Gadoid Fish Species Research Articles

Evaluation of Lipid Damage, Microbial Spoilage and Sensory Acceptance of Chilled Pouting (Trisopterus luscus), an Underutilized Lean Fish Species

The present study focused on the use of pouting (Trisopterus luscus), an underutilized gadoid fish species, as a fresh product of potential commercial interest. Accordingly, non-degutted pouting specimens (145–195 g and 15–22 cm) were stored under chilling conditions (0 °C) for microbial, chemical and sensory analyses to evaluate their commercial quality and shelf life. A progressive quality loss (p < 0.05) was detected for this lean species (5.58 g lipids·kg−1 muscle) as the storage time increased, as determined through microbial (aerobes, psychrotrophs and Enterobacteriaceae counts), lipid hydrolysis (free fatty acid value), lipid oxidation (conjugated diene and triene, thiobarbituric acid reactive substance, and fluorescence values) and sensory acceptance assessment. A detailed comparison to related lean fish species revealed that the pouting exhibited a fast quality breakdown under refrigeration conditions. Thus, after 9 d of chilled storage, the psychrotroph counts exceeded the acceptable limits (8.54 log CFU·g−1), and the fish specimens were found to be rejectable, with the sensory panel, external odor and eye appearance being the limiting factors. In contrast, the pouting specimens exhibited high quality after 3 d of storage, with the quality being still acceptable after 6 d. According to the current search for novel, underutilized species, pouting is proposed as a promising source.

Unraveling the microbiota of the fish parasite Pseudoterranova decipiens in codfish (Gadus morhua) reveals a fish-related bacterial community

Anisakidae, mainly represented by the species Anisakis simplex and Pseudoterranova decipiens, are one of the most commonly zoonotic nematodes present in marine fish species. Apart from public health risks directly linked to the parasite itself, little is known on the effects of the migrating nematodes on the hygienic quality of the fish fillet due to bacteria it carries. In the present study, the cultivated bacterial community on and in individual P. decipiens larvae deriving from codfish is reported. Four isolation media were included and evaluated to increase the bacterial diversity isolated, and identification of the bacterial growth was performed by a combination of Matrix-Assisted Laser Desorption Ionization Time-Of-Flight mass spectrometry and 16S rRNA gene sequencing. Results revealed that the microbiota of P. decipiens larvae comprises both potential spoilage bacteria and human opportunistic pathogens, and that a combined isolation on the general isolation medium tryptone soy agar and a medium supplemented with artificial seawater resulted in the highest bacterial recovery in terms of diversity and enumeration. Dissimilarity analysis also revealed similar, though unique, bacterial communities between nematodes originating from the same fish suggesting that anisakid microbiota compositions are reflections of the microbial assemblages in the fish host as an individual, and that the gut microbiome is diverse within gadoid fish species originating from the same geographical habitat. Future research should, based on the results in the present study, further elaborate on the comparison of the bacterial communities of both the larva and the codfish from which it was isolated, and, explore the extrapolation potential towards other fish and nematode species. Also, the actual degree of risk beyond the simple presence of the parasite due to carriage of opportunistic bacteria should be examined, as well as the nematode's true effect on spoilage.

Human risk associated with potential exposure to heavy metals in a gadoid fish species from selected markets in Benin City, Nigeria

