The growth and survival of experimental batches of hatchery-reared spat of Ostrea edulis L. and Crassostrea gigas thunberg,using different methods of tray cultivation

The seasonal growth and survival of experimental batches of hatchery-reared spat of the European oyster (Ostrea edulis) and the Pacific oyster (Crassostrea gigas) was followed in North Wales during the period 1972 to 1975. Three methods of tray cultivation were compared. These were: (a) trays suspended from a raft in the Menai Straits, (b) trays supported on trestles on the foreshore of the Menai Straits, and (c) trays in a laboratory nursery system which were supplied with sea water from Conwy estuary via a pumped storage system.Growth of oysters in the nursery system was consistently inferior to that of oysters kept at either site in the sea. Although in several years there were significant differences between the growth of oysters on the raft and in trays supported by trestles, on average neither site consistently produced larger oysters.Survival was significantly better in the nursery system for both species of oyster, but no consistent differences in survival were observed between either site in the sea.Seasonal growth of both species of oyster as well as the mortality of O. edulis were positively related to temperature. It was concluded on the basis of cost that (i) cultivation in systems employing pumped sea water would not be viable in the long term, and (ii) raft cultivation would only be suitable for post-hatchery sized oysters up to about 5 g live weight.     

Development and distribution of the non-indigenous Pacific oyster (<Emphasis Type="Italic">Crassostrea gigas</Emphasis>) in the Dutch Wadden Sea

Pacific oysters (Crassostrea gigas) were first observed in the Dutch Wadden Sea near Texel in 1983. The population increased slowly in the beginning but grew exponentially from the mid-1990s onwards, although now some stabilisation seems to be occurring. They occur on a variety of substrates such as mussel beds (Mytilus edulis), shell banks, dikes and poles. After initial settlement spat may fall on older individuals and congregate to dense clumps and subsequently form reefs. Individual Pacific oysters grow 3–4 cm long in their first year and 2–3 cm in their second year. Many mussel beds (Mytilus edulis) are slowly taken over by Pacific oysters, but there are also several reports of mussel spat settling on Pacific oyster reefs. This might in the end result in combined reefs. Successful Pacific oyster spat fall seems to be related to high summer temperatures, but also after mild summers much spat can be found on old (Pacific oyster) shells. Predation is of limited importance. Mortality factors are unknown, but every now and then unexplained mass mortality occurs. The gradual spread of the Pacific oyster in the Dutch Wadden Sea is documented in the first instance based on historical and anecdotal information. At the start of the more in-depth investigation in 2002, Pacific oysters of all size classes were already present near Texel. Near Ameland the development could be followed from the first observed settlement. On dense reefs each square metre may contain more than 500 adult Pacific oysters, weighing more than 100 kg per m2 fresh weight.     

Combined effects of temperature and diet on growth and biochemical composition of the Pacific oyster Crassostrea gigas (Thunberg) spat

Temperature and quality of the available food are important factors that influence the physiology of oysters; however, the combined effects have not been well studied. We evaluated the impacts of the temperature and diet on the growth, survival and biochemical composition in the Pacific oyster Crassostrea gigas spat, cultured in the laboratory for 8 weeks at 23, 26, 29 and 32°C and fed Isochrysis sp.‐Pavlova lutheri (IP) and Dunaliella tertiolecta (Dt). The growth and biochemical composition showed a pattern, which changed in response to rising temperature. The shell length was significantly longer, in spat fed the IP diet, except at 32°C, where both diets produced poor growth results. The survival was <50% after 5 weeks at 32°C, whereas at all other temperatures it was >88%. High temperatures directly increased lipids and saturated fatty acids, while the proteins, carbohydrates and unsaturated fatty acids decreased. High temperatures achieved in the environment, as those reached on clear summer days during low tides, are an important stressor in oyster spat, especially when the quality of the available food is poor.     

