Tissues Of Bream Research Articles

Quantitative titanium imaging in fish tissues exposed to titanium dioxide nanoparticles by laser ablation-inductively coupled plasma-mass spectrometry

Imaging studies by laser ablation–inductively coupled plasma mass spectrometry have been successfully developed to obtain qualitative and quantitative information on the presence/distribution of titanium (ionic titanium and/or titanium dioxide nanoparticles) in sea bream tissues (kidney, liver, and muscle) after exposure assays with 45-nm citrate-coated titanium dioxide nanoparticles. Laboratory-produced gelatine standards containing ionic titanium were used as a calibration strategy for obtaining laser ablation–based images using quantitative (titanium concentrations) data. The best calibration strategy consisted of using gelatine-based titanium standards (from 0.1 to 2.0 μg g−1) by placing 5.0-μL drops of the liquid gelatine standards onto microscope glass sample holders. After air drying at room temperature good homogeneity of the placed drops was obtained, which led to good repeatability of measurements (calibration slope of 4.21 × 104 ± 0.39 × 104, n = 3) and good linearity (coefficient of determination higher than 0.990). Under the optimised conditions, a limit of detection of 0.087 μg g−1 titanium was assessed. This strategy allowed to locate prominent areas of titanium in the tissues as well as to quantify the bioaccumulated titanium and a better understanding of titanium dioxide nanoparticle spatial distribution in sea bream tissues.Graphical abstract

Equilibrium sampling of suspended particulate matter as a universal proxy for fish and mussel monitoring

Bioaccumulation of persistent and hydrophobic organic compounds in the aquatic environment puts secondary consumers, such as fish, at risk. To assess their exposure, monitoring programs with high numbers of individuals have been conducted worldwide over decades that require major efforts and raise ethical issues. This study aimed at testing suspended particulate matter (SPM) as an alternative and accessible abiotic matrix to estimate the internal exposure concentrations of such chemicals in fish and mussels. Muscle tissues of bream (Abramis brama), tissues of zebra mussels (Dreissena polymorpha) and SPM were collected from four major German rivers, Elbe, Danube, Saar and Saale, in 2018 within the national monitoring program of the German Environmental Specimen Bank. We used (i) total solvent extraction for biota samples to quantify the lipid-normalized concentrations of polychlorinated biphenyls, polycyclic aromatic hydrocarbons and hexachlorobenzene and (ii) passive equilibrium sampling of SPM to derive equilibrium partitioning concentrations in lipids and (iii) set these independent data sets into context. Since the ratio of lipid-normalized concentration / equilibrium partitioning concentration in lipids was in most cases < 1.0, SPM may serve as a conservative proxy for the internal concentration of bream and mussels, although bream of high age (i.e., older than 10 years) showed a tendency for this ratio to exceed 1.0. This observation indicates that age-dependent biomagnification can exceed the predictions based on thermodynamic equilibrium relative to SPM.

Fatty acid composition and lipid quality indices of bream Abramis brama (Linnaeus, 1758) of Lake Kotokel (Western Transbaikalia)

This paper describes the study of fatty acid (FA) composition and lipid quality indices of bream Abramis brama (Linnaeus, 1758) from Lake Kotokel (Western Transbaikalia). In the muscle tissues of bream sampled in 2009 and 2019, high levels of polyunsaturated fatty acids (PUFA), including essential docosahexaenoic (DHA), eicosapentaenoic (EPA), and arachidonic acids were measured. Indicators of nutritional quality based on the fatty acid composition showed that the values of the hypocholesterolemic/hypercholesterolemic (HH) ratio indices were sufficiently high. The atherogenicity (AI) and thrombogenicity (TI) indices, which are indicators for the nutritional value, were less than 1 in the studied fish. In terms of flesh-lipid quality (FLQ), bream had the highest proportion of total EPA + DHA. According to the obtained data for the composition of fatty acids in the muscle tissue of the studied fish from Lake Kotokel, the anthropogenic load on Lake Kotokel has not yet had a statistically significant effect on the fish muscle quality.

