Origin identification method by multiple trace elemental analysis of intermuscular bones in grilled eel products produced in Japan, China, and Taiwan

Trace elemental composition in intermuscular bones of grilled eel fillets was analyzed to discriminate the geographic origin of eel products derived from Japan, China, and Taiwan. The intermuscular bones were decomposed with nitric acid-hydrogen peroxide, and twelve elements (Li, Ti, V, Mn, Ni, Co, Zn, Rb, Sr, Ba, Pb, and U) were analyzed by inductively coupled plasma mass spectrometry. Trace elemental composition including six elements: V, Co, Sr, Ba, Pb, and U, in intermusucular bones were significantly different between Japanese domestic eels and imported eels from China and Taiwan. The average content of lead in Japanese eels was 1/4 to 1/6 that in eels imported from China and Taiwan. The data of elemental content in intermuscular bones were used for linear discriminant analysis, and two discriminant models were constructed. In the Japan–China discriminant model, the discriminant probabilities between Japanese origin and Chinese origin were 82.5 and 93.3 %, respectively. In the Japan–Taiwan discriminant model, the discriminant probabilities between Japanese origin and Taiwanese origin were 87.5 and 87.0 %, respectively. Therefore, trace elemental analysis is effective for country-of-origin identification of eels processed as grilled eel fillets.     

Dietary accumulation of polychlorinated biphenyls, chlorinated pesticides and mercury by cultivated eels, Anguilla anguilla L.

Abstract. Polychlorinated biphenyls (PCBs), chlorinated pesticides and mercury were analysed in cultivated eels, Anguilla anguilla L., and their food. In one experiment the eels were mainly fed with a low-fat diet. In another experiment cultivated eels were fed a high-fat diet. Both experiments showed that the major part of the organochlorine compounds and mercury present in the diet was retained by the eel. The retention of the organochlorine compounds and mercury was estimated at 50–70% after an exposure period of about 1 year.
Although the mechanisms of accumulation of mercury and organochlorine compounds clearly differ, no differences in retention were found. The remaining mercury, PCBs and pesticides which were not retained possibly pass through the alimentary canal rather than being accumulated first and metabolized or excreted during the feeding period.
Due to these high levels of accumulation monitoring levels of PCBs, chlorinated pesticides and mercury in the diet is essential for protection of the quality of cultivated eels.     

Ascorbate-2-sulfate as a dietary vitamin C source for Atlantic salmon (Salmo salar): 2. Effects of dietary levels and immunization on the metabolism of trace elements

Atlantic salmon fingerlings were fed a vitamin C deficient diet for four months. The fish were then provided a dry, practical fishmeal based diet supplemented with 0, 500 or 5000 mg vitamin C/kg as L-ascorbic acid or equivalent amounts of ascorbate-2-sulfate. After six weeks on these diets ten fish in each group were injected with a soluble antigen (NIP₁₁-LPH). Six weeks thereafter blood, liver, kidney, spleen and vertebrae were examined for trace elements. The livers were also analysed for metallothionein. The vitamin C deficient fish were anemic despite the significantly elevated iron concentrations in the liver. Vitamin C had no positive effect in lowering tissue levels of cadmium. The highest level of dietary vitamin C given as ascorbic acid reduced the liver selenium concentrations. In response to antigen injection, the fish in all groups showed increased levels of hepatic metallothionein, copper, zinc and cadmium, while hepatic selenium and iron levels were less affected. The elemental composition in other organs was affected by the antigen injection to a minor extent.     

