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The accumulation of 17 human pharmaceuticals (HPs) was investigated in the muscle of three fish species characteristic of the “Rio de la Plata Basin” with different feeding habits and of relevance for human consumption: Megaleporinus obtusidens, Salminus brasiliensis, and Prochilodus lineatus. Fish were sampled in fall and spring from 8 localities distributed along 500 Km of the Uruguay River. Atenolol and carbamazepine were the most frequently detected HPs (>50%), but at concentrations always below 1 μg/kg wet weight (w/w). Hydrochlorothiazide, metoprolol, venlafaxine, propranolol, codeine, and the carbamazepine metabolite, 2-hydroxycarbamazepine, were accumulated at higher levels showing maximum concentrations between 1 and 10 μg/kg (w/w), but infrequently (, Macarena Rojo, the sampling and partially the sample analysis were granted by the Fish and Fisheries Program of the Administrative Commission of the Uruguay River (CARU). The study was also granted by CONICET (PIP2012-2014-0090) and ANPCyT (PICT2014-1690). The scientific facilities of ICRA have been co-financed by the Spanish Ministry of Economy and Competitiveness (MINECO) and by the European Regional Development Fund (ERDF) in the frame of the Catalonia ERDF Operative programme 2007–2013. This work was partly supported by the Generalitat de Catalunya (Consolidated Research Group: Catalan Institute for Water Research 2014 SGR 291). S. Rodriguez-Mozaz also acknowledges the Ramon y Cajal program (RYC-2014-16707) and. Diana Álvarez-Muñoz the support of the project XENOMETABOLOMIC (CTM2015-73179-JIN) (AEI/FEDER/UE).

Hydrolysates of slaughtering plants by-products are among the most promising feedstuffs for aquafeed formulations, supplying diets with amino acids and small peptides which perform functions ranging from palatability enhancers to nutrient-rich ingredients to immunity modulators. This study evaluated growth performance, blood and immunological parameters, and gene expression of food intake-regulating hormones in juvenile dourado Salminus brasiliensis (Cuvier, 1816) (25.07 ± 3.9 g) fed vegetable-based diets supplemented with swine liver hydrolysate [SLH] (30, 60, 90, 120, 150, and 180 g kg−1). Hematological and immunological factors did not change for either vegetable- or swine liver hydrolysate-based diets. Feed consumption was improved in fish fed a diet containing 30 g kg−1 SLH, while 150 g kg−1 of inclusion improved growth performance. Results suggest an effect of feeds on cocaine and amphetamine regulated transcript (CART) expression, which had higher expression levels in the hypothalamus of fish fed the diet containing 150 g kg−1 of SLH. Cholecystokin (CCK) expression levels only increased in fish fed 60 g kg−1 SLH compared to the control diet, and this may be related to gastric tract filling rather than dietary peptides.

Molecular data of Henneguya chydadea Barassa, Cordeiro and Arana, 2003, found in the gill filaments of Astyanax lacustris bred in fish farm in the State of Mato Grosso do Sul, Brazil was obtained in order to estimate their phylogenetic position among other platysporines myxosporean. The prevalence of the parasite was 28.1% and the range intensity was 1-3 plasmodia per fish. The shape and measurements of mature myxospores were consistent with the characteristics previously defined to H. chydadea. The SSU rDNA sequence of the myxospores of H. chydadea resulted in a total of 1405 nucleotides, and this sequence did not match any of the myxozoan available in the GenBank. Phylogenetic analysis showed H. chydadea within the clade of histozoic myxosporeans and closed together with Henneguya rotunda and Myxobolus pantanalis reported in the gill arch and fins and gill filaments of Salminus brasiliensis respectively. Nonetheless, the SSU rDNA sequences of H. chydadea, H. rotunda and M. pantanalis have only 85.2% and 84.4% similarity, respectively. This is the first molecular study of a Henneguya species that parasitizes a fish belonging to the genus Astyanax in South America. The importance of myxosporeans introduction to new locations along with infected cultured host is emphasized.