Impact of habitation conditions on metabolism in the muscles, liver, and gonads of different sex and age groups of bream

Impact of the factors of the aquatic environment is an inevitable aspect of the life of fish as poikilothermic animals and provokes responses in their organisms. The study focused on determining peculiarities in the composition of the metabolic products in the tissues of different age and sex groups of common bream Abramis brama (L.) depending on the living conditions in the water reservoirs of the Upper Volga. The fish were captured in the fattening period in summer and autumn, measured, weighed, identifying sex, maturity stage of the gonads and age. In the muscles, liver and gonads of bream, we analyzed the contents of water, dry matter, lipids, protein, ash and carbohydrates using the standard techniques. The contents of biochemical components in the organism of bream were to a higher degree determined by the peculiarities of the living conditions rather than sex and age of the individuals. In the muscles and liver of bream living in the conditions of increased water temperature and low concentration of oxygen, the concentrations of protein and ash were lower. In the same tissues of bream from the water bodies with high concentrations of pollutants in the water and benthic deposits, we found increased fat content. The muscles of male bream contained less protein and more carbohydrates than females and juvenile individuals, and the muscles of juveniles had less fat. The environmental factors had greater influence on the content of the metabolic products in the liver of bream than sex, and only females had higher ash content than males. The testes had more fat and less protein than the ovaries. During the transition of the gonads from maturity stage II to III, the contents of dry matter and lipids in them decreased. We determined that the environmental factors have stronger impact on biochemical parameters in the tissues of bream than age, because we found no general age patterns in the dynamics of biochemical components, except the liver, in which the highest content of organic compounds was found in individuals aged 6 to 10 years. Water heated by the Hydro Power Plant positively influenced the young bream, as indicated by higher content of metabolic products in individuals aged 5+ than older groups and bream from the surveyed water bodies. Monitoring of the physiological condition of bream focusing on the contents of metabolic products in the tissues may provide necessary data for successful regulation of bream populations in the water reservoirs of the Upper Volga.

Determination of Pharmaceuticals, Heavy Metals, and Oxysterols in Fish Muscle.

The present study aimed to assess the levels of 98 multi-class pharmaceuticals including cardiovascular drugs, antidepressants, hypnotics, antibiotics, and sulfonamides occurring in the muscle tissue of fish caught in the Baltic Sea. The following fish species were collected: perch (Perca fluviatilis); flounder (Platichthys flesus); turbot (Scophthalmus maximus); plaice (Pleuronectes platessa); cod (Gadus morhua callarias); bream (Abramis brama); crucian (Carassius carassius). Additionally, in the examined fish muscle the levels of heavy metals and trace elements were determined (As; Ag; Au; Ba; Cd; Co; Cr; Cu; Hg; Li; Mo; Ni; Pb; Sb; Se; Sn; Tl; V) as well as the levels of cholesterol and its 5 derivatives (7-ketocholesterol; 7α-hydroxycholesterol; 7β-hydroxycholesterol; 5β,6β-epoxy-cholesterol; 5α,6α-epoxycholesterol). In the performed studies 11 out of 98 examined pharmaceuticals were detected in fish muscle. The levels of pharmaceuticals in fish muscle varied depending on the species. In the tissues of bream and crucian, no pharmaceuticals were found. Mercury, lead and arsenic were detected in the muscles of all examined fish. Based on the hazard factor for Hg, Pb, Cd, Ni (target hazard quotient, THQ < 1), it was found that the consumption of the studied fish does not constitute a health risk. However, the THQ for As remained >1 indicated possible risk from those metals. In the examined fish muscle the total cholesterol oxidation products (COPs) level of oxysterols were, respectively: 6.90 (cod) μg/g–4.18 μg/g (perch), which corresponded to 0.7–1.5% of cholesterol. The main COPs evaluated were 7-ketocholesterol (0.78 ± 0.14–1.79 ± 0.06 μg/g), 7β-hydroxycholesterol (0.50 ± 0.04–3.20 ± 2.95 μg/g) and 5β,6β-epoxycholesterol (0.66 ± 0.03–1.53 ± 0.66 μg/g). The assessment of health hazards due to contaminations is necessary, which may help to introduce national legislation and global standards aimed at reducing or even eliminating the exposure to contaminants.

Depletion of praziquantel from gilthead sea bream (Sparus aurata) muscle plus skin

The depletion pattern of praziquantel (PZQ) from gilthead sea bream (Sparus aurata) muscle plus skin was determined in this study. Fish averaging 100.2 ± 17.7 g and kept at 25oC received a PZQ-dosing of 150 mg/kg fish for 3 days. Muscle plus skin of each of ten fish were collected on days 1, 2, 3, 4, and 6 days post-treatment. Depletion of PZQ from the edible gilthead sea bream tissues was rapid, as its concentrations declined to 0.04 μg/g as early as 24 h post-treatment, while was undetectable at 72 h. This information confirms the fact that PZQ is depleted fast from farmed animals including fish such as the gilthead sea bream and its levels in edible tissues failed below the detection limit in approximately 75 dd.

