Mercury in fish: concentration vs. fish size and estimates of mercury intake.

Total mercury concentrations were determined in different fish size classes of commercial importance such as, conger eel (Conger conger), starry ray (Raja asterias), forkbeard (Phycis blennoides), frostfish (Lepidopus caudatus), striped mullet (Mullus barbatus), red gurnard (Aspitrigla cuculus) and yellow gurnard (Trigla lucerna) in order to evaluate variations in consumer exposure to mercury as a function of fish consumption of a spectrum of different sizes. The highest mean levels of total mercury were detected in conger eel (0.80 microg g(-1)) and starry ray (0.75 microg g(-1)). Forkbeard (0.67 microg g(-1)), frostfish (0.59 microg g(-1)) and striped mullet (0.55 microg g(-1)) showed slightly lower levels, while red gurnard (0.33 microg g(-1)) and yellow gurnard (0.22 microg g(-1)) exhibited the lowest concentrations. The results of linear regression analysis showed a significant relationship between mercury concentrations and fish size for all species. Consequently, dietary consumption of larger size specimens leads to an increase in the exposure level for consumers. Understanding by consumers of all factors leading to an increase of exposure to mercury is the first step to enable them to make decisions about eating fish.     

Mercury content in Chilean fish and estimated intake levels.

The intake of fish products is a major public health concern due to possible methyl mercury exposure, which is especially toxic to the human nervous system. This pilot study (n = 46) was designed to determine mercury concentrations in fish products for national consumption (Chilean jack mackerel, hake, Chilean mussel, tuna) and for export (salmon, Patagonian toothfish, swordfish, southern hake), and to estimate the exposure of the general population. The fish products were collected from markets in Talcahuano, Puerto Montt and Santiago. Samples were analyzed at the National Environmental Center by cold vapor atomic absorption spectrophotometry. Mercury levels in swordfish and one canned tuna sample exceeded levels prescribed by national and international standards. The remaining two export products (Patagonian toothfish, also known as Chilean sea bass, and salmon) complied with international limits, which are more demanding than Chilean regulations. Theoretical estimates of mercury intake varied from 0.08 to 3.8 microg kg(-1) bw day(-1) for high fish consumers, exceeding the provisional tolerable intake for tuna, Chilean seabass, Chilean jack mackerel and swordfish. This group appears to be at the greatest risk from mercury contamination among the Chilean population.     

Mercury speciation in piscivorous fish from mining-impacted reservoirs

Guadalupe Reservoir (GUA), California, and Lahontan Reservoir (LAH), Nevada, U.S. are both affected either directly or indirectly by the legacy of gold and silver mining in the Sierra Nevada during the nineteenth century. Analysis of total mercury in fish from these lentic systems consistently indicate elevated concentrations (>1 microg x g(-1) wet weight; hereinafter, all concentrations are reported as wet weight unless indicated otherwise) well above the U.S. Environmenal Protection Agency's human consumption advisory level for fish (<0.3 microg x g(-1)). Replicate X-ray absorption near edge structure (XANES) analyses on largemouth bass and hybrid striped bass from GUA and LAH were performed to determine predominant chemical species of mercury accumulated by these high-trophic-level piscivores that are exposed to elevated mercury through trophic transfer in mining-impacted lentic systems. Despite distinct differences in mercury source, the proximity of the source, and concentrations of complexing ligands, results of XANES analysis clearly indicated that mercury accumulated in these individual fish from the two reservoirs were dominated by methylmercury cysteine complexes. These findings are consistent with results from commercial fish species inhabiting marine environments which are presumed to include differing mercury sources (e.g., atmospheric, hydrothermal, or benthic). The dominance of methylmercury cysteine complexes in muscle tissues of fish obtained from such contrasting environments and exposure conditions suggests that a generic toxicological model for the consumption of fish could be applicable over a wide range of ecologic settings.     

