The aquatic environment is a reservoir of many species that have not yet been exploited at a global level and have not been extensively investigated. The aim of the present work was to study the microbial populations, the bacterial... more
The aquatic environment is a reservoir of many species that have not yet been exploited at a global level and have not been extensively investigated. The aim of the present work was to study the microbial populations, the bacterial communities and physicochemical parameters (pH, water activity, humidity, salinity) in raw, frozen, boiled, dehydrated and salted final products of two sea cucumber species (Holothuria polii and Holothuria tubulosa) originating from the Hellenic seawaters. The results indicated that all products were found at acceptable levels from a microbiological point of view. The metabarcoding analysis of the 16S rRNA gene revealed the existence of several different bacterial groups, the presence and abundance of which were mainly dependent on product type, even though some moderate differences in the microbiota profile between the two sea cucumber species were also detected in some of the products. Overall, the present work deals with an underexplored aquatic produc...
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Fresh and minimally processed fish and seafood spoil due to the action of a consortium of microorganisms, the so-called specific spoilage organisms (SSOs) that have the ability to dominate and produce metabolites that directly affect the... more
Fresh and minimally processed fish and seafood spoil due to the action of a consortium of microorganisms, the so-called specific spoilage organisms (SSOs) that have the ability to dominate and produce metabolites that directly affect the sensory properties of the product, resulting in its rejection by the consumers. The selection of SSOs is affected by fish origination, processing, and storage conditions and various implicit factors such as antagonism for nutrients and microbial interactions. The metabolic products of SSOs causing the spoilage are various volatile compounds that mainly come from the assimilation of nonprotein-nitrogen of fish flesh. Qualitative and quantitative determination of SSOs is of great interest, and current molecular techniques provide us with powerful tools for exploring the diversity and dynamics of SSOs. The inhibition of SSOs by applying appropriate preservation strategies can retain fish freshness and extend shelf life. Elucidation of SSOs’ metabolic potential and activity and the estimation of the growth and population level provide us with tools for rapid evaluation of fish freshness/spoilage status and remaining shelf life.
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Rapid chilling in the presence of nisin caused a dose-dependent reduction in the populations of several Gram-negative bacteria, despite the fact that appreciable structural injury to the outer membrane was not detected. Pseudomonas... more
Rapid chilling in the presence of nisin caused a dose-dependent reduction in the populations of several Gram-negative bacteria, despite the fact that appreciable structural injury to the outer membrane was not detected. Pseudomonas aeruginosa was most affected, followed by Pseudomonas fragi, Salmonella enteritidis PT4, PT7 and Escherichia coli, respectively. Addition of nisin after the chilling treatment had no effect. The results are ascribed to a transient susceptibility caused by phase changes in the lipids associated with the outer membrane, which are rapidly reversed when the cells return to higher temperatures. Combinations of chilling shock, nisin and EDTA gave much lower reductions of Salmonella and Pseudomonas on chicken skin in comparison with broths. This is attributed to a buffering of the temperature shock experienced by adherent bacteria and binding of the nisin by food particles.
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The aim of the present work was to study the microbiota profile of gilthead seabream (Sparus aurata) fillets stored either aerobically or under Modified Atmosphere Packaging (MAP) conditions at 0, 4, 8 and 12°C, via 16S rRNA metabarcoding... more
The aim of the present work was to study the microbiota profile of gilthead seabream (Sparus aurata) fillets stored either aerobically or under Modified Atmosphere Packaging (MAP) conditions at 0, 4, 8 and 12°C, via 16S rRNA metabarcoding sequencing. Throughout storage, sensory assessment was also applied to estimate fillets’ end of shelf-life. Results indicated that storage conditions strongly influenced the shelf-life of the fillets, since the sensorial attributes of air-stored samples deteriorated earlier than that of MAP-stored fillets, while higher temperatures also contributed to a more rapid products’ end of shelf-life. Metataxonomic analysis indicated that Pseudomonas was by far the dominant genus at the end of fillet’s shelf-life, in the vast majority of treatments, even though a sporadic but noteworthy presence of other genera (e.g, Shewanella, Carnobacterium, Brochothrix etc.) at the middle stages of MAP-stored fillets is also worth mentioning. On the other hand, a completely different profile as well as a more abundant bacterial diversity was observed at the end of shelf-life of MAP-stored fillets at 12°C, in which Serratia was the most dominant bacterium, followed by Kluyvera, Hafnia, Rahnella and Raoultella, while Pseudomonas was detected in traces. The findings of the present work are very important, providing useful information about the spoilage status of gilthead seabream fillets during several storage conditions, triggering in parallel the need for further studies to enrich the current knowledge and help stakeholders develop innovative strategies that delay the growth of key spoiler players and consequently, retard spoilage course.