Tetraploid induction in tropical oysters,Crassostrea belcheri (Sowerby) and Crassostrea iredalei (Faustino)

Tetraploid induction has been conducted on temperate oysters but not on tropical oysters. In this study, different heat shocks (32, 35 and 38°C) and cold shocks (1, 4 and 7°C) were used to induce tetraploidy in two tropical oyster species, Crassostrea belcheri and Crassostrea iredalei, through meiosis I inhibition. Temperature shocks were applied on the newly fertilized eggs at 8–10 min post fertilization and terminated when second polar bodies began to form in the control eggs. The ploidy of the larvae and spat was determined via direct chromosome count. The percentage of larval survival until Day 20 was low (between 0.4% and 42.9%) for both temperature shocks and oyster species. No surviving larva was recorded for induction at 1, 4 and 38°C. Tetraploid spat was only recorded in C. iredalei but the percentage is low through heat shock induction of 32 and 35°C. This study shows that the tetraploid induction success rate was slightly higher in C. iredalei compared to C. belcheri. No surviving tetraploid spat were recorded for both oyster species through the cold shock method. This study shows that heat shock can be used to inhibit meiosis for the production of tetraploids but more experiments need to be conducted to determine the optimum temperature when dealing with tropical oysters.     

Growth of the oyster Crassostrea corteziensis (Hertlein, 1951) in Sonora, Mexico

This is the first evaluation of growth and survival of spat of the Cortez oyster Crassostrea corteziensis (Hertlein) produced under controlled conditions in a coastal area in the state of Sonora, Mexico for aquaculture purposes. A suspended culture technique, used for the Pacific oyster C. gigas, was used. The Cortez oyster has an isometric shell growth during the first 13 months, reaching 71.3±1.9 mm length, 52.6±1.3 mm thickness and 25.1±0.8 mm width. Allometric growth was found between total weight and length, thickness and width (survival was 70%). The relationships between particulate organic, inorganic material, chlorophyll a and environmental parameters with growth are described. Growth rates of C. corteziensis were affected by temperature with retardation at less than 18°C. For aquaculture purposes, it is recommended that spat be sowed after winter, and oyster harvest occur at the end of autumn. According to the von Bertalanffy equation, Cortez oysters would reach the traditional exploitation size of 65 mm (mean length) at harvest. Finally, the results of this study have shown that C. corteziensis is a good candidate for aquaculture projects in this region.     

The Effects of Stocking Density,Bag Mesh Size,and Bottom Sediment on the Growth and Survival of the Eastern Oyster,Crassostrea virginica,with Emphasis on Controlling Oyster Spat Fouling

This study was designed to determine if oyster spat fouling upon adult oysters, Crassostrea virginica, cultured in coastal Georgia could be controlled by stocking density, bag mesh size, substrate type, and tidal level (intertidally or subtidally). Oyster gowth and survival was also monitored for each treatment. Sediment type had no effect on the number of spat per oyster either in intertidal or subtidal areas. Greater growth occurred in subtidal bags placed on sandmud and sandclay substrates. Intertidal mud and sandhnud bottom treatments showed the least growth. Survival of oysters grown intertidally (64%) was better the those cultured subtidally (27%). Mesh size of the oyster growing bags -had no effect upon oysler fouling or growth (shell length) and survival of the oysters they contained. Stocking density did affect oyster fouling, with lower fouling per oyster in higher density treatments. Density had no effect on oyster growth (shell length) or survival at the levels tested. Heavy fouling occurred on all oysters in the mesh and stocking density experiments while they were suspended off-bottom, but an I l -fold decrease in fouling occurred after bags were placed on the sublidal river bottom.     

Effects of the winter Monsoon on the growth,mortality, and metabolism of adult oysters in Kinmen Island,Taiwan

The Pacific oyster, Crassostrea gigas, is cultivated intertidally in Kinmen Island by both a traditional way of growing oysters on the surface of stone blocks, nicknamed “rock oysters”, and a recently introduced and more efficient way of hanging them in clusters on horizontal nylon lines, i.e. “hanging oysters”. We investigated the growth and mortality of both types of oysters from late July to early December 2003, and measured condition index (CI) and rates of oxygen consumption and ammonium excretion for the hanging oyster. Growth of oyster shells stopped in early October for the hanging oysters and early December for the rock oysters. Mortality rates were higher for hanging oysters than rock oysters. Hanging oyster's O/N ratio and CI, determined by a home-made CI meter that measured the volume of oyster's inner shell cavity with high precision, decreased significantly in October. Hanging oysters were apparently in poor physiological condition during the winter Monsoon, which is characterized by cold and persistently strong wind. On Kinmen Island the monsoon season begins in late September and is accompanied by declining seawater temperature and high seston loads in oyster farms. Chlorophyll a concentrations and seston food quality decreased significantly in early October after the winter Monsoon began. The hanging oyster's poor acclimation to the local climate was probably caused by the import of its spat from southwest coast of Taiwan where it is warmer than Kinmen Island in fall and winter. We recommend that oyster growers collect spat locally or from areas of similar climate.     

