Repopulation and culture of the Pacific Calico scallops in Bahia Concepcion, Baja California Sur, Mexico

The Pacific Calico scallop, Argopecten ventricosus (Sowerby), is the most important commercial species in Bahia Concepcion. Catches declined steadily from 1991 to 1993 as a result of overexploitation, forcing the adoption of management measures. The Government has now established regulations for exploitation and scallop culture development. In 1994, Centro Interdisciplinario de Ciencias Marinas (CICIMAR) and the Fisheries Department of the Mexican Government initiated research on the feasibility of increasing scallop biomass through a reseeding programme to protect artisanal fishing. The use of onion bags to collect spat in Bahia Concepcion (1988-1994) demonstrated that settlement was cumulative from January to March. At Punta Coloradito, there were two peaks, in January and early March. Commercial collectors were deployed in February at El Indio and in April at El Remate. In June, about one million juvenile scallops were placed in an enclosure, held until mid-August and then released. Mass mortality (>80%) of the scallops was observed in September, increasing to 99% in October. The high water temperature and predators may be responsible for the mortalities.     

Yields of great scallop, Pecten maximus, larvae in a commercial flow-through rearing system in Norway

Survival, growth and yield of competent great scallop (Pecten maximus) larvae were investigated during a full production season in a commercial hatchery in western Norway. Broodstock were collected from natural scallop beds and 12 groups were induced to spawn during the period December 2002 to July 2003. Larvae were reared on a large scale in 36 flow-through tanks (3500 l) at 17±1 °C and continuously fed a mixture of five algal species produced in an indoor continuous-flow system. Large variations in larval performance between spawning groups and tanks were observed, but the results were as good as earlier results using the batch system and prophylactic addition of chloramphenicol. Growth from days 3–24 averaged 4.8 μm day⁻¹±0.8 (sd) and survival 22.4%±21.8 (sd). Mean yield of day 3 larvae was 7.1%±10.0 (sd) and 26.6%±25.9 (sd) for those surviving to day 24. Yield was significantly correlated to larval survival. Larval success was related to initial larval density, algal concentration and season. It was found that the best production regime had an initial larval density lower than 6 ml⁻¹ and algal concentration of less than 12 μl⁻¹ regardless of season. Seventeen tanks met these criteria and produced a mean yield of 0.5 larvae ml⁻¹ to settlement. Flow-through systems are currently regarded as the only feasible method for viable hatchery production of P. maximus larvae in Norway.     

Production of bactericidal substances by a marine vibrio isolated from cultures of the scallop Argopecten purpuratus

A marine vibrio (strain C33) having inhibitory effects on the growth of the pathogen Vibrio anguillarum-VAR was isolated from seawater used in mass culture of the north-Chilean scallop Argopecten purpuratus. This bacterial isolate demonstrated broad inhibitory activity on several bacterial strains, including some pathogenic vibrios. Ethyl acetate extracts of extracellular products of strain C33 were separated by thin layer chromatography (TLC), and three fractions thus obtained were found to have antimicrobial activity when tested using microplate bioassays. One of the fractions (A2) having marked antimicrobial activity, was further purified using TLC and analyzed by IR spectrophotometry and NMR'H and was characterized on a preliminary basis as an aliphatic hydroxyl ether. This compound demonstrated bacteriostatic activity against the important marine pathogens Vibrio parahaemolyticus and V. splendidus, and as discussed in the paper, may be useful in developing natural strategies for the control of pathogens in mass cultures of Argopecten purpuratus and possibly other molluscs affected by these bacteria.     

