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1.
The New Zealand dredge oyster Tiostrea lutaria Hutton is an incubatory ostreid species that produces fully developed pediveliger larvae, which typically settle shortly after release from the parent. Broods of larvae obtained by opening incubating oysters provide a potential method of spat production, but only a small proportion of the broods obtained in this way are the late‐stage, ready‐to‐settle pediveligers. The majority of the broods are gastrula‐, trochophore‐ and veliger‐stage larvae. Experiments were undertaken to determine whether these early stages, as well as the pediveliger stage, could be reared through to settlement, and so make spat production based on opening incubating oysters much more efficient. Experiments conducted at three temperatures (ambient, ambient + 3 °C and ambient + 6 °C) and under three food regimes (with and without cultured microalgae and without dissolved organics) were unsuccessful in ex‐parent rearing of early larvae (gastrulae and trochophores). Later stage larvae, both veligers and pediveligers, were successfully reared, and high (> 75%) but variable levels of settlement were achieved. Ex‐parent rearing did not benefit from elevated temperatures or the presence of food, and settlement of spat from these prematurely released larvae may be reduced in the presence of food. The ability to rear veliger larvae, as well as pediveligers, greatly increases the potential to use the opening of incubating adult oysters during the breeding season as a source of dredge oyster spat.  相似文献   

2.
Hatchery propagation of pearl oysters is relatively new and optimal hatchery protocols are still being developed. While in the hatchery, pearl oyster spat are supplied a constant and reliable food source and are protected from fluctuations in environmental conditions and predators. This study investigated the hypothesis that retaining blacklip pearl oyster, Pinctada margaritifera (L.), spat in the hatchery for longer periods, prior to transfer to the ocean, would improve growth and survival during early nursery culture. Results showed that the longer spat were retained in the hatchery, the smaller their average size at grading (3.5 months of age). At grading, spat transferred 3 weeks after settlement had a mean dorso–ventral shell height (DVH) of 9.2 ± 0.4 mm with 34% of individuals retained on a 10‐mm mesh. However, spat retained in the hatchery until 5, 7 and 9 weeks after settlement, had a mean DVH of 9.0 ± 0.4, 7.8 ± 0.3 and 6.3 ± 0.4 mm respectively. Only 10% of spat transferred 9 weeks after settlement were retained on a 10‐mm mesh at grading. The results probably reflect superior nutrition available in the ocean and indicate that pearl oyster spat should be transferred from the hatchery as soon as possible after settlement in order to maximize growth.  相似文献   

3.
This is the first evaluation of growth and survival of spat of the Cortez oyster Crassostrea corteziensis (Hertlein) produced under controlled conditions in a coastal area in the state of Sonora, Mexico for aquaculture purposes. A suspended culture technique, used for the Pacific oyster C. gigas, was used. The Cortez oyster has an isometric shell growth during the first 13 months, reaching 71.3±1.9 mm length, 52.6±1.3 mm thickness and 25.1±0.8 mm width. Allometric growth was found between total weight and length, thickness and width (survival was 70%). The relationships between particulate organic, inorganic material, chlorophyll a and environmental parameters with growth are described. Growth rates of C. corteziensis were affected by temperature with retardation at less than 18°C. For aquaculture purposes, it is recommended that spat be sowed after winter, and oyster harvest occur at the end of autumn. According to the von Bertalanffy equation, Cortez oysters would reach the traditional exploitation size of 65 mm (mean length) at harvest. Finally, the results of this study have shown that C. corteziensis is a good candidate for aquaculture projects in this region.  相似文献   

4.
Growth of the natural European flat oyster (Ostrea edulis L.) spat from the Mar Menor (Murcia, Spain) was studied in the Mediterranean Sea over 18 months. The oysters were cultured in two types of containers, stackable plastic Galician trays and plastic mesh pots, deployed at a depth of 15 m hung from a long-line. Two size classes of spat were used, Class I spat (initially 53 mm in size and 19 g in weight) and class II spat (initially 31 mm, 4 g). The best results were observed in the class I oysters grown in the trays, which yielded a substantial biomass (24.77 kg m–2), the survival rate was 69% and commercial size (60 mm) was attained by all the oysters within 9 months of the start of the experiment. The observed growth of the class II oysters was poor, attaining a mean of not more than 50 mm and 18 g; the survival rate ranged between 25–74% and only between 8–13% of the class II spat attained commercial size.  相似文献   

