Stress responses in rainbow trout Oncorhynchus mykiss alevins

Serum electrolyte and nonelectrolyte status in freshwater juvenile Persian sturgeon Acipenser persicus

Status of serum electrolyte and nonelectrolyte variables can be used for managing sturgeon species cultured in freshwater or living in seawater. The aim of the present study was to evaluate serum biochemical variables in clinically healthy juvenile Persian sturgeon Acipenser persicus cultured in freshwater. Serum samples from 11 females and 10 males were analyzed, and levels (mean +/- SD) of the following variables were compared between sexes: glucose (Glc; 5.58 +/- 1.25 mmol/L for females and 8.56 +/- 1.80 mmol/L for males), total cholesterol (TC; 2.50 +/- 0.45 and 2.40 +/- 0.65 mmol/L), triglyceride (TG; 7.13 +/- 2.68 and 5.14 +/- 1.27 mmol/L), blood urea nitrogen (BUN; 1.28 +/- 0.2 and 1.01 +/- 0.2 mmol/L), total protein (TOP; 55.84 +/- 8.77 and 41.44 +/- 8.62 g/L), inorganic phosphate (P(i); 6.19 +/- 1.02 and 5.23 +/- 0.49 mmol/L), calcium (Ca; 2.80 +/- 0.43 and 2.63 +/- 0.32 mmol/L), magnesium (Mg; 0.9 +/- 0.23 and 0.99 +/- 0.22 mmol/L), sodium (Na; 152.80 +/- 13.81 and 156.38 +/- 12.67 mmol/L), potassium (K; 2.64 +/- 0.58 and 2.27 +/- 0.39 mmol/L), and chloride (Cl; 143 +/- 13.85 and 151.67 +/- 21.08 mmol/L). There were no differences in TC, Ca, Mg, Na, K, or Cl between sexes. The Glc value was lower in female Persian sturgeon than in males, whereas the values of TG, BUN, TOP, and P(i) were higher in females than in males. Freshwater adaptation may affect serum ion concentrations in juvenile Persian sturgeon.

Dietary lipid level induced antioxidant response in Manchurian trout, Brachymystax lenok (Pallas) larvae

This study was designed to determine the nutritional lipid requirement of Manchurian trout and to investigate the effects of lipid concentrations on the antioxidant status in larvae with experimental diets with different lipid levels. Oxidative stress differences between different organs and tissues were also assessed. Manchurian trout larvae were fed for 35 days and, during that period, growth and survival, the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and content of malondialdehyde (MDA) in viscera, muscle, gill and brain of four diets, lipid levels from 15 to 30%, and control treatment were measured. Growth rates were similar, but survival was low, between high and low dietary lipid levels. SOD activity was stimulated in viscera, muscle and brain in high lipid diets, but reduced in gills with increased lipid content. SOD was kept lower in the control group. GPX activity was inhibited in viscera and stimulated in gill, muscle and brain. CAT activities were enhanced by all treatments and showed the lowest values in the control. Lipid peroxidation of the diet was promoted in all organs, excluding the gill which showed no regular pattern. MDA content increased with increased dietary lipid levels in viscera, muscle and brain. Our results indicate that the most appropriate lipid requirement is probably 20-25% and a higher dietary level of lipids might induce oxidative stress in Manchurian trout larvae. The brain and gill were probably the most sensitive organs to oxidative damage.

Effects of metal mining effluent on Atlantic salmon (Salmo salar) and slimy sculpin (Cottus cognatus): using artificial streams to assess existing effects and predict future consequences

In the summer of 2000, the effects of metal mine discharge on fish growth and exercise performance were assessed at a Zn-Pb-Cu mine in New Brunswick, Canada. Juvenile Atlantic salmon (Salmo salar) were exposed to 0%, 20%, and 80% treated metal mine effluent in a mobile, fish-only artificial stream system. Fish were fed commercial salmon pellets throughout the study. Young-of-the-year slimy sculpins (Cottus cognatus) were exposed to the same treatments in a multitrophic level, modular artificial stream system or mesocosm, in which the fish were dependent on seeded algae and invertebrates for nutrition. Treatment concentrations were chosen to represent existing discharge dilutions (80%) and a scenario of reduced effluent discharge (20%) as predicted upon mine closure (scheduled for 2008). Al, Ba, B, Fe, Mn, Sr, Tl, Ti, and Zn increased in a concentration-dependent fashion across the three treatments. Salmon body burdens of Ba, Cd, Li, Cu, Mn, Se, Sr, and Zn were increased in the 80% treatment, while Tl increased across all treatment levels. Mortalities and depressions in growth in both fish species paralleled treatment concentrations (80%>20%>0%). Salmon liver weight was significantly greater in fish exposed to 20% and 80% effluent in a concentration-dependent fashion. Exercise performance in fish, as assessed by the ability to recover from forced exercise, showed little effect of treatment. The contamination of the receiving environment by mine discharges has led to loss of fish, making it impossible to study the system in situ. However, the use of the artificial stream systems enabled us to assess effects of present conditions on fish, as well as the potential impacts of mine reclamation. The 20% discharge predicted following mine reclamation is potentially favourable for the reinstitution of native fishes into the system.

