Perch Muscle Research Articles

Transcriptome analysis identifies potential molecular mechanisms for growth of fast muscle in Chinese perch juvenile

Chinese perch (Siniperca chuatsi) is an important commercial fish species in China. Understanding the molecular mechanisms of growth and development of skeletal muscle is helpful for selection breeding and improving the growth rate of Chinese perch. We analyzed histological and transcriptomic differences in fast muscle of Chinese perch between 30 days post hatching (dph) and 60 dph using histological sections and high-throughput RNA-Seq. The results showed that the diameter of muscle fibers in 30 dph Chinese perch was mainly distributed in range of 30 − 40 μm, and that of 60 dph was primarily in the range of 40 − 50 μm. 34 differentially expressed genes (DEGs) were identified in the fast muscle of Chinese perch between 30 and 60 dph, of which 9 were up-regulated and 25 were down-regulated (60 dph vs 30 dph). The DEGs, including MYH4, ENO3, Bag3, krt13 and krt18, are associated with muscle cell differentiation and fusion in Chinese perch. The analysis of the protein–protein interaction network of DEGs revealed that FOS, junb and EGR1 may involve in the development of fast muscle. KEGG enrichment results showed that the up-regulated genes in the 60 dph were associated with several pathways related to metabolism and protein synthesis, such as glycosphingolipid biosynthesis and aminoacyl-tRNA biosynthesis. The results suggest that the development of fast muscle in Chinese perch from 30 to 60 dph is accompanied by an increase in muscle fiber diameter and changes in gene expression related to muscle cell differentiation and protein synthesis.Abbreviations: DEGs, differentially expressed genes; dph, days post hatching; FC, fold change; FDR, False Discovery Rate; GO, Gene Ontology; KEGG, Kyoto Encyclopedia of Genes and Genomes; MyHCs, Myosin heavy chains; qRT-PCR, quantitative real-time PCR.

Development and validation of a LC-MS method for the quantification of microcystins in fish for their monitoring in environmental and food context

Cyanobacterial blooms in aquatic ecosystems can result in the accumulation of cyanotoxins in other organisms. Fish can potentially accumulate large amounts of cyanotoxins through their direct interaction with contaminated water and the ingestion of cyanobacterial cells. As a human food source, this can result in a potential health risk. Investigating and monitoring this risk requires analytical methods sufficiently robust to be suitable for different fish species. This study, therefore, aimed to optimize and validate an UHPLC-MS/MS method for the quantification of eight microcystin congeners and nodularin in five different fish species. The limits of detection and quantification were 1 and 3 μg kg−1, respectively. The linearity of the method was very good, with calculated R2 values above 0.99. The mean recovery of the method was within the acceptable range of 70.0%–120.0 %, the repeatability was not higher than 12.6 %, and the highest intra-laboratory reproducibility was 18.7 %. The estimated range for the expanded measurement uncertainty was between 29 % and 58 %. Moreover, multiple fish from Flemish waters were analyzed to show the method's applicability. Multiple microcystin congeners were detected (up to 88.3 μg kg−1 sum of analyzed microcystins) in the liver and viscera of perch and sander. Small amounts of MC-LR and MC-YR (up to 6.1 μg kg−1) were also detected in perch muscle tissue.

The Regulatory Role of Myomaker in the Muscle Growth of the Chinese Perch (Siniperca chuatsi).

The fusion of myoblasts is a crucial stage in the growth and development of skeletal muscle. Myomaker is an important myoblast fusion factor that plays a crucial role in regulating myoblast fusion. However, the function of Myomaker in economic fish during posthatching has been poorly studied. In this study, we found that the expression of Myomaker in the fast muscle of Chinese perch (Siniperca chuatsi) was higher than that in other tissues. To determine the function of Myomaker in fast muscle, Myomaker-siRNA was used to knockdown Myomaker in Chinese perch and the effect on muscle growth was determined. The results showed that the growth of Chinese perch was significantly decreased in the Myomaker-siRNA group. Furthermore, both the diameter of muscle fibers and the number of nuclei in single muscle fibers were significantly reduced in the Myomaker-siRNA group, whereas there was no significant difference in the number of BrdU-positive cells (proliferating cells) between the control and the Myomaker-siRNA groups. Together, these findings indicate that Myomaker may regulate growth of fast muscle in Chinese perch juveniles by promoting myoblast fusion rather than proliferation.

