rock or milky (59–79 mm), and flat oysters (71–77 mm) and at the bottom, black-lip (73–97) and Pacific oysters (76–104 mm).

Figure 3.—Frames of sticks bearing two year old oysters on an intertidal rack in Merimbula Lake, NSW. Photograph by I. R. Smith, NSW Fisheries.

16 Marine Fisheries Review from the 1950’s until the 1990’s. The structural remains of the early farming methods, such as wooden pegs driven into the mud bottom, rock culture (slabs of rocks standing upright in the mud), and bottom culture (shell spread out on a prepared base) can still be seen in some estuaries and a few dredge bed areas are still operational today. The southern Queensland oyster industry flourished from the 1870’s to 1910 but declined after that (Smith, 1981/82). Although originally largely a dredge bed industry, it also involved the harvesting of oysters that occur naturally Figure 4.—Trays supporting fourth generation breeding lines of Sydney rock oys­ in the intertidal zone, which was called ters, Port Stephens, NSW. “bank oystering” (Smith, 1981/82), and is referred to as “bottom culture” in NSW. Some Queensland farmers also experi­ The Sydney rock oyster industry in oysters are grown subtidally on rafts or on mented with rocks, shells, and sticks as NSW and Queensland is wholly depen­ floating culture (Fig. 5) (Nell, 1993). To alternative substrata on which to grow dent on natural spatfall, which has always reduce the amount of tarred timber used oysters (Smith, 1981/82). been abundant and reliable (Nell, 1993; in the construction of oyster racks, the Disaster struck the industry in 1895 Beattie, 2001). The industry, therefore, intertidal longline system, with horizon- when mudworms killed large numbers has been reluctant to selectively breed tally suspended plastic tubes of 41 × 91 of oysters (Smith, 1981/82). The indus­ oysters (Nell et al., 2000) or use triploid cm, developed by South Australian oyster try also suffered oyster mortalities from oysters (Nell, 2002) since the financial farmers, is being used by an increasing floods in the rivers, theft, and the lack of outlay for all hatchery-produced spat is number of farmers in NSW (Fig. 6). secure oyster bank tenure. However, the larger than for natural spat. It takes the During the 1950’s and 1960’s the mudworm was the single largest cause Sydney rock oyster on average 31/2 years NSW Sydney rock oyster industry ex­ of production decline (Smith, 1981/82). to reach plate size (50 g whole weight), hibited consistent growth as production In the 1970’s outbreaks of QX disease the most popular size grade. The larvae methods improved and total lease area caused by the haplosporidian parasite of Sydney rock oysters are set on tarred increased. However, around 1970, pro­ Marteilia sydneyi (Perkins and Wolf, hardwood sticks and they grow intertid­ duction rapidly increased from about 10 1976) led to a further decline (Nell, ally on timber frame trays (1.8 × 0.9 m) to 14 million dozen or 6,000 to 8,400 t 1993). Since 1936, Queensland oyster (Fig. 4) with plastic mesh bottoms which (wet weight including shell). Much of farmers have imported half-grown oys­ are placed on timber racks. Alternative this increase was attributed to the rise in ters from NSW to grow them to market growing systems, such as baskets and the number of farmers who transported size (Smith, 1981/82). tumblers, are also being used, and some oysters from estuary to estuary to take

Figure 5.—Frames of sticks suspended below PVC pipes in floating culture, Wallis Lake, NSW. Photograph by I. R. Smith, NSW Fisheries.

63(3) 17 advantage of differences in the timing of prime growing or fattening conditions. This practice, known as “highway oyster farming,” developed from the mid 1960’s onwards. Production rates stabilized during the 1970’s at around 13 million dozen (7,800 t) per year. Highway oyster farming was particularly prominent in Port Stephens, which produced a lot of spat which were taken by truck to other estuaries for growing. In autumn, large quantities of oysters were taken to the northern rivers of NSW for winter “fat­ tening” and returned to Port Stephens for marketing in the spring (Nell, 1993). Unfortunately, when Pacific oysters were found in Port Stephens in 1984 (Holliday and Nell, 1985), the transfer of oysters to the northern estuaries was greatly re­ stricted to prevent the spread of Pacific oysters further north. Attempts to grow Sydney rock oys­ ters in Tasmania and South Australia failed owing to poor spatfall and slow Figure 6.—Intertidal longline culture of Pacific oysters, Franklin Harbour, Cowell, growth rates (Olsen, 1994). Since 1997, South Australia. one company with its own hatchery in Albany, WA, has been successfully producing spat from a strain of Sydney rock oysters obtained from Shark Bay. The oysters are successfully farmed near Albany (lat. 35°S), far south of the limit of their natural distribution in Shark Bay (lat. 25°S), WA. Pacific Oysters The Pacific oyster was introduced into Tasmania, Victoria, South Australia, and Western Australia in five shipments from 1947 to 1970 (Medcof and Wolf, 1975). None of the oysters transplanted to South Australia and Western Australia survived; however, some of the oysters in Tasma­ nia survived (Medcof and Wolf, 1975), as did a small isolated population in Victoria (Coleman and Hickman, 1986). The Pa­ Figure 7.—Intertidal basket culture of Pacific oysters, Little Swanport, Tasmania. cific oyster was illegally introduced into Port Stephens, NSW, in 1984 (Holliday and Nell, 1985). mania rapidly expanded (Dix, 1991). It The Tasmanian oyster hatcheries pro­ Farming of the Pacific oyster in developed its own way of growing and duce almost exclusively “black” Pacific Tasmania began in the 1960’s (Wilson, handling oysters and adopted the basket oysters, which have a black mantle and 1970; Sumner, 1974; Dix, 1975). Wild culture system (Fig. 7). The baskets are shell, but they also maintain and produce caught spat were collected and grown made of folded plastic mesh and are some “golden” oysters, which have an using the same stick and tray system generally around 28 cm wide and 47 cm orange/bronze or “golden” mantle and as used in NSW at that time (Wilson, long. Some farmers also use plastic trays shell. They are rather slow growing, 1970; Sumner, 1980a, b). With the (93 x 93 cm) for intertidal culture (Fig. 8). presumably because they have been development of hatchery production of These trays can be stacked 6–14 high for derived from only a few oysters and spat in the 1980’s, the industry in Tas- subtidal culture. are most likely inbred. It is claimed