Trace metal levels in eels grown in power station cooling water

Measurements have been made of heavy metal concentrations in eels grown in condenser discharge water and cooling-tower pond water to ascertain if abnormal metal accumulation occurs under these conditions. Eels from other locations were also analysed to provide comparative data. Cadmium, copper, iron, nickel and zinc concentrations were measured in liver and muscle tissue. Comparison of the metal concentrations in the eels maintained in the three experimental regimes with those from other sites does not indicate any abnormal accumulation in those fish kept at an elevated temperature. The fastest growing eels in condenser water appear to develop new tissues more rapidly than they accumulate metals, thus reducing the specific metal concentration.There is considerable variation in metal concentrations in eels, with particularly high liver cadmium concentrations being observed in eels collected from polluted areas of the Bristol Channel. Muscle cadmium levels, however, are generally low and constant and would not appear to constitute a human health risk from food consumption.     

Selenoneine,total selenium,and total mercury content in the muscle of fishes

Levels of the selenium-containing imidazole compound selenoneine and overall organic selenium were measured in the muscle of fishes by speciation analysis. The method involves monitoring ⁸²Se levels by liquid chromatography inductively coupled plasma mass spectroscopy using a gel filtration column. Selenoneine levels were found to be highest in swordfish muscle (concentration 2.8 nmol/g tissue). The selenoneine contents of bigeye tuna, Pacific bluefin tuna, albacore, yellowfin tuna, and alfonsino muscle were 1.3–2.6 nmol/g tissue. In muscle of these fishes, most organic selenium (9–42%) was present as selenoneine. In other fish species, such as Pacific sardine, greeneye, skipjack, Pacific mackerel, horse mackerel, red sea bream, and Japanese barracuda, selenoneine levels were 0.1–1.4 nmol/g tissue, accounting for 3–34% of organic selenium. In contrast, muscle of Japanese conger, Japanese anchovy, chum salmon, Pacific saury, white croaker, and marbled sole contained levels of selenoneine below the level of detection (<0.05 nmol/g tissue). Mercury and selenium contents were 0.01–5.12 nmol/g tissue and 1.4–19.1 nmol/g tissue. The Se-to-Hg molar ratio varied from species to species, ranging from 1 for swordfish to 217 for marbled sole.     

Lipid content and fatty acid composition of muscle,liver, ovary and eggs of captive-reared and wild silver Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis> during artificial maturation

ABSTRACT:   Changes in lipid content and fatty acid composition of muscle, liver and ovary of captive-reared and wild silver Japanese eel Anguilla japonica were examined during artificial maturation induced by salmon pituitary homogenate (SPH) injections. Although the relative levels of n-3 and n-6 highly unsaturated fatty acids (HUFA) in liver and ovary were higher than in muscle in both captive and wild silver eels before SPH injection, these tended to decrease with maturation. The relative levels of n-6 HUFA in muscle, liver, ovary and eggs of wild silver eels were remarkably higher than those in captive eels. Therefore, we attempted to alter the ratio of n-6 HUFA in eggs by feeding eels a diet supplemented with linoleic acid-rich plant oil. Although the percentage of n-6 polyunsaturated fatty acids to total fatty acids in eggs of eels fed the supplemented diet was similar to wild silver eels, the percentage of n-6 HUFA remained remarkably lower than in wild silver eels. Hence, it appears that the supplemented diet affected the fatty acid composition of eggs, but did not result in much conversion of linoleic acid to its higher homologs in eels.     

Humoral immune response of Japanese eel, Anguilla japonica Temminck & Schlegel, to Pleistophora anguillarum Hoshina, 1951 (Microspora)

A humoral response of Japanese eel, Anguilla japonica Temminck & Schlegel, to the microsporean Pleistophora anguillarum Hoshina was demonstrated using immunoblotting and an enzyme-linked immunosorbent assay (ELISA). Japanese eel immunoglobulin was purified by affinity chromatography. The immunoglobulin was composed of 25-kDa light chains and 72-kDa heavy chains. The ELISA values of P. anguillarum antibodies in naturally infected fish sera were significantly higher than those of clinically healthy fish. Spore proteins from the microsporean were separated by electrophoresis and subjected to analysis by Western blot. Sera from naturally infected fish showed different reaction patterns to the spore proteins. While the sera randomly selected from naturally infected eels all showed a significant positive reaction to P. anguillarum antigens, the mucus from only three out of the nine infected eels reacted positively in the ELISA test. Subsequent analyses indicated that there was no significant difference in the amount of mucus immunoglobulin among the tested eels. Therefore, the generally lower ELISA values of mucosal anti-P. anguillarum antibodies from the infected eels tested were evidently not caused by a lack of immunoglobulin per se, but seem to be the result of a lack of anti-P. anguillarum antibodies in the mucus and/or a lower affinity in the anti-P. anguillarum antibodies that were present.     