不同pH对海湾扇贝胚胎发育及幼虫生长发育的影响

为探究pH对海湾扇贝(Argopecten irradia)胚胎发育及幼虫生长发育的影响,本研究以pH 8.0~8.2为对照组,分析不同pH (分别为7.6~7.7、7.3~7.4、7.0~7.1和6.7~6.8)对海湾扇贝胚胎及幼虫的影响。结果显示,随着pH的降低,各实验组孵化率降低,畸形率增高,孵化时间延长,且幼虫个体明显小于对照组(P<0.05)。D形幼虫期与壳顶幼虫期幼虫存活率与生长速率均显著低于对照组(P<0.05)。幼虫发育至第8天时,pH 7.0~7.1与pH 6.7~6.8实验组的存活率分别为6.1%和5.6%,而对照组为75.2%,除pH 7.6~7.7组外,各实验组生长速率均在3.4 μm/d及以下,基本呈现生长停滞状态。眼点幼虫附着率与对照组差异显著(P<0.05),第7天时,pH 6.7~6.8实验组附着率仅为31.7%。研究表明,海水pH变化对海湾扇贝早期胚胎及幼虫生长发育具有显著影响,该研究为评估pH变化对海湾扇贝等经济贝类资源和养殖产业的影响提供了参考资料。     

The effects of epibionts and predators on the growth and mortality rates of Argopecten purpuratus cultures in southern Chile

Epibiont and predator effects on the growth and mortality of the northern scallop Argopecten purpuratus were evaluated in cultures in southern Chile.The most common epibionts were bryozoans, hydrozoans and algae in both study sites, Metri Bay (41°36; 72°43W) and Chidhuapi Channel (41°49S; 73°05W).After 12 months of culture in pearl nets and lantern nets, the scallops size did not show statistically significant differences in cultures with and without epibionts in both study sites nor were there differences in the growth either with or without the presence of predators (decapod crustaceans). The growth rate was higher in Chidhuapi Channel than in Metri Bay.Mortality was concentrated in the initial phase of culture in pearl nets. During the culture phase in lantern nets, the mortality rate was lower than 3%. The mortality rate in scallops with epibionts was higher than when these were removed in the culture phase in pearl nets. In Metri Bay the mortality rate with predators was higher than without predators. Epibionts and predators did not affect mortality in the culture phase in lantern nets.Epibionts and predation are important factors in the early mortality of scallops and therefore in the success of culture. Epibiosis, however, is not important in scallop growth in southern Chile. This is related to the composition of the epibionts and to the low temperatures which probably limit the growth of algae and invertebrates.     

有效预防海湾扇贝面盘幼虫解体病的试验

扇贝的面盘幼虫解体病的发病主要因素为亲贝性腺发育不成熟所致。预防的有效措施,应在亲贝促熟上下功夫。利用发生面盘幼虫解体病的亲贝进行了生产性育苗实验研究,并取得了成功,培育出海湾扇贝稚贝20亿枚,单位水体出苗量368万枚/m3。     

Strategies for enhancement of natural bay scallop, Argopecten irradians irradians, populations; A case study in the Niantic River estuary, Connecticut, USA

We investigated strategies to enhance populations of bay scallops,Argopecten irradians irradians (Lamarck, 1819), in a presumablyrecruitment-limited natural habitat. At present, the Niantic Riverestuary supports only a minor bay scallop population that is harvestedrecreationally. Three enhancement strategies were evaluated; (1)collection and redistribution of natural spatfall, (2) introduction andover-wintering of hatchery-reared stock into natural habitat to providenew spawning stock, and (3) over-wintering of hatchery-reared stock insuspension culture for creation of mobile spawner sanctuaries. Anassessment of natural bay scallop recruitment in the Niantic Riverconducted in 1997 indicated that few spat were found, they were widelydispersed within the river, and peak spawning occurred in late July1997. Direct re-seeding was evaluated as an enhancement measure byplanting hatchery-reared scallops ( 38 mm shell height) insmall-scale, 100-m² plots at different times and densities.Time of planting and the inferred predation intensity were major factorsaffecting survival; whereas, planting density had no significant effect.Approximately 9,000 scallops (35–45 mm shell height), broadcastwithin an eelgrass bed in November 1997, had high over-winter survivaland underwent gametogenesis and spawning during 1998. Of 26,000 bayscallops ( 45 mm shell height) over-wintered in suspensionculture from 1998–1999, approximately 60–80%survived, and these scallops spawned in mobile sanctuaries, during thesummer of 1999. There is good potential for using aquacultural methodsfor enhancement of bay scallop populations when natural recruitment ispoor and habitat and environmental conditions are not limiting.     