The study ascertained the levels of Cadmium (Cd), Copper (Cu), Lead (Pb) and Zinc (Zn) in the Atlantic cod (Gadus morhua) of mean weight 679 ± 16.05 g, from selected markets in Benin city, Nigeria, by Atomic Absorption Spectrometric technique, in order to ascertain their suitability for human consumption. The mean concentrations of heavy metals in G. morhua ranged from 0.03 mg/kg Cd at New Benin market to 52.85 mg/kg for Zn at Ramat market while there was no significant difference (p>0.05) in the mean concentrations of heavy metals in fish between markets. The estimated daily intake (EDI) values for heavy metals ranged from 0.0032 mg/person/day for Cd to 1.70 mg/person/day for Zn while the estimated annual intake (EAI) values for heavy metals ranged from 1.17 mg/person/year for Cd to 620.5 mg/person/year for Zn. The estimated quantity consumed (EQC) values ranged from 0.000064 mg/meal for Cd to 0.034mg/meal for Zn while the theoretical maximum daily intake (TMDI) was 2414 mg/person/day. The margin of exposure (MOE) values for heavy metals ranged from 0.63 for Cd to 4.19 for Cu while the total toxicity of mixtures (TTM) value was 4.82. The toxic/hazard quotient (TQ) values ranged from 0.24 for Cu to 1.60 for Cd while the total heavy metal load in fish by market, ranged from 41.26 mg/kg at New Benin market to 59.27 mg/kg at Ramat market. The mean concentrations of Cd, Pb and Zn in G. morhua exceeded the thresholds established for heavy metals in fish by CODEX Alimentarius, Commission Regulation and Food and Agriculture Organization of the United Nations (FAO), thus making them the metals of critical ecological concern. The implication is that G. morhuamust be consumed with caution in order to avert health problems associated with excess concentrations of Cd, Pb and Zn.Keywords: heavy metals, Gadus morhua, toxic/hazard quotient, markets, Nigeria

Atlantic Haddock (Melanogrammus aeglefinus) Larvae Have a Magnetic Compass that Guides Their Orientation.

SummaryAtlantic haddock (Melanogrammus aeglefinus) is a commercially important species of gadoid fish. In the North Sea, their main spawning areas are located close to the northern continental slope. Eggs and larvae drift with the current across the North Sea. However, fish larvae of many taxa can orient at sea using multiple external cues, including the Earth's magnetic field. In this work, we investigated whether haddock larvae passively drift or orient using the Earth's magnetic field. We observed the behavior of 59 and 102 haddock larvae swimming in a behavioral chamber deployed in the Norwegian North Sea and in a magnetic laboratory, respectively. In both in situ and laboratory settings, where the magnetic field direction was modified, haddock larvae significantly oriented toward the northwest. We conclude that haddock larvae orientation at sea is guided by a magnetic compass mechanism. These results have implications for retention and dispersal of pelagic haddock larvae.

Mitochondrial acclimation potential to ocean acidification and warming of Polar cod (Boreogadus saida) and Atlantic cod (Gadus morhua)

BackgroundOcean acidification and warming are happening fast in the Arctic but little is known about the effects of ocean acidification and warming on the physiological performance and survival of Arctic fish.ResultsIn this study we investigated the metabolic background of performance through analyses of cardiac mitochondrial function in response to control and elevated water temperatures and PCO2 of two gadoid fish species, Polar cod (Boreogadus saida), an endemic Arctic species, and Atlantic cod (Gadus morhua), which is a temperate to cold eurytherm and currently expanding into Arctic waters in the wake of ocean warming. We studied their responses to the above-mentioned drivers and their acclimation potential through analysing the cardiac mitochondrial function in permeabilised cardiac muscle fibres after 4 months of incubation at different temperatures (Polar cod: 0, 3, 6, 8 °C and Atlantic cod: 3, 8, 12, 16 °C), combined with exposure to present (400μatm) and year 2100 (1170μatm) levels of CO2.OXPHOS, proton leak and ATP production efficiency in Polar cod were similar in the groups acclimated at 400μatm and 1170μatm of CO2, while incubation at 8 °C evoked increased proton leak resulting in decreased ATP production efficiency and decreased Complex IV capacity. In contrast, OXPHOS of Atlantic cod increased with temperature without compromising the ATP production efficiency, whereas the combination of high temperature and high PCO2 depressed OXPHOS and ATP production efficiency.ConclusionsPolar cod mitochondrial efficiency decreased at 8 °C while Atlantic cod mitochondria were more resilient to elevated temperature; however, this resilience was constrained by high PCO2. In line with its lower habitat temperature and higher degree of stenothermy, Polar cod has a lower acclimation potential to warming than Atlantic cod.