Технология рыбных биокрипсов на основе термомодифицированных тканей балтийского леща

A technology of snack molded product based on minced meat and bone of small Baltic bream is developed. Bream tissues without entrails and head were pre-modified at a temperature of more than 100°C and ncreased pressure. Fine bone meal was added into the composition of the minced products. Fish dough was rolled thinly, molded and brought to readiness by hot drying. Ready biocrips have a pleasant organoleptic properties. The chemical composition, energy and biological value of finished products are substantiated. The functionality of biocrips in terms of calcium and phosphorus content is shown. The technology allows efficient use of the underlying tissues of bream. The products are recommended for the prevention of musculoskeletal diseases, in the diet of athletes and people sticked to an active lifestyle.

Justification of the recipe and technology for dried fish-vegetable snacks based on thermomodified Baltic bream tissues

Justification of the recipe and technology for dried fish-vegetable snacks based on thermomodified Baltic bream tissues

Complement factor D homolog involved in the alternative complement pathway of rock bream (Oplegnathus fasciatus): Molecular and functional characterization and immune responsive mRNA expression analysis.

The complement system serves conventional role in the innate defense against common invading pathogens. Complement factor D (CfD) is vital to alternative complement pathway activation in cleaving complement factor B. This catalytic reaction forms the alternative C3 convertase that is crucial for complement-mediated pathogenesis. In this study, rock bream (Oplegnathus fasciatus) CfD (OfCfD) was characterized and OfCfD mRNA expression was investigated. OfCfD encodes 277amino acids (aa) for a 30-kDa polypeptide. A domain analysis of the deduced OfCfD aa sequence showed a single serine protease trypsin superfamily domain, a serine active region, three active sites, and three substrate-binding sites. Pairwise sequence comparisons indicated that OfCfD has the highest identity (84.5%) with Oreochromis niloticus CfD. The phylogenetic tree revealed a common ancestral origin of CfD members, with fish CfD distinct from other vertebrate orthologs. The structural arrangement of the OfCfD gene (2451bp) contained five exons interrupted by four introns. A spatial transcriptional analysis indicated that OfCfD transcripts constitutively expressed in all of the examined rock bream tissues, and that they were highest in the spleen and liver. In addition, OfCfD transcripts were immunologically upregulated by lipopolysaccharide (LPS) (12h p.i.), Streptococcus iniae (12h p.i.), rock bream iridovirus (RBIV) (6-12h p.i.), and poly I:C (6h p.i.) in spleen tissue. OfCfD is a trypsin protease and its recombinant protein showed strong protease activity similar to that of trypsin, indicating its catalytic function in the alternative pathway. Together, our findings suggest that OfCfD might be involved in immune responses in rock bream.

Persistent organic pollutants in muscle of fish collected from the Nové Mlýny reservoir in Southern Moravia, Czech Republic.

The aim of the present study was to investigate the content of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in muscle tissues of fish, i.e. carp (Cyprinus carpio, L.), bream (Abramis brama, L.) and pike perch (Stizostedion lucioperca, L.) from the middle Nové Mlýny reservoir and compare our results with previous corresponding studies. Samples were analysed by gas chromatography with ion trap tandem mass spectrometry. The highest contents of all pollutants were determined in muscle tissue of bream. The analysis of HCHs showed that β-HCH was the most abundant. PCB congener 28 was evaluated as the predominant PCB congener. The metabolite p,p’-DDE exhibited the highest concentration of all the monitored metabolites. The monitoring confirmed significantly (P < 0.01) higher concentrations of OCP and PCB in muscle of bream compared to carp and pike perch. The contents of pollutants in our study were found to be lower in comparison to the findings of some previous studies.