Breeding cycle of the northern scallop, Argopecten purpuratus (Lamarck, 1819) in southern Chile

The gametogenic cycle of the northern scallop, Argopecten purpuratus (Lamarck, 1819) was studied in southern Chile. This species has a high commercial value and is cultivated in northern Chile, the location of its natural habitats. It has recently been introduced into southern Chile where advantages such as suitable sheltered locations protected from wave action favour its mass culture. However, there are also potential disadvantages, such as lower water temperatures, which could affect reproduction. The results of the monthly variations of the gonadosomatic index and the frequency of maturity stages in specimens cultivated in Metri Bay (41° 36′S; 72° 43′W) and in those kept on the seabed in Quihua Channel (41° 50′S; 73° 05′W), suggest that the maturity and spawning period of this species extends from the end of spring through autumn. This pattern was more pronounced in Metri Bay, where levels of maturity were higher, due to higher summer water temperatures, than in Quihua Channel. Specimens at different maturity stages are found throughout the year, which seems to be associated with a rapid gonad recovery. The general pattern of the gametogenic cycle of specimens in the cultures does not differ from that recorded in the natural habitat of the species. The data available suggest that during reproduction temperature changes are more important than the relative values of the temperature. This evidence would support the possibility of mass culture of this species in southern Chile, outside its natural distribution area that extends from Corinto, Nicaragua (12°S) to Valparaíso, Chile (33°S).     

Bacteria in the culture of the scallop Argopecten purpuratus (Lamarck, 1819)

The scallop Argopecten purpuratus is one of themajor resources of commercial importance in Chilean aquaculture. One of themajor limiting factors for the culture of this species has been mass mortalityoccurring during production of juvenile seed organisms where massmortality of veliger larvae has been attributed to the presence of pathogenicbacteria in scallops and hatchery systems. Bacteriological studies havedemonstrated that in addition to bacterial pathogens, beneficial bacterialspecies capable of improving scallop larval survival may also be isolated fromscallops and hatchery systems. Research has been carried out on thedetermination of the feasibility of implementing beneficial bacteria in thecontrol of culture pathogens, thus reducing the need for chemotherapeuticmethods. The present review analyzes bacteriological research data on thedifferent roles of bacteria associated with scallop culture and discussesrecentdata on the implementation of beneficial bacteria in biological control ofpathogens in larval mass cultures of Argopectenpurpuratus.     

Reproduction of hatchery-reared and transplanted wild bay scallops, Argopecten irradians irradians, relative to natural populations

Efforts to restore bay scallop populations in the United States throughtransplantation of wild stock and reseeding of hatchery-reared individuals haveincreased due to declines in natural populations, yet little is known of thecomparative spawning patterns and relative reproductive investment of thesedifferent groups. In this study, spawning patterns of wild scallops from asource population in Northwest Harbor, New York and of scallops transplanted toa distant site in the same embayment (Flanders Bay) were similar.Hatchery-reared scallops held in pearl nets in Hallock Bay, New York showed thesame temporal spawning pattern and level of reproductive investment as scallopsfrom adjacent wild populations and wild scallops held in pearl nets. We suggestthat hatchery-reared scallops may be equally valuable as potential broodstockfor reseeding operations as wild scallops of the same size, provided thatappropriate conditioning and rearing practices are maintained. Both wild andhatchery-reared scallops may be transplanted a short period (i.e. 2–4weeks) prior to expected spawning to provide a source of potential broodstockinareas where natural population densities are low.     