Vitamins are dietary, organic compounds required for normal growth, reproduction and health of animals, fish included. Dietary vitamins also drive immunological responses of fish and information in that regard is still scarce. This work studied dietary vitamin A requirement of dourado Salminus brasiliensis, a novel target of intensive fish farming and research efforts. Juvenile dourado were stocked in 500-L tanks and fed for 101 days with six diets containing 1115.3; 3126.4; 8818.1; 18,256.1; 24,185.3 and 30,270.4 IU vitamin A kg−1 diet, and then sampled for growth performance indices, carcass composition, vitamin A contents in liver, hematological figures and leukocytes respiratory activity (LRA). Sub groups (n = 8) were inoculated intraperitoneally with Aeromonas hydrophila suspension (106 CFU) and sampled for hematology and LRA one week later. A break point for weight gain was detected at 3143 IU vitamin A kg−1 diet and the lowest specific growth rate was recorded for fish fed diets containing 1115.3 IU vitamin kg−1 diet, which also had lowest erythrocyte count and blood hemoglobin contents. Hematocrit and total plasma protein of fish decreased after bacterial challenge, regardless of dietary vitamin A contents. Dietary vitamin A requirement of dourado was determined at 8500 IU kg−1; although higher levels did not hamper performance and health, they are not recommended given the possibility of hypervitaminosis. The higher leukocytes activity related to vitamin A administration is a solid indicative of immunomodulation activity of this vitamin for the species.

Diets for carnivorous fish ordinarily contain large proportion of fish meal (FM), a high-cost and restricted feedstuff. Animal by-product hydrolysates are high-quality feedstuffs and potential surrogates to FM in fish diets. This study evaluated the performance of juvenile dourado Salminus brasiliensis, a carnivorous Characin, fed with increasing levels of swine liver hydrolysate. Juvenile dourado (4.57 ± 1.25 g) were stocked into 20,300-L, indoor plastic tanks (15 fish per tank), closed-loop recirculating system in a totally randomized experimental design (n = 4), and fed to apparent satiation for 61 days with practical diets containing graded levels of swine liver hydrolysate – SLH (0, 70, 140, 210 and 280 g kg− 1). Fish fed the SLH14 diet had higher feed intake and weight gain. Fish fed the SLH28 diet had the lowest rates of feed efficiency ratio (FER), protein efficiency ratio (PER), energy retention ratio (EER) and protein retention ratio (PRR). Diets containing in excess of 140 g SLH kg− 1 probably caused reduction of protein synthesis by fish, possibly resulting from higher proportion of small peptides and free amino acids in the feedstuff, which possibly elicited higher amino acid catalysis and increased nitrogen excretion. The lowest values of blood lysozyme were recorded for fish fed diet SLH7; on the other hand the oxidative burst was not influenced by the diet. Higher nitrogen excretion was recorded for in fish fed diets containing the highest levels of hydrolysate. Ultrafiltration of swine liver hydrolysates may elicit increasing the proportion of the product in fish diets and further studies on the economic feasibility of swine liver hydrolysate may shed additional light regarding its use as surrogate protein sources.

Sport fishing is an activity responsible for moving millions of dollars around the world. However, this activity is also considered to cause habitat degradation and promoting several negative effects on the ichthyofauna. The ``Iguacu Dourado'' project, presented here, seeks to intensify the potential of sport fishing in the Iguacu River Basin. Although not explicit, the project intends to introduce Dourado (Salminus brasiliensis), as well as to encourage sport fishing of the species in the Iguacu River Basin. Twenty specimens were captured in the Salto Santiago and Salto Osorio reservoirs from 2003 to 2016, thus indicating that the invasion of S. brasiliensis can be successful and extremely harmful to the endemic fauna of the basin. We believe that the so-called project is characterized by an attitude of eco-vandalism, promoting the illegal release of species outside its area of occurrence. Awareness-raising measures as well as educational programs should be addressed so that the population can be informed about the issue of invasion of non-native species.

