Dry Flesh Weight Research Articles

Growth Performance of Mytilus galloprovincialis Lamarck, 1819 under an Innovative Integrated Multi-Trophic Aquaculture System (IMTA) in the Mar Grande of Taranto (Mediterranean Sea, Italy)

The cultivation of the Mediterranean mussel, Mytilus galloprovincialis Lamarck, 1819, has been tested in an innovative Integrated Multitrophic Aquaculture system (IMTA) in the Mar Grande of Taranto, as part of the EU-funded Remedialife project. This farming method could solve several problems including the low growth rate in mesotrophic environments while reducing the environmental impact of fish mariculture. Three productive cycles have been carried out. The first (2018–2019, traditional experiment) was conducted in three long lines around six cages of the fish farm in order to evaluate total mussel production under the innovative IMTA system and quality for human consumption by analyzing the concentration of culturable heterotrophic bacteria, total and fecal coliforms, Escherichia coli and Salmonella spp. in mussel tissues. In addition, 17 polycyclic aromatic hydrocarbons (PAHs), including 16 EPA priority compounds and seven polychlorinated biphenyls (PCBs), which are indicators of PCB contamination in the environment, were analyzed using gas chromatography in conjunction with a mass spectrometer. The second cycle (2020–2021, horizontal distance experiment) aimed to test the influence of fish cages on mussel growth by placing mussels near and far from the fish cages. The third cycle (2021–2022, vertical distance experiment) aimed to overcome the phenomenon of “heat waves” that can occur in the Mar Grande of Taranto during summer by testing the growth performance of mussels at two different depths (1 and 12 m). The following parameters were measured: Shell Length, L (mm); Shell Dry Weight, SDW (g); Flesh Dry Weight, FDW (g); Condition Index, IC = FDW/SDW. The results showed that the best growth performance was obtained near the fish cages and at a depth of 12 m. Moreover, the indicators of microbial contamination and concentrations of chemical compounds analyzed in mussel tissues cultured under the innovative IMTA system were in compliance with the reference values of European regulations.

Genetic diversity of Libyan date palms cultivars using amplified fragment length polymorphism and biochemical analysis

Phoenix dactylifera L. is a flowering plant species commonly known as the date palm and is widely cultivated in most Middle East countries, including Libya. The present study analysed the biochemical and genetic diversity of fully mature eight Libyan date palm cultivars grown in different regions using the amplified fragments length polymorphism (AFLP) technique. Six pairs of AFLP molecular marker combinations were utilised to discriminate the eight date palm genotypes. Fruit dimensions (length x diameter) varied based on the type; Majhool Alheelo fruit had the highest value (15.29 cm2), while the lowest value was for Alkhadraya fruits (7.9 cm2). Reducing sugar content ranged from 10.4 per cent of flesh dry weight in Umfetity cultivars to 61.2 per cent in Sufeer-genab, which also showed the highest polymorphism percentage (P%=4.9), while Alkhadarya was the lowest (P%=0.519). The phylogenetic tree indicated that the most distantly related cultivars were Sufeer-genab, Alhamraya and Majhool Alhelo. The two most closely related cultivars were the Alsaeedy Show and Alkhadarya, grown in different regions. Our results indicate that the nutritional and genetic diversity of Libyan cultivars is not closely matched with the growing region.