墨西哥湾扇贝选育系早期发育与生长

在水温28~29℃、盐度24~25条件下,研究墨西哥湾扇贝(Argopecten irradians concentricus)选育系的早期发育及幼虫和稚贝的生长。受精卵经50 min发育至卵裂,经22~24 h发育至D形幼虫,经11 d发育至眼点幼虫并出现足,进入附着变态阶段。选育系的胚胎发育时间和浮游幼虫前期壳长、壳高与对照系比较差异不显著(P0.05);浮游幼虫后期及至附着变态阶段,选育系与对照系的壳长和壳高差异显著(P0.05)。选育系的附着变态率和存活率与对照系比较均差异显著(P0.05),且优势明显。本研究表明,墨西哥湾扇贝浮游幼虫发育前期缓慢,幼虫后期、稚贝期生长迅速;壳长和壳高的生长速度不同步,幼虫前期壳长生长快于壳高,后期壳高生长快于壳长,并于第28~30天时壳高超过壳长。墨西哥湾扇贝选育系在幼虫和稚贝阶段生长速度明显快于对照系,具有明显的生长优势及生长潜力。     

Genetic linkage map of bay scallop, Argopecten irradians irradians (Lamarck 1819)

The bay scallop (Argopecten irradians irradians Lamarck 1819) has become one of the most important aquaculture species in China. Genetic improvement of cultured bay scallop can benefit greatly from a better understanding of its genome. In this study, we developed amplified fragment length polymorphisms (AFLPs) and simple sequence repeat markers from expressed sequence tags (EST‐SSRs) for linkage analysis in bay scallop. Segregation of 390 AFLP and eight SSR markers was analysed in a mapping population of 97 progeny. Of the AFLP markers analysed, 326 segregated in the expected 1:1 Mendelian ratio, while the remaining 74 (or 19.0%) showed significant deviation, with 33 (44.6%) being deficient in heterozygotes (A/a). Among the eight polymorphic EST‐SSR loci, one marker (12.5%) was found skewing from its expected Mendelian ratios. Eighteen per cent of the markers segregating from female parent were distorted compared with 21% of the markers segregating from male parent. The female map included 147 markers in 17 linkage groups (LGs) and covered 1892.4 cM of the genome. In the male map, totally 146 AFLP and SSR markers were grouped in 18 LGs spanning 1937.1 cM. The average inter‐marker spacing in female and male map was 12.9 and 13.3 cM respectively. The AFLP and SSR markers were distributed evenly throughout the genome except for a few large gaps over 20 cM. Although preliminary, the genetic maps presented here provide a starting point for the mapping of the bay scallop genome.     

Relationships among environment, spawning and settlement of Queen scallop in the Ría de Arosa (Galicia, NW Spain)

This study examines the relationship of the reproductive and reserve storage cycles and spat settlement of the Queen scallop (Aequipecten opercularis) to environmental factors. The possibility of farming this species from spat settled on collectors is considered. The gonad condition index shows maximum values between mid-May and early August. Another peak occurs in mid-November. In spring and summer, the energy needed for gametogenesis is derived from food, although it is possible that direct transfer may occur from the digestive gland to the gonad. The glycogen and lipid content of the reserve organs reaches maximum values between late summer and early autumn. The energy requirements related to gametogenesis, which begins in autumn, involve the consumption of accumulated reserves with the resulting reduction in the condition indices. There is a positive correlation between temperature and the condition indices of the digestive gland, the adductor muscle and their lipid and glycogen content, respectively. Two settlement periods were recorded, one in winter, which could not be associated with the spawning of the experimental animals, and another in summer, which coincided with the spawning that took place in spring. The reduced gonad indices recorded at the end of the summer and in winter did not lead to settlement.     

