Observations on simulated depuration trials with Manila clam, Tapes philippinarum Adams and Reeve

Simulated depuration trials with Manila clams. Tapes philippinarum Adams and Reeve, were undertaken to test the effect of stocking density, seasonal temperature, water flow rate, salinity and the addition of cultured algae on oxygen levels and some other variables of water quality. Equations produced by multilinear regression analysis provided useful systems-management information for predicting the conditions required to maintain oxygen levels within known limits for satisfactory depuration of other commercial species of bivalve molluscs in temperate climates.     

Effect of dried algae diets on conditioning and fecundity of Manila clam, Tapes philippinarum (Adams and Reeve)

Abstract The effectiveness of live-algae replacement diets for the conditioning and spawning success of adult Manila clam, Tapes philippinarum (Adams and Reeve), was assessed. Two dried diets were tested: a diet of dried Tetrasetmis suecica (Kylin) Butch, and a mixed diet of dried T. suecica (70%) and dried Cyclotella cryptica Reimann et al. (30%). These diets were compared with three live diets: Skeletonema costatum (Grev.) Cleve, Dunaliella tertiolecta (Butcher) and T. suecica. An unfed group was used as a control. The same ration (dry weight) of food was supplied for all groups at 6% of the dry meat weight per day. The broodstock were conditioned for 7 weeks. After 4 weeks none of the animals was ready to spawn. After 6 weeks all the diets promoted spawning and after 7 weeks the unfed group also spawned. It seems that dried algal diets are effective for conditioning and spawning of Manila clams, as the dry meat weight, condition index and fecundity of broodstock fed these diets were significantly greater than for unfed animals. However, the fecundity and proportion of parental lipid released in the eggs of clams conditioned with dried diets was lower than for the clams conditioned with live algae.     

Condition index and air survival time to compare three kinds of Manila clam Tapes philippinarum (Adams & Reeve) farming systems

The effects of maintaining the burrowing Manila clam in suspended culture in the sea on flesh weight changes or on condition are not yet known. This work analyses these effects using the condition index and the air survival time of clams. Samples of clams submitted to three different treatments (traditional farming on the lagoon bottom, lagoon suspended culture and open sea suspended culture) were investigated between July and November. The most sensitive of the eight condition indices for comparing the three different breeding systems was AFDW/SV. From the Tukey test (two-way ANOVA), AFDW/SV, exhibited the highest number of significantly different (P < 0.05) cases in a comparison between the month/treatment interactions. This index showed the highest values in lagoon suspension, whereas there was not much difference between bottom farming and sea suspension until after a four-month period: in November the suspended individuals recovered condition, whereas a fall was recorded in the traditional farming area. As regards air survival time, individuals in sediment were more resistant, except in November, when lagoon suspended ones were hardier. Suspended culture, which is necessary for hygiene and health reasons to market the product, is an advantageous necessity for farmers in both lagoon and sea, especially over periods of several months.     

Growth,mortality and reproduction of the transplanted Manila clam (Ruditapes philippinarum Adams & Reeve 1850) in Jiaozhou Bay

Samples of Manila clam (Ruditapes philippinarum Adams & Reeve 1850) were collected from May 2004 to April 2005 monthly, and plankton net trawling of planktonic larvae and bottom sediment sampling surveys were further conducted from May to October 2006 in Jiaozhou Bay. Based on the data collected, growth, mortality and reproduction of the transplanted Manila clam and the environmental effects were examined. The results showed that the enhanced clams grew well and showed a growth trend similar to the local wild ones. The main growth periods lasted from April to September, with the water temperature being the main factor affecting the growth, which was the same as that of the wild clams. There were also two reproduction cycles for the farmed Manila clams each year in Jiaozhou Bay and the main breeding period was from May to June. The phenomenon of delayed metamorphosis was quite common through larval development. The farmed clams could spawn when they reached sexual maturity, but they could not perform effective recruitment as many planktonic larvae died during metamorphosis and settlement. A preliminary study indicated that sediment perturbation and marine environment pollution were the main factors causing the death of larvae in the development process.     