四川省猪饲料微量元素含量盈缺分析及研究

通过对四川省德阳、威远、达州等地广大农户常用养猪饲料及日粮结构的实地调查,并采集当地常用养猪饲料样品和土壤样品92个,对其中的铁、铜、锰、锌、硒、碘、钴元素含量进行分析测定。根据测定值对农户常用养猪日粮进行概算,并与“中国瘦肉型生长肥育猪饲养标准”进行比较,结果表明:三个地区的两种日粮类型普遍缺乏锌元素,部分地区硒元素缺乏;而铁、铜、锰、碘元素含量均超过标准几倍至数十倍。饲料和土壤样品的微量元素含量具有区域性差异的特点。     

Discovering the dominance of the non-native European eel in the upper reaches of the Tone River system,Japan

To investigate the presence of non-native anguillid eels in Japanese waters, 141 eels were collected from seven sampling sites throughout the Tone River system. Genetic species identification showed an extraordinary dominance of the non-native European eel Anguilla anguilla in the uppermost site of the study area. Estimation of age from otoliths suggested that the European eels were introduced into the river in the 1990s, corresponding to previous reports from other Japanese water systems. Comparison of the von Bertalanffy growth curve parameters indicated that the European eels caught in the Tone River system appeared to have a similar or even higher growth rate than the same species in the original habitats in Europe. The long-term inhabitation and the normal development of European eels in Japanese waters suggest that regulations prohibiting the release of non-native eels and safeguards against accidental escape from culture ponds must be strictly maintained in order to ensure the conservation of the native Japanese eel.     

Nutritional comparison in muscle of wild,pond and factory cultured Japanese flounder (Paralichthys olivaceus) adults

Muscle proximate composition, amino acid profiles, fatty acid compositions and selected minerals of wild, pond and factory cultured Japanese flounder adults were compared in this study to elucidate their nutritive values and dietary nutrition requirements. Wild and pond cultured Japanese flounder flesh had higher crude proteins, but crude lipid contents of factory cultured fish were 3.8~4.0 fold greater. Major amino acids in Japanese flounder were aspartic acid, glutamic acid and lysine. Wild fish had higher levels of total amino acids, essential amino acids, nonessential amino acids and half‐essential amino acids and the contents in pond cultured samples were similar. Arachidonic acids (ARA), eicosapentaenoic acids (EPA), docosahexaenoic acids (DHA), polyunsaturated fatty acids (PUFA), DHA + EPA and n–3 PUFA in wild Japanese flounder were significantly higher than that in factory cultured fish, whereas fatty acid levels were close between pond cultured and wild fish. Japanese flounder were rich in zinc, iron and selenium, but poor in copper, chromium and nickel. Results indicated wild Japanese flounder had higher nutritional value and better meat quality, but the nutritional compositions of pond cultured fish were close to wild Japanese flounder, which suggested that pond culture of Japanese flounder offers broad application prospects.     