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Spoilage status of whole and filleted chill-stored meagre caught in January and July was evaluated using sensory, microbiological, 16S metabarcoding and Volatile Organic Compounds (VOCs) analysis. Based on the sensory analysis, shelf-life... more
Spoilage status of whole and filleted chill-stored meagre caught in January and July was evaluated using sensory, microbiological, 16S metabarcoding and Volatile Organic Compounds (VOCs) analysis. Based on the sensory analysis, shelf-life was 15 and 12 days for the whole fish taken in January and July, respectively, while 7 days for fish fillets of both months. For the whole fish, Total Viable Counts (TVC) at the beginning of storage was 2.90 and 4.73 log cfu/g for fish caught in January and July respectively, while it was found about 3 log cfu/g in fish fillets of both months. The 16S metabarcoding analysis showed different profiles between the two seasons throughout the storage. Pseudomonas (47%) and Psychrobacter (42.5%) dominated in whole meagre of January, while Pseudomonas (66.6%) and Shewanella (10.5%) dominated in fish of July, at the end of shelf-life. Regarding the fillets, Pseudomonas clearly dominated at the end of shelf-life for both months. The volatile profile of meag...
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The aim of the present work was to evaluate the effect of various hurdles such as aw and pH as well as the storage atmosphere on the microbiological and sensory changes of minimally processed (lightly brined or marinated with acetic or... more
The aim of the present work was to evaluate the effect of various hurdles such as aw and pH as well as the storage atmosphere on the microbiological and sensory changes of minimally processed (lightly brined or marinated with acetic or citric acid) European sea bass (Dicentrarchus labrax) fillets. The results indicated that the shelf-life of brined fillets stored aerobically was 6 d while that of vacuum and MAP-stored was 12 d, since a reduced growth rate of spoilage bacteria was recorded. The physicochemical characteristics such as aw and water phase salt (WPS) were not considerably changed, while the oxygen levels into the packages ensure the microbiological safety of the product. The fillets marinated with acetic acid exhibited a longer shelf-life at 30 and 40 d under aerobic and reduced oxygen conditions, respectively, while the products marinated with citric acid were at 25 and 35 d respectively. A low pH resulted in reduced or even limited microbial levels, especially for the ...
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In the present work, the profiles of bacterial communities of whole and filleted European sea bass (Dicentrarchus labrax), during several storage temperatures (0, 4, 8 and 12 °C) under aerobic and Modified Atmosphere Packaging (MAP)... more
In the present work, the profiles of bacterial communities of whole and filleted European sea bass (Dicentrarchus labrax), during several storage temperatures (0, 4, 8 and 12 °C) under aerobic and Modified Atmosphere Packaging (MAP) conditions, were examined via the 16S rRNA High-Throughput Sequencing (HTS) approach. Sensorial attributes were also assessed to determine products’ shelf-life. Results indicated that shelf-life was strongly dependent on handling, as well as on temperature and atmosphere conditions. HTS revealed the undisputed dominance of Pseudomonas from the very beginning and throughout storage period in the majority of treatments. However, a slightly different microbiota profile was recorded in MAP-stored fillets at the middle stages of storage, which mainly referred to the sporadic appearance of some bacteria (e.g., Carnobacterium, Shewanella, etc.) that followed the dominance of Pseudomonas. It is noticeable that a major difference was observed at the end of shelf-...
