硬壳蛤的人工育苗技术

硬壳蛤 (Mercenariamercenaria)亲贝于 2 0 0 0年由美国引入大连 ,采用阴干和温度变化刺激对其进行人工催产 ,亲贝诱导排放比例可达 80 %。水温 18～ 2 6℃ ,2 0 .5～ 2 4 0h胚胎发育到面盘幼虫 ,孵化率达 94 %。浮游幼虫前期饵料以湛江等鞭金藻 (Iscochrysiszhanjiangensis)为主 ,逐渐添加新月菱形藻 (Nizschiaclosterium) ,后期以新月菱形藻为主。硬壳蛤幼虫温度、盐度的适宜范围分别为 19～ 2 7℃、2 5 .0～ 3 3 .6。饵料以混合投喂效果最佳 ,湛江等鞭金藻次之。浮游幼虫培养 12～ 17d ,幼虫壳长达 2 0 0～ 2 10 μm ,采用在培养池底铺砂做附着基 ,幼虫变态率达 2 1% ,稚贝培养 3 0d后可达 1mm左右     

硬壳蛤稚贝的中间培育技术

2001年6月至10月和2002年8月至10月对硬壳蛤稚贝中间培育进行了试验研究。中间培育选择了潮间带池塘底播、池塘网箱、海区吊挂网袋和育苗池网箱等方式。池塘底播试验在黄海北部庄河海域潮间带池塘(泥底)和渤海营城子海区的潮间带池塘(砂底)进行。结果表明:不同中间培育方式稚贝的日生长量和成活率存在显著性差异(P<0.05),采用网箱和网袋的中间培育方式能够明显地提高稚贝的生长速度和成活率,海上网袋、池塘网箱和育苗池网箱稚贝壳长日生长量分别为0.16mm·d~(-1)、0.14mm·d~(-1)、0.15mm·d~(-1),成活率大于98.0％,试验结束时稚贝的壳长大于10mm。底播方式培养稚贝在试验结束时壳长小于7mm,壳长日生长量小于0.06mm·d~(-1)。两地潮间带池塘的成活率差异极显著(P<0.01),试验结束时渤海营城子的成活率为96.0％。     

Exotic hard clam in Tokyo Bay identified as Mercenaria mercenaria by genetic analysis

ABSTRACT:   An exotic hard clam has been observed in Tokyo Bay since the mid-1990s, which has been morphologically identified as Mercenaria mercenaria . The authors have determined 444-bp partial nucleotide sequences of mitochondrial DNA (mtDNA) 16S rRNA gene of 31 hard clam individuals collected in three locations of Tokyo Bay. Phylogenetic analysis indicated all individuals to be M. mercenaria . Two shell interior colorations (white or purple) were observed, but no relationships between the colorations and mtDNA haplotypes were detected. Frequency of clam individuals having white or purple shell significantly differed among locations, which was accompanied by heterogeneous amounts of acid-volatile sulfides and organic matter and mud ratio.     

Hard clam,Mercenaria mercenaria,broodstocks: Genetic drift and loss of rare alleles without reduction in heterozygosity

Two nursery stocks of the hard clam, Mercenaria mercenaria, selected for fast growth were compared to corresponding wild populations in regard to allele frequencies at seven polymorphic enzyme loci. Although as few as 30–60 parents were spawned at each of four generations to produce these two broodstocks, neither line exhibited any reduction in heterozygosity. Both lines, however, showed evidence of genetic drift and loss of rare alleles, suggesting that a cross between them could result in a third genetically distinct line.     

硬壳蛤在北方地区的引种、人工育苗及养成技术

硬壳蛤营养和经济价值较高,贝壳又可作为高级工艺品、装饰品的原料。虽然硬壳蛤在美国东海岸整个蛤类渔获量中只占7%,但产值却占53%。硬壳蛤在美国、新英格兰和中大西洋各州、纽约、新泽西和弗及尼亚等地是最重要的经济贝类之一。     

Comparison of Three Culture Methods for the Intensive Culture of Northern Quahog Seed, Mercenaria mercenaria

