Factors influencing the quality of half‐pearls (mabé) produced by the winged pearl oyster,Pteria penguin (Röding, 1758)

The winged pearl oyster, Pteria penguin, is cultured primarily to produce half‐pearls (mabé). The mabé quality is influenced by culture techniques, but there is limited information in this field. P. penguin with mean (±SE) dorso‐ventral height of 250 ± 6.5 mm were used to investigate the influence of culture period and nucleus position on mabé quality. Oysters were relaxed using 1‐propylene phenoxetol, and five nuclei were glued at different positions to the inner surfaces of the oyster shells; three on the more concave left valve and two on the right valve. Nucleated oysters were then cultured for 10 months under commercial pearl farming conditions at Savusavu in Fiji. Nacre deposited at the base and top of the nuclei was measured monthly, from the 6th to the 10th months of culture and the different qualities of mabé produced at different positions were scrutinized. Nacre thicknesses at the base and top of the resulting mabé were significantly different at different months (P < 0.05) and the rate of nacre deposition was highest during the warmer months. The different positions of nuclei on the valve greatly affected the quality of mabé formed. After a 10‐month culture period, around 1 mm of nacre covered the nuclei although the best quality mabé were obtained after 9 months.     

Growth and survival of the pearl oyster Pinctada imbricata (Röding 1758) in supended and bottom culture in the Golfo de Cariaco, Venezuela

We evaluated growth and survival rates of Pinctadaimbricata in relation to environmental changes during nine months insuspended and bottom culture in the Golfo de Cariaco, Venezuela. Juveniles,measuring 13 mm in length, were cultured using two methods, (1) inSpanish-type baskets suspended at 3–4 m in depth from a longline and (2) in baskets embedded on the seabed (7–8 m indepth). At monthly intervals, we quantified mortality and took a sample ofoysters to determine shell length (dorsal-ventral axis) and the dry mass of theshell, muscle and remaining tissues. We also quantified the dry mass of foulingon the shells (a potentially important environmental factor). Survival rateswere slightly higher in suspended culture (98–100%), although notsignificantly higher than on the bottom. The growth rate was higher in suspendedculture than on the bottom culture, and the difference between culture methodswas greater for tissue and shell biomass than for shell dimensions. At the endof the study, oysters measured 55 mm in shell length for oysters insuspension and 45 mm for those on the bottom. Although growth wasnot significantly correlated with any environmental factor, it tended toincrease with increases in chlorophyll a during periods ofupwelling, thus suggesting that phytoplankton abundance enhanced the growth ofPinctada imbricata. The pearl oyster Pinctadaimbricata should be an excellent species for aquaculture activities,given its high rates of growth and survival in suspended culture and itseconomic importance in the Caribbean region.     

Growth of the fan mussel Pinna nobilis (Linnaeus, 1758) (Mollusca: Bivalvia) in experimental cages in the South Adriatic Sea

Juveniles of the fan mussel Pinna nobilis were collected in Mali Ston Bay from October to December 2006. Cages with juveniles were placed at three depths: 1, 3 and 5 m. At the end of a 2‐year growth period at 1 m depths, the average length was 244.1 ± 22.9 mm, at 3 m depths, specimens averaged 244.0 ± 25.3 mm, and at 5 m depths, the average length was 231.1 ± 22.5 mm. The average monthly growth of shell length for the total experimental period was 8.7 ± 5.3, 8.4 ± 4.5 and 7.6 ± 4.4 mm, at 1, 3 and 5 m depths respectively.     

Changes in shell dimensions of pearl oysters, Pinctada mazatlanica (Hanley 1856) and Pteria sterna (Gould 1851), during growth as criteria for Mabé pearl implants

The relationship between the shell dimensions of pearl oysters. Pinctada mazatlanica (Hanley 1856) and Pteria sterna (Gould 1851). was studied to determine the possible change of form of the shell during growth. The intention was to determine the number, size and location of nuclei that could be implanted in oysters used for Mabé pearl production. Using the database of our Pearl Culture Research Programme developed in Bahía de La Paz, México, we obtained measurements of 500 shells of P. mazatlanica and 500 shells of P. sterna, representing 3 years of continuous growth under extensive culture conditions. The height-length, height-thickness and the height-weight relationships of both species were analysed, as was the height-wing length relationship for P. sterna. There was isometric growth up to 100 mm shell height, and negative-allometric growth after 120-125 mm for P. mazatlanica. The height-thickness relationship followed a linear model, whereas the height-weight relationship was exponential. No clear allometric pattern was found in P. sterna and all relationships fitted the power equation.     