循环水养殖欧洲鲈鱼(Dicentrarchus labrax)重金属污染状况与富集分布特征

为了解并评估天津市某循环水养殖企业的养殖产品重金属安全性和分布规律,本研究采用电感耦合等离子体发射光谱法(ICP法)和原子荧光法(AFS法),对该封闭循环水养殖系统中欧洲鲈鱼(Dicentrarchus labrax)幼鱼、养殖中期和成鱼3个阶段的鱼体肌肉、肝脏和鳃中8种重金属(As、Cd、Cr、Cu、Ni、Pb、Zn和Hg)含量进行测定.结果显示,从生长阶段来看,随养殖过程推进,各重金属在欧洲鲈鱼体内分布特征不同,肌肉中As含量随时间增加而增加,最大值为1.93 mg/kg,Cu和Hg则相反,最大值分别为0.354和0.021 mg/kg;肝脏中As、Cd和Cu含量均随时间增加,最大值分别为1.47、1.09和143.00 mg/kg;鳃中As含量随时间增加而增加,最大值为0.321 mg/kg,Cr、Cu、Zn和Hg含量呈先降后升的趋势,最大值分别为0.356、45.8、19.2和0.0137 mg/kg.从组织分布特征来看,As含量为肌肉＞肝脏＞鳃,Cd、Cu和Zn含量均为肝脏＞鳃＞肌肉,Hg含量为肌肉＞鳃＞肝脏,Cr含量为鳃＞肝脏＞肌肉.可食部分,即肌肉中各重金属含量均符合食品安全国家标准(GB 2762-2012),参考鱼体重金属残留污染程度分级,该系统中的欧洲鲈鱼均属于未污染.水体样本,除养殖中期进水中Pb和Cd超标,其余重金属含量均符合我国渔业水质标准(GB 11607-89).表明该养殖系统中重金属污染在安全范围内.     

Variation in the demographic characteristics of yellow‐phase Japanese eels in different habitats of the Hamana Lake system,Japan

Abstract – Yellow‐phase Japanese eels (Anguilla japonica) were investigated in the Hamana Lake system, Japan, from 2003 to 2004 to understand how their demographic attributes vary within the lake system. A total of 779 yellow eels were collected during sampling in two inlet rivers and two brackish/saltwater lakes within the lake system. Female eels predominated, constituting 84% of the 75 sex‐determined eels in the river, and 50% of the 151 sex‐determined eels in the lakes. Total lengths (TL) of all eels examined ranged from 54.2 to 715.0 mm (mean = 320.4 ± 145.4 SD). In the inlet river, the TL of eels showed a significant positive relation with the distance from the river mouth. The estimated relative abundances of eels ranged from 0 to 1.8 eels·m^?2 effort (mean: 0.3 ± 0.41) in the river and was negatively correlated with the distance from the river mouth. This suggested that larger eels might tend to be distributed at lower abundances in upstream reaches of the river. Mean age of yellow eels determined by their otolith annuli was younger in the lake (N = 117, 3.3 ± 1.4 years) than in the river (N = 214, 4.3 ± 1.7 years). Growth rate was higher in the lake than in the river at age 1–2 years (131.9 and 104.4 mm·year^?1, respectively). The results of this study suggest that, although Japanese eels can adapt to various types of environments, significant differences can occur in population structures and growth patterns among habitats.     

Environmental DNA analysis reveals the spatial distribution,abundance, and biomass of Japanese eels at the river‐basin scale

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Origin identification method by multiple trace elemental analysis of short-neck clams produced in Japan, China, and the Republic of Korea

The correlations among the contents of trace elements in the shells of short-neck clams collected from Japan, China, and the Republic of Korea were examined. Origin-specific elemental content patterns were seen in clams originating from Japan, China, and the Republic of Korea. The crushed shells were decomposed with nitric acid–hydrogen peroxide, and the concentrations of ten elements (Li, V, Mn, Co, As, Rb, Mo, Ba, Pb, and U) in the shells were measured by inductively coupled plasma mass spectrometry. Some of the metal concentrations in the samples displayed clear geographical trends. The average concentration of Pb in Japanese clam shells was one-half to one-quarter that seen in Chinese or Korean clams. Average concentrations of As, Rb, and Ba in shells of Japanese origin were one-half those observed in Chinese or Korean clams. Linear discriminant analysis was applied to these analytical data, and four discriminant models were constructed. These discriminant models were able to distinguish the geographic origins of short-neck clams with 80.0–100 % accuracy. In particular, clams of Japanese origin were classified correctly ≥90 % of the time. Therefore, the trace elemental analysis of a short-neck clam shell is useful for identifying the country of origin of the clam.     