A dynamic energy budget model for abalone, Haliotis discus hannai Ino

Haliotis discus hannai Ino is one of the important mariculture species in China. Presently, H. discus hannai is extensively cultured in two coastal provinces in China, Shandong in the north and Fujian in the south, and is usually cultured in the “North-South Relay” mode. In order to simulate the growth of abalone in the north and south, an individual dynamic energy budget (DEB) model was constructed for abalone. Model simulation was done by STELLA software, using water temperature and food consumption as forcing functions, with 18 energy budget-related parameters. The DEB model was then validated by field data collected in a Relay-culture operation in 2017 to 2018. Model simulation revealed that, the simulated growth of abalone in non-relay culture scenarios was significantly lower than that in the Relay mode. In Sanggou Bay (in the north) and Xiuyu Sea (in the south), the shell length and dry flesh weight reached 6.3 cm and 10 g, or 5.29 cm and 4.6 g, respectively, as a result of simulated growth for 365 d of abalone seedlings at 2.8 cm and 0.3 g. While the abalone growth in Relay-culture reached a shell length of 6.8 cm and dry flesh weight of 10.9 g. Growth simulations by the DEB model in both length and weight were within the range of observations for abalone. And several goodness-of-fit indices (R-square, modeling efficiency and Theil's inequality coefficient) showed that the DEB model of abalone was able to reproduce abalone growth with acceptable accuracy. By simulating the growth of abalone in aquaculture under different environmental scenarios, the rationale behind the Relay-culture mode was proved at the individual organism level.

Improved methods for understanding the role of predation on dreissenid population dynamics

Impacts of dreissenid mussels (Dreissena spp.) on Great Lakes ecosystems are well documented, and a better understanding of mechanisms that cause variation in dreissenid abundance is needed. An outstanding question is how much dreissenid biomass is consumed by fish predation. A significant difficulty for investigating dreissenid consumption by fish is that dreissenids in stomachs are often a mix of indigestible shell and flesh, which can bias bioenergetics models and estimates of daily ration. Here, we develop an analysis to convert crushed shell and flesh mixtures found in fish diets to dry weight of digestible dreissenid flesh. Quagga Dreissena rostiformis bugensis and zebra Dreissena polymorpha mussels were used in separate dry weight analyses simulating stomach contents ranging from individual mussels to aggregates of each species. A species-specific dry weight relationship was observed when comparing flesh-only dry weight to total dry weight (shell + flesh) for individual dreissenid but not for aggregates. Thus, the model is applicable in providing more precise estimates of dreissenid flesh dry weight in fish diets.

Shell Mass, Biomass, Condition, and Reproductive State of the Invasive Bivalve Mytilopsis leucophaeata (Conrad, 1831) (Dreissenidae)

Basic information on shell dimensions, calcimass and periostracum mass, biomass, and the relation between the condition and reproduction of Mytilopsis leucophaeata was analyzed for a population in the North Sea Canal, the Netherlands. The mean dry flesh weight of individuals with a mean shell length of 12.5 mm showed a peak at the end of June. The mussel reached the highest mean dry flesh weight in the month before the spatfall started. The gonad index (GI) was high in June, followed by a period of decrease until September and a period of increase until November. The condition index (CI) peaked in June and decreased during the remainder part of the year. The range of CI was highest in May when the gonadal development progressed and was smallest in June when the gonadal development was complete. The CI decreased during the rest of the year. Quantile regressions showed a highly significant relation between CI and shell length. Based on the regression coefficients, the CI was maximal at a shell length of 11.4 mm and minimal at 12.5 mm. Condition index variation was highest within a shell length range of 10–15 mm.

Toward reference intervals for shellfish: An illustrative case of feeding and respiratory activities in the Pacific cupped oyster, Crassostrea gigas.