Heritability estimates for growth‐related traits in the Pacific oyster (Crassostrea gigas) using a molecular pedigree

Pacific oyster is one of the leading species in world aquaculture, but heritability estimation applying mixed‐family approach has not been actively pursued. In this study, heritability for growth‐related traits in the Pacific oyster was first estimated by creating a single cohort of 45 families in a full‐factorial mating design consisting of nine sires and five dams. A total of 270 offspring were analysed and parentage assignment inferred by six microsatellite markers achieved 100% success. All parents contributed to the spawn and a total of 42 full‐sib families were represented. Using an animal model, heritability estimates at 12 months of age were 0.49 ± 0.25 for shell height, 0.36 ± 0.19 for shell length, 0.45 ± 0.23 for shell width and 0.35 ± 0.17 for wet weight. Genetic correlation between shell height and wet weight was quite high (0.79 ± 0.25), suggesting that direct selection of shell height, which is an easily measurable trait, also improves wet weight. The results obtained in this study indicate that growth‐related traits could be improved by exploiting additive genetic effects through selective breeding.     

Growth and gonad development of the tropical black-lip pearl oyster, Pinctada margaritifera (L.), in the Gambier archipelago (French Polynesia)

The growth and reproductive cycle of cultured black-lipped pearl oysters, Pinctada margaritifera (L.), were studied in the Gambier Islands (134°52′ W, 23°07′ S) from September 2002 to August 2003. Temperatures were recorded throughout the year, revealing seasonal temperature variations between 22.3 and 27.8°C. The mean annual chlorophyll a value, as computed from satellite data, was 0.188 ± 0.075 μg L⁻¹. To study growth and reproduction, 720 two-year-old individuals were ear hung on long-lines suspended at a depth of 7 m. Samples were taken twice a month to obtain the following measurements: shell height; wet weight of flesh and total oyster; dry weight of adductor muscle, mantle and visceral mass; and glycogen content. Gonad development was also studied by histology on parallel samples. Growth was relatively fast during the first 6 months of the study: average shell height increased from 89.1 ± 9.1 to 119.7 ± 10.8 mm and total weight from 93.4 ± 24.5 to 155.1 ± 33.6 g, between September and the end of March. Subsequently, from April to August, no significant growth was observed for shell and flesh, while the muscle weight decreased significantly. Condition index (CI), defined as the ratio of wet weight of the visceral mass to shell weight, and histological changes in the gonad revealed 3 significant reproductive events of different intensities. The analysis of correlations revealed a specific effect of the chlorophyll a concentration on the growth of shell and soma, and one of the temperature on tissue glycogen content. This study also showed also that CI could be an efficient indicator of reproductive events in pearl oyster. It thus appears that the development of gonads goes on throughout the year in the Gambier Islands, without any detectable phase of sexual rest.     

When should pearl oyster,Pinctada margaritifera (L.), spat be transferred from the hatchery to the ocean?

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.     

Differential Growth of the Mussels Perna perna and Perna viridis (Bivalvia: Mytilidae) in Suspended Culture in the Golfo de Cariaco,Venezuela

We evaluated the growth of mussels Perna perna and Perna viridis in suspended culture in the Golfo de Cariaco in Venezuela. Juveniles were cultured for up to 13 mo on cultch strings suspended from longline, with monthly sampling for determination of shell length and dry weights of shell and soft tissues. Water temperature, oxygen, salinity, chlorophyll a, seston, and shell fouling were also monitored. In both species, growth during the first 5 mo (the stratification period in the region) was slow. Subsequently, the onset of the coastal upwelling period (November/December) generated lower temperatures and higher plankton levels, correlated with higher growth rates, particularly in P. perna, which by the end of the experiment had reached a mean length 1.3‐fold greater than that of P. viridis (95.3 ± 7.91 vs. 73.3 ± 6.99 mm) together with a 1.9‐fold greater somatic tissue. Likewise, reproductive activity differed between the two species, P. perna showing a higher gonad development and its reproductive activity starting earlier than that of P. viridis. Our results show that P. perna presents higher growth and survival than P. viridis in suspension culture, a fact related to a greater tolerance to the environmental characteristics of the Golfo de Cariaco.     