18 Marine Fisheries Review Figure 8.—Plastic oyster trays (93 × 93 cm), suspended from an intertidal longline, Georges Bay, St. Helens, Tasmania.

(Cameron2) that after several genera­ and Wolf, 1975) until 1984, when they intertidal zone in the upper reaches of tions of selective breeding these oysters were illegally introduced into Port Ste­ estuaries. They do not suffer from either breed “true” for the “golden” color and phens, NSW (Holliday and Nell, 1985). of the two haplosporidian diseases that only produce “golden” oysters. A small Before 1984/85, farmers in Port Stephens afflict Sydney rock oysters, namely niche market for “golden” oysters has caught Sydney rock oyster spat near the winter mortality, Mikrocytos roughleyi been developed in Asia. mouth of their estuary and grew their oys­ (Farley et al., 1988), and QX disease, The industry in South Australia devel­ ters relatively free of overcatch (spat set­ Marteilia sydneyi. oped in parallel with the Tasmanian one. ting on oysters and growing equipment) It began in the 1970’s with the importa­ in the upper half of the estuary. But as Flat Oysters tion of wild-caught spat from Tasmania Pacific oyster spat settle throughout the Beds of flat oysters were extensively and developed rapidly during the 1980’s estuary, farmers may need to take their dredged in bays and inlets in Victoria with the import of hatchery-produced Sydney rock oysters out of water once for (Saville-Kent, 1891), Tasmania (Sumner, spat from Tasmania (Olsen, 1994). up to 2 weeks during summer to kill off 1972), and South Australia (Olsen, 1994) Oyster hatcheries were established in the overcatch of Pacific oysters. in the 1800’s and the early 1900’s, but South Australia in the 1990’s, and the In 1985, regulations were introduced they became exhausted and in most cases industry now uses local hatchery spat as to control the number and spread of never fully recovered. After the natural well as spat purchased from Tasmania. Pacific oysters in NSW. In estuaries oyster beds were depleted, attempts to South Australian farmers have been par­ other than Port Stephens, oyster farmers farm flat oysters were made in Tasmania ticularly innovative and have developed are legally required to remove Pacific and Victoria but did not last more than 20 the intertidal longline oyster growing oysters from their leases. As a result of years because of siltation, disease, and a system which is now also used on a lim­ the overwhelming numbers of Pacific lack of government support needed to es­ ited scale for Sydney rock and Pacific oysters in Port Stephens, farmers there tablish a new industry (Sumner, 1980a). oyster cultivation in NSW (Fig. 6). were given permission by the NSW State Experimental flat oyster farming has Pacific oyster production in Australia government in 1991 to grow and market been tried in all Australian states except targets the half-shell market, which re- them. Cultivation of the species remains Queensland, but with the success of quires a uniform size oyster. Therefore prohibited in other estuaries. hatchery production of Pacific oyster the hatchery-produced Pacific oysters The proliferation of Pacific oysters in spat during the 1980’s, flat oyster farm­ are regularly graded to achieve a uniform Port Stephens has greatly increased the ing in Tasmania (Dix, 1980) and South size grade. The Pacific oyster farmers in overcatch of spat and thus the costs of Australia was abandoned and the much Tasmania and South Australia use con­ handling Sydney rock oysters. The Pacific hardier Pacific oysters were grown. There veyor belts and graders for grading and oyster has also spread to all oyster grow­ were also short-lived attempts to farm flat handling oysters in their sheds. ing estuaries south of Port Stephens (lat. oysters in Victoria and Western Austra­ Oyster farmers collected Pacific oysters 32°S), including Georges River/Botany lia during the 1990’s but no commercial sporadically in NSW from 1967 (Medcof Bay (lat. 34°S) and Wonboyn River (lat. leases were allocated (Hickman3). 37°S) but virtually none to the north of 3Hickman, N. Marine and Freshwater Resources 2Cameron, G. Camerons of Tasmania, Dunalley, Port Stephens. In NSW estuaries, Pacific Institute, Queenscliff, Vic. Personal commun., Tasman. Personal commun., 2001. oysters are mainly found in the lower 2001.