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The profiles of bacterial communities and volatile organic compounds (VOCs) of farmed red seabream (Pagrus major) from two batches during ice storage were studied using 16S metabarcoding (culture independent approach) and headspace Solid... more
The profiles of bacterial communities and volatile organic compounds (VOCs) of farmed red seabream (Pagrus major) from two batches during ice storage were studied using 16S metabarcoding (culture independent approach) and headspace Solid Phase Micro-Extraction—Gas Chromatography/Mass Spectrometry (SPME-GC/MS) analysis, respectively. Sensory attributes and microbiological parameters were also evaluated. At Day 12 (shelf-life for both batches based on sensory evaluation), using classical microbiological analysis, Total Viable Counts (TVC) were found at the levels of 7–8 log cfu/g, and Pseudomonas and/or H2S producing bacteria dominated. On the other hand, the culture independent 16S metabarcoding analysis showed that Psychrobacter were the most abundant bacteria in fish tissue from batch 1, while Pseudomonas and Psychrobacter (at lower abundance) were the most abundant in fish from batch 2. Differences were also observed in VOC profiles between the two batches. However, combining the ...
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Aromatic plants contain natural antioxidant constituents such as phenolic compounds, which have attracted a great deal of public and scientific interest because of their health--promoting effects as antioxidants. Five plants, Filipendula... more
Aromatic plants contain natural antioxidant constituents such as phenolic compounds, which have attracted a great deal of public and scientific interest because of their health--promoting effects as antioxidants. Five plants, Filipendula ulmaria (meadow sweet), Cratae-gus monogyna (hawthorn), Polygonum aviculare (polygonum), Potentilla anserina (silverweed), and Pelargonium purpureum (little robin), have been examined in order to determine their phenolic composition. Reversed-phase high performance liquid chromatography (RP--HPLC) was employed for the identification and quantification of phenolic compounds of the aforementioned plants. Gas chromatography–mass spectrometry method (GC-MS) was also used for identification of phenolic compounds after silylation. Analysis of the non-vo-latile and thermolabile phenolic compounds by GC-MS presupposes their conversion into volatile and thermotolerant derivatives. The derivatization process was optimized against reagents, temperature and rea...
Water-methanol extract from Filipendula ulmaria contains a variety of phenolic com-pounds, such as caffeic, p-coumaric and vanillic acid, myricetin, etc, which demonstrate anti-bacterial activity. Monitoring this activity in the broth... more
Water-methanol extract from Filipendula ulmaria contains a variety of phenolic com-pounds, such as caffeic, p-coumaric and vanillic acid, myricetin, etc, which demonstrate anti-bacterial activity. Monitoring this activity in the broth using absorbance measurements showed that species of the Enterobacteriaceae family were more resistant than other Gram--negative and Gram-positive bacteria tested. Acidic environment enhanced the antibacte-rial activity of Filipendula ulmaria extract when it was tested against Salmonella Enteritidis PT4 and Listeria monocytogenes Scott A. The efficacy of Filipendula ulmaria extract against selected foodborne psychrotrophic bacteria was also tested using solid laboratory media and low incubation temperatures for better simulation of food preservation conditions. Higher concentrations of the extract, compared to minimum inhibitory concentration deter-mined in the broth, were needed for satisfactory inhibition of spoilage bacteria. Potential use of Filipe...
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The aim of this study was to monitor quality changes and estimate the shelf-life of the thicklip grey mullet (Chelon labrosus), a candidate species for the diversification of the world aquaculture production, during ice storage.... more
The aim of this study was to monitor quality changes and estimate the shelf-life of the thicklip grey mullet (Chelon labrosus), a candidate species for the diversification of the world aquaculture production, during ice storage. Differences in shelf-life, microbial populations and TVB-N values were observed for fish caught in different months, but proximate composition did not differ between months. Based on sensory attributes, the shelf-life was 7 and 8 days for fish caught in October and December, respectively, when the APC was ca. 7.5–8.0 logs and Pseudomonas and/or H2S producing bacteria was 7.0–7.5 logs. TVB-N did not exceed 22 mg per 100 g throughout the storage. The moisture ranged from 73.7% to 78.3%, the protein content from 20.5% to 24.9%, the lipid content from 0.29% to 1.42% and the gross energy from 4.86 to 5.91 kJ g−1 of wet weight. Overall, this study provides stakeholders useful information for the quality of this fish species, contributing to food and nutritional se...