The sex-ratio reversal of the Japanese eel Anguilla japonica in the Kaoping River of Taiwan: The effect of cultured eels and its implication

The sex ratio of wild Japanese eels in the Kaoping River of southwestern Taiwan has been extremely skewed towards females in the recent years. However, the sex ratio skewed towards males after Typhoon Mindulle, July 2, 2004 then recovered to the previous female-dominated status in the following year. To determine why the sex ratio drastically changed, eels captured in the river were examined by both morphologic characteristics and otolith elemental signatures by solution-based inductively coupled plasma mass spectrometry (SB-ICPMS) and laser-ablation ICPMS (LA-ICPMS). Most of the eels collected in the river after the typhoon had a blue-gray colored back, with morphology and sex ratio similar to that of cultured eels, which differed from wild yellow eels which had a green colored back. The chemical signature in otoliths of eels with a blue-gray colored back was similar to that of cultured eels, with significantly lower Sr/Ca ratios but slightly higher Mn/Ca ratios than for wild eels. This confirmed that the reversal in eel sex ratio in the Kaoping River estuary resulted from cultured eels that had escaped from eel farms. Eel farmers estimated that about 30,000 eels escaped during the typhoon, sufficient to reverse the sex ratio of the eels in the river. Furthermore, silver eels caught in the estuary in the winter 2004 were also mostly males. The chemical signature in otoliths of these silver eels was similar to that of escaped cultured eels. Their morphology and mean GSIs, however, were comparable to wild silver eels. Thus, cultured eels that have escaped from eel farms can silver normally in the wild. Consequently, cultured eels may help to balance the sex ratio of the wild eel population and may contribute to the spawning stock of Japanese eel.     

苏州地区泥鳅与大鳞副泥鳅肌肉微量元素含量比较

为了评价泥鳅与大鳞副泥鳅营养与食品安全性,采用电感耦合等离子体一原子发射光谱法（ICP—AES）对苏州地区泥鳅与大鳞副泥鳅肌肉组织中的K、Ca、Na、Mg,P、Fe、Zn、Cu、Mn、Se、Cr、Pb、Cd、As14种元素含量进行测定与分析。结果显示：泥鳅与大鳞副泥鳅肌肉组织中均富含K、Ca、Na、Mg、P等常量元素,并含有人体所必需的Fe、Zn、Cu、Mn等微量元素,As未检测出,Cd、Pb的含量均低于国家限量标准。     

Effects of temperature on vitellogenesis in Japanese eel Anguilla japonica

ABSTRACT:   Cultured immature female Japanese eels acclimated to sea water at either 10 or 20°C were treated weekly with salmon gonadotropin fraction (sGTH) in order to investigate the effects of water temperature on artificial induction of ovarian maturation. In eels maintained at 20°C, ovulation was induced in 11 of 18 fish during the experimental period of 13 weeks, whereas at 10°C all fish showed a low gonadosomatic index (GSI) at the end of the experiment. Plasma vitellogenin levels were higher in eels kept at 20°C than in eels at 10°C throughout the experiment. However, no significant differences were observed in the plasma testosterone and estradiol-17β levels between groups. Eels pretreated with sGTHs at 10°C for 13 weeks were separated to two different temperature (10 and 20°C) groups, and received the same weekly sGTH injections. In eels transferred to 20°C, plasma vitellogenin levels, GSI and oocyte diameter were increased, but these values were maintained at low levels in eels that remained at 10°C. These results clearly indicate that water temperature is an important factor regulating vitellogenesis in the Japanese eel.     