The Quality Assurance and Laboratory Standards Committee of the American Society for Veterinary Clinical Pathology and the guidelines of the Clinical and Laboratory Standards Institute provide a framework for establishing reference intervals of physiological parameters in reputedly healthy individuals, humans, and terrestrial animals, respectively. This framework was applied for the first time to the Pacific cupped oyster, Crassostrea gigas. Reference intervals (RIs) would, first, be of interest for research purposes, including pathophysiology studies. RI determination is the first step before considering the use of RIs for field applications by farmers and marine shellfish health services. The purpose of this study was to propose reference intervals of feeding and respiration parameters, the clearance rate (CR), and oxygen consumption rate (OCR), in a reference population of hatchery-reared diploid Pacific oysters. A de novo, a priori, and a direct approach were applied. The reference values acquired from 214 healthy diploid C gigas (total wet weight 6.23-83.64g, DW 0.06-1.87g) were analyzed using a non-parametric statistical method. Reference intervals were proposed for CR, 0.7-4.1L/h/g dry flesh weight (DW), and OCR, 0.4-1.3mg O2/h/g DW in C gigas in a seawater at a temperature of 22℃ and a salinity of 32‰. Animals were fed 30-40 cells/µL of Isochrysis affinis galbana. The confidence intervals at 90% of the upper limits of the two parameters were found to be higher than those of the Clinical and Laboratory Standards Institute (CLSI) recommendations. Obtaining reference intervals is an important step and must be completed by proposed decision limits to facilitate the early detection of health disorders in C gigas.

Characterization of Attributes in Dehusked Coconut

Selected physical properties of dehusked coconut as length, width, thickness, geometric mean diameter, sphericity, surface area, bulk density and true density were investigated. Compositional changes in coconut fruits, including volume and weight, shell weight, weight of mature coconut water, wet and dry flesh weight, thickness of the flesh and shell were also evaluated. The average fruit length, major diameter and minor diameter were 99.2±13.3 mm, 91.5±8.9 mm, and 89.5±8.7 mm, respectively; while the sphericity, true density, bulk density and surface area were 0.90±0.05, 998±68.8 kg.m-3, 483±37.3 kg.m-3 and 274.2±50.4 cm2 , respectively. The frequency distribution of the major diameter and the fruit mass followed the Gaussian model. Correlations between fruit characteristics were also determined. Results indicated that fruit weight and total wet flesh weight were closely correlated, and both of these characteristics can be used as an indicator of fruit size.

Antioxidant activity of cell-wall components in netted melon flesh against ascorbic acid oxidation during fruit development

Melon (Cucumis melo) fruit is known to contain a high level of vitamin C, as do Valencia orange and Satsuma mandarin. Previously, we reported that cell-wall components of melon flesh demonstrated a marked effect in maintaining the UV absorbance of ascorbic acid (high antioxidant activity), compared with the flesh of 18 fruit species. In this study, changes in antioxidant activity against ascorbic acid oxidation were measured in water extract of alcohol-insoluble solids (AIS) of the flesh of three cultivars of melon ('Andesu', 'Gurandoru', and 'Life') during fruit development, between 10 and 51 days after anthesis (DAA). The antioxidant activity per unit weight was increased with fruit development in all cultivars, especially after 45 DAA. The flesh firmness and dry weight of AIS decreased with fruit development. As the main component of the water-soluble fraction is pectic substances, uronic acid and neutral sugar contents in the water-soluble fraction of AIS were determined. A marked increase in the neutral sugar content was observed, while the increase of uronic acid was comparatively low. In our previous study, the antioxidant activity, measured by the ascorbic acid oxidation method, was higher in low-methylated pectins than in high-methylated pectins. Antioxidant components in AIS of melon flesh are discussed.

Biometric evaluation of twelve olive cultivars under rainfed conditions in the region of Calabria, South Italy

Biometrics are widely considered in table olive and olive oil production. Fruit size, flesh content and flesh/pit ratio are among the most important parameters in table olive processing, whereas oil and water content are among the most important parameters in olive oil production. In this work, twelve parameters from drupes of 12 cultivars in three harvest years 2014, 2015, 2016 (Region of Calabria, South Italy) were studied. Fruit weight was highest in Nocellara Messinese cv (more than 5 g in all the three considered harvest years) for this reason these fruits are preferred for table olives processing. Ottobratica cv showed the lowest number of fruits/kg as a consequence of the high weight of its drupes. Pit or stone (endocarp) weight was lowest in Ottobratica, Pendolino and Roggianella cvs (less than 0.5 g). Fresh flesh (mesocarp) weight was highest in Nocellara Messinese cv (4.26 – 4.49 g) and in Picholine cv (3.68 – 3.88 g), whereas flesh dry weight was highest in Frantoio and in Roggianella (more than 40% on pitted fruit), these last two cvs also showed the lowest moisture content i.e. less than 60% on pitted fruit. The longest drupes (longitudinal diameter) were produced by Nocellara Messinese and Picholine cvs measuring more than 25 mm, these two cvs produced also the fruits showing the highest horizontal diameter more than 18 and more than 16 mm respectively. In 10 from 12 cvs the highest oil content was found on 2016 and Pendolino cv showed the lowest content on 2014 and 2015. Cultivar and harvest year showed a highly significant influence on the olive fruit biometrics.