A number of approaches have been utilized for growing bivalve hatchery seed (1 mm) to a size suitable for field planting (< 8 mm) but few have been directly compared. This study evaluated the growth and survival of northern quahog seed in three different culture systems and two different stocking densities. The three systems were: 1) a stacked-tray unit with downward water flow; 2) traditional upweller culture units with water flowing upward without seed bed expansion; and 3) upweller culture units with water flowing upward at fluidization velocities to provide seed bed expansion. The two stocking densities were 1.0 and 3.0 g whole wet weight clam/cm² respectively. During each trial period the seed clams were fed a 1% daily ration (% dry weight algae per wet weight clam per day) of the cultured diatom Chaetoceros muelleri . After 14 d of culture at the 1.0 g whole wet weight/cm² stocking density, seed clams (4.4 ± 0.6 mm initial shell length) under fluidized-flow condition exhibited better growth (0.54/d), and a greater final shell length (5.9 ± 1.0 mm). At the high density stocking conditions, after 28 d of culture, seed clams (4.2 ± 0.6 mm initial shell length) in the fluidized-flow culture conditions again exhibited better growth rate (0.031/d) and a greater final shell length (6.0 ± 1.0 mm). The preliminary evaluation of fluidized-flow for seed clam culture in land-based nurseries indicates its potential as a suitable alternative to raceway, downwelling, or traditional forced-flow culture methods.     

Seasonality of QPX disease in the Raritan Bay (NY) wild hard clam (Mercenaria mercenaria) population

Quahog Parasite Unknown (QPX) is a potentially lethal pathogen of the hard clam Mercenaria mercenaria along the northeastern coast of the United States. In the Raritan Bay wild clam population, QPX prevalence and infection intensity at three sites were examined by both histology and quantitative PCR in 2006. At two of three sites, QPX infection showed a seasonal pattern, with prevalence and weighted prevalence increasing through the spring, peaking in the summer and declining in the fall, while at the other site, the highest QPX prevalence and infection intensity were observed in the spring although overall prevalence at this site was generally low. Our data suggested that temperature may be an important environmental factor regulating the seasonal pattern of QPX disease in wild clams but also demonstrated that seasonal patterns vary from site to site, possibly linked to the clam density or other environmental factors. Over‐winter sampling and further investigations focusing on environmental factors, clam density and clam mortality as related to QPX infection are needed to better characterize and understand the seasonality of QPX disease.     

塘养条件下硬壳蛤生长规律的研究

试验结果表明,4-5月和9-10月,水温22~27℃时,为硬壳蛤快速生长期;11月至翌年2月,水温8~15℃时,生长缓慢;5-6月硬壳蛤处于繁殖期间,生长也较为缓慢。硬壳蛤壳长和壳高的相关关系为y=1.8479x 0.5923;壳长和体质量的相关关系为y=0.0002x3.1174。     

Size-based physical properties of hard-shell clam (Mercenaria mercenaria) shell relevant to the design of mechanical processing equipment

The knowledge of physical properties of food products is of fundamental importance for efficient design, dimensioning, manufacturing and operation of different mechanical equipment used in the processing of these products. Clams of different sizes are utilized during processing, thus, all the sizes must be given adequate consideration for efficient processing. This study was conducted to investigate the size-based physical properties of hard-shell clam (Mercenaria mercenaria) shell relevant to the design of mechanical processing equipment. The sizes of the clam shells were identified and categorized as small, medium and large; and its effect on the physical properties were studied. The parameters investigated were length, width, thickness, arithmetic and geometric diameters, surface area, sphericity, aspect ratio, moisture content, bulk and true densities, porosity, clam shell weight, coefficient of static friction and angle of repose. Increase in the length and width of clam shells increased the arithmetic and geometric diameters, and the surface area, but decreased the sphericity and aspect ratio. Moisture content, bulk and true densities, porosity and clam shell weight increased with increase clam shell size. Coefficient of static friction of clam shell was highest on rubber surface and lowest on glass surface, and was positively correlated with size; while angle of repose decreased with size. There was an excellent agreement between the prediction of the normal distribution and the actual distribution of the clam shell sizes. All the parameters were significantly different with respect to clam shell size at p < 0.05, which makes a strong case for the consideration of clam shell size during processing.     

Cryopreservation of trochophore larvae from the hard clam Mercenaria mercenaria: Evaluation of the cryoprotectant toxicity,cooling rate and thawing temperature

Aquaculture of hard clams Mercenaria mercenaria is a $65 million industry along the east coast and Gulf of Mexico coast in the United States. The goal of this study was to develop a preliminary protocol to cryopreserve trochophore larvae of hard clams. The objectives were to evaluate the: 1) toxicity of cryoprotectants, including dimethyl sulfoxide (DMSO), propylene glycol, ethylene glycol and glycerol, at 5, 10, 15 and 20% for exposure time of 1, 15, 30, 45, 60 and 75 min; 2) effects of cooling rates (5, 10, 20 and 30°C/min for the first trial; and 1, 3 and 5°C/min for second trial from 4 to ?80°C), thawing temperature (30, 40 and 50°C) and their interactions on post‐thaw viability. A basic protocol was concluded as: 15‐hr trochophore larvae mixed with DMSO or propylene glycol (5, 10%), equilibrated for 15 min, cooled in a programmable freezer from 4 to ?80°C at a cooling rate of 5°C/min and thawed at 50°C for 6 s. With this protocol, the immediate post‐thaw trochophore survival was 23 ± 14%, and survival to D‐stage was 27 ± 14%. This is the first report on larval cryopreservation in the hard clam and would have application for genetic breeding and seed production.     