Effects of temperature and photoperiod on the conditioning of the flat oyster (Ostrea edulis L.) in autumn

The production of the flat oyster Ostrea edulis (L.) natural spat in Europe has decreased almost by 60% in the past ten years. Thus, the importance of the production of oyster spat in hatcheries is evident. One of the critical steps in hatchery production is broodstock conditioning, especially difficult in autumn, when gonadal development is in resting period. Conditioning is influence by temperature, photoperiod and nutrition. In this work, the effects of two temperature and three photoperiod regimes on the conditioning of O. edulis were studied for three years by stereological analyses and registering number and dates of spawning and larval yield. Temperature had a positive effect on the gonadal development of O. edulis during conditioning. The percentages of germinal cells in oysters conditioned with a gradient of temperature (14–18°C) were double compared to oysters conditioned at 15°C. Oysters conditioned with longer photoperiods showed higher percentages of germinal cells. There was no interaction between temperature and photoperiod. Spawning was observed in the oysters treated with daylight (8–16 h) ten weeks from the beginning of conditioning. Flat oysters conditioned with 8 h and 8–12 h of daylight delayed the first spawning for a month. Total larval production was higher in the oysters treated with the longest daylight gradient. Gonadal and gametogenic development was a non‐synchronic process and the spawning extended for around two months. A protocol for flat oyster broodstock conditioning in autumn by using both a gradient of temperature (14–18°C) and daylight (8–16 h) is proposed.     

Ostreid herpesvirus OsHV‐1 μVar in Pacific oysters Crassostrea gigas (Thunberg 1793) of the Wadden Sea,a UNESCO world heritage site

The Wadden Sea is an extensive wetland area, recognized as UNESCO world heritage site of international importance. Since the mid‐1990s, the invasive Pacific oyster Crassostrea gigas (Thunberg 1793) population in the area has grown exponentially, having a distinct impact on the ecosystem. The recent spread of the emerging oyster pathogen Ostreid herpesvirus OsHV‐1 μVar worldwide and specifically in the oyster culture areas in the south of the Netherlands raised the question whether the virus may also be present in the Wadden Sea. In the summer of 2012 juvenile Pacific oysters were collected from five locations in the Dutch Wadden Sea. The virus was shown to be present in three of the five locations by real‐time PCR and sequencing. It was concluded that OsHV‐1 μVar has settled itself in Pacific oyster reefs in the Wadden Sea. These results and the recent discoveries of OsHV‐1 microvariants in Australia and Korea indicate that OsHV‐1 μVar and related variants might be more widespread than can be deduced from current literature. In particular in regions with no commercial oyster culture, similar to the Wadden Sea, the virus may go undetected as wild beds with mixed age classes hamper the detection of mortality among juvenile oysters.     

Changes in the distribution of epifaunal reefs and oysters during 130 years of dredging for oysters in Foveaux Strait,southern New Zealand

1. Foveaux Strait, a narrow seaway that is exposed to heavy wave action and strong tidal currents, has been the subject of an oyster fishery for over 130 years. Before the oyster fishery commenced the seafloor was extensively covered by epifaunal reefs that were tidally‐oriented, linear aggregations of patch reefs. 2. Patch reefs are formed by the bryozoan Cinctipora elegans cemented by encrusting bryozoa, ascidians, sponges, and polychaetes. The molluscan epifauna is dominated by the oyster, Tiostrea chilensis and bysally attached bivalves. Mortality of oysters is probably lower and recruitment and growth may be higher within the reef habitat. 3. Fishers found commercial densities of oysters occurred only on epifaunal reefs. Fishers exploited local groups of reefs. These groups form the patchily distributed oyster beds characteristic of this fishery. 4. Dredging for oysters progressively modified reefs until oysters were the only epifauna remaining. Dredges caught oysters more efficiently after the catch bag no longer became saturated with other epifauna. This heightened efficiency allowed fishers to rapidly reduce oyster density to commercial extinction. Oyster density has not rebuilt on oyster beds abandoned by fishers. 5. The rate of modification of epifaunal reefs was slower during the early years of the fishery but has accelerated, especially over the last 37 years. Frequency of disturbance increased as the numbers of vessels fishing grew and fishers developed speedier dredging methods. Intensity of disturbance also increased as heavier dredges were introduced and allowed focused fishing of reefs. 6. Oysters became reduced to low densities in the eastern and central areas that fishers then abandoned. The commercially exploited area subsequently expanded to the limits of Foveaux Strait. 7. With accelerated modification of oyster habitat, disease mortality has become more important. 8. Attempting to rebuild the fishery by oyster enhancement may be more successful conjoined with habitat restoration. Copyright © 1999 John Wiley & Sons, Ltd.     

