90 research outputs found
Development of biodegradable hybrid polymer film for detection of formaldehyde in seafood products
Despite the enormous accomplishments of current sensing methods, portable and sensitive sensing materials remains a challenging issue. Herein, a novel of a biodegradable hybrid polymer film was developed for quantitative analysis of formaldehyde seafood, including Lutjanus erythropterus, Euthynnus affinis, Caranx indicus, and Penaeus monodon at Sabah, Malaysia. In this research, starch and chitosan were introduced as the substrate to entrap Nash colorimetric reagents for the fabrication of biodegradable films for detection of formaldehyde. Under optimal conditions, excellent linearity (R2 = 0.9918) of colorimetric response was obtained in formaldehyde concentration ranges of 100 to 0 ppm, with a limit of detection and quantification calculated to be 5 and 16.8 ppm, respectively. The developed film was successfully applied to the identification and quantification of formaldehyde in four different seafood samples with satisfactory recoveries, and RSD values obtained range between 98.80%–104.65% and 0.12%–1.21%, respectively. The present research demonstrated short response time (within 5 min) that provides reliable methods for application in biosensing, which exhibited the advantage of this well-performing platform for application in the food, environmental, and medical disciplines sensing
Effect of different light intensities on prolactin and cortisol plasma concentration in farming African catfish (Clarias gariepinus) in RAS with low-water exchange
In the Bulgarian aquaculture sector, focusing research efforts on the technical specifications of the cultivation of African catfish (Clarias gariepinus) is important due to the need for more information. We aimed to assess the impact of light intensities on prolactin and cortisol levels as stress markers in African catfish. Fish were acclimated over an appropriate period to the short photoperiod (16D and 8L) and then distributed randomly to three groups, each separated by sex. Fish exposed to different light intensities (63, 51, and 40 lux, respectively) were followed for 45 days by lux meter. Blood samples were collected from the caudal vein using a 2 ml K2EDTA-coated syringe. A laser fluorescence reader assayed plasma prolactin and cortisol. The pituitary was removed from anesthetized fish and fixed for histological examinations. The results of our study suggest that increasing light intensity increases prolactin and cortisol levels in African catfish
The limnology of Lake Clark, Alaska
Thesis (M.S.) University of Alaska Fairbanks, 2002This study gathered baseline limnological data to investigate the thermal structure, water quality, phytoplankton, and zooplankton of Lake Clark, Alaska. Results indicate Lake Clark is oligotrophic and mixes biannually, but stratification is weak and thermoclines are deep. Longitudinal gradients were seen in measurements of temperature, suspended solids, turbidity, light penetration, algal biomass, and zooplankton density. Wind and tributary inputs determine the thermal regime. Glacially-influenced tributaries drive turbidity and light gradients by introducing suspended solids to the inlet end of the lake. Suspended solids likely create the algal biomass gradient by limiting the light available for photosynthesis in the inlet basin. Algal biomass and turbidity gradients may interact to create an area of high productivity and low predation risk, causing high zooplankton concentrations in the central basin. Oxygen supersaturation was discovered in the hypolimnion but remains unexplained. Because tributaries are glacially influenced, Lake Clark could be sensitive to global warming
Molecular Techniques for the Detection of Organisms in Aquatic Environments, with Emphasis on Harmful Algal Bloom Species.