A manganese superoxide dismutase with potent antioxidant activity identified from Oplegnathus fasciatus: Genomic structure and transcriptional characterization

In this study, we describe the identification and characterization of manganese superoxide dismutase, an important antioxidant enzyme acting as the chief reactive oxygen species (ROS) scavenger, from rock bream Oplegnathus fasciatus (Of-mMnSOD) at genomic- and transcriptional-levels as well as the biological activity of recombinant protein. The Of-mMnSOD protein portrayed distinct MnSOD family features including signature motifs, metal association sites and the typical active site topology. It was also predicted to be localized in mitochondrial matrix. The Of-mMnSOD had a quinquepartite genome organization encompassing five exons interrupted by four introns. Comparison of its sequence and gene structure with that of other lineages emphasized its strong conservation among different vertebrates. The Of-mMnSOD was ubiquitously transcribed in different rock bream tissues with higher levels in blood cells and metabolically active tissues. Transcription of Of-mMnSOD was kinetically modulated in response to investigational challenges using mitogens (lipopolysaccharide and poly I:C) and live-pathogens (Edwardsiella tarda and rock bream irido virus) in blood cells and liver tissue. The purified recombinant Of-mMnSOD possessed potential antioxidant capacity and actively survived over a range of pH (7.5–11) and temperature (15–40 °C) conditions. Collectively, findings of this study suggest that Of-mMnSOD combats against oxidative stress and cellular damages induced by mitogen/pathogen-mediated inflammation, by detoxifying harmful ROS (O2●−) in rock bream.

Structure, tissue distribution and estrogen regulation of splice variants of the sea bream estrogen receptor α gene

Estrogen actions are mainly mediated by specific nuclear estrogen receptors (ERs), for which different genes and a diversity of transcript variants have been identified, mainly in mammals. In this study, we investigated the presence of ER splice variants in the teleost fish gilthead sea bream (Sparus auratus), by comparison with the genomic organization of the related species Takifugu rubripes. Two exon2-deleted ERα transcript variants were isolated from liver cDNA of estradiol-treated fish. The ΔE2 variant lacks ERα exon 2, generating a premature termination codon and a putative C-terminal truncated receptor, while the ΔE2,3* variant contains an in-frame deletion of exon 2 and part of exon 3 and codes for a putative ERα protein variant lacking most of the DNA-binding domain. Both variants were expressed at very low levels in several female and male sea bream tissues, and their expression was highly inducible in liver by estradiol-17β treatment with a strong positive correlation with the typical wild-type (wt) ERα response in this tissue. These findings identify novel estrogen responsive splice variants of fish ERα, and provide the basis for future studies to investigate possible modulation of wt-ER actions by splice variants.

HIF-1α and -2α genes in a hypoxia-sensitive teleost species Megalobrama amblycephala: cDNA cloning, expression and different responses to hypoxia

Transcriptional responses to hypoxia are primarily mediated by hypoxia-inducible factor (HIF) alpha subunits, i.e. HIF-1alpha, -2alpha and -3alpha. In fish, the molecular constructions, expression characteristics and hypoxic regulation of HIF-alpha subunits are still not well known. In this study, we identified the HIF-1alpha and HIF-2alpha full-length cDNAs in a hypoxia-sensitive fish species Wuchang bream, Megalobrama amblycephala. The whole length of HIF-1alpha cDNA was 3,815bp, consisting of an open reading frame (ORF) encoding 774 amino acid (aa) residues. The HIF-2alpha cDNA totaled 3,121-bp including an 835-aa ORF. The Wuchang bream HIF-1alpha and HIF-2alpha subunits were structurally similar in the DNA-binding and dimerization domains, but differed in the transactivation domain. In adult fish, both HIF-1alpha and HIF-2alpha mRNAs were detected in different tissues under normoxic conditions. HIF-1alpha mRNA was highly expressed in the liver, gill and testis, whereas HIF-2alpha mRNA was abundantly expressed in most of the Wuchang bream tissues. Both HIF-1alpha and HIF-2alpha mRNAs were detected in all stages of embryogenesis and expressed in a ubiquitous pattern. In contrast to HIF-1alpha, the mRNA levels of HIF-2alpha fluctuated in different stages, with higher expression in the zygote, 8-, 28-, 48- and 52-hr post fertilization (hpf) embryos. During hypoxic treatment, the mRNA levels of HIF-2alpha were significantly (p<0.01) up-regulated to 910% in the liver and 320% in the kidney, whereas no significant changes of HIF-1alpha mRNA were observed in the corresponding tissues. These results suggest that the Wuchang bream HIF-1alpha and -2alpha would be involved in different physiological functions under normoxia and hypoxia situations.