63(3) 19 When the disease Bonamia was spread north of Port Stephens, suggesting declined from 1,111,171 dozen in 1993– discovered in 1991 (Adlard, 2000), all that there is a northern limit to the spread 94 to 62,000 dozen in 2000–01, a drop of interest in farming flat oysters in Victo­ of this parasite. Outbreaks of the disease 94%, as the disease in this river kills up to ria waned, even though oysters grown off are patchy within this range, and while 90% of all Sydney rock oysters annually. the bottom on subtidal longlines suffered mortality may occur in winter, most of the As the Pacific oyster is not affected by QX little or no effect from this disease (Hick- oysters do not die until the warmer spring disease, it has partially displaced Sydney man3). However, hatchery-produced flat weather of September or October. rock oysters in Georges River and now oysters have been produced and grown Winter mortality may kill up to 80% makes up 80% of the oysters on the fore- experimentally in NSW since 1998 and of the oysters in an area, and those oys­ shore of the upper reaches of the river. appear to have good market acceptance ters in their third winter (just before they An extensive three-year scientific (Heasman4). reach market size) are most susceptible. survey of QX disease Marteilia sydneyi In severe outbreaks, small spat may also is now being made in 18 oyster produc­ Tropical Oysters be affected (Nell, 2001). The severity ing estuaries. Samples are being stored In the northern waters of Queensland, of the kill can vary markedly between for winter mortality Mikrocytos roughleyi the coral rock or milky oyster, S. cucul­ years, estuaries, adjacent leases, and even testing at a future date. The farmers are lata, and the black-lip oyster, Striostrea within leases. being notified of the results so they can mytiloides, are harvested from rocky Oysters grown on trays and sticks take appropriate steps to minimize any foreshore areas where they have settled are about equally susceptible to winter spread of the disease. These strategies and grow naturally. Both these species mortality (Smith et al., 2000). Dry au­ will be refined in consultation with the have a strong flavor apparently due to a tumns (which cause high salinities), early industry. Since 1986, NSW Fisheries high iodine concentration and are very winters, and low temperatures increase prohibits farmers from moving oysters popular with north Queenslanders who the likelihood of a severe kill. Farmers from affected estuaries into disease-free are used to this flavor (Beattie, 2001). can reduce the impact of this disease by estuaries. Production is limited to selective har­ moving oysters further upstream to areas The practice of farming oysters im­ vesting and retention of broodstock. No of lower salinity before the end of autumn ported from QX disease-free estuaries oyster farming structures are permitted in (May) and by increasing the growing may have inhibited the development of these areas. The majority of areas cover height of the oysters to 15 cm above resistance in the local oysters in these es­ a maximum of 600 m foreshore length. normal elevation. Alternatively, farmers tuaries. However, since the appearance Farming trials of the black-lip oyster in can also sell their oysters for consump­ of QX disease in Georges River, NSW northern Queensland have been success­ tion before the onset of mortality. Fisheries has bred oysters for resistance ful (Beattie, 2001). to this disease for two generations and QX Disease reduced mortality by 22%. Oyster Diseases Outbreaks of “Queensland unknown” or QX disease (caused by another hap­ Bonamia Winter Mortality losporidian parasite, Marteilia sydneyi), Since 1986, mortalities as high as 80% Winter mortality is caused by the para- results in the deaths of large numbers of in the bluff oyster, Tiostrea chilensis, in site M. roughleyi, which occurs over the oysters. The disease is more commonly New Zealand have been caused by a southern or cooler half of the range in found in northern, warmer estuaries and Bonamia species different from Bon­ which Sydney rock oysters are farmed. was responsible for a decline in the oyster amia ostreae that afflicts Ostrea edulis The parasite was once thought to be a industry in southern Queensland and in in Europe (Hine, 1991). In the summer of haplosporidian, but current research is northern NSW during the 1970’s. The 1991, this Bonamia species was detected investigating the possibility that the para- life cycle of the parasite is thought to in Ostrea angasi in Victoria, Tasmania, site belongs to the Bonamia genus instead include an intermediate host, the identity and Western Australia (Adlard, 2000). A (Cochennec-Laureau et al., 2001). This of which remains unknown. While QX survey for Bonamia in flat oysters in five disease was first observed in the early mortalities may occur throughout most estuaries in NSW, where experimental 1920’s in Georges River, NSW (Rough- of the year, mortalities are highest in culture of flat oysters began in 1998, is ley, 1926). Oysters in the area between early autumn (March and April). As a planned for 2003/2004. Port Stephens and the Victorian border result of QX disease, production in the are particularly susceptible to winter mor­ Tweed, Richmond, and Clarence Rivers Mudworm tality. Although, large numbers of oysters in northern NSW during the past 26 years The mudworm Polydora websteri from infested estuaries were transferred decreased from 379,200 dozen in 1974/75 is the most damaging of four spionid for “fattening” during winter in the north- to 168,504 dozen in 2000/01—a drop of polychaete worms which infest and kill ern rivers of NSW from the mid 1960’s to 56%. In 1994, QX disease was first diag­ large numbers of Sydney rock oysters the mid 1980’s, winter mortality has not nosed in central NSW in Georges River (Nell and Smith, 1988). The mudworm (lat. 34°S) (Adlard and Ernst, 1995). also infests most commercial mollusks 4Heasman, M. P. Taylors Beach, NSW. Personal The disease had a devastating effect on including Pacific and flat oysters. The commun., 2001. Georges River oyster production which adult mudworm is up to 25 mm long,