DNA barcoding for detecting market substitution in salted cod fillets and battered cod chunks

The Italian Ministry of Agricultural, Food and Forestry Policies (MiPAAF) Decree dated 31 January 2008, which reports the Italian name for fish species of commercial interest, establishes that baccalà can be obtained exclusively from G. macrocephalus (Pacific cod) and G. morhua (Atlantic cod). This paper describes the COI-based DNA identification system to verify the substitution or misbranding of gadoid fish species and, consequently, its concordance with the labels on salted cod fillets shown as baccalà and on battered cod chunks labelled as bocconcini di baccalà. The analysis of interpretable sequences revealed that 55/65 dried salted cod fillet samples were detected as belonging to the family Gadidae, while 10/65 samples appeared to belong to the Lotidae family, while among battered cod chunks labelled as bocconcini di baccalà, the post-sequencing data analysis shows that the labels were completely wrong, with 28/40 samples from Pollachius virens and 12/40 samples from Brosme brosme. The substitution rate for products labelled on the market as baccalà in this study raises significant issues relating to food safety and consumer protection.

Extension of the shelf life of chilled hake (Merluccius merluccius) by a novel icing medium containing natural organic acids

Three combinations of two natural organic acids, citric acid (CA) and lactic acid (LA), in the form of novel flake icing systems were evaluated for the preservation of European hake (Merluccius merluccius), one of the most commercialised gadoid fish species in Europe. The flake icing systems were prepared with fresh water and 0.075%/0.050% (C-75 batch), 0.125%/0.050% (C-125 batch) and 0.175%/0.050% (C-175 batch) CA/LA, respectively. Aerobic mesophiles, psychrotrophs, proteolytic bacteria, anaerobes, Enterobacteriaceae, trimethylamine, lipid hydrolysis, primary, secondary and tertiary lipid oxidation events, and pH levels were evaluated in hake muscle in all batches during 13 d of chilled storage and the results were compared with sensory analyses. Significantly (p < 0.05) lower microbial counts were found in the C-175 batch for all five microbial groups investigated when compared with the control batch, with differences between batches of greater than 2 log CFU/g in the case of aerobes and anaerobes. The presence of organic acids in the icing systems also inhibited (p < 0.05) the increase in trimethylamine-nitrogen (TMA-N) content, with greater inhibition as the CA concentration in the ice increased. An inhibitory effect (p < 0.05) on fluorescent compound formation due to the presence of organic acids in the icing systems, which is indicative of tertiary lipid oxidation, was also observed at advanced storage times. These results correlated well with sensory analysis, which revealed that the shelf lives of the C-125 and C-175 batches were extended. The melting of the ice crystals containing the natural organic acid solutions, especially in the C-175 batch, exerted an antimicrobial washing effect that may explain the better protection of hake quality when stored in the proposed flake icing system.

Distribution of Mercury in a Gadoid Fish Species, Tusk (Brosme brosme), and Its Implication for Food Safety

The tusk (Brosme brosme) is a popular gadoid fish for human consumption, which also is susceptible to mercury accumulation. However, few data of mercury levels in tusk exist, and it is difficult to compare tusk fished from assumed contaminated areas with background levels. The aim of this study was to increase the information of mercury levels observed in tusk from the Northeast Atlantic Ocean. Samples of tusk were collected from seven different localities in open ocean areas, nine along the Norwegian coastal current (NCC), and from two fjord stations. Determinations of mercury in muscle and liver were carried out using inductive coupled plasma mass spectrometry (ICPMS) after microwave-assisted wet digestion. The highest concentrations of mercury in muscle were found in tusk captured from the fjords Hardangerfjord and Sorfjord, and had mean concentrations of mercury at 1.5 and 1.7 mg kg -1 wet weight (ww), respectively, where all of the tusk exceeded EU's upper limit of 0.5 mg kg -1 ww. The lowest concentrations of mercury were observed in tusk captured from the open ocean areas, and the concentrations ranged from 0.08 to 0.30 mg kg -1 ww. Mercury concentrations of tusk captured along the NCC ranged from 0.21 to 0.49 mg kg -1 ww. Mercury concentrations increased with the weight of the tusk, and variance analysis (ANOVA) of weight normalized mercury concentrations showed that there were significant differences in mercury concentrations between tusk collected from the open ocean, NCC and fjords, which indicates that differences in mercury concentration between different areas arecaused by other factors.