5.
This study was designed to determine if oyster spat fouling upon adult oysters, Crassostrea virginica, cultured in coastal Georgia could be controlled by stocking density, bag mesh size, substrate type, and tidal level (intertidally or subtidally). Oyster gowth and survival was also monitored for each treatment. Sediment type had no effect on the number of spat per oyster either in intertidal or subtidal areas. Greater growth occurred in subtidal bags placed on sandmud and sandclay substrates. Intertidal mud and sandhnud bottom treatments showed the least growth. Survival of oysters grown intertidally (64%) was better the those cultured subtidally (27%). Mesh size of the oyster growing bags -had no effect upon oysler fouling or growth (shell length) and survival of the oysters they contained. Stocking density did affect oyster fouling, with lower fouling per oyster in higher density treatments. Density had no effect on oyster growth (shell length) or survival at the levels tested. Heavy fouling occurred on all oysters in the mesh and stocking density experiments while they were suspended off-bottom, but an I l -fold decrease in fouling occurred after bags were placed on the sublidal river bottom.  相似文献   

6.
The Calafia mother‐of‐pearl oyster, Pinctada mazatlanica (Hanley), and the Rainbow nacre shell, Pteria sterna (Gould), represent an important resource for México because of their potential in pearl production. The present work deals with the effect of different sequences of nursery culture‐late culture on growth and survival of P. mazatlanica, from September 1993 to October 1994. The collected spat presented two main size groups: small (mean shell height of 7 mm), and large (13 mm). They were arranged into four experimental batches for each size group at a constant stocking density of 40–45 juvenile pearl oysters per Nestier cage. Three batches remained in nursery culture for 2, 4 and 6 months respectively, after which they were transferred to late culture in rail cages. A control group remained in nursery culture for 12 months. Growth was evaluated monthly and compared through anova and HSD Tukey tests. In addition to the shell height, width, depth (mm) and weight (g), data of shell volume (height × width × depth, in mm3) was also introduced to estimate and compare growth among the experimental groups. Mortality was estimated by counting the dead specimens every month and obtaining the percentage from a 100% initial survival at the start of the experiment. The juveniles showed different responses to the change from nursery culture to late culture; the level of each response varied significantly among the experimental groups at the end of the study. It seemed that a 6‐month period for nursery culture was propitious for P. mazatlanica.  相似文献   

7.
Hatchery-reared sea scallop (Placopecten magellanicus) spat weremonitored for growth and recovery in three experiments to determine themost suitable system for nursery culture. In Experiment I, four size classesof nursery-sized spat held at two depths from October to July exhibiteddeclining growth rates over the winter period and increased growth ratesin the spring. Overall, season, depth and initial size had a significantinfluence on the absolute and specific growth rates of scallops. Recovery,defined as number of scallops remaining after mortality and loss of spatthrough gear mesh, was influenced by season and initial size, but notdepth. Scallops in the 3.0 mm+ size class had higher growth rates andrecovery than those in the 1.4–1.6 mm, 1.7–1.9 mm and 2.0–2.9 mm sizeclasses. In Experiment II, two gear types containing similar size spat werecompared. Growth rates were significantly higher in 3.0 mm pearl nets thanin 3.0 mm collector bags, although recovery was similar between the twoequipment types. Experiment III, two stocking densities of nursery-sizedspat were compared in collector bags. Neither growth rate nor recoverywere significantly different for the two densities (2600 and 5200spat/collector bag) tested. Overall, these studies indicated that importantparameters for optimizing the growth and recovery of scallops in a farm-based nursery system include season, initial spat size, deployment depthand gear type.  相似文献   

8.
We investigated the early growth and reproduction of hatchery-produced Pacific oysters Crassostrea gigas raised in a suspended long-line facility in Gamakman Bay, off the south coast of Korea. In October 2009, 4?months after transplanting, shell length had increased from 27.4 (July) to 82.5?mm (October), and tissue weight had increased from 0.2 to 5.2?g, indicating that the oyster had reached a marketable size in this month. Histological studies indicated rapid gonad maturation, and the oysters spawned during August and October, with a peak in September. An enzyme-linked immunosorbent assay used to quantify egg biomass revealed that the oysters produced a relatively small quantity of eggs, ranging from 5.1?% (August) to 8.8?% (September) of their body weight. The low total carbohydrate reserve in the tissue recorded in August and September coincided with intense energy utilization due to spawning, while the protein maximum in September matched peak egg mass. Our results suggest that hatchery-produced seed could supply a portion of the spat required in Gamakman Bay as well as in other oyster culture grounds of Korea, where the oyster industry is facing a shortage in the supply of natural spat.  相似文献   

