The impact of freshwater metal concentrations on the severity of histopathological changes in fish gills: A statistical perspective.

The purpose of this study was to relate the severity of histopathological changes in fish gills with changes in metal concentrations of freshwater samples, and to use the relationships as premature warnings of impairment in aquatic fauna populations. The investigated species were the native barbel (Luciobarbus bocagei) and boga (Pseudochondrostoma sp.), and the introduced trout (Oncorhynchus mykiss), collected from 6 northern Portuguese rivers in a total of 249 individuals. The sampling sites have been linked to different ecological status by the official authorities. The sampling has been repeated 4 times to cover different hydrologic and environmental conditions. The analyzed metals were aluminum, arsenic, cadmium, cobalt, chromium, copper, manganese, nickel, lead and zinc. For each fish, 30 filaments of a gill arch were observed in a light microscope, and the histopathological changes evaluated according to a 6-degree gradation scale that combines the extent and severity of each lesion. The relationships between the histopathological and the chemical results were investigated by the non-parametric Goodman Kruskal gamma correlation and Partial Least Squares regression (PLS). The statistical results highlighted the importance of filament epithelium proliferation (FEP) as key biomarker to the toxicity of sub lethal concentrations of metals, because FEP was significantly correlated with all analyzed metals and explained through PLS regression by concentration changes of Cu, Zn, Mn, Cr and As. A refined regression analysis, where histopathological data on the 3 species were processed in separate, revealed that FEP severity is especially sensitive to changes in metal concentrations in boga. Thus, monitoring studies on the ecological status of northern Portuguese rivers would benefit in time and cost if FEP is used as biomarker and boga as species. Naturally, the option for this species depends on the availability of boga individuals along the stream reaches selected for the monitoring programs.

From catchment to fish: Impact of anthropogenic pressures on gill histopathology.

Gill histopathology was investigated in barbel (Luciobarbus bocagei) and nase (Pseudochondrostoma sp.) in sub-catchments of Paiva River (Portugal) located upstream and downstream of a Waste Water Treatment Plant (WWTP). Multivariate statistical analyses were performed to set up correlations between the species sample (n=24) and injury types (8). The results discriminate well edema and vasodilatation between reference (upstream) and disturbed (downstream) samples. Using a watershed model, time series of physico-chemical parameters and heavy metal concentrations were calibrated and validated for the entire Paiva River basin as to investigate the relationship between water quality and the gill histopathology results. Increased concentrations of heavy metal downstream, specifically of zinc and lead, coincided with a higher severity of histopathological alterations in the fish gills. Significant but less evident relationship between water quality parameters and severity of gill injuries in the analyzed fish species were also observed for fecal coliforms, water temperature and manganese. Notwithstanding the location of the samples upstream and downstream of the WWTP, contamination of Paiva River and its effect on gill injuries cannot be disconnected from other punctual and diffuse pollution sources acting in different sectors within the watershed, namely agriculture and forest management. The severity of histopathological alterations in the fish gills reflected differences in the type and concentration of contaminants in Paiva River, and consequently can be viewed as valuable indicator of water quality.

Gill histopathological and oxidative stress evaluation in native fish captured in Portuguese northwestern rivers.

The Northwestern Portuguese region is densely populated and highly industrialized, suffering from high anthropogenic pressure. To assess the biological effect of the several pollutants that are constantly released to the water, a biomarker-based biomonitoring is a promising approach that may provide early-warning signals of pollutants exposure. Fish gill is the first target of pollutants action, thus histopathological and biochemical changes may constitute potential biomarkers. To evaluate this hypothesis, three native fish species (barbel-Luciobarbus bocagei, chub-Squalius carolitertii and nase-Pseudochondrostoma sp.) were sampled in Northwestern Portuguese rivers, the gill histopathological changes were qualitative and quantitatively analyzed and the lipid peroxidation and glutathione-S-transferase activity were determined. A multivariate statistical analysis was performed to establish correlations between these biological responses, environmental variables and ecological status. The quantitative evaluation of the main histopathological changes and oxidative stress responses emphasize the differences, among species, in the responses to the presence of contaminants in water. Discriminant canonical analysis showed that filament epithelium proliferation, necrosis and GST activity were the main contributors to discriminate the ecological status classification. In addition, the results showed that a wide range of environmental factors are influencing fish physiology. In conclusion, the gill biological responses, although not reflecting specific contaminants, can be used as biomarkers of ecosystems perturbation.