Increasing microplastic exposure had minimal effects on fatty acid composition in zooplankton and yellow perch in a large, in-lake mesocosm experiment

Using 10 m diameter mesocosms in a Canadian boreal lake, we investigated the effects of microplastic (MP) exposure on the body weight and diet of yellow perch ( Perca flavescens) and the fatty acid composition of yellow perch and zooplankton. We exposed the aquatic ecosystem within seven mesocosms for 10 weeks to a mixture of polyethylene, polystyrene, and polyethylene terephthalate fragments, ranging in nominal addition concentrations from 6 to 29 240 particles L−1 (although realized water column concentrations were lower), as well as two negative controls. Increasing MP exposure did not affect yellow perch body weight (growth) or diet, or the overall fatty acid composition of yellow perch muscle or zooplankton. Results were highly variable across mesocosms. Despite high levels of MP ingestion by yellow perch, we did not find evidence of MPs leading to food dilution or any other effect where we could anticipate impacts on food web structure.

Биохимические показатели мышц судака из Рыбинского водохранилища и оценка риска их потребления

Fish, as a food component, is very beneficial for human health. It is rich in protein, valuable fatty acids, vitamins and minerals. However, when consuming it, there is a risk of toxic substances entering the human body that ac-cumulate in the tissues of aquatic organisms, for example, heavy metals. The purpose of the work is to determine the biochemical parameters in the muscles of pike perch from the reaches of the Rybinsk reservoir, which differ in anthropogenic load, and to assess the risks of human consumption of this species. The amount of water, dry matter, lipids, protein, minerals and carbohydrates in muscle tissue was determined using standard methods. To assess the threat to human health associated with the potential duration of exposure to heavy metals from walleye consumption, target and cumulative hazard ratios were calculated. The assessment of carcinogenic risk to human health was determined using the target and general cancer risk index. Calculated indicators were obtained based on data on the content of heavy metals in the muscles of pike perch, established earlier. In the muscles of pike perch specimens from the Sheksninsky and Volzhsky reaches, no significant differences between biochemical parameters were found. According to the ratio of protein and lipids in muscle tissue, the studied individuals belong to category A, and according to the amount of lipids – to fish with a low-fat content. The estimated dietary intakes for weekly intakes of heavy metals from pike perch meat was below the reference values. The target and total hazard coefficient turned out to be less than one, which indicates that there is no potential non-carcinogenic risk for humans when consuming pike perch meat. The target cancer risk indices for Cd, Pb, Al and Cr are within acceptable ranges. The total risk of developing cancer for these metals is more than 1 in 100,000.

No evidence of an association between size and levels of four per- and polyfluorinated substances (PFAS) in perch (Perca fluviatilis)

It was assessed how the size of perch (Perca fluviatilis) is related to levels of four per- and polyfluorinated substances (PFAS) in its muscle tissue. These were PFOS, PFNA, PFOA, and PFHxS, for which the sum, denoted as ΣPFAS4, has a tolerable intake derived by the European Food Safety Authority. The results indicate that, in contrast to, e.g., mercury levels, ΣPFAS4 levels in perch muscle do not increase with increasing weight of the fish, which implies that consuming larger perch does not increase the risk of exceeding the TWI of ΣPFAS4, in relation to consuming smaller perch. Therefore, for risk assessment, analyzing samples of smaller perch is sufficient, demanding less effort to catch. The credibility of the results was strengthened by applying the same statistical model to mercury levels in the same samples. As expected, larger fish had generally higher levels than small fish for mercury.

Squalene Supplementation as a Novel to Increase PUFA Content in Fish Tissues.

Squalene is an antioxidant that plays an essential role in fat metabolism. The study aimed to assess the effect of squalene supplied in feed on the growth performance, health status, and fatty acid profiles of muscle and liver of Siberian sturgeon, rainbow trout, and Eurasian perch. The experimental feeds containing 0%, 0.5%, and 1.0% squalene were prepared for each fish species. Hematological and biochemical indices, liver histology, and fatty acid profiling of muscle and liver were analyzed. Squalene supplementation was safe for fish, and no negative influence on growth status was observed. However, changes in the values of hematological and biochemical indicators were found, including the level of triglycerides in the blood of rainbow trout, and cholesterol in the blood of Eurasian perch. The addition of squalene influences the nucleocytoplasmic index values in all fish offered feed containing 1% squalene. The retention of squalene in the liver and muscle of experimental Siberian sturgeon was observed in both 0.5% and 1.0% squalene levels of feed. The PUFA and docosahexaenoic acid increase was observed in all fish in groups with squalene addition. Dietary squalene increases the content of PUFAs in tissues of the examined species.