Modeling sugar content of pineapple under agro-climatic conditions on Reunion Island

A process-based model simulating the change in total soluble solids (TSS (%)) in fruit flesh was developed to describe the effect of climatic conditions on the sugar content of 'Queen Victoria' pineapple at harvest on Reunion Island. Sugar content varies throughout fruit development according to three processes (the supply of carbohydrates to the fruit, fruit metabolism, and dilution) which are affected by environmental factors, mainly temperature, rainfall and fertilization. The ecophysiological model of soluble sugar accumulation was linked to SIMPINA, a crop model that accurately predicts the daily increases in flesh dry and fresh weight. When the process-based model and crop model were linked, the dry and fresh matter of the pineapple flesh, as affected by climatic conditions, could be used as inputs to predict the TSS (%) at harvest. The relative rate of transformation of carbon as sugars in the fruit flesh for the synthesis of compounds other than sugars was estimated during fruit growth. TSS (%) were compared for harvested fruit grown under eight agro-climatic conditions. In the flesh of fruit harvested close to maturity, i.e., at 1400 degree-days after flowering, TSS (%) were significantly related (r2 = 0.55, P < 0.001) to total soluble sugar content. The variability of TSS (%) between the eight agro-climatic groups ranged from 16.9 for pineapples grown in dry locations irrigated, under N-deficit conditions to 19.4 for pineapples grown in dry locations, without irrigation and without N deficiency. The variability of TSS (%) was substantial within each of the eight agro-climatic groups: standard deviations ranged from 0.9 to 1.5 for pineapples grown in dry locations, irrigated, without N deficiency and in dry locations, without irrigation and without N deficiency, respectively. For data from 14 experiments conducted under different climatic conditions, N fertilization, and irrigation conditions, the model predicted the TSS (%) at harvest with an RRMSE of 0.04. By linking this sugar model to the SIMPINA crop model, the impact of environmental conditions and cultural practices on the growth and development of pineapple are taken into account to predict the gustatory quality of pineapple grown on Reunion Island. The model could have a practical application to manage fruit quality, plan harvest, and marketing. (Resume d'auteur)

Response of Mytilus edulis to enhanced phytoplankton availability by controlled upwelling in an oligotrophic fjord