Effects of exposure to cadmium on some endocrine parameters in tilapia, Oreochromis niloticus.

The cadmium impact on interrenal and thyroid functions was assessed in tilapia, Oreochromis niloticus. Fish were exposed to 25 mg L(-1) of CdCl(2) during 24, 48, and 96 h. Exposure to 24 and 48 h induced a significant increase in plasma cortisol levels, whereas at 96 h no differences were found. A significant and sustained decrease in plasma T3 concentrations, and an over time increase in plasma glucose, was also found in exposed fish. The results of the current study show that acute exposures to sublethal cadmium concentrations induce changes in endocrine status and carbohydrate metabolism in O. niloticus.

Metabolic and osmoregulatory changes and cell proliferation in gilthead sea bream (Sparus aurata) exposed to cadmium.

The impact of cadmium on metabolism and osmoregulation was assessed in gilthead sea bream (Sparus aurata). Seawater acclimated fish were injected intraperitoneally with a sublethal dose of cadmium (1.25 mg Cd/kg body wt). After 7 days, half of the injected fish were sampled. The remaining fish were transferred to hypersaline water and sampled 4 days later. Gill and kidney Na(+)/K(+)-ATPase activities, plasma levels of cortisol, several metabolites and osmolytes, as well as osmolality were measured. Hepatosomatic index and condition factor were calculated. The expression levels of Na(+)/K(+)-ATPase, heat shock proteins (HSP70, HSP90) and proliferating cell nuclear antigen was assessed by western blotting. Cadmium treatment adversely affected the Na(+)/K(+)-ATPase activity, although, there was no perturbation in ion homeostasis and the animals were not compromised following transfer to hypersaline water. Increased cell proliferation and Hsp90 expression likely contributed to the attenuation of the deleterious effects of cadmium exposure.

Disruption of zebrafish (Danio rerio) embryonic development after full life-cycle parental exposure to low levels of ethinylestradiol.

Exposure of fish to the synthetic estrogen ethinylestradiol (EE2) has been shown to induce a large set of deleterious effects. In addition to the negative impact of EE2 in reproductive endpoints, concern has recently increased on the potential effects of EE2 in fish embryonic development. Therefore, the present study aimed at examining the effects of EE2 on the full embryonic development of zebrafish in order to identify the actual phases where EE2 disrupts this process. Hence, zebrafish were exposed to environmentally relevant low levels of EE2, 0.5, 1 and 2ng/L (actual concentrations of 0.19, 0.24 and 1ng/L, respectively) from egg up to eight months of age (F(1)), and the survival as well as the occurrence of abnormalities in their offsprings (F(2)), per stage of embryonic development, was investigated. A thorough evaluation of reproductive endpoints and transcription of vtg1 gene in the parental generation (F(1)) at adulthood, was performed. No significant differences could be observed for the two lowest EE2 treatments, in comparison with controls, whereas vtg1 transcripts were significantly elevated (40-fold) in the 2ng/L EE2 treatment. In contrast to the findings in the F(1) generation,a significant concentration-dependent increase in egg mortality between 8 and 24hours post-fertilization (hpf) was observed for all EE2 treatments, when compared with controls. The screening of egg and embryo development showed a significant increase in the percentage of abnormalities at 8 hpf for the highest EE2 concentration, a fact that might explain the increased embryo mortality at the 24 hpf time-point observation. Taken together, these findings indicate that the two lowest tested EE2 concentations impact late gastrulation and/or early organogenesis, whereas exposure to 2ng/L EE2 also disrupts development in the blastula phase. After early organogenesis has been completed (24 hpf), no further mortality was observed. These results show that increased embryo mortality occurs at EE2 levels below those inducing reproductive impairment and vtg1 gene induction in the male parental generation, thus suggesting that EE2 may impact some fish populations at levels below those inducing an increase in vtg1 transcripts. Hence, these findings have important implications for environmental risk assessment, strongly supporting the inclusion of embryonic development studies in the screening of endocrine disruption in wild fish populations.

Liver histopathology in brown trout (Salmo trutta f. fario) from the Tinhela River, subjected to mine drainage from the abandoned Jales Mine (Portugal).

