Evaluation of progeny of fourth generation Sydney rock oyster Saccostrea glomerata (Gould, 1850) breeding lines

The progeny of four 4th generation Sydney rock oyster Saccostrea glomerata (Gould, 1850) breeding lines that were selected for fast growth were compared in a 3‐year farming experiment. Oysters of the most improved breeding line (line 2) reached market size (≥50‐g whole weight) 15 months earlier than non‐selected control oysters (3 years and 5 months). The average reduction in time to market size for oysters of all four breeding lines was 12.5 months.     

湄洲湾牡蛎体重金属和石油烃的含量及评价

本文利用1998年4月和8月据湄湾环境调查资料,分析了牡蛎体重金属和石油烃的含量及分布。结果表明:湄洲湾福建炼油厂码头(上西)附近海域,牡蛎体重金属和石油烃的含量明显高于湾内其他养殖区。Cu、Cd、Zn 和石油烃的含量分布呈湾西岸水域>湾东岸水域>湾口水域。牡蛎体Cu污染指数的范围和平均值分别为0.17-0.88和0.30,属微污染到轻污染水平。Pb、Cd、Zn污染指数的范围和平均值分别为0.008-0.09、0.06-0.24、0.03-0.13和0.05、0.13、0.08,总体上属清洁水平。     

Total Mercury Bioaccumulation in Tissues of Carnivorous Fish (Micropogonias furnieri and Cynoscion acoupa) and Oysters (Crassostrea brasiliana) from Sepetiba Bay,Brazil

Total mercury (Hg) levels were determined by cold vapor atomic absorption spectrophotometry (CVAAS) in tissues of two species of carnivorous fishes and in the soft tissue of oysters caught in Sepetiba Bay, Brazil. Hg was distributed unevenly in the organs and tissues of the fish; the mean Hg content was highest in the kidneys (0.048 μg/g wet weight) and lowest in the gills (0.004 μg/g w.w.). Mean Hg levels were higher in the oysters (0.052 μg/g w.w.) than in the fish (0.022 μg/g w.w). The total Hg concentration did not exceed the maximum concentration for food allowed by Brazilian legislation in any of the fish and oyster samples analyzed. Moreover, the Hg concentrations observed were all within the maximum level for fish recommended by the Food and Agriculture Organization (FAO; 0.5 μg/g w.w.).     

Impacts of Lactobacillus plantarum in Depuration for Reducing Vibrio parahaemolyticus in Pacific Oysters (Crassostrea gigas)

This study investigated potential application of lactic acid bacteria (LAB) in depuration for reducing Vibrio parahaemolyticus in oysters. Lactobacillus plantarum ATCC 8014, which exhibited strong bactericidal effects against V. parahaemolyticus in vitro, was added to artificial seawater for depuration of Pacific oysters (Crassostrea gigas) inoculated with V. parahaemolyticus BE 98-2029 (O3:K6) to levels of about 10⁴ MPN/g at 15 ± 1 and 10 ± 1°C. Application of L. plantarum ATCC 8014 treatment (10⁷ CFU/mL) in oyster depuration did not enhance reductions of V. parahaemolyticus in oysters depurated at 15 ± 1°C but significantly decreased (p < 0.05) levels of V. parahaemolyticus in oysters depurated at 10 ± 1°C after 5 days (3.40 log reductions) when compared with controls (2.75 log reductions). It is not clear if a competitive exclusion by LABs to compete with V. parahaemolyticus binding sites in oyster tissues plays a role in the reduction of V. parahaemolyticus in the oysters. Further studies utilizing different types of LABs in oyster depuration might provide additional knowledge for application of LAB in depuration for decontaminating V. parahaemolyticus in oysters.     

Evaluation of the progeny of the fourth‐generation Sydney rock oyster Saccostrea glomerata (Gould, 1850) breeding lines for resistance to QX disease (Marteilia sydneyi) and winter mortality (Bonamia roughleyi)

The Sydney rock oyster breeding programme began in 1990 and initially focused on faster growth and resistance to winter mortality disease (WM, Bonamia roughleyi) before including QX disease (QX, Marteilia sydneyi) resistance in 1997. Four generations of oysters have now been exposed to these diseases at three sites in the Georges River, NSW, Australia (Lime Kiln Bar, LKB; Woolooware Bay, WB; and, Quibray Bay, QB). Non‐selected control oysters and lines developed at each site (Line 1 – LKB, Line 2 – WB, Line 3 – QB) were placed at the three sites alongside a new QX‐resistant line (Line 4) bred from QX survivors in other NSW estuaries. Line 1 oysters grew to a marketable size (>50 g) in two years with minimal losses following QX disease outbreaks: 28% mortality compared with 97% in controls. Losses in Line 3 oysters selected for WM resistance at QB were reduced by more than half (23% versus 52%). Line 2 performed best at WB, but this line showed excellent resistance to QX at LKB and WM at QB, indicating that breeding for resistance to both diseases is effective. However, selection of oysters for QX did not confer resistance to WM and vice versa.     