Effects of Hydraulic Dredging for Mercenaria mercenaria,Northern Quahog,on Sediment Biogeochemistry

A before‐after‐control‐impact (BACI) experiment was conducted to examine the effects of hydraulic clam dredging on sediment biogeochemistry of a leased shellfish bed of Mercenaria mercenaria, northern quahog, over the course of an entire growing season. Six study plots (0.67 ha each), three dredged and three not dredged, off of Milford, Connecticut, in Long Island Sound, were sampled from May to October 2009 for porewater fluxes of total ammonia, oxygen, and hydrogen. Particulate samples were also analyzed for grain size, total nitrogen, total carbon, total sulfur, and organic carbon. Statistical analysis indicated no significant difference between dredged and not dredged sites. Grain size and oxygen flux explained 22% of the variation in the total benthic species assemblages; grain size and either total carbon or organic nitrogen explained 18% of the variation in molluscan abundance. Our study demonstrates that one‐time hydraulic shellfish harvesting had minor effects on the sediment chemistry of a leased clam bed.     

Oxygen consumption and ammonia excretion of common wolffish Anarhichas lupus Linnaeus 1758 in an experimental-scale, seawater, land-based culture system

The oxygen consumption (0₂) and ammonia excretion (N) of juvenile and adult common wolffish was measured in culture tanks in the laboratory. The oxygen consumption and ammonia excretion were affected by temperature (C), fish size and feeding rate. For juveniles (0.5 kg; 7C) the diel oxygen consumption rate varied between 37 and 62 mg O₂ kg^-1 h^-1 and ammonia excretion between 2.3 and 5.7 mg N kg^-1 h^-1. The corresponding rates for adult fish (6.9 kg; 7C) were 29-44 mg O₂ kg^-1 h^-1 and 1.2–3.1 mg N kg^-1 h^-1. The weight-specific oxygen consumption (mg O₂ kg^-1 h^-1) was described by the following formulae: O₂ (7C) = 0.17* W^0.83 and O₂ (12C) = 0.39 * W^0.73 and the corresponding ammonia excretion (mg N kg^-1 h^-1) by: N(7C) = 0.024 W^0.75 and N(12C) = 0.073 W^0.60, where W is fish weight in g.     

硬壳蛤土池人工育苗技术

本试验对硬壳蛤（Mercenaria mercenaria Linnaeus）进行规模化土池人工育苗,包括亲贝培育、苗池清整、基础饵料培养、人工催产、浮游幼虫及稚幼贝培育、水质监测和敌害防除等。硬壳蛤土池育苗面积60亩,经过近7个月的人工培育,共培育苗种8.25亿粒（平均规格2861粒/kg）,每亩产蛤苗1375.68万粒,亩利润20675元。     

温度、光照和规格对硬壳蛤稚贝的潜砂活动的影响

在室内试验条件下研究了温度、光照和规格对硬壳蛤稚贝潜砂活动的影响。结果显示,温度、光照和规格对硬壳蛤稚贝潜砂活动都有显著影响（P〉0.05）。在水温8℃以上稚贝能够在较短的时间内潜砂,1小时内80%的稚贝能够潜入到砂中。光照强度的增加能提高稚贝潜砂的比例,3000～4000lx的光照下,90%左右的稚贝在2小时内潜入到砂中。10mm稚贝的潜砂比例要高于8mm和20mm的稚贝。     

美洲帘蛤软体部营养成分分析及评价

美洲帘蛤Mercenariamercenaria(Linnaeus,1758)又称硬壳蛤、北方帘蛤或小圆蛤,原产地分布在美国佛罗里达州Cawrence湾,墨西哥湾,加利福尼亚Hamboldt湾到英格兰海域,与我国的文蛤(Meretrixmeretrix)同属帘蛤科,是一种生长快,适应能力强,适温、适盐范围广,经济价值高的大型双壳贝类[1,2]。目前生产性人工育苗已成功[3],2000年山东省海洋水产研究所由美国引入种贝,2001和2002年连续两年成功地进行了工厂化育苗,滩涂养殖正在逐步走向规模化。本文对美洲帘蛤软体部做了比较全面的营养成分测定分析,并与贻贝等多种双壳贝类进行了比较[4],旨在为…     

Review of molluscan bivalve condition index calculations and application in Northern Quahogs Mercenaria mercenaria