Golden dorado (Salminus brasiliensis) is increasing in popularity as a target of recreational anglers practicing catch-and-release (C&R) in northern Argentina and bordering countries, however science-based best practices have yet to be developed for this iconic freshwater gamefish. We assessed the consequences of C&R on golden dorado captured by anglers on the Juramento River, in Salta, Argentina. Physical injury, physiological stress responses (blood glucose, lactate, pH), reflex impairment, and movement response post-release were compared among handling treatments for golden dorado. The 0 min and 2 min air exposure groups had significantly higher blood glucose and blood lactate concentrations relative to fish in the baseline group, while blood pH indicated evidence of acidosis in the 2 min air exposure treatment relative to baseline values. Golden dorado in the 2 min air exposure group also had significantly greater reflex impairment compared to fish without air exposure. An additional 24 golden dorado were affixed with radio tags to examine short-term (20 min) post-release behavior with air-exposure treatments of 0 min (n = 11) and 2 min (n = 9), as well as fish that were transported downstream in submerged recovery bags (n = 4). Subsequent relocations of tagged golden dorado were conducted every 1–2 days up to 8 weeks after capture. Upon immediate release, fish often exhibited fallback (−43 ± 49 m, n = 20), although post-release movement was not significantly different among treatment groups. Fallback distance was correlated with total reflex impairment scores. The translocated fish released downstream exhibited greater upstream movement immediately following release, with three fish returning to the location of capture within 4–12 days. No immediate mortality was observed for golden dorado in the physiology assessment, and limited evidence of short-term mortality was present for tracked fish (22 of 24 tagged fish movement detected >2 days post-tagging, ≤8% mortality). Our results indicate that minimizing air exposure should be advocated as part of guidelines for C&R for golden dorado. Our study also revealed that impairment of the equilibrium reflex is useful for anglers as an indicator for golden dorado vitality and potential need for monitoring recovery prior to release.

The dourado, Salminus brasiliensis (Cuvier, 1816) is a freshwater piscivorous Characin native to South American rivers. Owing to the high quality of its flesh and its fast growth, it is the object of both capture fisheries and fish farming. However, very little is known about the endocrine regulation of feeding and metabolism of dourado. In this study, cDNAs for orexin, CART and CCK were isolated in dourado, and their mRNA tissue distributions examined. In order to assess the role of these peptides in the regulation of feeding of dourado, the effects of fasting and feeding on mRNA expression levels of orexin, CART and CCK in the brain as well as CCK in the intestine were assessed. Whereas orexin and CCK have widespread mRNA distributions in the brain and peripheral organs, CART seems to be mostly limited to the brain. Orexin brain expression increased with fasting and displayed periprandial changes, suggesting it is involved in both long- and short-term regulation of feeding and appetite. CART and CCK hypothalamic expressions were not affected by fasting, but displayed periprandial changes with post-feeding decreases, suggesting roles in short-term satiation. CCK expression in the anterior intestine was not affected by fasting and did not display periprandial changes. Overall, our results suggest that orexin, CART and CCK are involved in the physiology of feeding of dourado.

The pollution from urban effluents discharged into natural waters is a major cause of aquatic biodiversity loss. Ecotoxicological testing contributes significantly to understand the risk of exposure to the biota and to establish conservation policies. The objective of the current study was to assess the toxicity of a river highly influenced by urban effluents (Atuba River, Curitiba city, Southern Brazil) to the early stages of development in four South American native fish species, investigating the consequences at the population level through mathematical modelling. The species chosen were Salminus brasiliensis, Prochilodus lineatus, Rhamdia quelen, and Pseudoplatystoma corruscans, ecologically important species encompassing different conservation statuses and vulnerability. The embryos were exposed from 8 to 96 h post fertilization to the Atuba River water, collected downstream of the largest wastewater treatment plant in the Metropolitan Region of Curitiba, and their survival rates and deformities were registered. The species S. brasiliensis and P. lineatus presented the highest mortality rates, showing high sensitivity to the pollutants present in the water. According to the individual-based mathematical model, these species showed high vulnerability and risk of extinction under the tested experimental conditions, even when different sensitivity scenarios of juveniles and adults were considered. The other two species, R. quelen and P. corruscans, showed a more resistant condition to mortality, but also presented high frequency and severity of deformities. These results emphasize the importance of testing the sensitivity of different Brazilian native species for the conservation of biodiversity and the application of models to predict the effects of pollutants at the population level.