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 518:139-152 (2015) - DOI: https://doi.org/10.3354/meps11036 Response of Mytilus edulis to enhanced phytoplankton availability by controlled upwelling in an oligotrophic fjord Tore Strohmeier1,*, Øivind Strand1, Marianne Alunno-Bruscia1,2, Arne Duinker3, Rune Rosland4, Jan Aure1, Svein R. Erga4, Lars J. Naustvoll5, Henrice M. Jansen1,6, Peter J. Cranford7 1Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway 2Ifremer, UMR 6539, 11 Presqu’île du Vivier, 29840 Argenton-en-Landunvez, France 3National Institute of Nutrition and Seafood Research, PO Box 2029 Nordnes, 5817 Bergen, Norway 4Department of Biology, University of Bergen, PO Box 7803, 5020 Bergen, Norway 5Institute of Marine Research, Nye Flødevig veien 20, 4817 His, Norway 6Institute for Marine Resources and Ecosystem Studies (IMARES), PO Box 77, 4400 AB Yerseke, The Netherlands 7Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y4A2, Canada *Corresponding author: tore.strohmeier@imr.no ABSTRACT: The controlled upwelling of nutrient-rich deep water in oligotrophic coastal regions has been proposed as a means of increasing phytoplankton and, subsequently, bivalve aquaculture production. This was tested as part of a large-scale upwelling experiment in an oligotrophic environment (Lysefjord, Norway). The mean chlorophyll a concentration in the upwelling area was consistently higher than at the control site (mean ± SD: 3.3 ± 1.9 and 1.5 ± 0.6 mg chl a m-3, respectively) during the 4 mo of controlled upwelling. After 2 mo with upwelling, the dry flesh weight of 1 yr old and 2 yr old mussels was 95% and 24% higher, respectively, than that of the mussels at the control site. The 1 yr old mussels (Mytilus edulis) at the upwelling site achieved up to 2.4-fold higher dry flesh weight compared to the control. Reproductive output was also higher at the upwelling site and only there, spawning of 1 yr old mussels was detected. Standardized clearance and respiration rates showed maximum values during the most intense period of tissue growth. Average ingestion rates were 40% higher at the upwelling than at the control site. Tissue growth and clearance rates were not correlated with the measured seston parameters, suggesting that food acquisition was responsive to other exogenous parameters and/or to increased endogenous energy demands. It was concluded that the sustained upwelling of nutrient-rich deep water in an oligotrophic fjord can increase phytoplankton biomass, resulting in improved mussel growth performance and increased aquaculture production carrying capacity. Thus, controlled upwelling represents a simple but effective ecosystem engineering approach for enhancing human food production. KEY WORDS: Bivalve aquaculture · Production carrying capacity · Physiology · Fjord ecosystems · Shell growth · Tissue growth Full text in pdf format PreviousNextCite this article as: Strohmeier T, Strand Ø, Alunno-Bruscia M, Duinker A and others (2015) Response of Mytilus edulis to enhanced phytoplankton availability by controlled upwelling in an oligotrophic fjord. Mar Ecol Prog Ser 518:139-152. https://doi.org/10.3354/meps11036 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 518. Online publication date: January 07, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Growth of Crassostrea gasar cultured in marine and estuary environments in Brazilian waters

The objective of this work was to evaluate the growth of the mangrove oyster Crassostrea gasar cultured in marine and estuarine environments. Oysters were cultured for 11 months in a longline system in two study sites - São Francisco do Sul and Florianópolis -, in the state of Santa Catarina, Southern Brazil. Water chlorophyll-α concentration, temperature, and salinity were measured weekly. The oysters were measured monthly (shell size and weight gain) to assess growth. At the end of the culture period, the average wet flesh weight, dry flesh weight, and shell weight were determined, as well as the distribution of oysters per size class. Six nonlinear models (logistic, exponential, Gompertz, Brody, Richards, and Von Bertalanffy) were adjusted to the oyster growth data set. Final mean shell sizes were higher in São Francisco do Sul than in Florianópolis. In addition, oysters cultured in São Francisco do Sul were more uniformly distributed in the four size classes than those cultured in Florianópolis. The highest average values of wet flesh weight and shell weight were observed in São Francisco do Sul, whereas dry flesh weight did not differ between the sites. The estuary environment is more promising for the cultivation of oysters.