5种常见珍珠贝的系统发育和遗传多样性分析

利用RAPD标记分析了珠母贝属常见的马氏珠母贝、大珠母贝、珠母贝、解氏珠母贝以及珍珠贝属常见企鹅珍珠贝的系统发育,同时分析了马氏珠母贝和大珠母贝不同地理种群的遗传多样性,并以邻接法（neighbor-joining,NJ）构建了种间及种群间的系统分支图。结果表明：（1）在珍珠贝5种9个种群中,大珠母贝的4个种群最早聚在一起分别成为2个姊妹群,这2个姊妹群聚合为1个单元群后,又与珠母贝聚在一起,然后才与马氏珠母贝姊妹群聚合成的单元群聚合,再与解氏珠母贝聚合,最后才与企鹅珍珠贝聚合;（2）珠母贝属4种珍珠贝进化程度由低到高的等级顺序为解氏珠母贝-马氏珠母贝-珠母贝-大珠母贝;解氏珠母贝是最晚形成的种类;（3）比较5种珍珠贝野生种群的Nei＇s多样性和Shannon多样性值为：马氏珠母贝（0.4111和0.5933）〉珠母贝（0.3971和0.5784）〉企鹅珠母贝（0.3831和0.5493）〉大珠母贝（0.3388和0.4999）〉解氏珠母贝（0.3016和0.4452）;（4）无论是马氏珠母贝,还是大珠母贝,野生种群的遗传多样性值均大于养殖种群。     

The effect of temperature on physiological energetics of a fast‐growing selective strain and a hatchery population of the Pacific oyster (Crassostrea gigas)

Growth is an important aquaculture trait, which has been one of the most important traits for genetic improvement in aquatic species. Numerous fast‐growing domesticated aquaculture organisms are being cultured, but the physiological processes underlying growth remain largely unexplored. The Pacific oyster (Crassostrea gigas) is one of the most widely farmed bivalves. In order to improve the productivity traits, a fast‐growing selective strain of C. gigas was established. In this study, we compared physiological energetics of the fast‐growing selective strain and an unselected hatchery population of C. gigas under different conditions of temperature. Components of energy gain (clearance rates, ingestion rates, absorption efficiency and absorption rates), energy loss (metabolic rates) and resulting energy budget (scope for growth) were analysed at four temperatures (15, 20, 25 and 30°C). The results indicated that selective breeding oysters had a higher energy gain compared to unselected oysters, but the selected strain and hatchery population of oysters did not significantly differ in metabolic rates at all tested temperatures (p > 0.05). The enhanced energy gain resulted in almost two times higher scope for growth in selective breeding oysters compared with unselected oysters. Physiological characteristics of C. gigas were greatly affected by temperature and showed a fluctuation with the increase in temperatures. The selective breeding oysters outperformed those of hatchery population in growth performance by an increased energy gain along with a similar energy loss. This study provided insight into physiological energetics accounting for growth improvements in fast‐growing selective strain of C. gigas.     

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.     

Mortality in single‐pair mating families of QX disease‐resistant and wild‐type Sydney rock oysters (Saccostrea glomerata)

QX disease causes mass mortalities among Sydney rock oysters (Saccostrea glomerata). To overcome commercial production losses, Industry & Investment NSW has been developing mass selected QX disease‐resistant breeding lines since 1997. This breeding programme has significantly reduced QX‐associated mortality in the Lime Kiln Bar (LKB) breeding line relative to non‐selected, wild‐type (WT) oysters. The current study assessed mortality in families produced by single‐pair mating between LKB and WT oysters. When these families were grown in a QX disease‐prone area, the progeny of LKB × LKB crosses had significantly lower mortality compared with LKB × WT or WT × WT families. Mortality in the different crosses was associated with infection by sporulating Marteilia sydneyi, the parasite responsible for QX disease. Overall, the study identified a strong association between parentage and mortality resulting from QX disease.