Sprinkling: a new method of distributing live algae food in marine coastal ponds used for Manila clam Tapes philippinarum (Adams & Reeve) intensive culture

Sprinkling, an agricultural irrigation technique, has been tested for the intensive culture of Manila clams up to marketable size (35-50 mm) in coastal ponds 400 m² in area. The sprinkling system is used for the distribution of seawater and live algal food Skeletonema costatum (Grev.) Clev. Sprinkling is a simple, low cost and efficient method of food distribution which resolves the major problem of decreasing bivalve growth associated with single point water entry in small-scale raceways. Uniform growth obtained with sprinkling is principally due to an even scattering of food over the whole surface area of large-scale ponds.     

Effects of mechanical stress in under-sized clams, Tapes philippinarum: a laboratory approach

The present study is a first attempt at evaluating the effects of repeated disturbance, such as that caused by mechanical fishing systems, on the target species, Tapes philippinarum, intensively exploited in the Lagoon of Venice (North-East Italy). In particular, in free-access fishing grounds, detrimental effects of dredging may be suffered by under-sized clams, which are disturbed by fishing tools many times throughout their lives before they are collected. Similar mechanical stress conditions are experienced by T. philippinarum in licensed areas, where they are farmed in aquaculture conditions and undergo the harmful impact of hydraulic dredging. To evaluate the effects of short-term mechanical stress, under-sized clams were subjected to experimental shaking in the laboratory, and detrimental effects on their well-being were investigated by applying the biomarker approach. Changes in physiological, biochemical and behavioural responses were evaluated by determining scope for growth, adenylate energy charge, survival in air time, reburrowing time, and shell damage level. Responses highlighted general worsening in clam condition as mechanical stress increased. Among the various measurements, survival in air and reburrowing time appeared particularly suitable as indices, their responsiveness and applicability suggesting their use in assessing mechanical stress due to dredging in field conditions.     

氯霉素在菲律宾蛤仔体内生物富集和残留消除规律的研究

在半静态条件下,研究了氯霉素在菲律宾蛤仔体内富集和消除规律。试验结果表明:菲律宾蛤仔对水体中氯霉素的富集能力较低,内脏团和肌肉部分的富集系数1.8;氯霉素的蓄积量随时间的延长和给药浓度的增加而增加,在6~8 d可趋平衡;各部位的富集和消除情况存在明显差异,内脏团的富集速度快于肌肉,肌肉的生物学半衰期长于内脏团。     

Metabolic characteristics of the Japanese clam Ruditapes philippinarum (Adams & Reeve) during aerial exposure

Some metabolic end‐products in tissues and physiological parameters of haemolymph of the Japanese clam Ruditapes philippinarum (Adams & Reeve) were investigated under aerial exposure at 15 °C with low relative humidity (RH) (22%) or high RH (91%). Acclimated clams in water at 15 °C were used as a control and to supply the low or high RH experiment. The low RH experiment was conducted at air exposure for 50 h (LH₅₀), and the high RH experiment for 50 h (HH₅₀) and 100 h (HH₁₀₀). Accumulation of succinate and alanine in the tissues proved that the clam shifted its metabolism to anaerobiosis. Lactate accumulation did not occur. Glucose concentrations in tissues increased slightly during exposure except for HH₅₀. The total free amino acid contents (363–410 μmol g^?1) were higher than those of glucose (530–804 μmol 100 g^?1), suggesting that the free amino acids might play a more dominant role in the metabolism. Increase in the haemolymph pco ₂ did not influence the acid–base balance in the haemolymph during exposure at both humidity conditions. Increase in the haemolymph ammonia from 48.2 to 57.1 μmol 100 g^?1 and to 131.0 μmol 100 g^?1 at LH₅₀ and HH₁₀₀, respectively, suggested that ammonia might function as an important buffering factor during aerial exposure. Retention values of the haemolymph po ₂ even at the longest exposure time (16.30 mmHg at LH₅₀ and 14.69 mmHg at HH₁₀₀) indicated that the clams depend partially on some aerobic manner.     