Molecular techniques to detect organisms in aquatic ecosystems are being gradually considered as an attractive alternative to standard laboratory methods. They offer faster and more accurate means of detecting and monitoring species, with respect to their traditional homologues based on culture and microscopic counting. Molecular techniques are particularly attractive when multiple species need to be detected and/or are in very low abundance. This paper reviews molecular techniques based on whole cells, such as microscope-based enumeration and Fluorescence In-Situ Hybridization (FISH) and molecular cell-free formats, such as sandwich hybridization assay (SHA), biosensors, microarrays, quantitative polymerase chain reaction (qPCR) and real time PCR (RT-PCR). Those that combine one or several laboratory functions into a single integrated system (lab-on-a-chip) and techniques that generate a much higher throughput data, such as next-generation systems (NGS), were also reviewed. We also included some other approaches that enhance the performance of molecular techniques. For instance, nano-bioengineered probes and platforms, pre-concentration and magnetic separation systems, and solid-phase hybridization offer highly pre-concentration capabilities. Isothermal amplification and hybridization chain reaction (HCR) improve hybridization and amplification techniques. Finally, we presented a study case of field remote sensing of harmful algal blooms (HABs), the only example of real time monitoring, and close the discussion with future directions and concluding remarks
The Suitability of Newton Reservoir to be Either a Coldwater or a Warmwater Fishery
Measurements were made of the water chemistry the distribution and relative abundance of net-plankton and the reproduction age and growth and food habits of largemouth bass in Newton Reservoir, Newton, Utah. Samples for chemical analysis were collected weekly from three sites and from several depths at each site. Plankton collections were made on a monthly basis. Data were compared with data in the literature and analyzed for possible ecological implications. Physical and chemical investigations of the water indicated favorable conditions for a warmwater fishery. The study of the surface net-plankton revealed a predominance of blue-green algae. The substratum of the littoral zone is characterized by material that has favored successful largemouth bass reproduction. Two and three year olds were dominant in the catch during the study. Growth in the reservoir was comparable to average rates of other studies. Analysis of stomach contents of largemouth bass revealed that they are largely
Riparian and microhabitat factors determine the structure of the EPT community in Andean headwater rivers of Ecuador
"This is the peer reviewed version of the following article: Vimos-Lojano, D.J., F. Martínez-Capel, and H. Hampel. 2017. Riparian and Microhabitat Factors Determine the Structure of the EPT Community in Andean Headwater Rivers of Ecuador. Ecohydrology 10 (8). Wiley: e1894. doi:10.1002/eco.1894, which has been published in final form at https://doi.org/10.1002/eco.1894. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] This research was conducted in the high-Andean basin of the Zhurucay River in southern Ecuador. In 4 river reaches, 19 sampling campaigns were conducted per reach spread over a period of 35months. The biotic samples were selected in the periods with greatest flow stability. Parallel to each sampling, 37 environmental variables grouped into 3 factors (riparian corridor, hydromorphology, and water quality) were recorded. The study aimed to analyse during periods of stable flow the influence of these environmental factors on the structure and density of the EPT community (Ephemeroptera, Plecoptera, Trichoptera) in a quasi-pristine aquatic ecosystem. Multivariate statistical analysis revealed that the Froude number, gravel type, and width/depth ratio are the most relevant hydromorphological variables explaining variations in EPT density. Xiphocentronidae, Contulma, and Helicopsyche were observed to have a relationship with the order of the river, while Ochrotrichia, Nectopsyche, and Phylloicus varied with the type of riparian vegetation. Phylloicus, Ochrotrichia, and Nectopsyche were common in lentic sites, while the proportion of gravel and the width/depth ratio restricted the genus Helicopsyche. The only relevant water quality factor was the total phosphorus, which was related with 2 taxa. In conclusion, although macroinvertebrates are currently employed in water quality studies, riparian vegetation and hydromorphological factors are determinant for their communities in pristine Andean rivers. Such factors are therefore crucial in the study of environmental flows and the assessment of the ecological integrity.This research was funded by the SENESCYTPIC 11-726 Project (Interpretation of hydro-ecological processes as a basis for assessing the ecological flow in the Paute and Jubones watershed), the hydroelectric company CELECEP, and DIUC (Investigation Department of the University of Cuenca). Thanks are due to the SENESCYT project PIC 11-715 (Impact of land use change in the hydrogeochemistry of Andean basins) for providing the hydrological data used in this study. Further, financial support was provided by SENESCYT through a fellowship granted to the first author for carrying out his doctoral programme and through the PROMETEO fellowship awarded to the third author. We are greateful to Ing. Andres Quichimbo for reviewing the hydrological data, and the staff of the Aquatic Ecology Laboratory at the University of Cuenca for their assistance and field logistics. Finally, the authors are grateful to Prof. Jan Feyen for constructive polishing edition the manuscript.Vimos-Lojano, D.; Martinez-Capel, F.; Hampel, H. (2017). Riparian and microhabitat factors determine the structure of the EPT community in Andean headwater rivers of Ecuador. Ecohydrology. 