Pacific oysters crassostrea gigas (Thunberg) of possible French origin in natural spat in the British Isles

• 1 Hatchery-reared Pacific oysters (Crassostrea gigas) grown in the British Isles and Guernsey originate from an introduction through quarantine of small numbers of oysters from British Columbia, Canada.
• 2 Previous electrophoretic analysis of samples of these oysters have shown the glucose phosphate isomerase locus to be monomorphic.
• 3 Recent analysis of oysters from a commercial hatchery in Guernsey revealed a second allele at low frequencies which was unexpected and was thought to indicate the presence of oysters from another stock.
• 4 Samples of hatchery-reared oysters from France showed that they were highly polymorphic and carried the unexpected allele and four others.
• 5 A natural spatfall of oysters from the River Teign (Devon) was sampled and these carried three alleles which were also found in the French C. gigas. This suggests that there has been movement of C. gigas possibly of French origin into this river.
• 6 This finding and its implications in terms of conservation and management are discussed.

     

Evaluating Sediment Accretion on a Relic Oyster Reef in Mobile Bay,Alabama

Abstract

Sediment traps were deployed at Fish River Reef (FRR), a relic oyster reef on the eastern side of Mobile Bay, and at Cedar Point Reef (CPR), a productive oyster reef on the western side of Mobile Bay, Alabama, from July through October 1999. Sediment accretion at FRR was two to three times greater than sediment accretion at CPR. The proportions of particulate organic matter and ash in the sediment at the two sites were similar. The proportion of coarse to fine sediment at CPR was greater than at FRR. Also, the sediment at FRR was black and had a sulfide odor suggesting anoxia, while the sediment at CPR was brown and odorless. Various fishes and invertebrates colonized the sediment traps at CPR, while those at FRR were devoid of live organisms. Oyster spat had settled on the shells in the traps at CPR but not on those at FRR. Results suggest that in order to restore oysters at FRR, cultch material should be dispersed during periods of peak larval settlement to prevent inhibitory levels of siltation on cultch before spat settle.     

Benthic community changes associated with intertidal oyster cultivation

A study of the environmental effects associated with the trestle cultivation of Pacific oysters, Crassostrea gigas Thunberg, was conducted at a commercial cultivation site in the River Exe estuary, Devon, England. Small, but significant, changes were detected in the macrofaunal community sampled beneath oyster trestles compared with that found in adjacent uncultivated areas. These changes were associated with an increase in organic and silt composition and a reduction in the depth of the oxygenated layer of the sediment beneath the trestles. Water velocity was decreased by the presence of the trestles which probably led to the increase in sedimentation rate observed beneath them. Although biological and physical changes were observed, they were relatively minor compared with the extreme environmental changes associated with the suspended culture techniques used for other bivalve species and fishes. However, other studies suggest that the environmental effects associated with oyster cultivation become more severe in areas of large-scale (hectares) cultivation.     

牡蛎礁修复的底物筛选：新、旧牡蛎壳附苗效果比较#br#

通过2019年室内和野外附着实验,检验了牡蛎壳(新壳和旧壳)和生物膜(有生物膜和无生物膜)对牡蛎附着量的影响。室内附着实验表明,在生物膜处理下新壳上牡蛎附着量显著高于旧壳(P<0.05);而在无生物膜对照组中,新、旧壳上牡蛎附着量无显著差异(P>0.05)。野外附着实验发现,生物膜显著提升了旧壳上牡蛎附着量,但对新壳上牡蛎附着量无显著影响。通过2020年野外附着实验,检验了牡蛎壳(新壳和旧壳)和潮区(滩面以上0.6 m和1.1 m)对牡蛎和藤壶附着量的影响。牡蛎附着量在每个潮区中,15 d、45 d和70 d时新壳均显著高于旧壳(P<0.05)。藤壶附着量仅在0.6 m潮区中、15 d时新壳显著高于旧壳,而45 d和70 d时,各潮区中新、旧壳上藤壶附着量均无显著差异(P>0.05)。研究发现,总体来看新壳的附苗效果好于旧壳,这种差异涵盖了整个牡蛎繁殖、附着及补充的高峰期。因此,牡蛎礁修复中应优先选取新壳作为底物。     