The objective of this study was to compare the occurrence of toxicopathic liver lesions in brown trout (Salmo trutta fario) from Tinhela River near the Jales Mine, both before implementation (2002) and after completion of the governmental mitigation program (2006). Fish were caught in April 2002 and May 2006, using an electrofishing system at four sites: S0, reference station; S1, S2 and S3 as contaminated stations. In 2002, the hepatosomatic index (HSI) was significantly higher for trout captured at the contaminated sites S2 and S3 than in S0. After the rehabilitation program, the HSI of fish sampled at the contaminated sites did not differ from the reference group. The liver of trout caught at S0 exhibited the normal parenchymal and stromal architecture described for the species and there were no pathological abnormalities. In contrast, fish sampled at S3 and S2 sites had diverse toxicopathic alterations. Specifically, livers from the two contaminated sites showed bile duct hyperplasia, often with mild epithelial dysplasia and fibrotic adventitial sleeve, foci of smaller and more basophilic hepatocytes and foci of hepatocellular necrosis; the latter conditions were frequently associated. Compared with the reference animals, increased hepatocellular vacuolization was found in livers from the polluted sites. Histopathological examination revealed differences among sampling sites in the severity and diversity of hepatic lesions clearly related to the proximity of the tailings. No pathological alterations were observed in the livers of brown trout caught in the same four areas of the Tinhela River after the mitigation program in 2006. In conclusion, our results supported that drainage from the abandoned Jales Mine had deleterious toxicological effects in brown trout. Our data suggested that the governmental mitigation program may have reduced the impact of Jales tailings.

Caracterização da mitocôndria isolada de fígado de tilápia-do-nilo (Oreochromis niloticus) e alterações da bioenergética mitocondrial causadas pela exposição herbicida oxifluorfena / Characterization of liver mitochondria from Nile tilapia (Oreochromis niloticus) and mitochondrial bioenergetics alterations caused by exposure to oxyfluorfen herbicide

Descreve-se um método de isolamento de mitocôndrias acopladas de tilápia-do-nilo Oreochromis niloticus, isoladas de células hepáticas de peixes adultos. As mitocôndrias estavam metabolicamente ativas, sendo capazes de realizarem fosforilação oxidativa, de acordo com os valores do quociente de controle respiratório. Os valores de controle respiratório obtidos com malato/piruvato (complexo I) e com succinato (complexo II) foram de 5,8±0,8 e 3,38±0,4, respectivamente. O potencial de membrana exibiu o valor de 197±4mV, quer se utilizasse malato/piruvato ou succinato como substrato. O procedimento de isolamento de mitocôndrias de O. niloticus permite o estudo do efeito de xenobióticos na bioenergética mitocondrial, tendo sido avaliada a ação da oxifluorfena (0,6mgL-1) na bioenergética mitocondrial. Os resultados demonstram que o tratamento com oxifluorfena influencia a capacidade fosforilativa dos peixes, interferindo na sua carga energética, o que poderá levar à sua morte.

A method for isolation of coupled mitochondria isolated from the liver of adult Nile tilapia Oreochromis niloticus is described for the first time. They were metabolically active, able to sustain oxidative phosphorylation, as shown by respiratory control ratio values, which were about 5.8±0.8 and 3.3±0.4 when respiring on malate/piruvate (complex I) or succinate (complex II), respectively, as substrate. Membrane potential exhibited a value of approximately 197±4mV for malate/piruvate or succinate. The procedure now described for the isolation of O. niloticus mitochondria is an important new tool, allowing the study about the effect of xenobiotics on mitochondrial bioenergetic, being evaluated the effect of oxyfluorfen (0.6mgL-1) in the liver mitocondrial bioenergetic. These results showed that phosphorylation was significantly affected by oxyfluorfen which contributed to the decrease on the liver cell energy charge and consequently led to the fish dead.

A stereological study of copper toxicity in gills of Oreochromis niloticus.

Stereological methods were used to estimate the volumetric density (V(V)) of the filamentar epithelium (FE, 39%), lamellae (L, 28%), central venous sinus (CVS, 14%), central axis (16%), mucous cells (MC, 2%) and chloride cells (CC, 1%) in the gill filament of control Nile Tilapia. The relative volumes of FE and L, and the relative volumes of CVS and central axis, varied inversely under exposure to copper, with high copper toxic levels declanching a chronic defence mechanism that was, nevertheless, overcome, and low copper toxic levels causing adaptation within a moderate acute phase type of response. Copper also induced a decrease of the V(V) (MC, gill filament) due to reduction of surface MC, despite the marked increase of stem MC at chronic exposure to high copper toxic levels. Diminution of the numerical density of filamentar CC was responsible for the decreased V(V) (CC, gill filament), although lamellar CC significantly increased at chronic exposure to low copper toxic levels. The present results demonstrate that cell relative volumes, mean volumes and numerical densities are dependent on the variations of the FE and L, which without a quantitative approach may be misinterpreted, thus stressing the importance of using stereological tools for analyzing histopathological patterns.