20 Marine Fisheries Review 1 mm wide and red in color. It lives on the inside of the oyster shell, where it gives rise to the formation of a mud blis­ ter, but maintains a tube across the lip of the shell to the outside. Healthy, rapidly growing oysters may be able to quickly cover the worm and its mud patch with shell, but weak oysters may die. Oyster losses due to mudworms are often high and the remaining infested oysters are unsaleable because of their poor condi­ tion and unsightly and foul smelling mud blisters, which rupture easily when the oysters are opened. In NSW, infested Sydney rock oysters can be left out of water in the shade for up to 10 days to kill mudworms and flatworms (see below), and some oyster farmers wash mud from oysters on their leases using boom-sprays on punts to lower the risk of infestation (Fig. 9). Figure 9.—Washing mud off oysters to control the mudworm, Botany Bay, Treating infested oysters in freshwater Sydney, NSW. Photograph by I. R. Smith, NSW Fisheries. for two days will kill mudworms without harming healthy oysters (Beattie, 2001). Some farmers have successfully used an iodine bath to kill mudworms. Oysters Flatworm I. mcgrathi can tolerate reduced salinities are left out to dry for 4–5 days, followed for some time, but reduced salinity may by a 2–3 h bath in an iodine-based disin­ Known as wafers or “leeches,” poly- affect reproductive behavior of the flat- fectant solution (0.1 g of active iodine per clad flatworms are common predators of worm larvae (O’Connor and Newman, liter of seawater), before returning to the oysters and other commercial bivalves 2001). Exposure to fresh water or satu­ lease. This treatment is more successful around the world. In NSW the flatworm, rated brine for 15 minutes is an effective in treating bad mudworm outbreaks than Imogine mcgrathi, was identified as a way to kill the adults. drying alone. threat to oyster production (Jennings and Pacific oysters in Australia have been Newman, 1996) in the early 1900’s. Flat- Heat Kill relatively free of most diseases, but they worms consume oysters at a rate of about Summer temperatures on exposed do suffer from mudworms. In Port Ste­ 1 oyster/flatworm/month, and when they leases can rise to 30–40°C and kill both phens, NSW, they are mainly affected occur in high numbers, they have devas­ Sydney rock and Pacific oysters. The by P. websteri. In Tasmania, farmers are tating effects (O’Connor and Newman, problem is most acute when low tides concerned about mudworms in Pacific 2001). Since the use of fine mesh trays coincide with the warmest period on a oysters, but they have not suffered serious (Fig. 3), cylinders, and baskets for oyster hot summer’s day (Potter and Hill, 1982). problems so far. In Tasmania, the mud- nursery culture (farming of single seed Some NSW farmers have installed irriga­ worm Boccardia knoxi is found in subtid­ oysters from 2–12 mm shell height), tion sprinkler systems on their leases and ally cultured Pacific oysters, whereas P. flatworm mortality has become a serious spray salt water over the oysters to keep websteri and P. hoplura occur in intertidal problem for Sydney rock, Pacific, and flat them cool. Other farmers use shade cloth oysters (Handlinger5). In South Australia oyster production in NSW. During low over trays to keep oysters cool and preda­ the mudworm in Pacific oysters is a prob­ tides, the fine mesh protects flatworms tors out, but unfortunately this practice lem in some bays in some years. This is from desiccation, allowing them to feed restricts water flow over the trays and rather surprising, as these bays are very on live spat. Regular inspection of spat in increases the risk of mudworm infesta­ oceanic; the water is very clear, and there nursery culture and increasing the mesh tions. Spraying oysters with seawater is no mud/silt on the bottom. The species size assist in controlling them. Worms keeps the oysters cooler than the shade of concern in South Australia are P. web­ can be killed by immersing oysters in cloth does (Potter and Hill, 1982). The steri, P. hoplura, and Boccardia chilensis hot water for 5–10 seconds or in fresh Sydney rock oysters that survive heat (Hone and Tonkin, 1993). water for 5 min (Beattie, 2001). stress grow well (Potter, 1983); however, Flatworms appear to be most abundant when flooding, as occurs in late summer in periods of prolonged drought when (February/March) in some years in the 5Handlinger, J. Department of Primary Indus­ tries, Water and Environment, Prospect, Tasman. estuarine salinities are relatively high. northern rivers in NSW, follows heat Personal commun., 2001. The reason for this is unclear, as adult stress, oyster mortalities from exposure