Use of premature New Zealand dredge oyster Tiostrea lutaria Hutton larvae for spat production

The New Zealand dredge oyster Tiostrea lutaria Hutton is an incubatory ostreid species that produces fully developed pediveliger larvae, which typically settle shortly after release from the parent. Broods of larvae obtained by opening incubating oysters provide a potential method of spat production, but only a small proportion of the broods obtained in this way are the late‐stage, ready‐to‐settle pediveligers. The majority of the broods are gastrula‐, trochophore‐ and veliger‐stage larvae. Experiments were undertaken to determine whether these early stages, as well as the pediveliger stage, could be reared through to settlement, and so make spat production based on opening incubating oysters much more efficient. Experiments conducted at three temperatures (ambient, ambient + 3 °C and ambient + 6 °C) and under three food regimes (with and without cultured microalgae and without dissolved organics) were unsuccessful in ex‐parent rearing of early larvae (gastrulae and trochophores). Later stage larvae, both veligers and pediveligers, were successfully reared, and high (> 75%) but variable levels of settlement were achieved. Ex‐parent rearing did not benefit from elevated temperatures or the presence of food, and settlement of spat from these prematurely released larvae may be reduced in the presence of food. The ability to rear veliger larvae, as well as pediveligers, greatly increases the potential to use the opening of incubating adult oysters during the breeding season as a source of dredge oyster spat.     

Farming triploid oysters

Although the commercial benefits of triploidy have been evaluated in the Pacific oyster Crassostrea gigas (Thunberg, 1793), eastern oyster C. virginica (Gmelin, 1791), Sydney rock oyster Saccostrea glomerata (Gould, 1850) and European flat oyster Ostrea edulis (Linnaeus, 1750), so far this technique has only been commercialised for Pacific oysters.

Commercial production of triploids on the West Coast of North America began in 1985. Since then production of triploids has greatly increased and the use of tetraploid males to fertilise eggs from diploids to produce batches of 100% triploids has been developed. In 1999/2000, triploid Pacific oysters made up 30% of all Pacific oysters farmed on the West Coast of North America. Some hatcheries now use tetraploid males instead of chemical or physical stress to produce triploids. The rapid uptake of triploid and tetraploidy techniques has been facilitated by the almost total dependence that these oyster industries have on hatcheries for the supply of seed. This industry in the Pacific Northwest of the US and in British Columbia, Canada, would not have developed to its current size without hatchery seed supplies. Triploids are preferred over diploids in summer because diploids are less marketable when in spawning condition.

There was only limited interest in triploidy production in France until 1999, when IFREMER began to make sperm from tetraploids available to commercial hatcheries. In 1999/2000, only 10% to 20% of all the hatchery-supplied Pacific oyster spat were triploids, but with the use of sperm from tetraploid oysters, this could increase sharply.

Elsewhere around the world, the commercial uptake of triploid oysters has been slow to develop. However, in countries where the production of Pacific oysters is based on hatchery supply of seed, it is likely that with the use of tetraploid oysters, the farming of triploid oysters will increase in the near future.     

Growth, fatness and gross biochemical composition of the Japanese oyster, Crassostrea gigas, in Stanway cylinders in the Bay of Arcachon, France

A new method of oyster cultivation, the Stanway oyster cylinder, has been investigated in the Bay of Arcachon since 1989. A comparative study was carried out between the growth of spat and 18-month-old Crassostrea gigas oysters, in cylinders and in traditional bags. The growth in height and in whole weight was lower in cylinders. In contrast, the tests showed a better quality of the meat, with higher condition index and higher carbohydrate content, and a better quality of the shell, with higher density and better shape. Therefore, because of the improvement in oyster quality, the use of the cylinder seems to be advantageous for the Arcachon oyster industry.     