Effects of thermal processing and various chemical substances on formaldehyde and dimethylamine formation in squid Dosidicus gigas

Trimethylamine oxide (TMAO) in squid is demethylated to dimethylamine (DMA) and formaldehyde (FA) during storage and processing. This study examined the effects of thermal processing and various chemical substances on FA and DMA formation in squid. The thermal conversion of TMAO was assessed by analysing four squid and four gadoid fish species, which revealed that FA, DMA and trimethylamine (TMA) were gradually produced in squid, whereas TMA increased and FA decreased in gadoid fish. A significant increase in both FA and DMA levels was observed in the supernatant of jumbo squid with increased heating temperature and extended heating time at pH 6-7. Ferrous chloride combined with cysteine and/or ascorbate had a significantly positive effect on FA formation in the heated supernatant of jumbo squid. No significant difference was observed in the levels of Cu and Fe in squid and gadoid fish. The capability of Fe(2+) to promote the formation of FA and DMA was not completely attributable to its reducing power in squid. Non-enzymatic decomposition of TMAO was a key pathway during the thermal processing of jumbo squid, and Fe(2+) was a crucial activator in the formation of FA and DMA.

The use of stable isotopes for authentication of gadoid fish species

The rise of processed seafood in international trade has increased the feasibility of fish species substitution. Gadidae fish species are sold commercially as salted fish, and differences in price between fish of different species may lead to falsification. The present study addresses this falsification issue by attempting to discriminate among salted Atlantic cod and salted saithe using isotope ratio mass spectrometry (IRMS) as well as the stable isotope ratios of carbon (δ13C) and nitrogen (δ15N). δ15N in tissues with lower turnover rates (bone and skin) and in tissues with greater turnover rates (muscle) can be used to authenticate the species of salted fish samples when distinguishing between Atlantic cod and saithe.

13C NMR as a tool for authentication of different gadoid fish species with emphasis on phospholipid profiles

The aim of this study was to evaluate if phospholipid profiles obtained by 13C nuclear magnetic resonance (NMR) spectroscopy is characteristic enough to separate species of lean gadoid fish. 13C NMR data were obtained from muscle lipids of five categories of lean gadoid fish, namely, north-east arctic cod and Norwegian coastal cod ( Gadus morhua), haddock ( Melanogrammus aeglifinus), saithe ( Pollachius virens), and pollack ( P. pollachius). A total of 27 fish caught at the same location on the Norwegian coast in the traditional fishing season (March/April) in 2006 were analysed. The sn-2 position specificity of 22:6n-3 (docosahexaenoic acid, DHA) in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) for the different species/stocks were investigated, and the full 13C NMR spectra applied in multivariate analysis. Stereospecific distribution calculations showed significant differences among species in the distribution of 22:6n-3 in PC and PE, and the pollack group displayed the lowest values for 22:6n-3 in sn-2 position, both in PC and PE. This first screening showed that by using the 13C NMR fingerprint of muscle lipids, linear discriminant analysis gave a correct classification rate of 78% according to the five categories of lean gadoid fish, while successful classification (100%) was achieved with Bayesian belief networks (BBN) predictions.

A simple molecular approach to distinguish between two Arctic gadoid fishes Arctogadus glacialis (Peters, 1874) and Boreogadus saida (Lepechin, 1774)

Correct phenotypical identification of and discrimination between Boreogadus saida and Arctogadus glacialis is challenging, especially for larvae and young fish. We propose the use of a single microsatellite genetic marker, Gmo8, to distinguish between the two gadoid fish species. Amplified allele frequencies differed considerably, with B. saida (n = 97) being almost exclusively monomorphic at this locus, whereas A. glacialis (n = 136) is highly polymorphic. There was a clear separation between the amplified allele ranges for the two species. The species specific properties of Gmo8 enables the use of this marker to distinguish between B. saida and A. glacialis.