Characterization of myosin heavy chain (MYH) genes and their differential expression in white and red muscles of Chinese perch, Siniperca chuatsi

Fish skeletal muscle is composed of two anatomically and functionally different fiber layers, white or fast and red or slow muscles. Myosin, the major structural protein of fish skeletal muscle, contains multiple myosin heavy chain (MYH) isoforms involved in the high plasticity of muscle in response to varying functional demands and/or environmental changes. In this study, we comparatively assayed the cellular and ultrastructural feature of white and red skeletal muscles. Then, a total of 28 class II myosin heavy chain genes were identified in by searching the Chinese perch genome database. Among them, 14 genes code for the fast-muscle-type myosin heavy chain, and 7 genes code for the slow-muscle-type myosin heavy chain. Further, the different isoform gene structures, function domains, phylogenetic relations, and muscle-fiber type-specific expression were characterized. This is the first systematic work on the molecular characterization of class II myosin heavy chain isoforms and the differential analysis of their expression in red and white muscle tissues in Chinese perch Siniperca chuatsi. Our work provided valuable information for a better understanding of myh genes and their molecular characteristics, and the correlations of multiple myosin isoforms with potential functions in response to varying functional demands and/or environmental changes.

Биоаккумуляция тяжёлых металлов и других токсичных элементов в мышцах рыб бассейна р. Волги

The purpose of this work was to study the accumulation of heavy and toxic elements in the muscles of the main commercial fish of the Volga River basin. Sampling was carried out throughout the Volga River, in areas that are characterized by varying degrees of industrial development. In the course of the work, tissue samples of the main species of commercial fish were selected (about 300 samples in total). The analysis of the selected material was carried out by a set of methods: induction coupled plasma mass spectrometry, flamу atomic absorption spectroscopy and cold steam atomic absorption. Based on this analysis, the levels of accumulation of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Sr, Cd, Sb, I, Hg, Pb in the muscles of the main species of commercial fish were determined. Graphs of the distribution of the concentration of elements in the muscles of perch depending on the area of fishing are given: the maximum concentration of the sum of toxic elements in the muscles of perch is characteristic of the Rybinsk reservoir and the area of the village of TsaganAman, and the minimum – for the upper Volga and delta. The dependence of accumulation of As, Cd, Hg, Se, I and Br in the muscles of perch on the mass of fish has been assessed. It was found that the concentration of Hg and Se in the muscles of the perch is directly proportional to the weight of the fish.

Feeding Features of the Nine-Spined Stickleback Pungitius pungitius (Gasterosteidae) In Water Bodies of the North-West of Russia

The diet of the nine-spined stickleback Pungitius pungitius has been studied in two water bodies in the north-west of Russia: in the subarctic lake Krivoe (Karelia) and the estuary of the Neva River (Leningrad Oblast). Diptera larvae (Chironomidae, Ceratopogonidae, Simuliidae, and Limoniidae) and planktonic crustaceans formed the basis of the food bolus of fish; however, their abundance and weight ratios differed in the studied water bodies. The seasonal changes of the dominant groups of food objects of the stickleback of Lake Krivoe have been revealed. Additionally to invertebrates and fish eggs, which form the basis of the stickleback diet in winter season, aquatic mosses as well as filamentous and diatom algae present in the fish diet in summer. The comparison of the nitrogen isotope composition of the muscles of stickleback, perch, and invertebrates shows that the stickleback of Lake Krivoe occupies the third trophic level, approaching predatory fish in δ15N values (5.2–8.6‰). A specific feature of the diet patterns of P. pungitius is the transition from a diverse diet of the summer–autumn period to a monotrophic animal diet (chironomid larvae and fish eggs) of the under-ice winter–spring period.