9.
Three Pavlova species were evaluated for their nutritional value as diets for growth and survival of the Cortez oyster Crassostrea corteziensis spat during late‐nursery cultivation at a hatchery. Microalgae were provided as monospecific diets (Pavlova salina, P. sp. C50 and P. sp. C53) and in binary combinations of diets 1+2, 1+3 and 2+3 at 80–90 × 103 cells mL?1 for 21 days. Juveniles experienced high survival rates and grew well with all dietary treatments, but binary diets yielded greater survival and growth of spat. From the three binary treatments, Diet 6 (P. sp. C50 and P. sp. C53) promoted significantly (P<0.001) fastest growth of juveniles in shell height (0.19 mm day?1), shell length (0.14 mm day?1), total wet weight (0.04 g day?1) and dry weight of meat biomass (0.024 g day?1). For all shell dimensions, the lowest growth rates occurred with Diets 2 (P. sp. C56 alone) and 3 (P. sp. C50 alone). These results highlight the importance of testing microalgal diets for bivalve spat rather than just relying on published nutritional values.  相似文献   

10.
Between 1995 and 1997, a traditional Norwegian oyster poll with an attachednursery was used for the production of scallop (Pecten maximus) spat.During summer 1997, four batches of 2 mm scallop spat were placed in thenursery. In June, hydroids (Obelia) caused problems with fouling andaccumulation of sediment in the nursery. Thereafter, the scallop spat wereheavily infested with tube dwelling polychaets (Polydora sp.). Thepolychaets were both introduced with poll water and reproduced inside thenursery. Infested spat suffered high mortalities. Although the spat could have been affected by the hydroids, as well as shortage of food, Polydorainfestations were considered the main cause of the mortalities. Dead andinfested spat were continuously sorted out and discarded, but the infestationproblems persisted. As a result, the scallop spat did not represent anycommercial value for the company, and in September, the nursery wasemptied. In total, approximately one million spat – representing onethird of Norway's intensive scallop spat production in 1997, was lost.  相似文献   

11.
We report the results of survival and growth in size and dry mass of spat of the Caribbean pearl oyster Pinctada imbricata cultivated under outdoor (field culture) and indoor (Laboratory) conditions. Field group fed on environmental seston. Laboratory groups were fed with mono, binary and ternary mixtures of three cultivated algae: Isochrysis galbana (Ig), Tetraselmis chuii (Ig) and the Chaetoceros sp. (Ch‐A, isolated from north‐eastern Venezuela). After 30 days of trial, fatty acid profiles of spat were determined along with growth in length and height shell, adductor muscle and soft tissue dry mass. During the field grow‐out phase (field culture), samplings were performed at days 1, 15 and 30 to measure environmental variables of phytoplankton biomass (chlorophyll a), dissolved oxygen, seston, temperature and salinity. A significant increase in size and soft tissue mass occurred in spat fed the diets including the tropical diatom (Chaetoceros sp.). In contrast, monoalgal diets of Tc and Ig yielded no significant differences in size and mass of spat, compared with the field culture. These results suggest that nutritional requirements of cultivated spat for specific fatty acids of physiological importance for marine bivalves, such as: 16:0, 16:1n‐7, 18:2n‐6, 20:4n‐6, 18:3n‐3 and 20:5n‐3, were satisfied from microalgal diets with Ch‐A, alone or in combination, compared with spat fed from the field culture.  相似文献   

12.
Tetraploid induction has been conducted on temperate oysters but not on tropical oysters. In this study, different heat shocks (32, 35 and 38°C) and cold shocks (1, 4 and 7°C) were used to induce tetraploidy in two tropical oyster species, Crassostrea belcheri and Crassostrea iredalei, through meiosis I inhibition. Temperature shocks were applied on the newly fertilized eggs at 8–10 min post fertilization and terminated when second polar bodies began to form in the control eggs. The ploidy of the larvae and spat was determined via direct chromosome count. The percentage of larval survival until Day 20 was low (between 0.4% and 42.9%) for both temperature shocks and oyster species. No surviving larva was recorded for induction at 1, 4 and 38°C. Tetraploid spat was only recorded in C. iredalei but the percentage is low through heat shock induction of 32 and 35°C. This study shows that the tetraploid induction success rate was slightly higher in C. iredalei compared to C. belcheri. No surviving tetraploid spat were recorded for both oyster species through the cold shock method. This study shows that heat shock can be used to inhibit meiosis for the production of tetraploids but more experiments need to be conducted to determine the optimum temperature when dealing with tropical oysters.  相似文献   