Condition index (CI) is a widely used parameter in ecological and physiological studies. For molluscan bivalves, no universal consensus exists for CI calculation. A literature review revealed that a total of 19 methods have been used for CI calculation in molluscan bivalves. To evaluate the CI calculation in northern quahogs Mercenaria mercenaria (also called hard clams), market‐sized clams at 12–14 months old (n = 300 from three populations) were collected for gravimetrical and volumetric measurements. Significant correlations were identified among body sizes (body length, height and width), body weights (total weight, wet meat weight, dry meat weight, wet shell weight, dry shell weight) and body volume (p < .0001, R values ≥ .800). Referencing previously used CI equations for molluscan bivalves, a total of 18 equations were evaluated the suitability, considering non‐lethal measurements, for northern quahogs through correlation analysis of the CIs from different equations. With equations constructed as the percentages of dry or wet meat weight out of total weight, dry shell weight, dry shell plus meat weight, body volume, body length*height*width, shell length or cubic of shell length, CIs were significantly correlated, meaning that these equations were exchangeable. Specifically, three equations with non‐lethal measurements (percentages of total body weight out of total body volume, body length*height*width or cubic of body length) were evaluated effective. Overall, this publication provided a review for CI calculations in molluscan bivalves and evaluated the CI equations for northern quahogs.     

硬壳蛤稚贝对淡水浸泡、干露和低温的耐受能力

试验表明:水温26～30℃,随着稚贝规格的增大,对淡水的耐受能力增加,壳长784μm的稚贝淡水浸泡30min无死亡,浸泡120min稚贝死亡率为23 3%;壳长1 32mm的稚贝浸泡3h无死亡,浸泡16h死亡率为100%。气温28～30℃,壳长为1 54mm的稚贝干露24h无死亡;干露36h和48h的死亡率分别为20 0%和63 3%。壳长6～8mm的稚贝0℃下22d无死亡,49d死亡率为70%;在-2 5℃下12d无死亡,34d死亡率为90%。硬壳蛤对低盐具有较强的耐受力,并具有较强的耐干露力。     

颗粒浓度对文蛤、硬壳蛤和菲律宾蛤仔保留效率的影响

本研究通过在养殖水体中添加底泥或单胞藻调节悬浮颗粒浓度,研究了悬浮物数量浓度和质量浓度变化对文蛤(Meretrix meretrix)、硬壳蛤(Mercenaria mercenaria)和菲律宾蛤仔(Ruditapes philippinarum)保留效率的影响。结果显示,文蛤、硬壳蛤及菲律宾蛤仔的保留效率分别在粒径为8、6和6 μm时达到最大值,分别为51.1%、59.6%和62.6%。随着数量浓度的增加,文蛤在低(4.32× 107 cells/L)、中(5.27×107 cells/L)、高(6.65×107 cells/L) 3个数量浓度下保留效率达到最大值时的最小粒径逐渐增大,分别为9、13和14 μm,保留效率最大值分别降至49.7%、33.4%和26.2%;与文蛤相似,菲律宾蛤仔保留效率达到最大值时的最小粒径也分别增大至9、12和14 μm,但最大保留值无明显变化;硬壳蛤保留效率的最大值保持不变,但达到最大值时的最小粒径略有增大,分别为8、9和10 μm。随质量浓度的增加,文蛤和菲律宾蛤仔在低(5.7 mg/L)、中(11.8 mg/L)、高(23.3 mg/L) 3个质量浓度下的保留效率最大值和达到最大值时的最小粒径均无明显变化;硬壳蛤保留效率最大值显著降低,分别为60.7%、27.6%和25.5%,但保留效率达到最大值时的最小粒径保持不变。研究表明,文蛤和菲律宾蛤仔的保留效率对食物颗粒数量浓度变化更敏感,而硬壳蛤的保留效率受质量浓度变化影响较大。     

饵料种类、温度和规格对硬壳蛤的同化率的影响

试验结果表明,温度和规格对硬壳蛤同化率的影响不显著(P>0.05);饵料种类对硬壳蛤同化率影响显著(P<0.05).其中小球藻和湛江等鞭金藻的同化率显著高于小新月菱形藻(P<0.05),而小新月菱形藻又显著高于扁藻(P<0.05).     

虾池文蛤养殖技术研究

在对虾养殖病害困扰的情况下,为充分利用本地区位优势,在坚持池塘养殖中国对虾的同时,转向虾池单养文蛤或与对虾混养取得成功。养殖面积128hm~2,总产文蛤692382.6kg,对虾19490kg。利用文蛤的生物沉降作用与虾贝生态互补特性,充分利用水域生产力并改善养殖生态条件(适度搭配),本研究成功进一步从理论与实践证明虾贝适度混养的可行性。