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The cultivable microbiota isolated from three sea bass products (whole, gutted, and filleted fish from the same batch) during chilled storage and the effect of primary processing on microbial communities in gutted and filleted fish were... more
The cultivable microbiota isolated from three sea bass products (whole, gutted, and filleted fish from the same batch) during chilled storage and the effect of primary processing on microbial communities in gutted and filleted fish were studied. Microbiological and sensory changes were also monitored. A total of 200 colonies were collected from TSA plates at the beginning and the end of fish shelf-life, differentiated by High Resolution Sequencing (HRM) and identified by sequencing analysis of the V3–V4 region of the 16S rRNA gene. Pseudomonas spp. followed by potential pathogenic bacteria were initially found, while Pseudomonas gessardii followed by other Pseudomonas or Shewanella species dominated at the end of fish shelf-life. P. gessardii was the most dominant phylotype in the whole sea bass, P. gessardii and S. baltica in gutted fish, while P. gessardii and P. fluorescens were the most dominant bacteria in sea bass fillets. To conclude, primary processing and storage affect mic...
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Nisin is a bacteriocin produced by Lactococcus lactis subsp. lactis, which is active against Gram-positive organisms including bacterial spores. It is not generally active against Gram-negative bacteria, yeasts and fungi. Gram negatives... more
Nisin is a bacteriocin produced by Lactococcus lactis subsp. lactis, which is active against Gram-positive organisms including bacterial spores. It is not generally active against Gram-negative bacteria, yeasts and fungi. Gram negatives show nisin-sensitivity when their outer membrane permeability is altered by various means, such as treatments with chelators, e.g. EDTA, osmotic shock, heating, freezing, freeze-drying, high- pressure etc. Application of chelators and nisin is effective against Gram-negatives when exogenous nisin is added. Nisin produced in situ and chelators are not an effective combination, since nisin production follows the pH drop caused by sugar fermentation, and this interferes with the sequestering ability of the chelators. Presence of nisin during thermal inactivation of Gram-negatives though is effective. Bacteria become structurally injured during heating showing sensitivity to agents like SDS and deoxycholate and extended detection times by impedimetry. Th...
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Summary Water-methanol extract from Filipendula ulmaria contains a variety of phenolic compounds, such as caffeic, p-coumaric and vanillic acid, myricetin, etc, which demonstrate antibacterial activity. Monitoring this activity in the... more
Summary Water-methanol extract from Filipendula ulmaria contains a variety of phenolic compounds, such as caffeic, p-coumaric and vanillic acid, myricetin, etc, which demonstrate antibacterial activity. Monitoring this activity in the broth using absorbance measurements showed that species of the Enterobacteriaceae family were more resistant than other Gram-negative and Gram-positive bacteria tested. Acidic environment enhanced the antibacterial activity of Filipendula ulmaria extract when it was tested against Salmonella Enteritidis PT4 and Listeria monocytogenes Scott A. The efficacy of Filipendula ulmaria extract against selected foodborne psychrotrophic bacteria was also tested using solid laboratory media and low incubation temperatures for better simulation of food preservation conditions. Higher concentrations of the extract, compared to minimum inhibitory concentration determined in the broth, were needed for satisfactory inhibition of spoilage bacteria. Potential use of Fil...
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The aim of the present study was to assess the microbiological quality of farmed sea bass (Dicentrarchus labrax) fillets stored under aerobic conditions and modified atmosphere packaging (MAP) (31% CO2, 23% O2, 46% Ν2,) at 0, 4, 8, and 12... more
The aim of the present study was to assess the microbiological quality of farmed sea bass (Dicentrarchus labrax) fillets stored under aerobic conditions and modified atmosphere packaging (MAP) (31% CO2, 23% O2, 46% Ν2,) at 0, 4, 8, and 12 °C using Fourier transform infrared (FTIR) spectroscopy and multispectral imaging (MSI) in tandem with data analytics, taking into account the results of conventional microbiological analysis. Fish samples were subjected to microbiological analysis (total viable counts (TVC), Pseudomonas spp., H2S producing bacteria, Brochothrix thermosphacta, lactic acid bacteria (LAB), Enterobacteriaceae, and yeasts) and sensory evaluation, together with FTIR and MSI spectral data acquisition. Pseudomonas spp. and H2S-producing bacteria were enumerated at higher population levels compared to other microorganisms, regardless of storage temperature and packaging condition. The developed partial least squares regression (PLS-R) models based on the FTIR spectra of fi...