Seasonal Trends and Tissue Distribution of Organochlorine Pollutants in Wild and Farmed Gilthead Sea Bream (Sparus aurata) from the Western Mediterranean Sea and Their Relationship with Environmental and Biological Factors

Seasonal trends and tissue distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in gilthead sea bream (Sparus aurata) samples from the Western Mediterranean were investigated. Hexane extracts of white and red muscle, liver, and gills from wild and cultured specimens were purified by normal-phase high-performance liquid chromatography, and selected OCPs and PCBs were determined by gas chromatography coupled to mass spectrometry as indicators of contamination. The limits of detection for the analytical methodology allowed was 0.25 ng/g. Data obtained showed the presence of DDTs and PCBs in the different tissues, with the highest concentration of pollutants being in tissues of higher lipid content. Concentrations of organochlorine compounds in sea bream tissues strongly correlated with seasonal changes and the biological cycle of the species. In general, cultured fish had lower concentrations of contaminants and smaller season variability than wild fish. Trace levels of contaminants were found in fish muscle throughout the year, but always below the guidelines recommended for human consumption.

Stable isotope determination in wild and farmed gilthead sea bream ( Sparus aurata) tissues from the western Mediterranean

Stable isotopes of carbon and nitrogen ( δ 13C and δ 15N) have been determined in wild and farmed gilthead sea bream ( Sparus aurata) samples of white and red muscle, liver, gills and gonads. First, δ 13C and δ 15N values were determined in samples with and without lipid removal to check the possible effect of lipid content on the stable isotope values of the different tissues studied. Differences were found for δ 13C in all tissues studied apart from white muscle of wild fish, the tissue with the lowest lipid content. For δ 15N values no differences were found in wild fish tissues. Liver from farmed fish showed lower δ 15N value after lipid removing. Further conclusions were based on results obtained from lipid-free samples. δ 13C of cultured fish tissues showed a mean depletion of 2.9 ± 0.4‰ compared to wild specimens, suggesting different sources of carbon in the diet, probably due to the feed used during sea-cage culture. Cultured gilthead sea bream tissues were significantly more enriched in nitrogen than wild specimens by an average of 1.5 ± 0.2‰ in white muscle, indicating a slight increase in the trophic level. Determination of stable isotope signatures of gilthead sea bream tissues allows clear discrimination between wild and cultured sea bream, and characterisation of differences in diet and feeding conditions in any tissue studied.

Distribution of peptidase activity in teleost and rat tissues

Peptides play important roles in cell regulation and signaling in many tissues. The actions of peptides are regulated by peptidases. Although the activity of these enzymes has been thoroughly characterized in mammals, little is known about their presence or function in fish. In the present study, we compared the activity of several peptidases in selected tissues (pituitary gland, different brain areas, kidney and gills) of the gilthead sea bream and rainbow trout with that found in similar rat tissues (lungs studied in place of gills). Soluble puromycin-sensitive aminopeptidase showed the highest values in the pituitary gland of the sea bream, whereas the membrane-bound form was found to be more active in the trout kidney. Very high levels of activity of aminopeptidase N were detected in trout and sea bream plasma. In contrast, the highest levels of activity of aminopeptidase B were found in rat tissues, with the exception of the gills of the trout. Aminopeptidase N levels tended to be higher in sea bream tissues with respect to those of trout. In contrast, the level of activity of aminopeptidase B was found to be consistently much higher in trout tissues than in those of the sea bream. Prolyl endopeptidase activity was principally detected in the pituitary gland and in the brain areas of teleosts. These differences between species could be related to different mechanisms of osmoregulation in saltwater- and in freshwater-adapted fish.

Molecular characterisation of sea bream (Sparus aurata) transforming growth factor β1

A transforming growth factor β1 (TGF β1) full length cDNA was characterised and sequenced from the head kidney of sea bream (Sparus aurata) previously challenged with a nodavirus. The cloned cDNA of 1778bp contains a predicted open reading frame of 379 amino acids, which includes the mature peptide region of 112 amino acids. The regulating region of the peptide possesses four potential N-linked glycosylation sites (N-X-T/S), as well as an RGD integrin binding site, an RKKR tetrabasic cut site and nine conserved cysteines all characteristic of the TGF β superfamily. Compared to other teleost TGF β1 genes, the sea bream TGF β1 is most closely related to hybrid striped bass (Moronesaxatilis ×M. chrysops) TGF β1 (80% amino acid identity).The genomic organisation of TGF β1 was determined through the generation of contiguous PCR clones. The sea bream TGF β1 gene is approximately 3·6kb in length and consists of five coding regions. Two introns are absent in comparison to the genomic organisation of rainbow trout Oncorhynchus mykiss TGF β1, whilst an additional intron not present in other sequenced TGF β genes, but present in the trout TGF β1 gene, is conserved in sea bream.A reverse transcription polymerase chain reaction (RT-PCR) assay was developed to study TGF β expression in different sea bream tissues. Constitutive TGF β1 expression was detected in the liver, brain, muscle, kidney, heart, gills and spleen of sea bream, as well as in head kidney macrophages and blood leucocytes.

