Studies on triploid oysters in Australia: farming potential of all-triploid Pacific oysters, Crassostrea gigas (Thunberg), in Port Stephens, New South Wales, Australia

Triploid Pacific oysters Crassostrea gigas farmed in Port Stephens, NSW had an exceptionally fast growth rate and reached a whole weight of 55 g in 13 months versus 20 months for diploids. Mortality of the triploids (24.5±2.94%) was significantly lower (P<0.05) than that of the diploids (40.0±2.26%) over the duration of the experiment (July 2002–February 2004). Unfortunately, this advantage was offset by discoloration of the meats of the triploids when they were in better condition than the diploids over summer (October 2003–March 2004). However, discoloration of meat of triploids had cleared up by April 2004 and neither did they suffer this problem from April–September 2003. The triploids also had a lower peak condition than the diploids. Oysters in peak meat condition, i.e. spawning condition, are preferred for the half shell trade in Australia and in this study, there was at least a six‐month period prior to discoloration, when the triploids were large enough and had sufficient meat condition for marketing on the half shell.     

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。     

Towards development of large-scale hatchery cultivation of larvae and spat of the pearl oyster Pinctada mazatlanica in Mexico

The results of a series of pilot-scale runs with P. mazatlanica larvae from 2004 through 2006 are reported. Preliminary runs in 2004 and 2005 used broodstock collected in summer, when massive spawning of wild populations naturally occurs. However, results of larval development were very poor and failed to produce spat in both years. In 2006, ripe broodstock were still collected in summer, but also in the spring time, based on the hypothesis that the gonads in this season were in better reproductive condition that in summer. Three larval runs were conducted in 2006: two in spring and one in summer. Larvae growth and survival greatly increased in both spring runs, ending with two successful productions of spat (∼ 20 × 10³ and ∼ 100 × 10³ juveniles). The summer larval run in 2006 failed again to produce spat. Additionally, the first run of April 2006 refers to an experiment that evaluated two different larval culture conditions: constant temperature (27 °C) and low stocking density (3-4 larvae ml^− 1) versus variable temperature (24-28 °C) and high stocking density (8-9 larvae ml^− 1). The first trial significantly increased larval survival and growth, which in turn resulted in greater numbers of settled spat, in comparison of the second trial, where survival, growth, and settlement of spat were significantly lower. Also in 2006, the quality of seawater used at the hatchery was evaluated with microbiological and chemical tests. The implication of these tests, together with results from all experiments are analyzed and discussed in terms of the potential development of large-scale hatchery cultivation of P. mazatlanica larvae in Mexico.     

Effect of Stocking Density on Growth and Survival of the Rainbow Pearl Oyster <Emphasis Type="Italic">Pteria sterna</Emphasis> (Gould 1852) during Nursery and Late Culture in Bahía de La Paz,Baja California Sur,México

Growth and survival of the rainbow pearl oyster, Pteria sterna (Gould 1852), was evaluated in field culture at Bahía de La Paz, México. Mexican made Nestier^TM trays were used in nursery culture from March to July 1999 at four different stocking densities (25, 50, 75 and 100 individuals/tray). Late culture proceeded from July 1999 to March 2000 in sandwich nets and rail cages. Each artifact received 70 to 75 individuals. We studied the long-term effect of nursery culture stocking treatments. Growth patterns were examined using shell volume (height × width × depth, in cm³). Survival was estimated monthly. Growth and survival were acceptable regarding routine operations, but variations in this experiment depended on stocking density and type of late culture device. The interaction of density and culture device was significant for shell volume at the end of the experiment (F = 3614.14; p < 0.0001). Final shell volume depended on stocking density in nursery culture (F = 8.09, p < 0.001), but culture device had no influence (F = 0.76; p = 0.3). The results indicated that growth and survival in nursery culture were not proportionally related with stocking density. The change to late culture improved overall response. Advantages in growth were favorable for D50 C only. Rail cages promoted better survival than sandwich nets. Based on the natural behavior of P. sterna, the Optimal Stocking Density may be higher than the ranges tested in the present study. We recommend new strategies to improve the actual culture technology for P. sterna. A 3-dimensional culture unit might be an important advantage for this species regarding territorial exploitation and efficiency of spatial management in the production cycle.     

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.     

海南岛沿岸牡蛎体内六六六的时空变化特征分析及风险评价

于2006—2011年间每年的3月份,在海南岛沿岸选取的4个重要港湾（马袅港、东寨港、八所港、榆林港）采集近江牡蛎（Crassostrea rivularis Gould）成体30只,用气相色谱法测定其六六六（HCHs,包括α-、β-、γ-、δ-HCH）含量。结果显示,2006—2011年近江牡蛎体中HCHs含量范围是未检出～1.16 ng.g-1,平均含量是0.15 ng·g-1,与1985年海南岛贝类体内的HCHs残留量相比,20多年间浓度降低至原来的1/45。在这6年中HCHs含量于2006—2008年先略微下降,之后小范围上下波动,但总体上呈平稳的趋势;样品中HCHs区域平均含量由高到低依次为马袅港〉东寨港〉八所港〉榆林港。通过对HCHs的组分特征分析,认为海南岛采样海域周围近年没有新的HCHs污染源输入。与世界其他海域贝类体内HCHs含量比较,海南岛沿岸牡蛎体内HCHs残留量较低,符合中国《海洋生物质量》一类质量标准。通过计算安全消费量,认为海南岛沿岸海域牡蛎体内HCHs致癌风险和暴露风险均在可接受的范围之内。