Physiological changes of sturgeon Acipenser naccarii caused by increasing environmental salinity

The possible repercussions of osmoregulatory processes on some indicators of classical and oxidative stress were examined during gradual acclimation of sturgeons (Acipenser naccarii) to full seawater (35% salinity) and after a period of 20∼days at this salinity. Erythrocyte constants and levels of cortisol, protein and glucose in the plasma were determined. In addition, plasma osmolality and muscle-hydration values, as well as liver and heart protein, were determined. Catalase, glutathione peroxidase and superoxide dismutase activities and lipidperoxidation levels were measured in blood (plasma and red blood cells) and tissue (liver and heart). A number of physiological responses, such as disturbance in body fluid, activation of osmoregulatory mechanisms, augmented antioxidant defences in blood and alteration of energy metabolites, were detected with increasing environmental salinity. After 20 days at 35% salinity, plasma osmolality, erythrocyte constants and muscle water content all returned to values usual for low environmental salinity, indicating that osmoregulatory processes have achieved their objective. However, cortisol values, antioxidant enzyme activities in the blood (plasma and red blood cells), lipid peroxidation in plasma, and hepatic proteins did not return to initial values, showing that osmoregulatory processes cause major physiological changes in the fish.

Stress-induced changes of plasma antioxidants in aquacultured sea bass, Dicentrarchus labrax

Antioxidant plasma activities of ascorbate, alpha-tocopherol and glutathione peroxidase were analysed in adult male sea bass, Dicentrarchus labrax, in normal conditions and after hypoxia-recovery. In addition, tank measurements of temperature, pH, salinity and chlorine changes were carried out. Ascorbate and alpha-tocopherol were measured using a high-pressure liquid chromatography method and glutathione peroxidase activity enzymatically. Ascorbate and alpha-tocopherol showed a relationship with the velocity of body growing in normal and hypoxia-recovery conditions. In sea bass exposed to hypoxia, only ascorbate and alpha-tocopherol levels were significantly lower compared with the control group. Slope study and expression percent of antioxidants reduction after stress conditions revealed a predominant role of plasma alpha-tocopherol. Sea bass subjected to variations of salinity and chlorine showed a significant decrease in plasma alpha-tocopherol. A relationship could be suggested between antioxidant defence and fish response in aquaculture.

Limits to exhaustive exercise in fish

Exercise to exhaustion leads to severe metabolic, acid-base and ionic changes in fish. It has been shown that several abiotic and biotic factors can limit burst exercise performance and the recovery process in fish. This article reviews the importance of body size, temperature, fasting/starvation and training on the ability of fish to perform and recover from exhaustive exercise. It is concluded that the constraints placed on a fish prior to and following exercise reflects the large intra-specific variability in the physiological response to exercise in fish.

Metabolism and detoxification of nitrite by trout hepatocytes

Nitrite (NO2-) is one of the most important toxicants to fish. Freshwater fish are especially sensitive, particularly salmonids. Nitrite uptake is thought to occur via the HCO3-, Cl- -exchanger at the gill epithelia with nitrite substituting for chloride. In this way freshwater fish accumulate nitrite in the blood up to 100-fold from the surrounding water. Another source, endogenous nitrite as a degradation product of nitric oxide, rarely leads to pharmacologically relevant concentrations. We developed a new method for the determination of nitrate (NO3-) in biological samples and used it to measure nitrite oxidation in isolated rainbow trout (Oncorhynchus mykiss) hepatocytes which were found to detoxify nitrite to the almost non-toxic nitrate. Detoxification is inhibited by 0.05 mM bumetanide and 0.1 mM furosemide but not by SITS and DITS, suggesting the involvement of the Na+, K+, 2Cl- -cotransporter with nitrite or nitrate substituting for chloride. Oxidation of nitrite is strongly accelerated by 0.05 mM uric acid. The efficacy of this antioxidant suggests that similar reactions are involved as known for haemoglobin [33]. However, in the case of trout liver also membrane bound detoxificating activity can be observed which is also enhanced by uric acid. ATP concentrations remained constant in the hepatocytes during all experiments demonstrating that hepatocyte energy status was not influenced by nitrite oxidation. Thus nitrite resistance in fish is governed by at least two mechanisms, nitrite uptake and the rate of detoxification. It is unknown whether fish actually differ in their ability to distinguish between chloride and nitrite during branchial uptake, but evidence presented in this paper suggests a significant contribution of detoxification pathways to a possible nitrite tolerance of fish.