이매패류 3종의 크기 및 수온에 따른 여수율과 노닐페놀 흡수율의 관계

본 연구에서는 두 개의 크기집단의 바지락(Ruditapes philippinarum), 재첩(Corbicula japonica), 홍합(Mytilus edulis)을 세 개의 수온 조건(5, 13 그리고 <TEX>$18^{\circ}C$</TEX>)에서 용존 노닐페놀에 노출시킴으로써 개체 크기와 수온 변화가 여수율과 용존 노닐페놀 흡수율에 미치는 영향을 조사하였다. 이를 통해 이매패류의 여수율과 유기화합물질 흡수과정의 관련성에 대해 평가하고자 하였다. 단위무게당 여수율(<TEX>$CR_{wt}$</TEX>)은 모든 개체 크기와 온도 범위에서 홍합(0.3-4.9 L <TEX>$g^{-1}\;h^{-1}$</TEX>)이 가장 높았으며, 재첩(0.44-1.98 L <TEX>$g^{-1}\;h^{-1}$</TEX>), 바지락(0.08-0.6 L <TEX>$g^{-1}\;h^{-1}$</TEX>) 순으로 나타났다. 한편 단위무게당 노닐페놀의 흡수율은 종 간 뚜렷한 차이를 보이지 않았다. 단위무게당 여수율과 노닐페놀 흡수율은 일반적으로 개체의 크기가 증가함에 따라 감소하고, 온도가 증가함에 따라 증가하는 경향을 보였다. 세 종 모두에서 노닐페놀 흡수율은 여수율과 높은 상관관계를 보였다. 한편 노닐페놀 흡수율은 같은 여수율 범위에서 홍합, 재첩, 바지락 순으로 증가하였다. 여수율과 노닐페놀 흡수율의 높은 상관관계로부터 여수율이 이매패류의 용존 유기화합물 흡수에 중요한 역할을 한다는 것을 추정할 수 있다. The present study was conducted to evaluate relationship between nonylphenol uptake rate and clearance rate of Ruditapes philippinarum, Corbicula japonica and Mytilus edulis. Variation of the temperature and body size of the bivalves was used to modulate clearance rate and nonylphenol uptake rate in this experiment. Clearance rate and nonylphenol uptake rate experiments were determined for two different size classes of the bivalves (R. philippinarum: 0.35, 0.73 g, C. japonica : 0.047, 0.1000g, M. edulis: 0.30, 0.37 g; mean flesh dry weight) and three different temperature regime (5, 13 and <TEX>$18^{\circ}C$</TEX>). Weight-specific clearance rate in all animal size and temperature ranges increased in the order of R. philippinarum, C. japonica and M. edulis. The weight-specific nonylphenol uptake rate did not show specific trend among species. The clearance rate and nonylphenol uptake rate generally decreased with animal size and increased with water temperature. For all three species nonylphenol uptake rate had a strong relationship with clearance rate. For a given clearance rate ranges, the nonylphenol uptake rate was in the order of R. philippinarum > C. japonica > M. edulis. The results suggest that water ventilation capacity of filter-feeding organisms is an important physiological factor controlling uptake rate of dissolved nonylphenol.

Growth and food sources of Pacific oyster Crassostrea gigas integrated culture with Sea bass Lateolabrax japonicus in Ailian Bay, China

Shell length and tissue growth of Pacific oyster Crassostrea gigas integrated culture with Sea bass Lateolabrax japonicus were monitored during April–October 2010 in Ailian Bay, China. And also, the food sources of the oyster were analyzed and quantified by stable carbon and nitrogen isotope methods. Results showed that the increment of shell length and flesh dry weight of oyster cultured at cage area were greater than that at control area significantly (P < 0.05). Enrichment of δ13C and δ15N in oyster tissue at the cage area relative to the control area was significant (P < 0.05). Based on the simple linear mixing model, the contribution rate of the fish feces and waste fish feed to oyster was 29.27 and 5.59 %, respectively. This work demonstrates that the differences in growth performance of oyster between cage area and control area were resulted from the utilization of organic matter derived from fish aquaculture. Integrated filter-feeding bivalves culture with marine fish can reduce the environmental impact of organic waste from fish-farming activities.