Effect of incubation temperature on the embryonic development and yolk‐sac larvae of the Pacific red snapper Lutjanus peru (Nichols & Murphy, 1922)

The effect of incubation temperature on embryonic development and yolk‐sac larva of the Pacific red snapper Lutjanus peru were evaluated by testing the effect of 26, 28 and 30°C, as this is the natural thermal interval reported during the spawning season of Pacific red snapper in the Gulf of California, Mexico. Sixteen developmental stages were observed. The incubation temperature affected the rate of development and time to hatching, being shorter at 30 than at 26°C, but no significant effect (P < 0.05) on larval length at hatching was registered. The depletion rate of yolk sac and oil globule was affected by incubation temperature particularly during the first 12 h post hatching (hph). At the end of the experiment (48 hph), significantly (P < 0.05) larger larvae were recorded at 26°C (TL = 3.22 ± 0.01 mm) than at 28° (TL = 3.01 ± 0.02 mm) and 30°C (TL = 2.97 ± 0.05 mm). Incubation of newly fertilized eggs at 26°C produces larger larvae, which may help to improve feeding efficiency and survival during first feeding.     

长牡蛎壳金选育群体生长性状的选择效应

长牡蛎是一种世界性的养殖贝类,同时是我国最重要的经济贝类之一,壳色美观和快速生长是目前长牡蛎遗传育种的2个重要目标。2010年通过长牡蛎壳色性状的家系选育,获得了壳白、壳黑、壳金和壳紫4种壳色品系。实验以第二代壳金品系为基础群体,对长牡蛎壳金群体的生长性状进行定向选育,分析了长牡蛎壳金选育群体壳高性状的选择反应、遗传获得和现实遗传力。结果显示,养成阶段选择组的壳高均大于对照组,350日龄后表现出显著的生长优势;幼虫期,壳高性状的平均选择反应、遗传获得和现实遗传力分别为0.549±0.277、3.717%±2.611%和0.339±0.171,养成期分别为0.436±0.138、8.253%±1.014%和0.270±0.086。选择组的贝壳金黄色和外套膜金黄色比例分别提高了22%和10%。研究结果为长牡蛎壳金优良品系培育提供了重要基础资料。     

Occurrence and density of Pacific saury Cololabis saira larvae and juveniles in relation to environmental factors during the winter spawning season in the Kuroshio Current system

The occurrence and density of Pacific saury Cololabis saira larvae and juveniles were examined in relation to environmental factors during the winter spawning season in the Kuroshio Current system, based on samples from extensive surveys off the Pacific coast of Japan in 2003–2012. Dense distributions of larvae and juveniles were observed in areas around and on the offshore side of the Kuroshio axis except during a large Kuroshio meander year (2005). The relationships of larval and juvenile occurrence and density given the occurrence to sea surface temperature (SST), salinity (SSS), and chlorophyll‐a concentration (CHL) were examined by generalized additive models for 10‐mm size classes up to 40 mm. In general, the optimal SST for larval and juvenile occurrence and density given the occurrence was consistently observed at 19–20°C. The patterns were more complex for SSS, but a peak in occurrence was observed at 34.75–34.80. In contrast, there were negative relationships of occurrence and density given the occurrence to CHL. These patterns tended to be consistent among different size classes, although the patterns differed for the smallest size class depending on environmental factors. Synthetically, the window for spawning and larval and juvenile occurrence and density seems to be largely determined by physical factors, in particular temperature. The environmental conditions which larvae and juveniles encounter would be maintained while they are transported. The survival success under the physically favorable but food‐poor conditions of the Kuroshio Current system could be key to their recruitment success.     

Aquaculture potential of the basket cockle (Clinocardium nuttallii). Part 2: effects of stocking density and depth on second year grow‐out performance of three size cohorts in intertidal and off‐bottom suspended culture

We investigated the effects of culture mode (intertidal and off‐bottom suspended culture) and initial stocking density (5%, 10%, 35% and 70% bottom cover) on survival, growth and condition indices of three size cohorts (16, 22 and 32 mm initial shell length) of the basket cockle, Clinocardium nuttallii, during a second year of grow‐out. In addition, we evaluated the effects of depth (2, 4 and 6 m) in suspended culture. All size cohorts demonstrated significantly higher growth rates, soft‐tissue biomass and condition indices in the off‐bottom suspended system compared to the intertidal one. In suspended culture, however, C. nuttallii exhibited sub‐optimal survival, shell deformities and heavy fouling. For all size cohorts, stocking density had a significant effect on most growth and condition parameters, except meat yield indices, in both culture modes. An initial maximum stocking density of 10% cover is recommended for all size cohorts. Culture depth did not have a consistent statistically significant effect on any of the growth or condition parameters. Depending on the grow‐out scenario, stocking density and harvestable size chosen, the cumulative harvestable proportion after the second year of grow‐out constituted 15.5–63.1% of the seed planted. Our results could be used to develop and improve culture techniques for C. nuttallii and other cockle species.     