Changes of Activity of Energy and Ion Exchange Enzymes and the Energy Substrates Content in Tissues of Perca fluviatilis and Rutilus rutilus under Toxic Water Pollution

The paper deals with impact of toxic pollution on activity of energy and ion exchange enzymes in roach and perch. Significant changes in content of energy substrates in liver, gills and muscles of perch and roach were established depending on season and toxic load. The glycogen content in liver of perch specimens from the polluted lake (Kyrilivske) was lower than in specimens from the control lake (Babyne). Also, lower activity of SDH in muscles and gills of roach has been established. It should be noted that roach was characterized by higher variability of the studied enzymes' activity. This indicates the species specificity of the metabolic reactions of the studied fishes to counteract toxic pollution.

The circadian rhythm regulates branched-chain amino acids metabolism in fast muscle of Chinese perch (Siniperca chuatsi) during short-term fasting by Clock-KLF15-Bcat2 pathway.

As an internal time keeping mechanism, circadian rhythm plays crucial role in maintaining homeostasis when in response to nutrition change, meanwhile, branched-chain amino acids (BCAAs) in skeletal muscle play an important role in preserving energy homeostasis during fasting. Previous results from our lab suggested that fasting can influence peripheral circadian rhythm and BCAAs metabolism in fish, but the relationship between circadian rhythm and BCAAs metabolism, and whether circadian rhythm regulates BCAAs metabolism to maintain physiological homeostasis during fasting remains unclear. This study shows that the expression of 15 core clock genes, as well as KLF15 and Bcat2 is highly responsive to short-term fasting in fast muscle of Siniperca chuatsi, and the correlation coefficient between Clock and KLF15 expression is enhanced after fasting treatment. Furthermore, we demonstrate that the transcriptional expression of KLF15 is regulated by Clock, and the transcriptional expression of Bcat2 is regulated by KLF15 by using dual-luciferase reporter gene assay and Vivo-Morpholinos mediated gene knockdown technique. Therefore, fasting imposes a dynamic coordination of transcription between the circadian rhythm and BCAAs metabolic pathways. The findings highlight the interaction between circadian rhythm and BCAAs metabolism, and suggest that fasting induces a switch in KLF15 expression through affecting the rhythmic expression of Clock, and then KLF15 promotes the transcription of Bcat2 to enhance the metabolism of BCAAs, thus maintaining energy homeostasis and providing energy for skeletal muscle as well as other tissues.

Insight into bioavailability of various insect meals for European perch (Perca fluviatilis): A nutritional and stable isotopic evaluation

The present study evaluated nutritional composition, stable isotopic signature, apparent digestibility coefficient (ADCs), and relative contribution of seven insect meals, namely black soldier fly (Hermetia illucens) (BSF), common housefly (Musca domestica) (CHF), yellow mealworm (Tenebrio molitor) (YMW), lesser mealworm (Alphitobius diaperinus) (LMW), house cricket (Acheta domesticus) (HC), banded cricket (Gryllodes sigillatus) (BC) and field cricket (Gryllus assimilis) (FC), on European perch (Perca fluviatilis), a potential aquaculture species in Europe.Nutritional composition on a dry matter basis varied widely across insect species. YMW, HC, and BC appeared to contain high protein content (>70%), whereas lower content was found in defatted BSF, LMW, and CHF (ranging 55–59%), adult FC remained intermediate (66.83%). Lipid levels were highest in LMW and CHF (27.72% and 26.53%, respectively), medium in BSF, HC, BC and FC, and lowest in the highly defatted YMW (8.14%). Methionine and lysine were the first limiting amino acids in all insect meals. Heatmap visualization indicated considerable similarity in amino acid profile between fishmeal and YMW. Most insect meals contain a high amount of saturated, monosaturated fatty acids and a lack of n-3 fatty acids. Although macro-minerals were lower in insect meals than in fishmeal, the trace minerals of YMW, BSF, HC, and FC surpassed fishmeal, implying that insect meals are an excellent source of trace minerals.The digestibility of nutrients and energy differed significantly among insect meals. Dry matter ADC varied from 67.91% (YMW) to 85.02% (LMW), with LMW and CHF significantly higher than YMW. Protein ADC was lowest in YMW (69.03%) and greatest in LMW (91.94%) and CHF (93.53%). BSF and HC exerted absolute lipid digestibility (104.86 and 99.99%, respectively), followed by LMW (94.75%), whereas BC had the lowest lipid digestibility among insect meals. Energy digestibility favored BSF, CHF, FC, HC, and LMW, but not BC and YMW. Ash and phosphorus digestibility did not differ among insect meals.FC contributed significantly to perch muscle development (mean and interquartile range; 23.9, 10.6–33.8%), followed by CHF (19.8%, 8.8–29.7%), whereas BC imprints relatively low contribution (12.6%, 7.4–17.4%). The stable isotope and mixing models provide insight into the role of ingredients in the accretion of perch muscle as well as in nutritional complementarity among them in satisfying nutrient requirements, thus growth performance of perch.