A preliminary study of the behaviour and vitality of reseeded juvenile great scallops, of three sizes in three seasons

In order to have a better understanding of recessing in great scallop, Pecten maximus and consequently the causes of mortality at reseeding, this study has monitored, at different seasons, the dispersion and recessing of different sizes of juveniles (about 15, 30 and 45 mm, called small, medium and large) after seeding. Moreover, the aim was to see when small spat (15 mm) could be seeded, and thus reduce the costs of intermediate culture.Three monitoring approaches were used together: (1) continual observations by remote video camera, of a defined area (less than 1 m²) containing 10 scallops from each size group; (2) daily monitoring of behaviour with divers along three bottom lines, with 20 × 1 m² plots each and nine marked scallops per plot; and (3) the biochemical content of the muscle: adenylic energetic charge and storage of energy reserves (glucides, proteins, lipids).The video monitoring identified but did not quantify predator behaviour, particularly at night. The role and behaviour of spiny crab, Maia squinado, and of small predators has clearly been shown, such as: (a) small crustaceans, Inachus sp., breaking the edges of scallop valves; and (b) small gobies, Pomatoschistus pictus, pecking the tentacles of the scallop mantle.For the monitoring by divers, filtering appeared much too difficult to look at for it was very disturbed by divers, and anyway the resumption of filtering came immediately after seeding. On the other hand, diver monitoring of dispersal and recessing was quite easy to do with a minimum of practice. On the basis of dispersal, the best seasons for seeding appear to be spring or summer. In autumn, two-thirds of small and medium juveniles are missing 3 days after seeding, but we could not observe whether they had been eaten by predators or had just moved and recessed farther. There was no experiment in winter owing to adverse conditions for scallop seedings.Biochemical analyses confirmed the unsuitability of autumn for scallop seeding, because of very low glucide content in this season.The adenylic energetic charge in the smooth part of the muscle showed that stress before seeding (aerial exposure, handling), and post-seeding behaviour (swimming, recessing) have a high energetic cost for scallops. In summer and autumn, 3 days after seeding, none of the three size batches recovered their initial vitality.     

Remediating sulfadimethoxine-contaminated aquaculture wastewater using ZVI-activated persulfate in a flow-through system

Antibiotic resistant bacteria can result from the improper discharge of water from the aquaculture farming industry. This calls for the development of a low-cost remediation technology. Our research verified the use of ZVI-activated persulfate (PS) to treat antibiotic-contaminated aquaculture discharge water in a flow-through system. We selected sulfadimethoxine (SDM) as a representative antibiotic residual and tested SDM degradation under varying parameters: activator dose, initial pH, chloride concentration, activator dose and timing. The results demonstrated that increasing the ZVI dosage significantly decreased SDM degradation due to the scavenging effects for the persulfate radical (SO₄⁻). SDM decomposition occurred when SO₄⁻ attacked the aniline moiety via electron transfer prior to undergoing hydrogen abstraction/addition on the sulfonamide. A high pH produced the fastest degradation with reaction rates following the order pH 11 > > pH 9 > pH 3 > pH 5. A high Cl⁻ concentration (>100 mM) enhanced SDM degradation because of the production of chlorine radicals. The experiment results from ZVI sequential addition indicated that only a small continual input of ZVI was sufficient to generate SO₄⁻ to react with SDM. We used a flow-through concept for the real discharge water that was spiked with SDM prior to treating with PS/ZVI. The results showed that our system was able to remove approximately 68% of SDM from filtered and 74% from unfiltered discharge water. These results provide proof-of-concept that our PS/ZVI system could potentially be developed to remediate antibiotic-contaminated aquaculture wastewater.     

影响海湾扇贝中间育成效果的因素探讨

影响海湾扇贝中间育成效果的主要因素有:育成器具种类(A)、换袋时间(B)、网孔大小(C)和装苗量(D)。正交试验和方差试验表明,A、C、D为提高保苗率的敏感因素,B、C、D为提高生长效果的显著因素。试验结果提出:网箱或圆锥形袋的保苗率明显优于扁袋;每隔15～30天更换一次网袋可显著加快贝苗的生长速度,网孔大小以2mm为适宜,每袋最终实际装苗量应在2000只以内。     

Addition of bacteria bioencapsulated in Artemia metanauplii to a rearing system for halibut larvae