63(3) 21 to prolonged periods of fresh water are have spawned out, is considered to be an rock oyster harvests peaked in the mid increased. important marketing advantage, and the 1970’s at 13 million dozen or 7,800 t In South Australia, Pacific oyster farm­ farmers are interested in growing triploid (Nell, 1993), and Pacific oyster produc­ ers face the twin hazards of “dodge” tides, Pacific oysters. tion in Tasmania was only 0.1 million which occur when the diurnal cycle is in­ dozen (Dix, 1991). Since then, produc­ terrupted and there is no clear distinction Selective Breeding tion of Sydney rock oysters has declined between consecutive tides. A prolonged Oyster breeding programs to select (Nell, 1993) while that of Pacific oysters period of low tides can be a consequence for fast growth in Sydney rock oysters increased. By 1999/2000, annual produc­ and major heat kills of oysters can result. in NSW (Nell et al., 2000) and Pacific tion of Sydney rock oysters had stabilized The intertidal longline system was devel­ oysters in Tasmania (Ward et al., 2000) at 8 million dozen, and annual production oped to avoid them. It allows the farmer were established in 1990 and 1994, of Pacific oysters from Tasmania, South to quickly alter the growing height of the respectively. Both programs have been Australia, and Port Stephens, NSW, had oyster cylinders to obtain some relief, successful in increasing the growth climbed to 6.5 million dozen (Table 1). catching the tide at an earlier time. rates. Great success has been achieved This amounts to only an 11% increase in the selection of Sydney rock oysters in total production of oysters in Aus­ Genetic Improvement for fast growth (Nell et al., 1996, 1999) tralia over the past quarter of a century. and disease resistance (Nell and Hand, in During this time, Australia’s population Triploidy press). Time to market size (50 g whole increased by 36% from 14 to 19 million In NSW (lat. 27–37°S), triploid Sydney weight) for diploid and triploid progeny people (Australian Bureau of Statistics, rock oysters reach market size (50 g whole of a third generation breeding line was 2001). So these figures show a declining weight) on average 6 months earlier than reduced by 7 and 10 months, respectively, share of this market by oysters. In Aus­ the usual 3.5 years for diploids. Triploids out of 38 months for the diploid control tralia, oysters are mainly consumed on also survive and hold their meat condition (R. Hand, unpublished data, 2002). This the half-shell as an appetizer. better than diploids in winter and spring study also showed that the growth advan­ Exports of both Sydney rock oysters (Nell et al., 1994; Hand et al., 1998a; Nell tages of triploidy and selective breeding and Pacific oysters to various countries and Maguire, 1998). Triploids also grow are synergistic (Nell6). Preliminary data in Asia totals around AUD $3 million or faster than diploids at high water tempera­ show that time to market was reduced by 6% of the value of oysters produced in tures (Hand et al., 1998a), that is, in lower 7 months for progeny of fourth generation Australia in 1999/2000 (ABARE, 2000). latitudes in Australia. In addition the mor­ breeding lines selected for fast growth in They are for the gourmet market. Aus­ tality of triploid oysters is less than half Port Stephens, NSW. It is expected that a tralia imports frozen and chilled Pacific that of diploid oysters that are exposed 12 month reduction in time to market will oysters on the half shell from New Zea­ to winter mortality (Hand et al. 1998a, be achieved in another 4 generations, or 8 land and canned smoked oysters from b). Although triploids may suffer some years, of selection. Asia. In 1999/2000, the total value of discoloration of meat in summer and Mortality from QX disease was re­ imported oysters was AUD $5 million autumn, for farmers who want to grow duced from 86% to 64% in progeny of a (ABARE, 2000). a winter crop that is partially resistant to second generation disease resistance line Some specialization by the Sydney winter mortality, triploid oysters may be as compared with controls, in Georges rock oyster farmers in NSW has long a future option (Hand and Nell, 1999; River, NSW (Nell and Hand, in press). existed. They set and sell spat on sticks Hand, 2002). Farmers want to purchase On the basis of these and other results as “caught sticks” or single seed spat more triploid Sydney rock oyster spat, but from overseas it is anticipated that 4 scraped off sticks or plastic slats. Some the supply is limited because hatcheries generations, or 8 years, of selection farmers sell half-grown oysters to those lose many larvae when they are 2–8 days can reduce mortality rates from 64% who specialize in finishing oysters to old and post-settlement mortality of spat to 10%, thus producing a “QX disease market size over a 6–12 month period. (0.5–2.0 mm shell height at 1–6 weeks of resistant” oyster. The 10% mortality level There are no uniform oyster grade speci­ age) is high (Heasman et al., 2000). is an “acceptable” level for the Sydney fications for Sydney rock oysters; how- Farmers in Tasmania (lat. 42–43°S) rock oyster industry, and is the same as ever, traditional size grades for Sydney (Maguire et al., 1994b) and South when the oysters are not afflicted by any rock oysters are: Plate, Bistro, and Bottle Australia (lat. 32–35°S) (Nell, 2002) disease. Unfortunately, the partially QX grade oysters with an average whole had slow growth rates and poor meat disease resistant oyster is a host for the weight of 50, 45, and 35 g, respectively, condition in their triploid Pacific oysters parasite, Marteilia sydneyi. which equates to a shell height of around in the 1990’s. Taste tests showed that 77, 73, and 66 mm, respectively. More consumers liked triploids, but Maguire Harvesting and Marketing recently a “cocktail” grade has become et al. (1994a) reported a 6% incidence of Oyster production has remained commonly used to describe small oysters brown patches on their meats and none relatively stable since annual Sydney that do not meet traditional standards. on the diploid controls during summer. These oysters are usually small, 25 g 6Nell, John A. Port Stephens Fisheries Centre, However, the superior meat condition of NSW Fisheries, Taylors Beach, NSW 2316, (58 mm), and are commonly sold in “all the triploids in autumn, after the diploids Australia. Unpubl. data., 2002. you can eat” seafood buffets.

22 Marine Fisheries Review Table 1.—The oyster industry1 of Australia in 1999/2000.

Weight/dozen Total oyster Avg. farm gate Million Area available No. of oyster State and species Dozens of oysters (g) weight (t) price/dozen AUD $ for prod. (ha) farming operations

New South Wales Sydney rock oyster 7,899,454 530 4,187 3.59 28.4 4,088 493 Pacific oyster 399,662 610 244 4.26 0.9 7212 632 Queensland Sydney rock oyster 220,400 650 143 2.77 0.6 548 128 Tropical oysters3 25,000 650 16 2.51 0.1 594 109 South Australia Pacific oyster 2,516,000 750 1,887 3.73 9.4 1,900 94 Tasmania Pacific oyster 3,561,179 750 2,671 3.71 13.2 1,800 117 Total 14,621.695 9,148 52.6 9,116 1,004

1 After ABARE (2000). There is also experimental production of the local strain of the Sydney rock oyster in WA and the flat oyster in NSW, Tasmania, and WA. 2 These figures are also included above as many farmers in Port Stephens, NSW, grow both Sydney rock, Saccostrea glomerata, and Pacific oysters, Crassostrea gigas. 3 Coral rock or milky, S. cucullata, and black-lip oysters, Striostrea mytiloides combined. 4 There are an additional 61 km of foreshore leases.