Essential elements and contaminants in tissues of commercial pelagic fish from the Eastern Mediterranean Sea

BACKGROUND: It is important to determine the concentrations of essential and non‐essential metals in fish for human health. The essential elements and contaminants (Pb and Cd) were determined seasonally in the muscle and liver of some pelagic fish species round herring (Etrumeus teres), chub mackerel (Scomber japonicus), golden grey mullet (Liza aurata) and Mediterranean horse mackerel (Trachurus mediterraneus) from the Iskenderun Bay, Eastern Mediterranean Sea. RESULTS: The Na, K, Ca and Mg were the most abundant elements in muscle and liver tissues. The Na, K, Ca and Mg concentrations in fish tissues were between 51.7 and 3426 mg kg^?1. Muscle accumulated the lowest levels of elements. Trace element and contaminant levels in muscle were highest in spring and summer. The Cu, Zn and Cr concentrations were highest in summer. The Ni, Mn and Fe concentrations were highest in spring. The maximum Pb concentrations in the muscle and liver of fish species was 0.39 and 0.80 mg kg^?1 in autumn. The maximum Cd concentration in the muscle of fish was 0.27 mg kg^?1 in spring and the maximum Cd concentration in the liver was 0.78 mg kg^?1 in summer. CONCLUSION: The Cr, Pb, Cd, Cu and Zn levels in muscle were found to be lower than permissible limits reported by various authorities. Estimated weekly and daily intake for Pb and Cd by consumption of fish muscle were far below the PTWI and PTDI values established by FAO/WHO. Copyright © 2009 Society of Chemical Industry     

Organochlorine pesticide residues in European sardine, horse mackerel and Atlantic mackerel from Portugal.

This paper reports the results for the surveillance of nine organochlorine pesticides (HCH isomers (alpha, beta, e, gamma), p,p'-DDD, p,p'-DDT, p,p'-DDE, p,p'-DDD, HCB and aldrin) in muscle of three fish species, European pilchard (Sardina pilchardus), Atlantic horse mackerel (Trachurus trachurus) and Atlantic mackerel (Scomber scombrus). Analytical methodology included n-hexane extraction, clean-up with 2% deactivated Florisil, and quantification with gas chromatography-electron capture detection (GC-ECD). The highest mean concentrations were found for p,p'-DDT in sardine and mackerel at levels of 30.1 and 109.9 microg kg(-1), respectively, and for p,p'-DDD in horse mackerel at 51.9 microg kg(-1). Three species had higher levels for S-DDT than S-HCH. The estimated daily intake of organochlorine pesticides in the three species showed that in sardine, the highest EDIs were found for aldrin, at 1.8 ng kg(-1) bw day(-1), which represents 1.8% of the acceptable daily intake (ADI), and for ss-HCH, at 4.0 ng kg(-1) bw day(-1), representing 0.4% of ADI. Lowest values were found for Atlantic mackerel. Statistical analysis to determine the differences in mean concentrations of pesticides between species, and any correlation between groups of residues related with each one of the species, was undertaken.     

Alteration of the electrophoretic pattern of myofibrillar proteins in fish mince during frozen storage

A study was made of the variations in the electrophoretic profile of myofibrillar proteins in the muscles of blue whiting (Micromesistius poutassou R.), horse mackerel (Trachurus trachurus L.) and mackerel (Scomber scombrus L.). It was shown that all species presented different deterioration patterns during frozen storage. The fish were caught at two separate times of the year (winter and summer) and were stored frozen at -18°C for 1 year. The results indicate that during frozen storage, electrophoretic patterns varied according to species. Comparison of myosin heavy chain/actin (MHC/A) ratios indicates that blue whiting is the species that undergoes most alteration, and that this is more intense in fish caught in the summer than in the winter. Alteration of the MHC/A ratio was similar in horse mackerel and mackerel caught in the winter, whereas in the summer horse mackerel proved to be the most stable species. In all cases, the reduction of the MHC/A ratio was due essentially to alteration of the MHC, an effect which was particularly marked in blue whiting. Tropomyosin remained stable throughout the storage period in all three species.     