菲律宾蛤仔土池人工育苗试验报告

于１９９５年５～８月，利用对虾养殖土池乾地菲律宾蛤仔人工育苗试验，将２００亩土 池经清淤，铺沙等改造后使用。作了蛤仔的亲贝蓄养，诱导产卵，受精孵化和浮游幼虫培养，获得附着稚贝平均为２３１０万粒／亩，面盘幼虫至附着稚贝的成活率为１１．６％，试验结果表明，在北方地区用土池培育蛤仔种苗是可行的。     

Effect of temperature and relative humidity on the tolerance of the Japanese clam, Ruditapes philippinarum (Adams & Reeve), to air exposure

Laboratory studies showed that higher relative humidity (RH) and lower air temperature increase the tolerance of the Japanese clam, Ruditapes philippinarum (Adams & Reeve), to exposure. Aerial respiration of the clam was also measured. At high RH, the exposure time which gave 50% survival (LT₅₀) was 1.97 and 1.75 times longer than in low RH at air temperatures of 15 and 25 °C, respectively. At 15 °C, all clams previously acclimatized at 15 °C survived for 58 h at low RH and 102 h at high RH. These differences can potentially be exploited to improve the shipment of clams. The aerial respiration experiment showed that the increase of the oxygen consumption rate at 25 °C was greater than that at 15 °C, following an increase in exposure time. The aerial respiration rates of the clams were ≈ 41.6% and 50.0% of those in water at 25 and 15 °C, respectively. The survival of the clams in air was dependent on aerobic rather than anaerobic respiration.     

菲律宾蛤仔高密度育苗技术

设计和制造了可以大规模应用于菲律宾蛤仔（Ruditapes philippinarum）等经济贝类苗种生产的高密度幼体培育系统、高密度稚贝培养系统,并建立了与之相配套的贝类育苗新工艺。克服了传统育苗方式占地面积大、生产效率低、种苗质量和产量不稳定的弱点,具有低消耗、高质量和高效益的突出特点,是贝类育苗工艺的变革。利用这一育苗技术,可以充分发挥高密度、集约化生产的优势,通过对苗种培育过程中水质、饵料和环境条件的全面控制,消除或减少敌害生物的影响,提高幼体的抗逆能力,从而杜绝抗生素的使用;在降低育苗生产的环境污染同时,向养殖户提供健康、优质的贝类苗种,是一种与环境相协调的、可持续的水产苗种培育模式。     

Evaluation of lipid spray beads for the delivery of water-soluble materials to a marine suspension-feeder, the Manila clam Tapes philippinarum (Deshayes 1853)

We describe the development and evaluation of a new microparticle for delivering low-molecular weight, water-soluble materials to suspension feeders. Spray beads successfully incorporated materials dissolved in an aqueous phase or as dry particulate, within a triacylglyceride bead composed of tripalmitin, 600 mg g⁻¹ tripalmitin/400 mg g⁻¹ triolein, or 600 mg g⁻¹ tripalmitin/400 mg g⁻¹ fish oil.
Riboflavin was successfully incorporated (up to 44 mg g⁻¹ lipid) and retained (up to 98% over 24 h in seawater) as dry particles in all three mixtures of lipid. Aqueous oxytetracycline hydrochloride or polymeric dye were incorporated (45.6 mg g⁻¹ lipid and 18.1 mg g⁻¹ lipid, respectively) and retained best (99% and 94%, respectively) in spray beads composed of tripalmitin. The addition of triolein or fish oil to the lipid bead reduced incorporation and retention efficiencies for aqueous core materials by up to 75%.
Manila clam seed readily ingested and digested lipid microparticles, spray beads and lipid-walled microcapsules. Microparticles composed of tripalmitin were excreted with their payloads intact. Intact microparticles composed of 600 mg g⁻¹ tripalmitin/400 mg g⁻¹ fish oil were largely absent in faecal strands suggesting successful release and delivery of microparticle contents to clams.
Spray beads composed of tripalmitin softened with 400 mg g⁻¹ fish oil represent an effective microparticle type for delivering low-molecular weight, water-soluble materials to aquatic suspension feeders.     