Growth and survival of the Calafia mother-of-pearl oyster Pinctada mazatlanica (Hanley 1856) under different sequences of nursery culture–late culture at Bahía de La Paz, Baja California Sur, México

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.     

Growth performance and biochemical composition of the oysters Crassostrea sikamea,Crassostrea angulata and their hybrids in southern China

The Kumamoto oyster (Crassostrea sikamea) and the Portuguese oyster (C. angulata) are important aquaculture species which naturally coexist along the southern coast of China. To understand the potential feasibility of hybridization between the two species, we conducted two‐by‐two factorial cross‐experiments in Beihai (Guangxi province), and also compared the survival and growth of the hybrids to that of the two parental progenies during the grow‐out period from July 2014 to July 2015. Genetic analysis confirmed that the hybrid spats were true hybrids. Additionally, the biochemical composition of the 1‐year‐old oyster progenies was determined. In July 2015, the mean shell height of the hybrids was 42.98 ± 6.29 mm, which was higher than that of the Kumamoto oyster progeny. The cumulative survival rate of the hybrids was 26.37 ± 1.32%, which was higher than that of the progeny of the Portuguese oyster. Mean lipid content of the hybrids was 13.65 ± 1.63% of dry weight, which showed obvious heterosis compared to those of the two parental progenies. Observation of gonads revealed that all hybrids were completely fertile. Furthermore, relative expression of the lipid homeostasis genes, SREBP (sterol regulatory element‐binding proteins), PPARα (peroxisome proliferator‐activated receptor) and INSIG (insulin‐induced gene) were found to vary between parental progenies and the hybrids, thus providing a possible reason for difference in the lipid contents of these experimental groups. Overall, the hybrids were viable, rich in lipid and completely fertile and thus could serve as a promising aquaculture stock for oyster breeding in southern China.     

Effects of diets on the growth performance and shell pigmentation of Pacific abalone

This study investigated the effects of natural and artificial diets on growth performance and shell pigmentation of cultured abalone. A 7‐month feeding trial was conducted on 12 000 Pacific abalones (Haliotis discus hannai) with four diets including two extruder‐processed test diets (with & without addition of oleopaprika carotenoids), Pacific dulse (Palmaria mollis) and a combination of Pacific dulse and a test diet. The results showed that the two test diets resulted in higher survival of abalone, but with a lower growth rates when compared with Pacific dulse alone (P < 0.05). The combination diet achieved the highest survival and growth rates. The Pacific dulse resulted in abalone with dark‐brown shells, which are preferred by Asian markets. The test diets led to 52% and 55% of the animals with pink coloured shells and the supplementation of oleopaprika did not affect shell pigmentation. The aqueous acidic extracts from both dark‐brown and pink shells showed blue colour; HPLC‐MS chromatography revealed that the pigments in the extracts were consistent with a biliverdin and a cysteine‐biliverdin. These results are valuable for the development of abalone feed and the control of abalone shell colouration.     

Growth variations within a farm of mussel (Mytilus galloprovincialis) held near fish cages: importance for the implementation of integrated aquaculture

Fish farming releases extensive amounts of particulate organic waste that can be exploited by bivalves in integrated culture. We tested if mussels Mytilus galloprovincialis cultured at two depths (1 and 6 m) in a raft, moored 170 m from a fish farm had greater growth than bivalves held 550 m from the fish cages. Mussel growth was monitored monthly, covering the second phase of the culture, from thinning‐out to harvest (March to November 2011). We also studied if fish solid and dissolved nutrients increased the organic content of the seston and chlorophyll‐a levels near the fish cages through weekly samples. Results showed no differences in seston, chlorophyll and physiochemical characteristics of the water among rafts. Maximum growth and Condition Index (CI) occurred during spring–summer (April–August), when mussels had access to greater food quality and quantity. Mussels cultivated close to the cages showed similar shell length, weight and CI compared with mussels distant from the fish farm. Average shell length, meat dry weight and CI at harvest were 76.31 mm, 2.51 g and 23%. Bivalves cultured distant from the fish cages displayed 26% higher biomass than the other raft at the end of the experiment. Differences in biomass were explained by the significantly higher recruitment of mussel seed observed at the raft distant from the fish cages from June to November. The lack of a significant enhancement in growth of the bivalves cultured next to finfish is discussed.     