Most Sydney rock oysters leave the according to meat quality employing Future farms live in the shell, packed in bags three meat grades: export (top grade), or boxes. Live Sydney rock oysters premium, and thrifty. These grades are In NSW and southern Queensland, keep best at 8–15°C and, being a hardy based on a meat/shell ratio and visual the number of oyster farmers and the intertidal species, will survive for 2–3 assessment of meats. area under cultivation will most likely weeks. Live Pacific oysters should be The main requirement for success­ decline, as small unprofitable operations held at the usual food refrigeration ful oyster culture is the availability of leave the industry and “poor” leases are temperature, around 4°C, and have a good quality water, which has sufficient handed back to the government. The typical shelf life of 7–10 days. Some plankton and good currents to promote government allows farmers to exchange farmers open their oysters and sell them growth and conditioning and, from a “poor” growing areas for “better” ones. on the half-shell directly to restaurants, public health point of view, no patho­ Cultivation of Pacific oysters in Port Ste­ clubs, and passing trade. Traditionally, genic bacteria. The Australian Shellfish phens, NSW, and flat oysters in southern smaller oysters in NSW were sold at Quality Assurance Program (ASQAP), NSW may increase. Once the hatchery about two dozen meats to a 250 ml glass a national program, is modeled on the production problems of the Sydney rock jar; however, this market has declined as National Shellfish Sanitation Program oyster have been resolved, the industry the market for small oysters on the half of the United States, and requires that may take advantage of improved breed­ shell has been developed. Most oysters shellfish harvest areas be classified on ing lines for fast growth and disease are sold in supermarkets or fish shops; the basis of a sanitary survey and the resistance. Triploids will then be used the remainder is consumed in restau­ results of an ongoing water-sampling for out-of season marketing of oysters rants and clubs. program. This program has been ap­ in autumn and winter, when diploids Similar specialization exists in the plied to aquaculture shellfish growing are spawned out and have thin meats. industries farming Pacific oysters in areas in Tasmania, South Australia, and Unfortunately, all attempts at producing Tasmania and South Australia. Some Western Australia and to one harvest tetraploid Sydney rock oysters have been farmers specialize in nursery culture and area in Queensland. Classification unsuccessful. Therefore, triploid induc­ others in finishing oysters to market size, of the first harvest area in NSW was tion in this species will continue to rely as in NSW. The size grades for Pacific completed in June 2001, and in August on chemical methods of induction, rather oysters in Tasmania and South Austra­ 2002, over 25% of the State’s produc­ than the simpler and more effective way lia are Jumbo (> 100 mm), Large (85– tion area was classified as Approved, of fertilizing eggs from diploids (2n) with 100 mm), Standard (70–85 mm), Buffet Conditional Approved, Conditional sperm from tetraploids (4n) to produce (60–70 mm), and Bistro (50–60 mm shell Restricted, Restricted, or Prohibited batches of 100% triploid (3n) spat (Nell, height) with approximate shell heights Area for harvesting. The NSW pro- 2002). It is important that either the trend and whole weights (g) of Pacific oysters gram currently requires that all oysters to sell oysters at a smaller size (e.g. bistro of 100 (93), 85 (75), 70 (57), 60 (45), and harvested in that state be depurated for instead of plate size) is reversed or the 50 (33) mm, respectively. Pacific oysters 36 h at ambient temperature 24–25°C price for bistro oysters is increased, be- are sold in three forms: fresh unopened before marketing for human consump­ cause the sale of small oysters for a small (by far the most common), fresh opened, tion; however, with the implementation price has greatly reduced profitability and frozen opened. Both the unopened of the ASQAP, the requirement for within sections of the industry. and opened oysters require refrigeration depuration will be determined by the There is still some room for Pacific during storage and transport. These two classification of a harvest area, as is the oyster cultivation to expand using sub- industries also attempt to market oysters case in other Australian states. tidal longlines in Tasmania and South