13.
The Pacific oyster Crassostrea gigas is a representative bivalve mollusc that is widely cultured in the world and is the largest molluscan group cultured in China. In order to assess the feasibility of improving survival of C. gigas through genetic selection, the heritability and genetic correlations for growth and survival traits between different life stages were examined. Genetic parameters were estimated based on intraclass correlations of 49 full‐sib families (29 half‐sib families) in larvae (4 and 20 days after fertilization) and spat (140 days after fertilization) stages. The heritability for growth traits in larvae and spat was 0.30–0.86 and 0.53–0.59, respectively, and varied with ages. The heritability of survival was low in larvae (0.13 ± 0.05 and 0.17 ± 0.04, respectively for 4 and 20 days after fertilization) but medium (0.39 ± 0.07) in spat, suggesting that selection for increasing spat survival was feasible. The genetic correlation between growth traits within age was medium to high and positive (ranging from 0.47 to 0.96, respectively, between shell length (SL) and shell height (SH) at 20 days and between SL and SH at 140 days after fertilization), suggesting that selection to improve single growth trait will cause positive response in another growth traits in C. gigas. The genetic correlations between survival and growth traits at 140 days were low but positive (ranging from 0.23 to 0.27, respectively, between survival and SH and between survival and SL at 140 days after fertilization), suggesting that selection for survival may not have a negative response in growth. Overall, this study suggests that survival traits should be taken as improving target of next selection breeding programme in C. gigas.  相似文献   

14.
Temperature and quality of the available food are important factors that influence the physiology of oysters; however, the combined effects have not been well studied. We evaluated the impacts of the temperature and diet on the growth, survival and biochemical composition in the Pacific oyster Crassostrea gigas spat, cultured in the laboratory for 8 weeks at 23, 26, 29 and 32°C and fed Isochrysis sp.‐Pavlova lutheri (IP) and Dunaliella tertiolecta (Dt). The growth and biochemical composition showed a pattern, which changed in response to rising temperature. The shell length was significantly longer, in spat fed the IP diet, except at 32°C, where both diets produced poor growth results. The survival was <50% after 5 weeks at 32°C, whereas at all other temperatures it was >88%. High temperatures directly increased lipids and saturated fatty acids, while the proteins, carbohydrates and unsaturated fatty acids decreased. High temperatures achieved in the environment, as those reached on clear summer days during low tides, are an important stressor in oyster spat, especially when the quality of the available food is poor.  相似文献   

15.
Scallop Pecten maximus spat (1.3–2.1 mm shell height) from different settlement groups were transferred from hatchery to land‐based nursery at different ages and sizes. Chemical content, growth and survival were compared at transfer time and after 1 and 8 weeks of nursery growth. Growth was lowest and mortality highest in the first week after transfer. Mean shell height growth was 21.5–71.4 μm day?1 and ash‐free dry weight (AFDW) growth ?2.7 to 10.3 μg day?1. Spat from the first settlement group attained a larger size and weight than spat from larvae settled 3 days later, but had a lower daily growth rate (%). Keeping the late‐settled spat a longer time in the hatchery to reach a bigger size before transfer seemed not to improve subsequent nursery growth. Survival showed a large variation with mean survival ranging from 32% to 74%. A substantial reduction in lipid content was found after transfer to the nursery. Sterol content at transfer was the only lipid class correlating with survival in the nursery. Based on the results, it is justified that spat groups of different settlement age are included in production of 15‐mm great scallop spat if they are transferred from the hatchery at the same age.  相似文献   

16.
Pacific oysters (Crassostrea gigas) were first observed in the Dutch Wadden Sea near Texel in 1983. The population increased slowly in the beginning but grew exponentially from the mid-1990s onwards, although now some stabilisation seems to be occurring. They occur on a variety of substrates such as mussel beds (Mytilus edulis), shell banks, dikes and poles. After initial settlement spat may fall on older individuals and congregate to dense clumps and subsequently form reefs. Individual Pacific oysters grow 3–4 cm long in their first year and 2–3 cm in their second year. Many mussel beds (Mytilus edulis) are slowly taken over by Pacific oysters, but there are also several reports of mussel spat settling on Pacific oyster reefs. This might in the end result in combined reefs. Successful Pacific oyster spat fall seems to be related to high summer temperatures, but also after mild summers much spat can be found on old (Pacific oyster) shells. Predation is of limited importance. Mortality factors are unknown, but every now and then unexplained mass mortality occurs. The gradual spread of the Pacific oyster in the Dutch Wadden Sea is documented in the first instance based on historical and anecdotal information. At the start of the more in-depth investigation in 2002, Pacific oysters of all size classes were already present near Texel. Near Ameland the development could be followed from the first observed settlement. On dense reefs each square metre may contain more than 500 adult Pacific oysters, weighing more than 100 kg per m2 fresh weight.  相似文献   