Seasonal changes in the proximate chemical compositions and fatty acids of chub mackerel (Scomber japonicus) and horse mackerel (Trachurus trachurus) from the north eastern Mediterranean Sea

The effects of seasonal variations on the proximate chemical compositions and fatty acid profiles of chub mackerel (Scomber japonicus) and horse mackerel (Trachurus trachurus) captured in the north‐eastern Mediterranean Sea were investigated. Protein fluctuations were observed in two species for all seasons. The lipid content of both species was lower in winter than in autumn and spring. In all seasons, the major fatty acids in both species were observed to be palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1 ω9), eicosapentaenoic acid (20:5 ω3) and docosahexaenoic acid (20:6 ω3). Chub mackerel and horse mackerel exhibited seasonal fluctuations in their fatty acid contents. The fatty acid profile of the two species had a higher degree of unsaturation during winter. The levels of EPA in chub mackerel in winter, spring and autumn were 5.96%, 4.86% and 4.33%, respectively, while those of DHA were 24.94%, 18.75% and 17.12%, respectively. The levels of EPA in horse mackerel in winter, spring and autumn were 5.42%, 5.03% and 4.86%, respectively, while those of DHA were 14.96%, 13.31% and 11.10%, respectively. The PUFA (polyunsaturated fatty acids) values and ω3/ω6 ratios in the two species were highest in winter. The results indicate that chub mackerel and horse mackerel captured in the north‐eastern Mediterranean Sea, which are among the most important fish in Turkey and of international commercial value, are a good source of nutrition for human consumption in terms of their proximate chemical composition and fatty acids.     

Total mercury levels in muscle tissue of swordfish (Xiphias gladius) and bluefin tuna (Thunnus thynnus) from the Mediterranean Sea (Italy).

This study was carried out to determine the current levels of total mercury in the muscle tissue of swordfish (Xiphias gladius) and bluefin tuna (Thunnus thynnus) caught in the Mediterranean Sea with the purpose of ascertaining whether the concentrations exceeded the maximum level fixed by the European Commission Decision. In addition, specimens of each species were divided into different ranges of weight to investigate the influence of size on mercury accumulation in order to provide data upon which commercial fishing strategies and marketing of swordfish and bluefin tuna may be based. Higher mean levels of total mercury were found in bluefin tuna (1.02 microg g(-1) wet wt) than in swordfish (0.49 microg g(-1) wet wt). In 4.3% of swordfish and in 44.3% of bluefin tuna analyzed, total mercury concentrations exceeded the maximum level fixed by the European Commission Decision (Hg = 1 microg g(-1) wet wt). Besides, for bluefin tuna the total mercury level variability observed, due to size, suggests that there should be greater regulatory control by the authorities.     

Characterisation of furan fatty acids in Adriatic fish

Furan fatty acids (F-acids) were characterised in the fillet of European hake (Merluccius merluccius), horse mackerel (Trachurus trachurus), common sole (Solea solea), European anchovy (Engralius encrasicolus), Atlantic mackerel (Scomber scombrus), European pilchard (Sardina pilchardus) was harvested in Adriatic Sea during the spring and the summer. The main F-acids were of the saturated series: 12,15-epoxy-13-methyleicosa-12,14-dienoic acid [MonoMe(11,5)] in European hake and 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid [DiMe(11,5)] in all the other fish species; 12,15-epoxy-13,14-dimethyloctadeca-12,14-dienoic acid, 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid and 14,17-epoxy-15,16-dimethyldocosa-14,16-dienoic acid were present in all fish species in trace amounts. Other identified F-acids were the olefinic congeners 12,15-epoxy-13,14-dimethyleicosa-12,15,16-trienoic acid and 12,15-epoxy-13,14-dimethyleicosa-10,12,14-trienoic acid. European pilchard had the highest F-acids content (30 mg/100 g fillet), whereas horse mackerel showed the lowest content (less than 0.1 mg/100 g fillet). Eicosapentaenoic acid (EPA) was positively correlated with MonoMe(11,5) and DiMe(11,5), showing that the biosynthesis of docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) is presumably competitive with that of F-acids.     