63(3) 23 Australia in 5–15 m depths. In NSW, I. Intraspecific studies of Crassostrea gigas in Australia. IV. Sensory evaluation of triploid and Saccostrea commercialis. Mar. Biol. 54: and diploid Pacific oysters, Crassostrea gigas there is also a need for farmers to ex- 157–169. (Thunberg), in Tasmania. In J. A. Nell and G. change “poor” growing areas for “better” Catterall, C.P., and I. R. Poiner. 1987. The poten­ B. Maguire (Editors), Evaluation of triploid growing areas. As the Tasmanian and tial impact of human gathering on shellfish Sydney rock oysters (Saccostrea commercia­ populations with reference to some NE Aus­ lis) and Pacific oysters (Crassostrea gigas) on South Australian industries are totally tralian intertidal flats. Oikos 50:114–122. commercial leases in New South Wales and reliant on hatchery production of spat, Cochennec-Laureau, B., F. Le Roux, F. C. J. Tasmania, p. 178–193. Final Report to FRDC, most oysters produced probably will be Berthe, and M. P. Hine. 2001. Could Mikro­ September, 1994, NSW Fisheries, Port Ste­ cytos roughleyi be mis-classified haplosporid­ phens Research Centre, Taylors Beach, NSW from improved breeding lines and their ian? Book of Abstracts, World Aquaculture and University of Tasmania, Launceston, Tas. hybrids. As for Sydney rock oysters in Society, p. 61. ______, N. C. Gardner, J. A. Nell, G. N. Kent, Coleman, N., and N. Hickman. 1986. Pacific and A. S. Kent. 1994b. Studies on triploid oys­ NSW, triploids will be used for out-of oyster found in Victoria. Aust. Fish. 45(6): ters in Australia. II. Growth, condition index, season oyster marketing of oysters. Fortu­ 8,10. glycogen content and gonad area of triploid nately in Australia, tetraploid broodstock Dix, T. G. 1975. Farming the sea. In M. R. Banks and diploid Pacific oysters, Crassostrea gigas and T. G. Dix (Editors), Resources of the sea, (Thunberg), in Tasmania. In J. A. Nell and G. is available to produce batches of 100% p. 93–100. Symposium of the Royal Society B. Maguire (Editors), Evaluation of triploid triploid Pacific oysters (Nell, 2002). of Tasmania, Hobart. Sydney rock oysters (Saccostrea commercia­ The industry in NSW, Queensland, ______. 1980. Growth of the native oyster lis) and Pacific oysters (Crassostrea gigas) on Ostrea angasi using raft culture in Tasmania, commercial leases in New South Wales and Tasmania, and South Australia is keen to Australia. Aquaculture 19:109–115. Tasmania, p. 37–71. Final Report to FRDC, expand its markets by increasing oyster ______. 1991. The Pacific oyster, Crassostrea September, 1994, NSW Fisheries, Port Ste­ gigas, in Australia. In W. Menzel (Editor), phens Research Centre, Taylors Beach, NSW exports. This may improve local market Estuarine and marine bivalve mollusk culture, and University of Tasmania, Launceston, Tas. prices of oysters. The implementation of p. 315–318. CRC Press, Boca Raton, Fla. Malcolm, W.B., 1987. The Sydney rock oyster. the ASQAP is facilitating oyster exports Farley, C.A., P. H. Wolf, and R. A. Elston. 1988. Agfact F3.1.1, Department of Agriculture, A long-term study of “Microcell” disease in Sydney, NSW, 12 p. from Australia. oysters with a description of a new genus, Medcof, J. C., and P. H. Wolf. 1975. Spread of Mikrocytos (g.n.), and two new species, Mik­ Pacific oysters worries NSW culturists. Aust. Acknowledgments rocytos mackini (sp.n.) and Mikrocytos rough­ Fish. 34(7):32–38. leyi (sp.n.). Fish. Bull. 86:581–593. Nell, J. A. 1993. Farming the Sydney rock oyster I wish to thank Frances Dorman, NSW Hand, R. E. 2002. Commercialisation of triploid (Saccostrea commercialis) in Australia. Rev. Sydney rock oysters, Saccostrea glomerata, Fish. Sci. 1:97–120. Fisheries for the map of oysters growing in New South Wales—Growth, survival and ______. 2001. Diseases of Sydney rock areas. I also thank Colin Sumner, Ross meat condition. PhD thesis, University of oysters. Fishnote, NSW Fisheries, Wollstone­ Lobegeiger, Kerry Jackson, and Steve Tasmanian, Launceston, 205 p. craft, NSW. ______and J. A. Nell. 1999. Studies on ______. 2002. Farming triploid oysters. McOrrie and Drs. Wayne O’Connor, triploid oysters in Australia. XII. Gonad Aquaculture 210:69–88. Geoff Allan, and Rosalind Hand for their discolouration and meat condition of diploid ______, E. Cox, I. R. Smith, and G. B. Magu­ critical comments and suggestions on this and triploid Sydney rock oysters (Saccostrea ire. 1994. Studies in triploid oysters in Austra­ commercialis) in five estuaries in New South lia. I. The farming potential of triploid Sydney review. Finally I thank the oyster farmers Wales, Australia. Aquaculture 171:181–194. rock oysters Saccostrea commercialis (Iredale and hatchery operators who provided me ______, ______, and G. B. Maguire. and Roughley). Aquaculture 126:243–255. 1998a. Studies on triploid oysters in Austra­ ______and G. B. Maguire. 1998. Commer­ with information on farming and hatch­ lia. X. Growth and mortality of diploid and cialisation of triploid Sydney rock and Pacific ery techniques. triploid Sydney rock oysters Saccostrea com­ oysters, Part 1: Sydney rock oysters. Final mercialis (Iredale and Roughley). J. Shellfish Report to Fisheries Research and Develop­ Literature Cited Res. 17:1115–1127. ment Corporation (FRDC), NSW Fisheries ______, ______, I. R. Smith, and G. B. Final Report Series, Report No. 10, NSW ABARE. 2000. Australian fisheries statistics Maguire. 1998b. Studies on triploid oysters in Fisheries, Port Stephens Research Centre, 2000. Canberra, ACT, 55 p. Australia. XI. Survival of diploid and triploid Taylors Beach, NSW, 121 p. Adlard, R. 2000. Bonamia spp. disease of flat Sydney rock oysters, Saccostrea commercia­ ______and R. E. Hand. In press. Evaluation oysters. In M. Heasman, and I. Lyall (Edi­ lis (Iredale and Roughley) through outbreaks of the progeny of second generation Sydney tors), Proceeding of the workshops held on of winter mortality caused by Mikrocytos rock oyster Saccostrea glomerata (Gould 3 March 2000 at the Sydney Fish Markets: roughleyi infestation. J. Shellfish Res. 17: 1850) breeding lines for resistance to QX problems of producing and marketing the flat 1129–1135. disease Martelia sydneyi. Aquaculture. oyster Ostrea angasi in NSW, p. 24–27. NSW Heasman, M., L. Goard, J. Diemar, and R. B. ______, A. K. Sheridan, and I. R., Smith. Fish. Res. Inst., Cronulla, NSW. Callinan. 2000. Improved early survival of 1996. Progress in a Sydney rock oyster Sac­ Adlard, R D., and I. Ernst. 1995. Extended range molluscs. Aquaculture CRC Project A.2.1. costrea commercialis (Iredale and Rough- of the oyster pathogen Marteilia sydneyi. NSW Fish. Rep. Ser.: Rep., 29, NSW Fisher­ ley) breeding program. Aquaculture 144: Bull. Eur. Assoc. Fish Pathol. 15:119–121. ies, Port Stephens Fisheries Centre, Nelson 295–302. Anderson, T. J., and R. D. Adlard. 1994. Nucleo­ Bay, NSW, 63 p. ______and I. R. Smith. 1988. Management, tide sequence of rDNA internal transcribed Hine, P. M. 1991. The annual pattern of infection production and disease interactions in oyster spacer supports synonymy of Saccostrea by Bonamia sp. in New Zealand flat oysters, culture. In D. I. Bryden (Editor), Fish dis­ commercialis and S. glomerata. J. Molluscan Tiostrea chilensis. Aquaculture 93:241–251. eases. Refresher course for veterinarians, Stud. 60:196–197. Holliday, J. E., and J. A. Nell. 1985. Concern Sydney, May 1988, p. 127–133. Proceedings Australian Bureau of Statistics. 2001. Year book over Pacific oyster in Port Stephens. Aust. 106, Post Graduate Committee in Veterinary Australia. Canberra, ACT, p. 130–134. Fish. 44(11):29–31. Science. University of Sydney, NSW. Bailey, G. N. 1975. The role of molluscs in Hone, P., and S. Tonkin. 1993. Zapping the mud- ______, I. R. Smith, and C. C. McPhee. 2000. coastal economies: the results of midden worm menace. Southern Fish. 1(1):28–29. The Sydney rock oyster Saccostrea glomerata analysis in Australia. J. Archaeol. Sci. 2: Jennings, K. A., and L. J. Newman. 1996. Four (Gould 1850) breeding programme: progress 45–62. new stylochid flatworms (platyhelminthes: and goals. Aquaculture Res. 31:45–49. Beattie, K., 2001. Oyster culture in Queensland. polycladida) associated with commercial oys­ ______, ______, and A. K. Sheridan. Queensland Dep. Primary Ind., Brisbane, ters from Moreton Bay, southeast Queensland, 1999. Third generation evaluation of Sydney Qld. 28 p. Australia. Raffles Bull. Zool. 44:493–508. rock oyster Saccostrea commercialis (Iredale Buroker, N. E., W. K. Hersberger, and K. K. Chew. Maguire, G. B., B. Boocock, G. N. Kent, and N. and Roughley) breeding lines. Aquaculture 1979. Population genetics of family Ostreidae. C. Gardner. 1994a. Studies on triploid oysters 170:195–203.