Nutritional parameters of dorsal and ventral fillets in summer and winter from farmed yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

The nutritional profile of dorsal and ventral portions of fillets from farmed yellowtail kingfish (YTK) (Seriola lalandi, Valenciennes, 1833) was assessed in winter and summer months to evaluate if there were differential distributions of proximate constituents, fatty acid composition and mineral content seasonally and through the dorso‐ventral axis. The proximate composition of YTK fillets varied between the two anatomical locations examined. In particular, a relatively large variation was observed in crude fat content, which decreased significantly from ventral to dorsal portions of the fillet and was inversely proportional to moisture and protein content. Higher crude fat content was also observed in the fish sampled in summer, compared to those sampled in winter. The omega 3/6 ratio remained constant between fillet portions but was significantly different between seasons (summer > winter). The index of nutritional quality for EPA and DHA was markedly different regarding to fillet portion and season (summer > winter, ventral > dorsal), and significant differences in the levels of potassium, phosphorus, magnesium and iron were also evident between the seasons examined. This study clearly shows differences in nutritional profiles of fillets from farmed YTK in South Australia relative to anatomical location and season. The increase in knowledge gained from this study may lead to improved farm management practices of YTK, which may extend to other commercially relevant species to enhance the production of premium farmed products.     

Early life history of yellow puffer,Chonerhinos naritus (Richardson, 1848) from Sarawak,Northwestern Borneo

The growth and morphological development including fins, spine distribution and pigmentation of larval and juvenile of hatchery‐reared yellow puffer, Chonerhinos naritus were described to provide essential information on the early life history of this species. The total length (TL) of newly hatched larvae was 3.42 ± 0.23 (mean ± SD) mm, reaching 5.66 ± 0.38 mm on 5 days after hatched (DAH), 7.80 ± 0.28 mm on 11 DAH, 9.88 ± 0.40 mm on 27 DAH and 10.92 ± 0.58 mm on 30 DAH. The yolk was completely absorbed in preflexion larvae at 4 DAH. The mouth opening started at 3 DAH of yolk sac larvae, while the teeth appeared starting from preflexion larvae at 7 DAH. Overall aggregate fin ray numbers including caudal fin attained full complement in postflexion larvae at 27 DAH. Several melanophores with appearance of small stellate were first appeared dorsally on the head of flexion larvae at 13 DAH, expanded at the dorsal region of the head, above the eye in juveniles at 30 DAH. The spines first appeared in preflexion larvae of C. naritus at 7 DAH, covering the ventral skin region below pectoral fin base and expanded to the ventral part of the body and nearly covered the whole abdomen region before the anus and below the eyes in juveniles. C. naritus remain as larvae for approximately 29 days, during which they metamorphose to the juvenile stage prior to sexual maturation. Observations in larvae development of C. naritus revealed similar characteristics with other Tetraodontidae species.     

Selection response and realized heritability for growth in three stocks of the Pacific oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

To estimate response to selection and realized heritability for shell height, a one-generation selection was performed in the Pacific oyster Crassostrea gigas using three stocks from China (stock C), Japan (stock J), and Korea (stock K). Applying about the same intensity of selection in the upward direction, three selected and three control lines were created, which were reared under the same environmental conditions at larvae, spat, and grow-out stages. Stock C and stock J showed significantly higher response to selection and realized heritability than stock K at spat and grow-out stages (P < 0.05). At harvest on day 360, the selected lines of stocks C, J, and K were 12.2, 12.2, and 7.9% larger than their control lines, respectively, for shell height. When averaged across the grow-out period, the genetic gain for stocks C, J, and K was 13.2 ± 1.2, 13.2 ± 1.0, and 7.2 ± 0.7%, respectively, and realized heritability was 0.334 ± 0.028, 0.402 ± 0.024 and 0.149 ± 0.027, respectively. The relatively high realized heritability estimate obtained for stock C and stock J indicates that there is genetic variation in the two stocks and that selective breeding by mass selection is very promising.