10(8):1-15. https://doi.org/10.1002/eco.1894S115108Albariño, R. J., & Balseiro, E. G. (2002). Leaf litter breakdown in Patagonian streams: native versus exotic trees and the effect of invertebrate size. Aquatic Conservation: Marine and Freshwater Ecosystems, 12(2), 181-192. doi:10.1002/aqc.511ALLAN, D., ERICKSON, D., & FAY, J. (1997). The influence of catchment land use on stream integrity across multiple spatial scales. Freshwater Biology, 37(1), 149-161. doi:10.1046/j.1365-2427.1997.d01-546.xAllan, J. 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Physicochemical, Sensory and Nutritional Properties of Foods Affected by Processing and Storage
Processing and storage can cause changes and interactions in food components that have effects on nutritional value, organoleptic characteristics or even food safety. This book includes 19 research works showing important and interesting advances, as well as new approaches, in this research topic. Four articles are dedicated to studying the effect of canning conditions (filling media and some ingredients) on the diverse parameters of quality for fish and pet foods. Three articles are devoted to studying the effects of dehydration (pre-treatments and drying procedures). One article is dedicated to monitoring the elaboration of a fermented and dehydrated product (sausage) using a portable NIRS device. The ninth article of this book studies the effect of low-dose electron beam irradiation on cooking quality, moisture migration, and thermodynamics, as well as the digestion properties of the isolated starches in newly harvested and dried rice. The next contribution studies the use of different preservatives to avoid the formation of undesirable volatile organic compounds in stracciatella cheese. Another article examines the impact of source material, kibble size, temperature, and duration on the efficiency of the aqueous extraction of sugars and phenolics from carob kibbles by conventional heat-assisted (HAE) and ultrasound-assisted (UAE) methods. In two articles, marinating with different extracts, alone or combined with other seasoning/conditioning methods, was essayed to tenderize beef or to improve the sensory quality of chicken leg and breast meat. The effect of various cooking methods on the quality, structure, pasting, water distribution and protein oxidation of fish and meat-based snacks is studied in the fourteenth article. The last five articles are dedicated to the study of the effects of storage on several foods (olive oil, blueberry, beetroot and Atlantic mackerel)
Management strategies to control sexual maturation in sea-reared Atlantic salmon (Salmo salar L.): Biomass management, light-manipulation and sterility
Pre-harvest sexual maturation in farmed Atlantic salmon, Salmo salar, remains a key biological bottleneck compromising biomass and financial output, production predictability, environmental respect, stock welfare and the overall sustainability of the on-growing industry. The management practices currently in place are not optimized and events of high maturation rate are still sporadically observed. From an ecological perspective, the escape of reproductively competent, domesticated Atlantic salmon constitutes a threat to the integrity of wild stocks. The forecasted expansion of the Scottish salmon industry compels the need for a comprehensive and more reliable control of sexual maturation. The general aim of this research project was to optimize the current management strategy (windows of light-manipulation and quality grading) and test alternative practices (lighting-technologies, selective harvest and triploidization) in the control of pre-harvest sexual maturation within the Atlantic salmon on-growing industry.
In that end, a number of trials were performed using stock reared in sea-cages on a full commercial-scale or in tanks on an experimental scale. The results of this project are organized around three experimental chapters dealing consecutively with body-size dimorphism, grading and harvest quality; light manipulations and triploidy. In each chapter, two original manuscripts either published or in review are included. In addition to these experimental results, a literature review chapter composed of two review papers on the photoperiodic synchronization and developmental regulation of maturation in salmonids and on morphological skin colour changes in teleosts (published) are presented.