The dourado Salminus brasiliensis is a freshwater species found in major South American rivers and has recently been cultivated in cage systems. As stocking density and handling are known stress factors in cage systems, we studied the combined effect of stocking density (of 30, 150 and 300 fish m − 3 ) and fish handling (consisting of the pursuit, capture and exposure of the fish to air for 30 s) on growth as well as biochemical and physiological responses of S. brasiliensis fingerlings. The endpoints measured were as follows: standard length and weight, blood hematocrit (Ht) and hemoglobin (Hb), plasma glucose and lactate, hepatic activities of the antioxidant enzymes glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST) and catalase (CAT), and the concentrations of Na + , K + , Cl − and Ca 2+ in the gills and plasma of S. brasiliensis fingerlings. Samples were taken every 20 days until the end of the experiment, on the 80th day. S. brasiliensis fingerlings that were not handled exhibited reduced growth at increased densities. In contrast, handled fish exhibited slower growth at all densities, suggesting that the effect of handling was greater than the effect of density in these fish. Enzymes related to oxidative stress were influenced by handling, indicating that stress is an important modulator of the antioxidant response. Antioxidant defenses were negatively influenced by handling, but only slightly influenced by density. On the 80th day, the Hb concentration, enzymatic activity of GR, GST, GPx and CAT in the liver, and concentrations of Na + and Cl − in the gills were higher in fish that had not been handled, in contrast to the glucose concentration, which was higher in the handled fish. However, the activity of GPx was influenced by stocking density in handled fish. The Ht and the concentrations of lactate, Na + , K + , Cl − and Ca 2+ were not influenced by the stress factors of stocking density or handling. The growth of S. brasiliensis was negatively affected by frequent handling stress, whereas stocking density only affected growth when fish were not handled, thus overcoming the effect caused by high densities.

In this report, we describe the morphology and histopathology of Myxobolus salminus n. sp., a parasite of the gill filaments of wild Salminus brasiliensis (dourado) from the Brazilian Pantanal. The small polysporic plasmodia were approximately 100 microm in diameter and the development was asynchronous. The mature spores were oval to pear shaped and had a smooth wall. The spore measurements were (mean+/-S.D., with range in parentheses): length 10.1+/-0.4 microm (9.6-10.5), width 6.1+/-0.4 microm (5.8-6.6) and thickness 5.0+/-0.6 microm (4.7-5.3). The polar capsules were elongated and of equal size: length 4.6+/-0.2 microm (4.3-4.8) and width 1.7+/-0.1 microm (1.5-1.9). The histological analysis revealed numerous plasmodia in the blood vessels of the gill filaments. The site of parasite development was the wall of the large-caliber blood vessel of the gill filament, with progressive growth towards the lumen, resulting in the obstruction of blood flow, congestion and perivascular edema. The ultrastructural study revealed that the plasmodial wall was composed of two membranes, had numerous pinocytic canals and was in direct contact with the basement membrane of the vessel. The development of the parasite was asynchronous, with mature spores, immature spores and young developmental stages randomly distributed throughout the plasmodium. The prevalence of the parasite was 4.4%, with male and female fish being infected.

Karyotype, mapping of nucleolar and 5S rRNA genes and distribution of constitutive heterochromatin supposedly AT-rich were characterized on two isolate populations of Salminus brasiliensis, the biggest characid fish, and three population of Salminus hilarii. The diploid number 2n=50 and the karyotype formulae (10M+20SM+20ST/A) were the same to Salminus species studied. The position of 18S rDNA cluster identified by FISH coincide with chromomycin A3 labeling (CMA+) in the long arm telomeric portion of sixth pair. Subtle differences for the disposal of the 5S rRNA gene in the chromosome of the Salminus are presented. The distribution of the constitutive heterochromatins and DA/DAPI+ bands are described.

Time series on fish mercury (Hg) development are rare for hydroelectric reservoirs in the tropics. In the central-western part of Brazil, a hydroelectric reservoir, called Lago Manso, was completed in 1999 after that background levels of fish Hg concentrations had been determined. The development for the first 3 years was studied in 2002. The objective of the present study was to determine development of fish Hg concentrations for a second three-year period after flooding. The bioaccumulation factor and certain abiotic and biotic factors, possibly affecting the availability and accumulation of Hg, were also examined. The results show that Hg levels in fish from Lago Manso have increased more than five times compared to the background levels observed before construction of the reservoir. At the same time, dissolved organic carbon has increased while dissolved oxygen has decreased indicating enhanced bioavailability of Hg. In the reservoir, Salminus brasiliensis had in average a Hg content of 1.1 microg g(-1) f.w., Pseudoplatystoma fasciatum 1.2, Serrasalmus marginatus/spilopleura 0.9, and Brycon hilarii 0.6 microg g(-1) f.w. The average fish Hg contents were higher downstream, except for B. hilarii. In the reservoir, the average Hg content of each species was in 2005 always over the consumption limit (0.55 microg total Hg g(-1) f.w.) recommended by WHO. Therefore, the people living around Lago Manso should be informed of the health effects of Hg, and fish consumption recommendations should be carried out. The accumulation of Hg varies widely between species as shown by the bioaccumulation factor which ranges between 5.08 and 5.59 log units. The observed variation is explained by differences in diet and trophic position with piscivorous fish exhibiting the highest mean Hg concentration, followed by carnivorous and omnivorous species. Carbon isotope analyses imply that trophic position is not the only cause of the observed differences in Hg levels between omnivorous B. hilarii, having a diet partly based on C(4) plants, and carnivorous S. marginatus as well as piscivorous S. brasiliensis, whose carbon sources are depleted in (13)C. The fact that the species have different carbon sources indicates that they belong to different food chains.