24 Marine Fisheries Review O’Connor, W. A., and L. J. Newman. 2001. Roughley, T. C. 1922. Oyster culture on the merata (Gould, 1850). Aquaculture 185: Predatory behaviour and halotolerance of Georges River, New South Wales. Tech. Ed. 197–205. stylochid flatworms, Imogine mcgrathi, from Ser. Technol. Mus., Sydney, NSW, 25, 69 p. Sullivan, M. E. 1984. A shell midden excavation Port Stephens, New South Wales, Australia. ______. 1925. The story of the oyster. Aust. at Pambula Lake on the far south coast of New Hydrobiol. 459:157–163. Nat. Hist. 2(5):163–168. South Wales. Archaeol. Oceania 19:1–15. Olsen, A. M. 1994. The history of the develop­ ______. 1926. An investigation of the cause Sumner, C. E. 1972. Oysters and Tasmania, Part ment of the Pacific oyster, Crassostrea gigas of an oyster mortality on the Georges River, 1. Tasman. Fish. Res. 6(2):1–15. (Thunberg) industry in South Australia. Trans. New South Wales, 1924–25. Proc. Linn. Soc. ______. 1974. Oysters and Tasmania, Part 2. Royal Soc. South Australia 118(4):253–259. NSW 51:446–491. Tasman. Fish. Res. 8(2):1–112. Pearson, M. 1981. Simple lime-burning meth­ Royal Commission of the Fisheries of Tasmania. ______. 1980a. Growth of Pacific oysters, ods in nineteenth century New South Wales. 1883. Government Printer, Hobart, Tas., p. Crassostrea gigas Thunberg, cultivated in Archaeol. Oceania 16:112–115. 8–11. Tasmania. I. Intertidal culture. Aust. J. Mar. Perkins, F. A., and P. H. Wolf. 1976. Fine struc­ Saville-Kent, W. 1891. Oysters and oyster- Freshwater Res. 31:129–135. ture of Marteilia sydneyi n.sp. haplosporidian culture in Australasia. Australasian Assoc. ______. 1980b. Growth of Pacific oysters, pathogen of Australian oysters. J. Parasitol. Advance. Sci. 3:550–573. Crassostrea gigas Thunberg, cultivated in 62:528–538. Smith, G. S. 1981/82. Southern Queensland Tasmania. I. Subtidal culture. Aust. J. Mar. Potter, M. A. 1983. Growth rates of cultivated oyster industry. J. Royal Hist. Soc. Queens- Freshwater Res. 32:411–416. Sydney rock oysters, Saccostrea (Crassostrea) land 11(3):45–48. Ward, R. D., L. J. English, D. J. McGoldrick, G. commercialis, in two estuaries in subtropical ______. 1985. The Queensland oyster B. Maguire, J. A. Nell, and P. A. Thompson. southern Queensland. Queensland J. Agric. fishery—an illustrated history. Queensland 2000. Genetic Improvement of the Pacific Animal Sci. 40:137–140. Department of Primary Industries, Brisbane, Oyster Crassostrea gigas (Thunberg) in Aus­ ______and B. J. Hill. 1982. Heat mortal­ Qld., 111 p. tralia. Aquaculture Res. 31:35–44. ity in the Sydney rock oyster, Saccostrea Smith, I. R., J. A. Nell, and R. D. Adlard. 2000. Wilson, R. 1970. Oyster farming spreads to Tas­ (Crassostrea) commercialis and the effective­ The effect of growing height and growing mania. Aust. Fish. 29(1):7–8. ness of some control methods. Aquaculture method on winter mortality in diploid and 29:101–108. triploid Sydney rock oysters Saccostrea glo­

63(3) 25