Concentration and Exposure Assessment of Mercury in Commercial Fish and Other Seafood Marketed in Oman

The results of this study present analytical data of the mercury levels in several fish and shellfish species to create awareness among individuals of the risks associated with consuming fish contaminated with mercury. Mercury concentrations varied from a mean of 0.02 mg/kg in Indian mackerel to 0.19 mg/kg in shark in both fresh and frozen fish, from 0.02 mg/kg in sardines to 0.18 mg/kg in skipjack tuna in canned fish, and from 0.02 mg/kg in Indian mackerel to 0.79 mg/kg in shark in dried fish. Shellfish contained a slightly higher amount of mercury than fresh or frozen fish with a mean of 0.09 mg/kg. Trophic position, followed by habitat, was the most important factors for variability in mercury concentrations in fish and shellfish. The maximum safe weekly intake (MSWI) values of mercury were significantly higher for herbivores than for carnivores. The MSWI value for total mercury in the case of consuming most (72%) fish species was more than 5 kg; however, the MSWI value was never more than 5 kg in most (66%) shellfish species. Risks were identified upon consumption of 120 g of dried shark when exceeding the provisional tolerable weekly intake threshold (1.6 μg/kg) for methylmercury. Therefore, fish‐eating populations should reduce the quantity of dried shark to efficiently diminish the exposure to mercury.     

Effect of brine freezing on the rancidity development during the frozen storage of small pelagic fish species

Brine freezing was applied to two small pelagic underutilised fish species (mackerel, Scomber scombrus; horse mackerel Trachurus trachurus). Rancidity development was studied during their frozen (–18 °C) storage up to 9 months, and quality change results were compared to common freezing conditions (control treatment). Fish samples treated under brine freezing conditions showed a higher lipid oxidation development (peroxide value and thiobarbituric acid index) and worse marks on some sensory attributes (general aspect, odour and colour) than control fish. However, samples treated under brine freezing conditions provided a lower lipid hydrolysis development (free fatty acid formation) and better scores for consistency. Comparison between both fish species led to a higher secondary lipid oxidation formation (thiobarbituric acid index) for mackerel, while horse mackerel showed to be more prone to interaction compound formation (fluorescence detection); however, both fish species showed the same shelf-life times (3 and 5 months for brine and control freezing conditions, respectively). As a result of the brine freezing conditions, an increase in NaCl content in white muscle of both species was observed. According to the results obtained in the present work, the brine freezing treatment is not recommended for these two small pelagic fish species.     

Mercury, arsenic, lead and cadmium in fish and shellfish from the Adriatic Sea

The aim was to measure concentrations of total mercury, total arsenic, lead and cadmium in common edible fresh fish and shellfish from various areas of the Adriatic Sea. Estimates of intake of these elements were made through seafood consumption by the general population. Samples were either wet digested for mercury and arsenic, or dry ashed for lead and cadmium analysis. Mercury was measured by cold vapour atomic absorption spectrometry (CV AAS) and arsenic, lead and cadmium by electrothermal atomic absorption spectrometry (ET AAS). Quality control procedures of analytical methods, which included analyses of dogfish muscle-certified reference material DORM-2, confirmed the acceptability of methods. The highest mercury and arsenic concentrations were found in hake ( Merluccius merluccius ) and the lowest in mackerel ( Scomber scombrus ). The respective values in hake were 0.373 ±0.075 and 23.3 ±3.6, and in mackerel 0.153 ±0.028 and 1.06 ±0.29 mg kg -1 fresh weight (mean ±SD). Lead and cadmium concentrations were about 10 times higher in shellfish than in analysed fish. The highest lead and cadmium concentrations were found in mussel ( Mytilus galloprovincialis ) and the lowest in hake. Respective lead and cadmium values in mussel were 0.150 ±0.009 and 0.142 ±0.017, and in hake were 0.007 ±0.004 and 0.002 ±0.001 mg kg -1 fresh weight. The concentrations of analysed elements were below acceptable levels for human consumption set by the Croatian Ministry of Health, except for total arsenic. The estimated intake of those trace elements included in this study through seafood consumption by the general population did not exceed the provisional tolerable weekly intake recommended by the Joint FAO/WHO Expert Committee on Food Additives.     