Fatty acid composition of female and male clams (Ruditapes philippinarum): energy intake and temperature reliance

We analysed the effect of temperature, coupled with food ingestion rate (IR), on the fatty acid (FA) profile of female and male clams conditioned in two groups: L (low IR at 14 and 18 °C) and H (high IR at 18 and 22 °C). Significant differences for group L, both 18L and 14L with low IR and slow gonadal development, owed to differences in energy balance between 18L clams (negative energy balance) and 14L clams (positive energy balance). Plasmalogens (DMA 18:0) and non‐methylene‐interrupted FAs might protect against reactive oxygen species and preserve the integrity of the cell membranes during food stress in 18L clams. Differences in composition for group H, both 18H and 22H with high food intake, positive energetic balance and complete and similar gonadal occupation index (GOI), probably owed to the greater energy levels at 18 °C than at 22 °C. Clams at 22 °C H increased the oxidation of short‐chained PUFA 18:3ω3 and 18:3ω6 to maintain the same GOI as 18H clams. Regarding the sexual differences, the greater accumulation of 20:5ω3 and 20:4ω6 in females might be related with oocyte maturation and release during spawning, while the greatest levels of 22:6ω3 in males might be involved in spermatocyte membranes synthesis.     

钝缀锦蛤形态性状对活体质量的影响

基于钝缀锦蛤 (Tapes dorsatus) 规模化养殖面临的种苗供应问题,采用单因素对比实验法,开展了钝缀锦蛤苗种繁育关键技术研究,为其种苗大规模培育提供参考。结果表明：1) 在人工控温条件下,采用虾塘复合藻代替纯种单胞藻对亲本进行促熟,促熟率比对照组提高了282.6%。2) 通过升温加阴干诱导等一系列措施进行催产,亲贝催产率比对照组提高了50.9%。3) 通过添加益生菌构建有益微生态系统,育苗期间不换水,幼虫浮游期成活率、生长速度和稚贝育成率等指标均显著高于对照组。4) 采用立体采苗器结合池底进行立体附苗,稚贝育成率和单位面积产量分别提高了76.6%和76.5%。5) 按体质量5%上选的亲贝作为选育组,稚贝的壳长、体质量和稚贝育成率分别比对照组提高了6.67%、17.03%和8.43%;壳长和体质量变异系数分别降低了29.13%和55.29%;稚贝期壳长和体质量的现实遗传力“h²”分别达到0.65和0.72。采用研究建立的集成创新技术进行钝缀锦蛤人工育苗,可获得显著的经济效益,为实现种苗的规模化生产奠定了基础。     

Hatchery production of diploid and triploid clams, Tapes dorsatus (Lamarck 1818): a potential new species for aquaculture

To assess the potential for hatchery production of the venerid clam, Tapes dorsatus, diploid and triploid clams were produced and ongrown until the spat reached 5–8 mm in size. Triploidy percentages at metamorphosis that ranged from 56 to 85% were induced using a 15-min exposure to 1 mg/l cytochalasin B. No differences were observed in the growth rate of sibling diploid and triploid T. dorsatus larvae. Survival of diploid clams to pediveliger stage was however higher. Post-metamorphic growth and survival of diploid and triploid clams remained the same until the clams were removed from the hatchery to outdoor nurseries. Throughout the larval and early spat phases of production, T. dorsatus growth was similar to that reported for the Manila clam, Tapes philippinarum. Based upon its ease of culture, rapid growth and marketability, T. dorsatus are thought to have considerable aquaculture potential.     