Allochthony, fatty acid and mercury trends in muscle of Eurasian perch (Perca fluviatilis) along boreal environmental gradients.

Environmental change, including joint effects of increasing dissolved organic carbon (DOC) and total phosphorus (TP) in boreal northern lakes may affect food web energy sources and the biochemical composition of organisms. These environmental stressors are enhanced by anthropogenic land-use and can decrease the quality of polyunsaturated fatty acids (PUFAs) in seston and zooplankton, and therefore, possibly cascading up to fish. In contrast, the content of mercury in fish increases with lake browning potentially amplified by intensive forestry practises. However, there is little evidence on how these environmental stressors simultaneously impact beneficial omega-3 fatty acid (n3-FA) and total mercury (THg) content of fish muscle for human consumption. A space-for-time substitution study was conducted to assess whether environmental stressors affect Eurasian perch (Perca fluviatilis) allochthony and muscle nutritional quality [PUFA, THg, and their derivative, the hazard quotient (HQ)]. Perch samples were collected from 31 Finnish lakes along pronounced lake size (0.03-107.5 km2), DOC (5.0-24.3 mg L-1), TP (5-118 μg L-1) and land-use gradients (forest: 50.7-96.4%, agriculture: 0-32.6%). These environmental gradients were combined using principal component analysis (PCA). Allochthony for individual perch was modelled using source and consumer δ2H values. Perch allochthony increased with decreasing lake pH and increasing forest coverage (PC1), but no correlation between lake DOC and perch allochthony was found. Perch muscle THg and omega-6 fatty acid (n6-FA) content increased with PC1 parallel with allochthony. Perch muscle DHA (22:6n3) content decreased, and ALA (18:3n3) increased towards shallower murkier lakes (PC2). Perch allochthony was positively correlated with muscle THg and n6-FA content, but did not correlate with n3-FA content. Hence, the quality of perch muscle for human consumption decreases (increase in HQ) with increasing forest coverage and decreasing pH, potentially mediated by increasing fish allochthony.

Characteristics of protein, lipid, and carbohydrate metabolism of fish of the Kremenchuk Reservoir in the prespawning period

The paper presents the results of scientific research aimed at studying the peculiarities of metabolism in the body of seven species of mature fish in the Kremenchuk reservoir in the pre-spawning period under ecological conditions that differ from existing ones according to the Dnipro Reservoir Rules of Operation. Somewhat increased levels of total protein accumulation were found during this period in the muscles of zander, perch, and gibel carp. More statistically significant differences between the content of total protein in the liver and muscles were found in other fish species, in particular in roach it was 51.2%, in bream – 57.8%, in European flounder, and zope – 40.6%. Slightly elevated total lipids were found in the muscles of these fish. Thus, in the muscles of silver bream, it was 12.07 mg/g of raw weight, and in the muscles of gibel carp – 18.5 mg/g, while in the muscles of all other studied species of fish, this figure was in the range of 6.7 to 8.71 mg/g of raw weight. The glycogen content in the muscles of different objects of the Kremenchuk reservoir in the pre-spawning period was different. Its highest content was found in the gibel carp muscle, which reached 74 mg/g of raw weight. Significantly lower (2.7 times) was the level of glycogen accumulation in zander muscles and 3.2 times – in roach muscles. In the muscles of bream, European perch and silver bream found close, relatively low levels of glycogen, which was in the range of 10 – 13 mg/g of raw mass, and the lowest level of its accumulation was recorded in the muscles of the zope (only 4.9 mg/g). The glycogen content of the liver of all studied fish species significantly exceeded that recorded in their muscles.