17.
The black‐lipped pearl oyster, Pinctada margaritifera, is the most important farmed species in French Polynesia and the basis of the most valuable export industry. Mass production of black pearls relies on a surgical operation requiring tissue from a donor pearl oyster to be grafted, together with a nucleus made of shell, into the gonad of a recipient oyster. Improving pearl size through family selection remains one of the main challenges for future aquaculture development. This study analyses the relative contribution of donor and recipient oysters to pearl size. To this end, hatchery‐produced donor oysters of two batches, large and small (based on shell height), were used to supply grafts for recipients, which were then monitored individually for their growth performance by recording shell height, width, and thickness, and total live weight (flesh + shells) every 6 months (four biometric measurement times) over 20 months of culture. Pearls issued from the two batches of donors showed no significant differences in nacre weight or thickness. In contrast, recipient oyster shell height and total weight were increasingly positively correlated with these pearl size parameters over the culture period, becoming significant at 8 months post‐grafting. Potential therefore exists to use shell height and oyster weight as phenotypic indicators for selective breeding of recipient oysters with high growth performance to increase pearl size in P. margaritifera.  相似文献   

18.
Production protocols as well as the origin of broodstock in hatcheries are the important factors determining the attributes of Crassostrea gigas oyster spat. Spat from diverse hatcheries may have different attributes for commercial activities. We described the biological performance (growth and condition index – CI) of spat stocks produced at different hatcheries (H1, H2, H3 and H4), and simultaneously cultivated in La Cruz lagoon (Mexico). Analysis of pathogens and genetic variability was performed for each stock. Temperature, salinity, chlorophyll a and seston were measured during samplings. Stocks showed similar growth patterns but each one showed a distinctive curve. Temperature was the governing factor on growth but its effect was variable depending on the stock and whether the temperature increases, stays high or decreases. Availability of food was high producing elevated CI. No presence of pathogens was detected and it was not possible to obtain amplicons of the mitochondrial regions. Despite differences in performance among stocks, all of them showed higher values (growth rates, CI, survival) than the standards reported for the Gulf of California. These findings are useful for the production and cultivation of C. gigas, but more studies are needed to understand the influence of hatchery protocols on spat quality.  相似文献   

19.
Additions of bacteria (strain CA2) as a food supplement to xenic larval cultures of the oyster Crassostrea gigas consistently enhanced growth of larvae during different seasons of the year. Bacterial enhancement of larval growth occurred when either Isochrysis galbana (ISO), I. aff. galbana (T-ISO) or Pseudoisochrysis paradoxa (VA-12) were used as algal foods. Additions of CA2 bacteria at 105 cells ml−1 to cultures of algal-fed larvae increased larval growth, the proportion of larvae that set to produce spat, and the subsequent size of spat. A lower proportion of slow-growing larvae in populations receiving additions of CA2 bacteria compared with populations of larvae fed only algae, suggests a bacterial nutritional contribution to larval growth. Manipulation of bacterial populations present in bivalve larval cultures is a potentially useful strategy for the enhancement of oyster production.  相似文献   

20.
The GreenshellTM mussel, Perna canaliculus, is a commercially important species forming New Zealand’s largest aquaculture export product. Losses of P. canaliculus spat from culture ropes between larval settlement and the time mussels reach initial reseeding size (c. 10 mm) are common. To test whether water velocity affects growth and retention of post-settlement P. canaliculus spat, and whether there is a threshold effect of increasing velocities on spat migration, a laboratory-based experiment was conducted. Spat were grown for 8 weeks in experimental tanks on culture ropes at four velocities typical of velocities within mussel farms (40, 10, 4, and 1 cm s−1). Spat migration was observed at all the velocities tested, but the number of spat migrating decreased as water velocity increased. Spat retention was highest at the 40 cm s−1 velocity. Mean spat size increased significantly with increasing water velocity. At the highest velocity tested (40 cm s−1), migration increased as the spat grew suggesting that migration was density-driven. The results of this experiment indicate the potential for mussel farmers to reduce seeded spat loss and to increase the growth rate of spat by modification of the water flow within their farms, or placement of seeded ropes in locations of certain existing water velocities, and indicate that velocities in the range 15–40 cm s−1 promote higher spat growth and spat retention for P. canaliculus.  相似文献   

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