Insulin-like growth factor I of Japanese eel, Anguilla japonica: cDNA cloning, tissue distribution, and expression after treatment with growth hormone and seawater acclimation

In an attempt to understand growth regulation in the Japanese eel, Anguilla japonica, we cloned insulin-like growth factor-I (IGF-I) cDNAs and examined their mRNA expression in several tissues. Two eel IGF-I (eIGF-I) cDNAs encoding preprohormones, eIGF-I-Ea1and eIGF-I-Ea2, were cloned from the liver by polymerase chain reaction (PCR). The preproIGF-Is were identical in signal peptide and mature IGF-I, but different in the E domain—eIGF-I-Ea2 mRNA was 36 bp longer than eIGF-I-Ea1 mRNA. Eel IGF-I was 83–94% identical with that of teleosts, 71% identical with that of dogfish, 87% identical with that of bullfrog and chicken, and 83% identical with that of humans. In both males and females the highest eIGF-I-Ea1 mRNA levels were observed in the liver, with detectable levels also found in the gills, heart, stomach, spleen, kidney, intestine, swim-bladder, muscle, and gonads. eIGF-I-Ea1 mRNA levels in the liver were higher in females than in males whereas in the intestine they were lower than in males. eIGF-I-Ea2 mRNA was detected in all the tissues examined and at similar levels in males and females. In this experiment higher eIGF-I-Ea1 mRNA levels were observed in the liver of larger glass eels than in those of smaller fish. eIGF-I-Ea2 mRNA levels were also higher in larger eels, although they were lower than IGF-I-Ea1 mRNA levels. Both eIGF-I mRNA levels in liver were positively correlated with the body size of the␣glass eels. Intraperitoneal injection of recombinant eel GH (reGH), 0.25 μg g⁻¹ body weight, into glass eels resulted in a significant increase in both eIGF-I mRNAs in the liver 1 day after injection compared with control fish, but no elevation was observed 2 days after injection. Incubation of liver slices with reGH at concentrations of 10, 100, and 1,000 ng mL⁻¹ for 24 h resulted in a significant concentration-dependent increase in the levels of both eIGF-I mRNAs. Higher levels of eIGF-I-Ea1 and Ea2 mRNA were observed in the gills ofseawater-reared eels than in those of freshwater-reared fish, but no differenceswere observed in the whole kidney. These results suggest that IGF-I is involved in the regulation of somatic growth and also in adaptation of the Japanese eel to seawater.     

Comparative Net Absorption of Chelated and Inorganic Trace Minerals in Channel Catfish Ictalurus punctatus Diets

Coefficients of net absorption for copper, iron, manganese, selenium, and zinc were determined for chelated sources (copper proteinate, iron proteinate, manganese proteinate, selenium proteinate, zinc proteinate) and inorganic sources (copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate, sodium selenite, zinc sulfate hep-tahydrate) of these elements with channel catfish Ictalurus punctatus . Fish weighing approximately 60 g were placed into 40-L aquaria (12 fish/aquarium) at a temperature of 28 f 2 C and fed either an egg white-based, purified diet or a soybean meal-based, practical diet with and without the test mineral sources for 6 wk then killed and feces collected from the hindgut. Treatments were arranged in a 2 × 2 factorial design. Absorption coefficients for the elements in the basal and mineral supplemented diets were calculated by the indirect indicator (chromic oxide) method and corrected for residual amounts of element in the basal diets. Net absorption of the chelated minerals was significantly higher ( p < 0.05) than net absorption of the inorganic minerals in both basal diets. Average percentage improvement in net absorption of chelated minerals over inorganic minerals was 39.3% in the purified diets and 81.1% in the practical diets. These results may indicate that appreciably lower amounts of chelated trace minerals than inorganic trace minerals can be used as supplements in catfish feeds.