The effects of acute and chronic ammonia exposure on growth, survival, and free amino acid abundance in juvenile Japanese sea perch Lateolabrax japonicus

Japanese sea perch, Lateolabrax japonicus is an economically important marine fish and is widely cultured in coastal area of China. In recent years, ammonia poisoning has seriously affected the yield and quality of perch, but data on its ammonia tolerance is sparse. This study used a sequential approach to evaluate how perch tolerate acute and chronic ammonia exposure. First, we estimated the effects of acute ammonia poisoning on perch (16.08 ± 0.12 g) and calculated 96-h LC50 that, based on linear interpolation (y = 2.64× – 99.11, R2 = 0.94 where y = % mortality and x = mg L−1 T-AN ammonia concentration), was 56.50 mg L−1 total ammonia nitrogen (T-AN). Then we measured the 42-d survival, growth and concentration of free amino acids in muscle of perch (16.12 ± 0.95) g reared in 0.00, 0.28, 0.57, 1.13 and 2.06 mg L−1 T-AN. The survival rate decreased when ammonia concentration exceeded 0.57 mg L−1 T-AN, but the weight gain, condition factor and hepatosomatic index were inhibited when ammonia concentration exceeded 0.28 mg L−1 T-AN. The changes in free amino acids concentration may be potentially related to the ammonia exposure. We recommend that Japanese sea perch not be exposed to ammonia concentrations >0.28 mg L−1 T-AN for prolonged periods of time.

Effect of starvation and refeeding on reactive oxygen species, autophagy and oxidative stress in Chinese perch (Siniperca chuatsi) muscle growth.

In skeletal muscle, autophagy regulates the development and growth of muscle fibres and maintains the normal muscle metabolism. Under starvation and refeeding conditions, the effect of reactive oxygen species (ROS) levels on skeletal muscle autophagy is still unclear, although the excessive accumulation of ROS has been shown to increase autophagy in cells. The purpose of this study was to explore the effects of starvation and diet after starvation on the autophagy of adult Chinese perch muscle, and to determine the level of ROS in the muscle. We performed zero (Normal control), three and seven starvation treatments on adult Chinese perch, and returned to normal feeding for 3 days after starvation for 7 days. In the muscles of the adult Chinese perch muscle after 3 days of starvation, the autophagy marker protein LC3 and the number of autophagosomes remained basically the same as in the normal feeding situation. However, on starvation for 7 days, the mitochondrial autophagy was sensitive and the number of autophagosomes increased, but the antioxidant-related molecules (malondialdehyde, catalase, glutathione S-transferase, glutathione and anti-superoxide anion) decreased and the accumulation of ROS was obvious. In addition, the extended starvation time also increased the level of LC3 protein. However, by refeeding after starvation this nutritional stress resulted in a decrease in ROS levels and a partial restoration of antioxidant enzyme activity. Our data show that in the adult Chinese perch muscle, starvation could reduce the antioxidant activity through the accumulation of ROS, and that the number of autophagosomes continues to increase. Refeeding after starvation could effectively compensate for the level of ROS, and restore the mRNA abundance of antioxidant genes and the activity of antioxidant enzymes to reduce autophagy and improve feed efficiency. Further research should optimize starvation conditions to reduce autophagy in muscles and maintain normal muscle metabolism.

Comparison of physicochemical properties of different tissues from China climbing perch Anabas testudineus and crucian carp Carassius auratus.

This study aimed to investigate nutrition in climbing perch Anabas testudineus which is an important nutritious economic freshwater fish in Asia and compare with Carassius auratus (crucian carp). Three kinds of tissues, including muscle, livers, and eggs, were isolated, respectively. Physicochemical properties including moisture, ash, protein, amino acids, fat, vitamins, and calcium contents in those tissues were determined. The results showed climbing perch muscle and liver contained less moisture, but more protein, amino acids, and vitamins than crucian carp muscle and liver. While moisture, ash, protein, and total amino acids contents of climbing perch egg were lower than those of crucian carp egg. Climbing perch egg had more fat, vitamins, and calcium than crucian carp egg. The amino acid profile was also performed, and 16 amino acids were identified and quantified in muscle, liver, and egg. Among tissues, the highest and lowest concentration of total amino acid content was found in crucian carp eggs and livers, respectively. Glutamic acid (Glu) and histidine (His) were the most and least amino acids in climbing perch and crucian carp tissues, respectively. Sixteen amino acids in climbing perch egg were less than those in crucian carp egg while it is an opposite case in muscle and liver, which amino acids of climbing perch tissues were more than those of crucian carp muscle and liver. Vitamin A of climbing perch was more than crucian carp in all three tissues, but vitamin E content in climbing perch liver was lower than that of crucian carp liver. Calcium content of muscle had no difference between two species. The abovementioned comparison of physicochemical properties of different tissues from China climbing perch and crucian carp will provide a necessary supplementary of freshwater muscle nutrition research, also was helpful for application of climbing perch.