Cloning of the cDNA for the putative calcium-sensing receptor and its tissue distribution in sea bream ( Sparus aurata)

The cDNA for the calcium-sensing receptor (CaSR) gene has been cloned from the marine teleost Sparus aurata, the sea bream. The isolated clones were 3.3 kb long with an open reading frame of 2820 bp, a 5 ′ UTR of 240 bp, and 3 ′ UTR of 248 bp. The gene codes for a mature peptide of 940 amino acids which has three principal domains; the extracellular region is more than half the total protein, there is a seven-transmembrane domain, and there is a short intracellular domain. There is considerable sequence identity, 91%, shared between the CaSR of sea bream and puffer fish but overall similarities with mammalian CaSR peptides vary between 44% for rat and mouse and 48% with human CaSR. Nevertheless, the 18 cysteine residues of the extracellular domain are present in all sequences so far analysed of which 9 form a cysteine-rich region in sea bream similar to mammalian CaSR. The distribution of CaSR in sea bream tissues detected by in situ hybridisation showed gene expression in epithelia associated with ion transport or ion regulation including the hind gut, chloride cells of the gills, operculum, gall bladder, pituitary adenohypophysis, and coronet cells of the saccus vasculosus; this distribution was confirmed by RT-PCR. By in situ hybridisation, CaSR gene expression was also present in olfactory nerves and leucocytes.

Cloning of the cDNA for Sea Bream (Sparus aurata) Parathyroid Hormone-Related Protein

This paper reports cloning of the cDNA for sea bream (Sparus aurata) parathyroid hormone-related protein (PTHrP). The gene codes for a 125-amino acid mature protein with a 35-residue prepeptide. The total gene sequence is 1.8 kb with approximately 75% noncoding. The N-terminus of the protein resembles mammalian and chicken PTHrP peptides with 12 of the first 21 amino acids identical and for which there is homology with mammalian parathyroid hormone. Toward the C-terminus, the nuclear transporter region between residues 79 and 93 in sea bream is 73% homologous to tetrapod PTHrP, and the RNA binding domain, 96–117, is 50% homologous, moreover starting with the conserved lysine and terminating with the lysine/arginine sequence. Sea bream PTHrP differs significantly from mammalian and chicken PTHrP, having a novel 16-amino acid segment between residues 38 and 54 and completely lacking the terminal domain associated in mammals with inhibition of bone matrix lysis. RT-PCR and in situ hybridization of sea bream tissues show that the gene is expressed widely and the results confirm observations of a PTHrP-like factor in sea bream detected with antisera to human PTHrP.

SIMULTANEOUS HPLC DETERMINATION OF SULFADIAZINE AND TRIMETHOPRIM IN CULTURED GILTHEAD SEA BREAM (SPARUS AURATA, L.) TISSUES

An HPLC method is described for the simultaneous determination of sulfadiazine (SDZ) and trimethoprim (TMP) residues in cultured gilthead sea bream tissues (muscle plus skin, liver, gills, fat, and kidney). Tissue samples are extracted with dichloromethane and the analytes are partitioned into hydrochloric acid, to be further analysed isocratically on a Nucleosil 100, C18 reverse-phase column, using a mobile phase of acetonitrile : 10 mM phoshoric acid (16:84, v/v). The UV detection is performed by using a spectrophotometric detector monitored at 271 nm. The limits of detection of SDZ and TMP in the edible part of fish are 3.1 ng/g and 18.2 ng/g at a signal to noise ratio of 3:1. The average recovery for SDZ is 82.1%, in muscle plus skin, and ranges from 77.8% to 87.4 % in the other tissues. The average recovery for TMP is 66.7% in muscle plus skin, and ranges from 71.7% to 83.1 % in the other tissues.