Feed preferences of dorado, Salminus brasiliensis , in the early stages of life was studied in larvae, stocked 5 days after hatching in three earthen commercial ponds (810 m 2 , 900 m 2 and 1480 m 2 ) at a density of 30 m − 2 . Larvae were fed on natural food from ponds supplemented with a commercial ration (40% crude protein), and for 12 days fish samples were taken daily in the morning and in the afternoon from each pond to analyze the food items present in the diet. Zooplankton available in the environment was also analyzed. Feeding was intensive since 94% of the larvae guts examined contained food. Since the commercial diet was not found in the dorado guts, the natural diet dominated the artificial food, but the cannibalistic behavior typically found in laboratory conditions was not observed. Insect larvae and cladocerans were the main prey items found in the gut of the larvae. In fish ponds dorado larvae can be considered a generalist feeder, since small amounts of different food items were consumed, but they tend to specialize in some items, according to their developmental stage.

It has been frequently demonstrated that mercury (Hg) concentrations in fish rise in newly constructed hydroelectric reservoirs in the Northern Hemisphere. In the present work, we studied whether similar effects take place also in a tropical upland reservoir during impoundment and discuss possible causes and implications. Total Hg concentrations in fish and several soil and water parameters were determined before and after flooding at Rio Manso hydroelectric power plant in western Brazil. The Hg concentrations in soil and sediment were within the background levels in the region (22-35 ng g(-1) dry weight). There was a strong positive correlation between Hg and carbon and sulphur in sediment. Predatory fish had total Hg concentrations ranging between 70 and 210 ng g(-1) f.w. 7 years before flooding and between 72 and 755 ng g(-1) f.w. during flooding, but increased to between 216 and 938 ng g(-1) f.w. in the piscivorous and carnivorous species Pseudoplatystoma fasciatum, cachara, and Salminus brasiliensis, dourado, 3 years after flooding. At the same time, concentrations of organic carbon in the water increased and oxygen concentrations decreased, indicating increased decomposition and anoxia as contributing to the increased Hg concentrations in fish. The present fish Hg concentrations in commonly consumed piscivorous species are a threat to the health of the population dependent on fishing in the dam and downstream river for sustenance. Mercury exposure can be reduced by following fish consumption recommendations until fish Hg concentrations decrease to a safe level.

This study examines the optimal weaning period in rearing larval dourado. This aim is achieved by comparing a series of differential weaning schedules, and by measuring the ontogeny of proteinase activities. Weaning from live food (curimba, Prochilodus lineatus , larvae) was carried out at the third, fifth or seventh day AH by gradual or total transition to formulated feed. Live food was either kept for two days after feeding the test diet (GW) or removed at the same day (TW). Acceptance of test diet started at the fifth day after hatching (AH) and larvae total length was higher ( P P P > 0.05). Survival was significantly lower ( P − 1 protein, mean ± SD) was detected at the third day AH and increased subsequently until the seventh day AH (7T), indicating stomach functionality at this time. Intestine proteinases activities (trypsin and chymotrypsin, 0.088 ± 0.0 and 0.018 ± 0.0 U mg − 1 protein, respectively) were detected as early as 12 h AH, before the onset of exogenous feeding. Digestive enzymatic contribution of live food was not clearly shown. Our findings corroborate the hypothesis that fish larvae will accept dry feed only when it is physiologically able to digest it, which happens when acid protease activity is detected, indicating stomach functionality. Our findings also demonstrate the importance of live food soon after hatching for dourado larvae and suggest that formulated feed could be offered, in a gradual form, as early as at the fifth day AH.