Evolution of capillary zone electrophoresis profiles of methanol soluble compounds during fish chilling: relation to freshness

 A methodology for assessing fish freshness based on the capillary zone electrophoresis analysis of methanol-soluble compounds extracted from white muscle is presented. Two fatty fish species, mackerel (Scomber scombrus) and horse mackerel (Trachurus trachurus), and two lean species, hake (Merluccius merluccius) and blue whiting (Micromesistius poutassou), were studied. Peaks were characterized by their retention times and intensities relative to imidazole, and the four species showed similar electrophoretic profiles. The intensity of peaks with short retention times decreased during chilling storage, and that of peaks with longer retention times increased during storage. The variability and calibration of the instrumental method were established by correlation analysis with the time of chilling and sensory measurements. Received: 22 April 1999 / Revised version: 9 July 1999     

Total mercury in muscle of benthic and pelagic fish from the South Adriatic Sea (Italy).

Total mercury concentrations were measured from the muscle of different kinds of fish: yellow gurnard (Trigla lucerna), red gurnard (Aspitrigla cuculus) red fish (Helicolenus dactylopterus), skate spp. (Raje spp.), goldline (Sarpa salpa), atlantic bonito (Sarda sarda), mackerel (Scomber scombrus), chub mackerel (Scomber japonicus) caught in the South Adriatic Sea (south Italy) in the period June/August 1995. The highest total mercury levels were found in the benthic marine organisms and particularly in skates (Raje spp.) whose values ranged from 0.05 to 2.65 mg/kg wet wt with a mean value of 1.02 mg/kg wet wt. As for pelagic species, the highest mean levels were observed in Atlantic bonito (0.34 mg/kg wet wt), while in goldline the mean content of total mercury was the lowest (0.07 mg/kg wet wt). According to the rules in force (Official Journal of the European Communities 1994) 53% of skate and Atlantic bonito samples showed concentrations exceeding the peak value of 1 mg/kg, while for the other species, only 28% of samples exceeded the peak value fixed at 0.5 mg/kg. Correlations between total mercury concentration and specimen weight were evident in all examined species except for goldline and skates.     

Determination of mercury in fish by cold vapour atomic absorption spectrometry using an automatic mercury analyzer

The concentration of mercury in fish samples from the Atlantic coast of Ghana was determined using a simple, rapid and accurate method. A mixture of HNO₃, HClO₄ and H₂SO₄ was used for complete oxidation of organic tissue. Mercury is detected by the cold vapour atomic absorption spectrometry technique using an automatic mercury analyzer developed at the National Institute for Minamata Disease (NIMD). In total, 56 samples covering 13 species of fish were analysed for total mercury. The concentration of mercury in the edible muscle tissue of these fish ranged from 0.004 to 0.122 μg g⁻¹ wet weight. All fish species sampled had concentrations less than the WHO limit of 0.5 μg g⁻¹ wet weight. The low concentrations of mercury detected in the samples do not constitute any significant mercury exposure to the general population through fish consumption.     

Hair mercury levels in relation to fish consumption in a community of the Moroccan Mediterranean coast

Coastal populations with high seafood consumption in the Mediterranean have a significant exposure to dietary methylmercury, and areas where environmental mercury pollution is an issue due to industrial activities are of special concern. The study was undertaken with the aim of assessing methylmercury exposure through fish consumption in a community of north Morocco and characterizing the relevant health risk. Concentrations of total mercury were determined in human hair, a biomarker of methylmercury exposure, and in locally consumed fish by cold vapour atomic absorption spectrophotometry. Based on consumption frequencies reported by the 108 subjects included in the study the weekly intake of methylmercury was estimated and biomarker data were evaluated in relation to the estimated intake and the sociodemographic characteristics of the population. Multiple regression analysis was employed for the interpretation of hair mercury data in relation to fish consumption frequency, gender and the age of individuals. Mercury concentrations in hair ranged from 0.22 to 9.56 µg g^-1 (geometric mean = 1.79 µg g^-1) and were closely related to fish intake. Fisherman and their families consumed fish three to five times per week and were the most exposed population subgroup. A high proportion of women of child-bearing age (50%) had relatively high levels of mercury in their hair (3.08-7.88 µg g^-1).     