Identification of Gadoid Species in Fish Meat by Polymerase Chain Reaction (PCR) on Genomic DNA

Identification of fish species is significant due to the increasing interest of consumers in the meat of sea fish. Methods focusing on fish species identification help to reveal fraudulent substitution among economically important gadoid species in commercial seafood products. The objective of this work was to develop a conventional PCR method for the differentiation of the following gadoid fish species in fish products: Alaska pollack ( Theragra chalcogramma), blue whiting ( Micromesistius poutassou), hake spp. ( Merluccius spp.), Atlantic cod ( Gadus morhua), saithe ( Pollachius virens), and whiting ( Merlangius merlangus). The species-specific primer pairs for gadoid species determination were based on the partial pantophysin I ( PanI) genomic sequence. Sequence identification was confirmed by cloning and sequencing of the PCR products obtained from the species considered. For the simultaneous detection of Alaska pollack, blue whiting, and hake spp., a quadruplex PCR system was constructed. Other gadoid species were detected in separate PCR reactions. After optimization of the reactions, the developed PCR systems were used for the analysis of codfish samples obtained from the Czech market and the customs' laboratories. This method represents an alternative approach in the use of genomic DNA for the identification of fish species. This method is rapid, simple, and reliable without the need for further confirmative methods. Furthermore, the identification of a mixture of more than one species is possible. The PCR system has been optimized for routine diagnostic purposes.

Methods of gadoid fish species identification in food and their economic impact in the Czech Republic: a review

The purpose of the present study was to give an overview of imported and traded gadoid fish species (&lt;i&gt;Gadiformes&lt;/i&gt;) in the Czech Republic and to describe available methods for their authentication. Due to the increasing interest of customers in the purchase of buy fish meat and other seafood animals, it is necessary to have available analytical methods with discriminating power of respective fish species. With regard to different values and prices of various fish species, these may be adultered. Until recently, electrophoretic, chromatographic and immunological methods based on the analysis of proteins extracted from fish musculature seemed to be promising. Using these methods, various fish species can be identified in fresh, chilled and frozen products. However, they often fail in heat treated products. Molecular biology methods based on DNA analysis are more reliable and suitable for the analysis of fish products that have been heat treated during the production process.

Comparison of the biophysical and trophic characteristics of the Bering and Barents Seas

Abstract The eastern Bering Sea and the Barents Sea share a number of common biophysical characteristics. For example, both are seasonally ice-covered, high-latitude, shelf seas, dependent on advection for heat and for replenishment of nutrients on their shelves, and with ecosystems dominated by a single species of gadoid fish. At the same time, they differ in important respects. In the Barents Sea, advection of Atlantic Water is important for zooplankton vital to the Barents Sea productivity. Advection of zooplankton is not as important for the ecosystems of the southeastern Bering Sea, where high levels of diatom production can support production of small, neritic zooplankton. In the Barents Sea, cod are the dominant gadoid, and juvenile and older fish depend on capelin and other forage fish to repackage the energy available in copepods. In contrast, the dominant fish in the eastern Bering Sea is the walleye pollock, juveniles and adults of which consume zooplankton directly. The southeastern Bering Sea supports considerably larger fish stocks than the Barents. In part, this may reflect the greater depth of much of the Barents Sea compared with the shallow shelf of the southeastern Bering. However, walleye pollock is estimated to occupy a trophic level of 3.3 as compared to 4.3 for Barents Sea cod. This difference alone could have a major impact on the abilities of these seas to support a large biomass of gadoids. In both seas, climate-forced variability in advection and sea-ice cover can potentially have major effects on the productivity of these Subarctic seas. In the Bering Sea, the size and location of pools of cold bottom waters on the shelf may influence the likelihood of predation of juvenile pollock.