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A literature search and systematic review were conducted to present and discuss the most recent research studies for the past twenty years on the application of non-thermal methods for ensuring the microbiological safety and quality of... more
A literature search and systematic review were conducted to present and discuss the most recent research studies for the past twenty years on the application of non-thermal methods for ensuring the microbiological safety and quality of fish and seafood. This review presents the principles and reveals the potential benefits of high hydrostatic pressure processing (HHP), ultrasounds (US), non-thermal atmospheric plasma (NTAP), pulsed electric fields (PEF), and electrolyzed water (EW) as alternative methods to conventional heat treatments. Some of these methods have already been adopted by the seafood industry, while others show promising results in inactivating microbial contaminants or spoilage bacteria from solid or liquid seafood products without affecting the biochemical or sensory quality. The main applications and mechanisms of action for each emerging technology are being discussed. Each of these technologies has a specific mode of microbial inactivation and a specific range of...
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High-resolution melting (HRM) analysis followed by sequencing was applied for determination of bacteria grown on plates isolated from farmed mussels (Mytilus galloprovincialis) during their storage at 4 °C. The V3-V4 region of the 16S... more
High-resolution melting (HRM) analysis followed by sequencing was applied for determination of bacteria grown on plates isolated from farmed mussels (Mytilus galloprovincialis) during their storage at 4 °C. The V3-V4 region of the 16S rRNA gene from the isolates was amplified using 16S universal primers. Melting curves (peaks) and high resolution melting curves (shape) of the amplicons and sequencing analysis were used for differentiation and identification of the isolated bacteria, respectively. The majority of the isolates (a sum of 101 colonies, from five time intervals: day 0, 2, 4, 6 and 8) from non-selective solid medium plates were classified in four bacterial groups based on the melting curves (peaks) and HRM curves (shape) of the amplicons, while three isolates presented distinct HRM curve profiles (single). Afterwards, sequencing analysis showed that the isolates with a) the same melting peak temperature and b) HRM curves that were >95% similar grouped into the same bacterial species. Therefore, based on this methodology, the cultivable microbial population of chill-stored mussels was initially dominated by Psychrobacter alimentarius against others, such as Psychrobacter pulmonis, Psychrobacter celer and Klebsiella pneumoniae. P. alimentarius was also the dominant microorganism at the time of the sensory rejection (day 8). Concluding, HRM analysis could be used as a useful tool for the rapid differentiation of the bacteria isolated from mussels during storage, at species level, and then identification is feasible by the sequencing of one only representative of each bacterial species, thus reducing the cost of required sequencing.
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The progressive ability of a six-strains L. monocytogenes cocktail to form biofilm on stainless steel (SS), under fish-processing simulated conditions, was investigated, together with the biocide tolerance of the developed sessile... more
The progressive ability of a six-strains L. monocytogenes cocktail to form biofilm on stainless steel (SS), under fish-processing simulated conditions, was investigated, together with the biocide tolerance of the developed sessile communities. To do this, the pathogenic bacteria were left to form biofilms on SS coupons incubated at 15°C, for up to 240h, in periodically renewable model fish juice substrate, prepared by aquatic extraction of sea bream flesh, under both mono-species and mixed-culture conditions. In the latter case, L. monocytogenes cells were left to produce biofilms together with either a five-strains cocktail of four Pseudomonas species (fragi, savastanoi, putida and fluorescens), or whole fish indigenous microflora. The biofilm populations of L. monocytogenes, Pseudomonas spp., Enterobacteriaceae, HS producing and aerobic plate count (APC) bacteria, both before and after disinfection, were enumerated by selective agar plating, following their removal from surfaces t...