杂色鲍杂交及选育育苗的效果研究

利用杂交结合选育的方法对我国南方主要鲍鱼养殖品种杂色鲍进行了育苗试验.试验共设置2个杂交组合,每个组合分5个试验平行组.结果表明,2个组即TW♀×HN♂和TW ♂×HN♀都取得了良好的育苗效果,其受精率分别为(97.23±1.52)%和(96.30±2.25)%;幼体附着率分别为77.02%和76.69%;幼体存活率分别为66.39%和66.89%;稚鲍壳长日增长分别为136. μm和133.8μm.剥离印d后,2个组合稚鲍的存活率分别达到了64.1%和74.2%,体现出良好的杂种优势和对环境的适应能力.TW#♀×HN ♂组合在受精率、幼体附着率和稚鲍壳长日增长率都高于其反交组合TW♂×HN ♀,而幼体和稚鲍的存活率都低于反交组合,但方差分析表明2个组合正反交的育苗效果在受精率、幼体附着率、幼体存活率和稚鲍壳长日增长率上无显著性差异(P>0.05),但在稚鲍的存活率上存在显著性差异(P<0.05).     

胶州湾菲律宾蛤仔生态容量评估及其碳汇功能

胶州湾是我国重要的菲律宾蛤仔(Ruditapes philippinarum)养殖基地,为探究湾内菲律宾蛤仔的生态容量及其碳汇功能,本研究采用Ecopath模型法评估了胶州湾菲律宾蛤仔的生态容量,并利用Ecosim模块动态分析了菲律宾蛤仔生物量扩大对胶州湾生态系统结构与功能特征的潜在影响,同时估算了胶州湾菲律宾蛤仔个体及种群水平的碳收支情况。结果显示,胶州湾菲律宾蛤仔的生态容量为239.9 t/km2,虽然整体水平尚未达到生态容量,但局部养殖区域已远超出了菲律宾蛤仔的生态容量;当胶州湾菲律宾蛤仔生物量从当前增加至生态容量时,生态系统总流量、容量、优势度和循环指数分别提高了16.0%、3.9%、47.1%和103.0%,而熵值降低了10.4%,表明此时生态系统具有更高的成熟度与稳定性,但菲律宾蛤仔生物量扩大至生态容量10倍时会对生态系统产生不利影响甚至崩溃;菲律宾蛤仔个体在1个养殖周期内约摄取3 310.1 mg C,其中约46.2%的碳沉降至海底,约13.2%的碳通过收获移出,如按菲律宾蛤仔生物量达到生态容量时计算,胶州湾每年将有1.5万t碳以生物沉积形式沉降至海底,有0.6万t碳以收获形式移出。研究结果为指导菲律宾蛤仔增养殖产业的健康可持续发展、阐明菲律宾蛤仔的碳汇功能提供了理论依据与数据支撑     

Evaluation of macroalgal detritus as food source for juvenile Manila clam,Ruditapes philippinarum: Effects on growth,amino acid content and fatty acid composition

Sufficient high‐quality microalgae are required for indoor nursery of juvenile Ruditapes philippinarum. However, culturing numerous microalgae to support clam feeding is a heavy burden on many hatcheries. The effects of detritus from the macroalgae Ulva pertusa, Chondrus ocellatus and Undaria pinnatifida on the growth, amino acid content and fatty acid profile of R. philippinarum were assessed as potential substitute diets. The green microalga Tetraselmis cordiformis served as comparative diet. Results revealed that the clams ingesting distinct diets presented no significant differences in growth of soft tissues, but the nutritional component of these clams differed dramatically. The clams fed with Undaria + Tetraselmis had the highest content of essential amino acids and proteins. In addition, the clams fed with single macroalgal diets and mixed macroalgal detritus and Tetraselmis showed significantly higher or statistically equal levels in n‐3/n‐6 ratio and docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratio with respect to Tetraselmis diets. The relative percentages of EPA and DHA in clams fed with Undaria were 28% and 63% higher than those fed with Tetraselmis, and the arachidonic acid abundances in clams ingesting Undaria + Tetraselmis and Tetraselmis were significantly higher than those in clams ingesting other diets. Together, the diets containing single Undaria or mixed Undaria + Tetraselmis produced Manila clams with nutritional advantages in terms of essential amino acids and polyunsaturated fatty acids. Thus, the detritus of macroalgae, especially Undaria, is an appropriate substitute diet, at least partially, for culture of nutrition‐improved R. philippinarum.