Enhanced shelf-life of chilled European hake ( Merluccius merluccius) stored in slurry ice as determined by sensory analysis and assessment of microbiological activity

Slurry ice, a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature, was evaluated as a new chilled storage method for whole European hake ( Merluccius merluccius), a gadoid fish species of remarkable commercial interest, and this method was compared with a control batch stored for 19 days in traditional flake ice. The results obtained in the sensory analysis indicated a significant extension of shelf-life – from 5 days (flake ice batch) to 12 days (slurry ice batch) – in the latter batch, mainly deriving from a better maintenance of both external and fresh odour, the appearance of the gills and consistency. The slurry ice batch exhibited a significantly lower increase in pH as compared to the flake ice batch, this indicating a better control of the former over alkalinising microflora. Thus, significantly lower counts of total aerobes and proteolytic bacteria were also attained in hake muscle stored in slurry ice, microbial numbers reaching average differences of ≈1 log unit before 12 days of storage and above 2 or 3 log units, respectively, when this period was extended up to 19 days. The formation of total volatile base-nitrogen and trimethylamine were also significantly lower in the slurry ice batch after 12 days of storage. According to the parameters assessed, storage of European hake in slurry ice extends the shelf-life of this species and allows a better maintenance of sensory and microbiological quality.

Quantifying and handling errors in instrumental measurements using the measurement error theory

AbstractMeasurement error modelling is used for investigating the influence of measurement/sampling error on univariate predictions of water content and water‐holding capacity (reference measurement) from nuclear magnetic resonance (NMR) relaxations (instrumental) measured on two gadoid fish species. This is a new way of using the measurement error theory. Reliability ratios illustrate that the models for the two fish species are influenced differently by the error. However, the error seems to influence the predictions of the two reference measures in the same way. The effect of using replicated x‐measurements is illustrated by simulated data and by NMR relaxations measured several times on each fish. The standard error of the physical determination of the reference values is lower than the standard error of the NMR measurements. In this case, lower prediction error is obtained by replicating the instrumental measurements. A new general formula is given for how to correct the least squares regression coefficient when a different number of replicated x‐measurements is used for prediction than for calibration. It is shown that the correction should be applied when the number of replicates in prediction is less than the number in calibration. This can be relevant for on‐line applications and in other situations where it is important to make fast measurements in the prediction phase. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Identification of gadoid fish species using DNA-based techniques

The polymerase chain reaction (PCR) technique was employed to obtain a 464 bp amplicon from the mitochondrial cytochrome b gene from gadoid species to study its ability to differentiate them. The sequences of this fragment from 16 species were analysed using a genetic distance method, and polymorphic sites were determined. The fragment was shown to be moderately polymorphic (151 sites), and this permitted the differentiation of most of the species. A phylogenetic tree construction using Tamura-Nei distances was employed to allow the identification of Gadidae species, each species resulted in a well-differentiated clade, with the exception of Gadus ogac and Gadus macrocephalus, which could not be differentiated. Based on the sequences obtained, three restriction enzymes, Dde I, Hinc II and Nla III, were selected to provide specific restriction profiles, which allowed the differentiation of 15 species of gadoids in a faster and less expensive way than sequencing. The PCR-restriction fragment length polymorphism methodology was also tested using commercial samples.

Effect of dietary lipid level on fatty acid β-oxidation and lipid composition in various tissues of haddock, Melanogrammus aeglefinus L.