In the first experimental chapters, we aimed at investigating the possibility of detecting and selectively harvesting a high proportion of sexually recruited fish before flesh quality deterioration. Results clearly showed that body-size dimorphisms between maturity cohorts at the end of the anabolic window of reproduction (June/July) are strong and standard predictors of maturation among related populations with the same freshwater history. Dimorphism can therefore be modelled to easily and accurately estimate maturation rate in a number of discrete rearing-units. If required, a high proportion of sexually recruited fish can be selectively harvested as superior quality product while leaving the immature fish for further on-growing. This provides an alternative to visual grilse grading that is not feasible in large-scale aquaculture systems, prevents downgrading and increases production predictability as compared to emergency harvests. Furthermore, our results showed immature males grow faster than immature females which should be further investigated to fully determine gender specific performances and nutritional requirements. Weight-grading performed earlier in the cycle affects the sex-ratio within individual pens and in turn apparent performance. This work also revealed that Atlantic salmon can exhibit significant variations in skin colouration resembling the onset of nuptial display but that are not related to sexual recruitment and do not correlate with reduced flesh quality. This originates from a lack of purine (silver) pigments which was also identified, to a larger extent, as characteristic of the nuptial display. This suggests a degree of desmoltification in these histologically immature fish. The instrumental colouration of the altered phenotype was shown to be improved towards a more silver-like appearance by direct ice-contact. This knowledge could facilitate post-harvest quality grading towards the most appropriate market channel and increase product acceptance and attractiveness.
The second experimental chapter investigated the possibility of improving photoperiodic manipulation used to suppress early maturation, currently applied for 6-months during the second winter at sea using wide-spectrum, high-intensity lighting systems. Our results showed that the window of continuous artificial-light (LL) exposure can be reduced to 4-months following its onset in early January without compromising its efficiency in suppressing pre-harvest maturation. In addition, alternative lighting technologies were also highly potent at suppressing sexual maturation. The mean-irradiance (intensity) generated within a commercial sea-cage was inversely proportional to the suppression of nocturnal plasma melatonin (light perception hormone) and negatively correlates with the maturation rate within the commercial sea-pen. Threshold levels of light-intensity required to achieve optimal (total) suppression of sexual maturation are suggested. Alternative, narrow band-width lighting-technologies (cold cathode and light-emitting diodes) present an array of technical, practical, economic and welfare benefits comparing to the system currently in use. Clear improvements of the photoperiod-manipulation strategy were demonstrated and these would reduce economic and environmental costs but also potential impacts on animal welfare.
The third experimental chapter showed the strong potential of sterile-triploid Atlantic salmon stocks both in freshwater and seawater. Triploid out-of-season smolts were produced for the first time using a classical accelerated "square-wave" photoperiod. Triploidization affected the smoltification pattern but had no detrimental effects on freshwater and early seawater performances under both a S0+ and S1 regime. This illustrates the need to adapt the timing of seawater transfer for successfully producing triploid Atlantic salmon post-smolts. Following one year of seawater rearing, the prevalence of external deformities was higher in triploids but remained within acceptable levels. Importantly, the incidence of vertebral deformities and ocular cataract was higher in triploids possibly due to their specific requirements. It is suggested that tailoring the diet to the nutritional requirements of triploids holds strong potential for remediation. This must be addressed if the use of sterile-triploid stock is to become a commercial reality.
The present research project provides means to optimize the maturation management strategy within the Atlantic salmon on-growing industry through light-manipulation, maturation detection and selective harvest, and quality grading. Proposed improvements have the potential to increase biomass and financial output, production predictability, environmental respect and animal welfare and will allow standardization of the overall control of pre-harvest sexual maturation. Their implementation provides a comprehensive strategy likely to favour a sustainable expansion of the Atlantic salmon industry. From a longer term perspective, the rearing of sterile-triploid stocks is promising and should be actively investigated to isolate domesticated strains from their wild conspecifics. This would also eliminate the need for on-growers to deploy a maturation management strategy that that might still affect stock welfare and remains, despite the strong improvements demonstrated, not 100% reliable, costly, technical and protracted
Effect of different farming sites and techniques on the growing performances and quality of Pacific oysters (Crassostrea gigas, Thunberg)
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