Theaim of this study was to determine whether it is possible to influence thespecies composition of the gut microflora in 70-days old halibut larvae(Hippoglossus hippoglossus L.) by addition of bacteriabioencapsulated in Artemia franciscana in two shortpulses.Two Vibrio strains, PB 1-11 and PB 6-1 were used. Twotreatments received each strain alone, a third treatment received the twobacterial strains in mixture, whereas in a control treatment no bacteria wereadded. Five fish tanks were included in each treatment. The bacteria werebioencapsulated in Artemia franciscana metanauplii duringashort-term incubation in bacterial suspensions of the specific strains, andwereadded in two pulses, on day 1 and day 10 of the experiment. Addition ofbacteriadid not increase the total number of colony-forming units (CFU) in the larvalgut. The total CFU in the water was lower in tanks added bioencapsulatedbacteria than in the control treatment (p < 0.05). Animmunocolony blot assay was used to measure the numbers of the specificbacteriaadded in samples of water, A. franciscana, and fishlarvae.At the end of the experiment on day 13, the strain PB 1-11 reached on average10% of the total CFU when added alone and 25% when added in mixture with PB6-1.Strain PB 6-1 reached at the end of the experiment 26.8% of the total CFU whenadded alone and 24.2% when added in mixture with PB 1-11, whereas thepercentages of PB 1-11 and PB 6-1 in the control fish were 12.7% and 10.8% ofthe total CFU, respectively. However, the differences between the experimentaltreatments compared with the control group were not significant(p > 0.05). The addition of bioencapsulated bacteria intwo pulses within a ten days period was therefore not sufficient to influencethe species composition of the microflora of the halibut larvae.     

Mortality control of scallop larvae in the hatchery

Larval mortalities occurring in molluscan hatcheries have often been associated with bacterial contamination, and more specifically with vibrios. Although batches of oyster and clam larvae have been routinely reared in the hatchery of Argenton (North Brittany, France) without antibiotics, high larval mortalities have been recorded with the great scallop, Pecten maximus, under similar conditions. For this species, an addition of antibiotics was found necessary and chloramphenicol was used at a concentration of 8 mg l^–1. However, this chemical has now been banned in Europe, making either substitution products or an improvement in the rearing procedures essential. Studies carried out have shown that neither a decrease in larval density (to 1 larva ml^–1) nor an increase in seawater change frequency (to one per day) had any positive effects. Furthermore, elective substances such as sugars were not suitable and the use of another antibiotic, erythromycin, led to inconsistent results. The only positive effects were obtained with lower levels of chloramphenicol, which does not resolve the problem. Because no alternative solutions have as yet been found, further research needs to be undertaken.     

海湾扇贝晚苗池塘底播及在褐潮暴发海区筏式养殖效果

为有效避开河北地区褐潮暴发与海湾扇贝养殖时间的重叠,为海湾扇贝产业健康持续发展提供技术支持,对海湾扇贝进行晚苗培育(4月初种贝入室,以下称晚苗)及池塘底播和筏式养殖实验。结果显示,池塘底播海湾扇贝晚苗培育的稚贝(壳长5.0–6.1 mm),经过139 d 的养殖,收获时平均壳长达59.7 mm,扇贝柱5.2 g。2012年筏式养殖海湾扇贝晚苗,收获时平均湿质量、鲜贝柱重和出贝柱率分别为28.7 g、3.8 g 和13.8%。2013年,晚苗收获时平均壳高、湿质量、鲜贝柱重和出贝柱率分别为50.3 mm、24.4 g、3.1 g 和12.7%。按1000 m3育苗水体计算,海湾扇贝晚苗培育可以节省燃煤45.5 t,节约成本6.75万元,养殖晚苗可以降低养殖成本11.6%。研究结果表明,海湾扇贝晚苗养殖技术可以有效规避褐潮暴发的不利影响,而且还可以节约养殖成本和节省能源。