Reproductive Cycles in Atlantic and Mediterranean Populations ofVenus nuxGmelin, 1791 (Bivalvia: Veneridae), from Southern Spain

ABSTRACT The recent reduction of catches of common shellfish in southern Spain has pointed out an overexploitation of these resources. For this reason, new shellfish resources have been investigated—among them, the venerid Venus nux Gmelin, 1791. To provide information to managers for a better regulation of this new fishery, we studied the reproductive cycle in the Atlantic (Huelva) and Mediterranean littoral (Malaga) of southern Spain from June 1999 to May 2000 using histology and changes in flesh dry weight. Histological examination of the gonads showed a long and asynchronous reproductive period. Spawning occurred throughout the year in both populations. Two different spawning peaks were observed: April/May for the Mediterranean population and June/July for the Atlantic one. These peaks correspond to the highest percentage of population in spawning stage, together with the greatest loss of tissue weight. During the annual reproductive cycle, new activation of the gonads from postactive stages occurred ...

Does bivalve mollusc polyculture reduce marine fin fish farming environmental impact?

The ability of bivalve culture in the proximity of an open water fin fish farm to reduce the environmental impact caused by organic wastes was tested. The experiment involved floating net cages containing cultured gilthead sea bream ( Sparus aurata) and European sea bass ( Dicentrarchus labrax) in the western Mediterranean. Two bivalve species, oyster ( Ostrea edulis) and mussel ( Mytilus galloprovincialis), were deployed for 3 months along a distance transect running from 0 to 1800 m from the fish cages. Shell growth, flesh dry weight, the concentration of stable isotopes of carbon and nitrogen, and metal accumulation (Cd, Pb, Cu and Zn) in the bivalves were analyzed. Bivalves showed significant growth compared with their respective starting sizes, although closeness to the fish farm did not enhance such growth. The stable isotopes content indicated that there was no relationship between the main input of organic matter from the fish farm (the feed) and the trophic behavior of the bivalves. Neither did metal accumulation show a trend along the distance gradient from the fish farm. All the results were consistent in indicating that neither oysters nor mussels fed on fin fish farming wastes. This work demonstrates that the polyculture of fin fish and bivalves does not represent an appropriate tool for reducing the environmental impact of fin fish aquaculture in open water.

Variability of the hemocyte parameters of Ruditapes philippinarum in the field during an annual cycle

A field monitoring of hemocyte parameters of the Manila clam Ruditapes philippinarum was conducted from July 2004 to September 2005 in Gulf of Morbihan (France), in order to assess (1) the factors controlling the hemocyte parameters of the Manila clam and (2) their relative contribution to the overall variability of these parameters. Monthly, sixty clams were sampled and total hemocyte count (THC), granulocyte and hyalinocyte counts, phagocytosis, phenoloxidase specific activity, length, flesh dry weight, and condition index were measured individually. Perkinsus sp. infection and Brown Ring Disease symptoms were also monitored. Temperature and trophic resource were also monitored. Results indicate that temperature controls granulocyte counts and subsequently THC. Other environmental factors had no direct influence on the measured hemocyte parameters. Almost all measured parameters were significantly affected by size/age and condition index. There were poor relationships between both pathologies and hemocyte parameters presumably because of low infection intensities. Nevertheless, high Perkinsus sp. infection intensity significantly increased total and granulocyte counts and decreased phagocytosis. An interesting result of this study is that the measured biotic and abiotic factors poorly contribute to the explanation of the total variability of hemocyte parameters. Granulocyte concentration was the best explained parameter. However, only 16.4% of its variance was explained by cumulating temperature, length, condition index and Perkinsus sp. infection effects. This study emphasizes the need for a better understanding of hemocyte functions and the factors modulating these functions.