Haddock ( Melanogrammus aeglefinus) is a gadoid fish species that deposits dietary lipid mainly in the liver. The fatty acid (FA) β-oxidation activity of various tissues was evaluated in juvenile haddock fed graded levels of lipid. The catabolism of a radiolabelled FA, [1- 14C]palmitoyl-CoA, through peroxisomal and mitochondrial β-oxidation was determined in the liver, red and white muscle of juvenile haddock fed 12, 18 and 24% lipid in the diet. There was no significant increase in the mitochondrial or peroxisomal β-oxidation activity in the tissues tested as the dietary lipid level increased from 12 to 24%. Peroxisomes accounted for 100% of the β-oxidation observed in the liver, whereas mitochondrial β-oxidation dominated in the red (91%) and white muscle (97%) of juvenile haddock. Of the tissues tested, red muscle possessed the highest specific activity for β-oxidation expressed on a per mg protein or per g wet weight basis. However, white muscle, which forms over 50% of the body mass in gadoid fish was the most important tissue in juvenile haddock for overall FA catabolism. The total lipid and FA composition of these tissues were also determined. This study confirmed that the liver was the major lipid storage organ in haddock. The hepatosomatic index (HSI; 10.0–15.2%) and lipid (73.8–79.3% wet wt.) in the liver increased significantly as dietary lipid was increased from 12 to 24% lipid. There was no significant increase in the lipid composition of the white muscle (0.8% wet wt.), red muscle (1.9% wet wt.) or heart (2.5% wet wt.).

Levels of polybrominated diphenyl ether (PBDE) flame retardants in animals representing different trophic levels of the North Sea food Web.

The levels of individual PBDE congeners were investigated in the invertebrate species whelk (Buccinum undatum), seastar (Asterias rubens), and hermit crab (Pagurus bernhardus), the gadoid fish species whiting (Merlangius merlangus) and cod (Gadus morhua), and the marine mammal species harbor seal (Phoca vitulina) and harbor porpoise (Phocoena phocoena). These species are all important representatives of different trophic levels of the North Sea food web. All six major PBDE congeners detected (BDEs 28, 47, 99, 100, 153, and 154) are most prevalent in the commercial Penta-BDE formulation. There is no evidence for the occurrence of the Octa-BDE formulation in the North Sea food web, since its dominant congener, BDE183, was never detected. BDE209, the main congener (> 97%) in the Deca-BDE formulation, was detected only in a minority of the samples and always in concentrations around the limit of detection. Since BDE209 is often the major BDE congener in sediments from the area, the main reason for its low concentrations in biota from the North Sea seems to be a relatively low bioaccumulation potential. This can either be due to a low uptake rate of the very large molecule or a relatively rapid excretion after biotransformation. Since all invertebrates investigated are sentinel species, they are highly representative for the area of capture. The highest lipid-normalized concentrations of PBDEs in the invertebrates occurred near the mouth of the river Tees at the East coast of the UK. The geographical distribution of the PBDEs can be explained by the residual currents in the area. The direction of these currents differs between the summer and the winter season as a result of the presence or absence of vertical summer stratification of the deeper waters north of the Dogger Bank. Summer stratification results in the development of a density-driven bottom water current formed after the onset of vertical stratification of the water column in May leaving the UK coast near Flamborough Head toward the Dogger Bank. In winter, the residual currents run in a more southerly direction and follow the UK coastline. The distribution pattern of the PCBs and p,p'-DDE in the invertebrates was entirely different from that of the PBDEs, which could be expected, since the use of these organochlorines in western Europe peaked in the 1960s and 1970s but has been forbidden more than two decades ago, whereas the production and use of the penta-BDE formulation is of a more recent origin. The higher trophic levels of the North Sea food web were represented by the predatory gadoid fish species whiting and cod and the marine mammal species harbor seal and harbor porpoise. The lipid-normalized levels of the six major PBDE congeners in fish were similar to the levels in the invertebrates, but a biomagnification step in concentrations of generally more than an order of magnitude occurred from gadoid fish to marine mammals. Based on the limited number of samples, no differences could be observed between harbor seal and harbor porpoise. In summary, the results in three species of sentinel invertebrates from a network of stations covering a major part of the North Sea basin showed that the estuary of the river Tees at the UK East coast is a major source for tri- to hexa-PBDEs. Throughout the food-chain, the most marked increase in (lipid-normalized) levels of all six PBDE congeners occurred from predatory (gadoid) fish to marine mammals, agreeing with the transition from gill-breathing to lung-breathing animals. This has serious consequences for the route of elimination of POPs, since their elimination from the blood into the ambient seawater via the gill-membrane is no longer possible.