Effect of dietary hydroxyproline supplementation on Chinese perch (Siniperca chuatsi) fed with fish meal partially replaced by fermented soybean meal

As a kind of biologically active molecule, hydroxyproline (Hyp) is abundant in fish meal (FM) but not in plant protein sources. It remains very challenging to replace FM with plant protein sources, particularly for carnivorous fish. This study aims to investigate the effect of dietary Hyp supplementation on Chinese perch (Siniperca chuatsi) fed with FM partially replaced by fermented soybean meal (FSM), with 46% FM as the positive control and 31% FM plus 15% FSM as the negative control. Based on the negative control diet, 0.5%, 1%, 1.5% and 2% of dietary crystal L-Hyp was supplemented to formulate four experimental diets, respectively. Although the replacement of 15% FM with FSM in the feed resulted in a significant decline in growth performance of Chinese perch, dietary supplementation of 1% Hyp could improve the growth performance with high mRNA levels of the gh and igf1 genes. Piecewise regression analysis revealed that a dietary level of 2.27% Hyp could achieve the maximum weight gain rate. With high mRNA levels of orexigenic genes (npy and agrp in the brain, and ghrelin in the gut) and low mRNA levels of anorexigenic genes (pomc and cart in the brain, and leptin-A in the liver), an appropriate level of Hyp could be added to the diet of Chinese perch as a food attractant to promote the appetite and increase food intake. Besides, partial replacement of FM with FSM might promote the deposition of amino acids in the muscle, which may not be affected by dietary supplementation of Hyp. Furthermore, dietary supplementation of Hyp affected the activity of prolyl hydroxylase (PHD) and the mRNA levels of type I collagen regulatory genes and coding genes of three prolyl 4-hydroxylase (P4H) isozymes in the muscle of Chinese perch to some extent. In addition, supplementation of an appropriate level of Hyp could significantly improve the collagen content and muscle quality (hardness, chewiness and springiness) of Chinese perch, which may greatly enhance its edible and nutritional values.

Mercury accumulation in muscle and liver tissue and human health risk assessment of two resident freshwater fish species in Flanders (Belgium): a multilocation approach.

Detrimental effects of chemical pollution-primarily caused by human activities-on aquatic ecosystems have increasingly gained attention. Because of its hydrophobic qualities, mercury is prone to easily bioaccumulate and biomagnify through the food chain, decreasing biodiversity and eventually also affecting humans. In the present study, accumulated mercury concentrations were measured in muscle and liver tissue of perch (Perca fluviatilis) and European eel (Anguilla anguilla) collected at 26 sampling locations in Flemish (Belgian) waterbodies, allowing a comparison of these species within a variety of environmental situations. Furthermore, effects of size and weight have been assessed, expected to influence accumulation and storage of pollutants. Mercury concentrations in perch ranged up to 1.7 μg g-1 dw (median: 0.29 μg g-1 dw) in muscle and from 0.02 to 0.77 μg g-1 dw (median: 0.11 μg g-1 dw) in liver tissue. For eel, these concentrations were between 0.07 and 1.3 μg g-1 dw (median: 0.39 μg g-1 dw) and between 0.08 and 1.4 μg g-1 dw (median: 0.55 μg g-1 dw) respectively. We found a correlation of accumulated mercury with length in perch, independent of location. Furthermore, a significant difference in accumulated mercury concentrations between the targeted species was measured, with the highest mean concentrations per dry weight in eel liver and muscle tissue. In perch, higher concentrations were found in muscle compared to liver tissue, while in eel, liver tissue showed the highest concentrations. These findings were further considered with concentrations corrected for lipid content, excluding the fat compartment, which is known to a hold negligible portion of the total and methyl mercury concentrations. This confirmed our previous conclusions, except for mercury concentrations in eel. Here there was no longer a significant difference between muscle and liver concentrations. Finally, health risk analyses revealed that only frequent consumption of local eel (> 71 g day-1) could pose risks to humans.