Physical properties of fresh young Thai coconut for maturity sorting

Young mature coconut is a widely consumed fruit consisting of soft white flesh and sweet white transparent aromatic juice. Judging the maturity of young coconut is difficult and thus a harvested crop typically features fruit of varying levels of maturity, which currently require manual grading. In an attempt to help reduce the time and costs associated with the grading process, the correlations between the physical, mechanical, physiological and acoustic properties of coconuts and their maturity levels were investigated. The analyses showed that specific gravity, husk rupture force and husk firmness showed a decreasing trend with progressing days after pollination. Other properties including resonant frequency, shell rupture force, shell firmness, total soluble solids, flesh thickness, wet flesh weight and dry flesh weight indicated an increase in values with days after pollination. The flesh thickness was the parameter best correlated with days after pollination. Maturity index based on the flesh thickness can be quantitatively predicted by multivariate partial least squares model. The best model used a combination of husk rupture force, shell firmness, shell rupture force, wet flesh weight and husk firmness ( R 2 = 0.991, standard error of prediction of 0.133 and bias of 0.004). A non-destructive model based on resonant frequency gave relatively good accuracy of prediction with R 2 = 0.927, standard error of prediction 0.386 and bias of 0.034.

NMR relaxometry as a potential non-invasive routine sensor for characterization of phenotype in Crassostrea gigas

MR imaging is the most appropriate non-invasive technique for quantifying the growth of somatic and gonad tissues and to determine sex in the Pacific oyster, Crassostrea gigas. However, this technique is too costly for field studies where oysters are used as bioindicators of environmental quality or to be applied routinely in hatcheries. We have tested the ability of low Nuclear Magnetic Resonance relaxometry, a much less expensive technique, to obtain phenotype parameters that can be used to monitor the physiological state of oysters. NMR measurements were carried out at three different periods using a low field spectrometer equipped with a 50 mm diameter probe to investigate 60 oysters in their first year of maturity, which were then dissected to measure internal shell cavity volume and dry flesh weight and to determine sex and gonad development. The NMR results showed that it was possible to determine both internal shell cavity volume and dry flesh weight in less than one minute with very high determination R 2 coefficients (0.95 and 0.94, respectively). The results showed also that it was possible to identify sex and gonad development, with success rates of 93% and 83%, respectively. For oysters with dry weight above 0.7 g, the success rate in identifying sex was 100%. Further studies are required to design an NMR probe that is appropriate for larger oysters and to improve sex discrimination and prediction of gonad development with larger study groups.

Digenean trematodes–marine mollusc relationships: a stable isotope study

The stable carbon and nitrogen isotopic composition of digenean trematode parasites and their marine mollusc hosts was investigated to describe the potential influence of parasites on their host and its different tissues, and to obtain further insight into their trophic relationships. Four parasite-host systems were studied: Labratrema minimus-Cerastoderma edule, Monorchis parvus-C. edule, Lepocreadiidae parasites-Nassarius reticulatus and Zoogonidae parasites-N. reticulatus. Among the 4 sampling occasions reported here and corresponding to the 4 parasite-host systems, isotopic shifts from pathologic (i.e. linked to disturbances in host metabolism) and mass-balance (i.e. linked to significant differences between host and parasite isotopic signatures) origins were observed only once. Both corresponded to delta 13C measurements of the L. minimus-C. edule system when the infestation load (percentage parasite dry weight compared to total flesh dry weight) was highest (9 to 25%, mean = 16%) over the sampling period. Overall, measurements indicate that digenean trematode parasitism induced low or no shifts in isotopic signatures of C. edule and N. reticulatus tissues. The 2 endoparasites L. minimus and M. parvus appeared to be slightly depleted in 13C compared to C. edule digestive gland and gonads, which were the most parasitized tissues. In contrast, no fractionation or low 15N trophic enrichments occurred in the parasites. These results highly contrast with the classical trophic enrichment reported in prey-predator systems but are in agreement with the scarce literature regarding other parasite-host systems. Our results indicate that (1) digenean trematodes mainly feed on digestive glands (the cockle tissue with which they are mainly associated) with a possible slight preference for lipids, and (2) fractionation due to parasite metabolism should be low due to abbreviated metabolic pathways and/or slight loss of materials through excretion, tegument diffusion and respiration.