Gametogenetic cycle and reproductive effort assessed by two methods in 3 age classes of Pacific oysters, Crassostrea gigas, reared in Normandy

Two methods were used to estimate the reproductive output of female Pacific oysters reared in Normandy: histology with image analysis and ELISA (Enzyme-Linked ImmunoSorbent Assay) which allowed the quantification of egg protein. Condition indices, gonad area and gametogenetic stages of the oysters were determined in the entire population (males and females) between May and October 2005. All investigations were performed in 3 age classes: oysters in their first, second or third years (corresponding to spat, half-grown and market-sized oysters, respectively). Both quantitative histology and ELISA provided similar results in terms of reproductive effort (illustrated by the gonado-somatic index, GSI) except during the GSI drop, corresponding to spawning, which was less marked with the ELISA method. Growth depended on oyster age, the sex ratio was well balanced and the reproductive cycle was synchronized in all age classes. In the 3 age classes, most of the oysters were ripe and ready to spawn on August 8, and ten days after the post-spawning stage was observed in 40% of spat oysters and 70% of half-grown and market-sized bivalves. The major difference between age classes was observed in the reproductive investment, with spat having a lower reproductive output. For example, in males and females, the gonad area reached 78–79% in the median animal section at full maturity (August 8) in half-grown and marketable oysters while it attained only 59% in spat. At the same time, GSI in females was, respectively in spat and the 2 oldest age classes, 33% (quantitative histology)–36% (ELISA) and 55% (quantitative histology)–60% (ELISA). The mean assessed gonad weight and fecundities increased with the age of the oysters: 1.3 g and 12 million eggs, 7.8 g and 135 million eggs, and 11.5 g and 146 million eggs in spat, half-grown and market-sized oysters, respectively. Marked differences thus appear between 2 and 3-year-old oysters and spat. As early as their first reproductive cycle, the young oysters not only showed the reproductive features of the species in Normandy, but also a pronounced lower reproductive effort. This lower energy demand could explain their higher survival rate.     

Biochemical changes in oyster tissues and hemolymph during long-term air exposure

The Pacific oyster Crassostrea gigas is a sessile bivalve that inhabits the intertidal zone and therefore frequently exposed to air during the tidal cycle. It is highly adaptive to hypoxic conditions. We have studied the physiological state of oysters during long-term exposure to air. The oysters became hypoxic when exposed to air or hypoxic seawater. The 50% lethal time of oysters exposed to air at 4, 15 and 20°C was 47.8, 15.9 and 12.2 days, respectively. The hemolymph pH decreased by day 3; however, it showed a slight increase by day 5 at both 4 and 20°C. The adenylate energy charge (AEC) values decreased rapidly on the first day of air exposure in the adductor muscle, mantle, gill and body trunk, and these decreases were accompanied by decreases in ATP concentrations and increases in AMP concentrations. The AEC values in all of the tissues had fallen to below 30% by day 50 of air exposure at 4°C. These data suggest that the energy state of oysters deteriorates rapidly with air exposure. Consequently, AEC values may be useful indices of the physiological state of the oyster during long-term exposure to air.     

Early growth and reproduction of hatchery-produced Pacific oyster Crassostrea gigas in Gamakman Bay off the southern coast of Korea

We investigated the early growth and reproduction of hatchery-produced Pacific oysters Crassostrea gigas raised in a suspended long-line facility in Gamakman Bay, off the south coast of Korea. In October 2009, 4?months after transplanting, shell length had increased from 27.4 (July) to 82.5?mm (October), and tissue weight had increased from 0.2 to 5.2?g, indicating that the oyster had reached a marketable size in this month. Histological studies indicated rapid gonad maturation, and the oysters spawned during August and October, with a peak in September. An enzyme-linked immunosorbent assay used to quantify egg biomass revealed that the oysters produced a relatively small quantity of eggs, ranging from 5.1?% (August) to 8.8?% (September) of their body weight. The low total carbohydrate reserve in the tissue recorded in August and September coincided with intense energy utilization due to spawning, while the protein maximum in September matched peak egg mass. Our results suggest that hatchery-produced seed could supply a portion of the spat required in Gamakman Bay as well as in other oyster culture grounds of Korea, where the oyster industry is facing a shortage in the supply of natural spat.