Oxidative stress response in gill and liver of Liza saliens, from the Esmoriz-Paramos coastal lagoon, Portugal.

Tissue-specific responses against oxidative stress and lipid peroxidation were analyzed in wild adult mullet (Liza saliens) caught in the Portuguese coastal lagoon Esmoriz-Paramos. Parameters measured were catalase (CAT), superoxide dismutase (SOD), and glutathione-S-transferase (GST) activities in liver and gill tissues and lipid peroxidation. The enzyme activities were related to gill histopathological alterations, as well as to heavy metals (Cu and Zn) concentrations in these tissues. Gill epithelium of L. saliens showed histological alterations, such as epithelial hyperplasia resulting in lamellar fusion, epithelial lifting, vasodilatation, and lamellar aneurisms, with a prevalence ranging from 62% to 92%. The highest Cu content was found in liver (379 mg x kg(-1)), while the highest Zn content was observed in gill (119 mg x kg(-1)). SOD and CAT activities showed differences between gill and liver. The highest activities found were SOD in gill (10.1 U/mg protein) and CAT in liver (39.2 mmol/min/mg protein). In gill, CAT activity was negatively related to both Cu levels and gill lifting, while a positive relationship was found between SOD activity and fish age. The positive relationship between Cu and CAT activity in liver suggests that an increase in metabolic level is related to Cu-induced oxidative stress. The decrease in gill CAT activity can be due to osmotic stress caused by damaged gill epithelium. CAT activity in liver is an appropriate biomarker of oxidative stress in the Esmoriz-Paramos lagoon.

Heavy metals in water, sediment and tissues of Liza saliens from Esmoriz-Paramos lagoon, Portugal.

Esmoriz-Paramos lagoon is an ecosystem of great ecological importance that is located on the northwest coast of Portugal and has been degraded as a result of industrial and anthropogenic activities. Concentrations of heavy metals (Cr, Cu, Pb and Zn) were measured in water, sediment and in tissues (liver and muscle) of Liza saliens, which is the dominant fish from the lagoon. Comparisons between metal concentrations in water and sediments were made with those in tissues of fish caught at the lagoon. Metals in water were quantified predominantly bound to particulate and equalled or exceeded the limit of chronic reference values. Metal concentrations in sediments varied among sampled sites. The relative order of concentrations was "Zn > Cu approximately Pb > Cr" the same pattern observed for metals in water. Metals in fish tissues showed higher concentrations in liver (262 mg CuxKg(-1) and 89 mg ZnxKg(-1)) than in muscle (<3 mg CuxKg(-1) and 26 mg ZnxKg(-1)), while Pb and Cr were not detected. These results suggest that Cu and Zn are the metals of major concern in the lagoon. Mullet detritivorous feeding habits, bioaccumulation pattern and the high sediment metals concentrations relative to the water suggest that sediments can be the most important source of contamination in this ecosystem. The positive relationship found between Cu in liver and fish length demonstrates that time of exposure is a crucial factor in bioaccumulation. Condition indices (K and HSI) in mullets from the lagoon were higher compared to mullets from sea, suggesting abnormal condition in the lagoon population. We conclude that metals chronic exposure in the lagoon can impose considerable fish stress. The results also show that the lagoon is an area of environmental concern.

Monitoring pollution in Esmoriz-Paramos lagoon, Portugal: liver histological and biochemical effects in Liza saliens.