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Bacterial diversity of whole gilt-head sea bream (Sparus aurata L. 1758) originating from Ionian and Aegean Sea aquaculture farms and stored at 0 (ice), 4 and 8 °C was determined by 16S rRNA gene amplicon sequencing method using the... more
Bacterial diversity of whole gilt-head sea bream (Sparus aurata L. 1758) originating from Ionian and Aegean Sea aquaculture farms and stored at 0 (ice), 4 and 8 °C was determined by 16S rRNA gene amplicon sequencing method using the Illumina's MiSeq platform. The composition of Aerobic Plate Counts (APC) was also monitored by 16S rRNA gene sequencing. The rejection time point of sea bream from either area, as determined by sensory evaluation, was about 14, 6 and 3 days at 0, 4 and 8 °C, respectively. APC was approximately 4.5 log cfu/g at day 0 and ranged from 7.5 to 8.5 log cfu/g at sensory rejection. Culture-depended analysis showed that Pseudomonas and Shewanella were the most abundant microorganisms grown on plates for both seas. Moreover, culture-independent analysis of DNA extracted directly from fish flesh showed that sea bream originating from different geographical areas exhibited different bacterial diversity. Pseudomonas and Psychrobacter were the dominant microorgani...
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Aromatic plants may be contaminated with a wide range of microorganisms, making them a potential health hazard when infused or added to ready-to-eat meals. To ensure safety, the effect of gaseous ozone treatment on the population of... more
Aromatic plants may be contaminated with a wide range of microorganisms, making them a potential health hazard when infused or added to ready-to-eat meals. To ensure safety, the effect of gaseous ozone treatment on the population of aerobic plate counts (APC), hygienic indicators (Escherichia coli, Enterococcus spp. and Enterobacteriaceae) and fungi was investigated for five dried aromatic plants: oregano, thyme, mountain tea, lemon verbena and chamomile. Selection, isolation and further fungi identification were based on the phenotypic and macro- and microscopic characteristics. Prior to ozonation, APC on five dried aromatic plants was in the range 5-7 log colony-forming units (CFU) g-1 . The APC exhibited a 4 log reduction, from around 6.5 to 2.5 in the case of oregano, and only a 1-2 log reduction for other herbs after 30 or 60 min of 4 ppm gaseous ozone treatment. Enterococcus spp. and E. coli were not detected on any of the tested dried aromatic plants. The fungi counts were 2-4 log CFU g-1 before ozonation. Aspergillus spp, Penicillium spp, Cladosporium spp, Alternaria spp, Fusarium spp., Ulocladium spp. and some unknown fungi were detected on plants before ozone treatment. Aspergillus spp. and/or Penicillium spp. were only detected on mountain tea and thyme plant material after 60 min of ozonation. The present study provides information about the efficiency of ozone on the microbial decontamination of dried aromatic plants. Treatment with gaseous ozone at 4 ppm for 30 min in the case of dried oregano and 60 min in the case of chamomile and lemon verbena could be used as alternative disinfection methods. © 2017 Society of Chemical Industry.
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As a tool for stock identification the body morphology and the free amino acid (FAA) profile variability were determined among farmed rainbow trout Oncorhynchus mykiss (Walbaum 1792) from different geographical areas throughout Greece,... more
As a tool for stock identification the body morphology and the free amino acid (FAA) profile variability were determined among farmed rainbow trout Oncorhynchus mykiss (Walbaum 1792) from different geographical areas throughout Greece, using geometric morphometrics and Reversed Phase-High-Performance Liquid Chromatography. Significant intraspecific body shape variation was detected among the fish stocks of different origin. Canonical Variate Analysis distinguished populations into two groups being consistent to a great extent with a previous population genetics study. General linear models did not support an association of haplotypes and diet with shape. However, shape was significantly correlated with origin, water temperature, geological-chemical-climatic zones, histidine and arginine. Therefore, morphological variation was primarily driven by environmentally induced differences among these zones being the result of phenotypic plasticity. Environmental cues and rearing conditions played the pivotal role in comparison to broodstock origin. Specimens presented different FAA profiles depending on their geographical origin. Principal Component Analysis showed a division between eastern and western Greece which might be owed to the existence of climatic fluctuations affecting the abiotic factors. This combined approach offers an important tool for stock identification thus assisting environmental risk assessments in evaluation of potential ecological effects and fostering research excellence in sustainable aquaculture management.
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ABSTRACT