Mechanical separation process for the value enhancement of Atlantic horse mackerel (Trachurus trachurus), a discard fish

Mechanically separated meat (MSM) is the product obtained by removing meat from bones by pressure application. Whole fillets and fish burgers from minced muscle and from mechanical separation of Atlantic horse mackerel (Trachurus trachurus) were evaluated immediately after processing (T₀) and after 90 days of storage at − 20 °C for parameters related to quality loss. Firstly, mechanical separation inhibited water losses (2.67% against 4.57 and 5.57% in whole fillets and burgers from minced muscle, respectively), but the colour of MSM was duller and redder than the samples from other groups. Horse mackerel contained low fat (< 1 g/100 g muscle), and high PUFAω3 content (around 57 g/100 g total fatty acids), especially EPA and DHA (around 52 g/100 g) regardless the treatment. However, the species was susceptible to oxidation, as revealed by the high TBARS content at T₀ (> 8 mg MDA-eq/100 g muscle). Nevertheless, Atlantic horse mackerel showed a high antioxidant capacity (ABTS, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid, DPPH, 2,2-diphenyl-1-picrylhydrazyl, and FRAP, ferric-reducing ability) at T₀ which may protect muscle against oxidative damages both during processing treatment and storage.Industrial relevanceThe mechanical separation process described in the article has been largely utilized for terrestrial animal products. However, it is seldom adopted by fish industry, especially for recovering discard fish species. Horse mackerel is an underutilized species, normally transformed into animal feed despite its high levels of omega-3 polyunsaturated fatty acids. Therefore this study was conducted in order to determine the effect of a mechanical separation technique on the physicochemical properties of horse mackerel. Our study showed that, although this species is susceptible to oxidative changes, mechanically separate meat can be a high-quality ingredient in burgers, nuggets, sticks, or even sauces which may represent a way for the valorisation of discard species.     

Emulsifying capacity of fish mince from several species during frozen storage

Abstract : As a functional property of protein, emulsifying capacity (EC) is of great technological interest. This article examines EC in fish mince from three species differing in fat content and in the pattern of deterioration during frozen storage—blue whiting (Micromesistius poutassou R), horse mackerel (Trachurus trachurus L) and mackerel (Scomber scombrus L)—caught during two seasons of the year in which physiological behaviour is expected to be different (winter and summer). EC and protein solubility were determined periodically. The results indicate the existence of a direct relationship between the fat content of the species used and its EC. Furthermore, in the species studied EC was independent of protein solubility and the amount of protein in the medium, both of which decline as a result of the formation of aggregates during frozen storage. This is not therefore a suitable method for determining protein quality during frozen storage.     

The effects of freeze-drying and storage on the FT-Raman spectra of Atlantic mackerel (Scomber scombrus) and horse mackerel (Trachurus trachurus)

FT-Raman spectroscopy was undertaken for quantitative characterization of lipids in horse mackerel (Trachurus Trachurus) and Atlantic mackerel (Scomber scombrus). Peroxide value of fish lipids and protein extractability of the fish lipids and muscles were also measured by titration and Bradford assay, respectively.     

Effects of storage time and chemical preservatives on the total volatile basic nitrogen content in chilean mackerel (Trachurus murphy) prior to fish meal production

Total volatile basic nitrogen (TVB-N) as a measure of protein degradation and total microbial counts or stored raw mackerel (Trachurus murphy), which had been treated with chemical preservatives, were compared with the TVB-N and microbial counts of untreated fish. In unpreserved fish, decomposition of fish protein was rapid. Treatment of mackerel with acetic (1000-5000 μg kg^?1), which was the most effective of the parameters studied, approximately halved the rate of increase in TVB-N compared with the untreated samples. Changes in the total microbial counts presented a similar trend.