The Esmoriz-Paramos lagoon is one important ecosystem located in the Northwest coast of Portugal. This study is concerned with the assessment of pollution of the lagoon contributed by urban, industrial and agricultural activities. The parameters selected for this aim were the occurrence of hepatic histological alterations and plasma blood biochemistry in Liza saliens, the dominant fish in this lagoon. Blood parameters were compared between mullets collected from the lagoon and from the sea and included plasma enzyme activities (aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP)), glucose (GLU) and total protein (TP). A positive relationship between hepatocyte vacuolization index and hepatosomatic index was found, suggesting that lipid accumulation could have contributed to the increase of liver weight. The hepatic alterations recorded included general diagnostic categories and additionally large areas of heterogeneous parenchyma, composed of hepatocytes with different spectrum of vacuolization. Liver histopathological evaluation revealed a sample prevalence of 34% for heterogeneous parenchyma, 31% for foci of necrosis and 9% for non-neoplastic lesions. No neoplastic lesions were found. Livers with heterogeneous parenchyma showed higher Cu and Zn content than livers without this category of lesion, suggesting that metals accumulated could trigger this hepatic alteration. AST was higher in mullets from the lagoon than in mullets from the sea, but no differences in ALP and ALT were found, suggesting a change in protein metabolism as an adaptive response to metals exposure. The higher glucose and protein contents observed in fish caught in the lagoon are consistent with a stress response and the measurement of plasma AST activity could be a sensitive indicator of lagoon fish stress. In conclusion, Esmoriz-Paramos lagoon biomonitorization, using indicator species will proceed to assess the impact of the restoration program under development by the Portuguese government.

Alterações histológicas em brânquias de tilápia nilotica Oreochromis niloticus causadas pelo cádmio / Histological alterations in gills of Nile tilapia Oreochromis niloticus caused by cadmium

Os efeitos histopatológicos do cádmio nas brânquias de tilápia Oreochromis niloticus foram estudados por microscopia óptica, usando 25mgl-1 de CdCl2 durante quatro dias, com o objetivo de identificar seus efeitos agudos na estrutura das brânquias. A morfologia geral das brânquias de O. niloticus é idêntica à de outros teleósteos, apresentando quatro pares de arcos branquiais com filamentos bem desenvolvidos. Situadas lateralmente, encontram-se as lamelas provenientes do eixo central dos filamentos. No epitélio filamentar foi possível identificar células de cloro, pavimentosas e mucosas. Os peixes expostos ao cádmio mostraram sinais de lesões epiteliais; edema intersticial, vasodilatação das lamelas, destacamento do epitélio lamelar e proliferação do epitélio filamentar. As alterações observadas também incluíram fusão nas lamelas como resultado de hiperplasia e hipertrofia epitelial, ruptura do sistema de células pilar, aneurismas e necroses.

The histopathogical effects of cadmium on the gills of tilapia Oreochromis niloticus were studied by light microscopy, using 25mgl-1 of CdCl2 during four days to identified the effects of short-term exposure on gills structure. The general morphology of O. niloticus gills is similar to the other teleostean fishes, showing four pairs of gills arches with well developed filaments. Bilaterally situated, secondary lamellae branches are found from the central axis of the filaments. The filamentar epithelium showed the chloride cells, the pavement cells and mucous cells. Fish exposed to cadmium showed signs of epithelial lesion, namely the interstitial edema, swollen of the lamellae, lifting and cellular proliferation of the filamentar epithelium. The changes of the gills also included lamellar fusion as a result of epithelial hyperplasia and hypertrophy, the breakdown of pillar cell system, and aneurisms with some ruptures and necrosis, especially in the filamentar epithelium.

Bioaccumulation of heavy metals in Liza saliens from the Esmoriz-Paramos coastal lagoon, Portugal.

Heavy metal (Cu and Zn) concentrations in liver, gills, and muscle of leaping grey mullet, Liza saliens, from the Portuguese Esmoriz-Paramos coastal lagoon were measured to evaluate their bioaccumulation as a function of sediment contamination. The highest metal concentrations were observed in the liver (254 mg Cu kg(-1)) and gills (114 mg Zn kg(-1)). Bioaccumulation factors (BAFs) were found to follow the order: Cu-liver>Cu-gills>Cu-muscle and Zn-gills>Zn-liver>Zn-muscle. The highest BAFs were observed in the organs mainly implicated in metal metabolism and a significant positive relationship was found between BAFs and fish age. These results suggest the loss of homeostatic capacity of L. saliens under chronic metal exposure leading to bioaccumulation. Furthermore, Cu-liver and Zn-gills accumulation can be good environmental indicators of metal stress in L. saliens.

The effect of paraquat on hepatic EROD activity, liver, and gonadal histology in males and females of Nile tilapia, Oreochromis niloticus, exposed at different temperatures.

The activity of fish monooxygenases has been used as a monitoring tool to evaluate contamination by cytochrome P450 inducing agents. In this study ethoxyresorufin O-deethylase (EROD) activity was analyzed in males and females of Nile tilapia exposed to a low concentration of paraquat (PQ) at 17 degrees C and 27 degrees C. PQ-treated fish showed a high hepato-somatic index, except females acclimated at 17 degrees C. No differences were found for the gonado-somatic index (GSI) between males. However, PQ-treated females showed high GSI values (6.46+/-1.75) when compared with the control group (2.30+/-0.26) maintained at 27 degrees C. Males and females exposed to PQ showed higher microsomal protein values than the control group (9.46+/-0.22 vs. 6.20+/-0.18 at 17 degrees C; 9.51+/-0.35 vs. 4.70+/-0.19 mg of protein at 27 degrees C, in PQ-treated and control groups, respectively). The EROD activity was high in females exposed to PQ when compared with the control group at 17 degrees and 27 degrees C. The liver histology showed that PQ also caused some hepatic alterations of parenchyma, like vacuolization, necrosis, and an increase of macrophages aggregates and eosinophilic granular cells. Females exposed to PQ showed a greater increase of late-vitellogenic (22.2+/-3.2) and mature (12.1+/-2.0) percentage of oocytes than the control group (9.9+/-3.0 and 8.0+/-4.3, respectively), and a lower percentage of primary oocytes (8.0+/-3.3) at 27 degrees C. In short, this work has advanced new knowledge on the influence of gender in biotransformation activity and the reproductive activity of Nile tilapia exposed to a low concentration of paraquat, and demonstrated that their effects could be observed at different temperatures.

Effect of cortisol on some osmoregulatory parameters of the teleost, Oreochromis niloticus L., after transference from freshwater to seawater

Este estudo foi realizado com o objectivo de testar os efeitos do cortisol na aclimatação da tilápia Oreochromis niloticus (L.) à água salgada. As tilápias (n=42) foram injectadas intraperitonealmente com cortisol e directamente transferidas de água doce para água salobra (15ë). As alterações da osmolaridade, concentração em cloretos (Cl-), os níveis plasmáticos de cortisol e a actividade branquial da Na+, K+-ATPase foram medidas (6, 12, 24, 48, 72 e 168 horas) após a transferência para água salobra. A osmolaridade e a concentração em Cl- aumentou imediatamente após a transferência até às 12-24h. O grupo injectado com cortisol (F) mostrou níveis plasmáticos de cortisol mais elevados do que o grupo controlo (C) que manteve os níveis iniciais durante a experiência. A actividade branquial da Na+, K+-ATPase dos peixes do grupo C começou às primeiras horas após a transferência e teve um pico às 48h. As diferenças entre a actividade enzimática da Na+, K+-ATPase dos grupos F e C foram significativas (P<0,05) em água doce, o que confirma o efeito exógeno do cortisol.

Mucormicose por Rhizopus sp. em peixes: apresentaçäo do primeiro caso em Portugal / Mucormycosis due to Rhizopus sp. in fishes: first case described in Portugal

This paper describes the first case of fish-boces (Chondrostoma polylepsis) with cutaneous lesions caused by Rhizopus sp. The results point out the role of fish-boces as a surveillance sentinel of cutaneous mucormycosis infections in aquatic recreation areas

Efeito da suplementaçäo da dieta com NaCl no crescimento de tilápia Oreochromis niloticus cultivada em diferentes salinidades / Effect of supplemental dietary sodium chloride on growth rate of tilapia Oreochromis niloticus reared in variable salinities

Este estudo foi realizado com o objectivo de testar o efeito de uma dieta suplementada com cloreto de sódio no crescimento de tilápia Oreochromis niloticus cultivada em água doce e em água salobra a 10 e 20ë. Foi fornecida uma dieta suplementada com 8 por cento de NaCl durante o período de aclimataçäo de três semanas. Após esse período, os peixes foram diretamente transferidos para tanques com água doce e água salobra a 10 e 20ë, para o estudo do crescimento de 180 dias. A suplementaçäo com NaCl aumentou o crescimento dos peixes cultivados em água doce nos primeiros 30 dias (P<0,05), mas näo se observaram diferenças significativas entre os outros grupos. No final do ensaio, os peixes cultivados em água salobra a 10ë apresentaram os melhores resultados de crescimento (P<0,05). Nesse período, os peixes cultivados em 20ë de salinidade mostraram lesöes externas, perda de escamas, desorientaçäo de escamas e inchaço do abdómen