Differential effects of low pH and aluminium on the caudal neurosecretory system of the brook trout, Salvelinus fontinalis

Brook trout were subjected to soft water at pH 6·5, 5·5 or 5·0 without aluminium added, or to water at pH 5·5 with 200,300 or 500 μg Al I^-1 added. The response of the caudal neurosecretory system to low pH or aluminium was evaluated after one week by measuring the urotensin I and urotensin II concentrations in the urophysis by radioimmunoassay, and by morphometric analysis of the caudal neurosecretory cells. A positive correlation was found between urotensin I concentrations and acidity, and a negative correlation was found between urotensin II concentrations and total aluminium in the water. Morphometric indices (cell size and proportion of lobed nuclei in the caudal neurosecretory cells) suggested increased synthetic activity in the caudal neurosecretory cells of fish at pH 5·5 compared to pH 6·5.     

The distribution of zinc and copper in plasma, erythrocytes and erythrocyte membranes of rainbow trout (Salmo gairdneri)

1. The zinc and copper concentration of plasma was determined in rainbow trout, lake trout, walleye and whitefish. 2. These fish had mean plasma zinc concentrations ranging from 9.3 to 15.1 ppm and copper concentrations from 0.6 to 1.3 ppm. 3. In rainbow trout, the concentration of zinc and copper is greater in the erythrocyte membrane than in the total erythrocyte. 4. Ultrafilterable plasma zinc and copper concentration in rainbow trout was determined to be 0.03 and 0.019 ppm, respectively. 5. Dialysis of rainbow trout plasma against 20 mM EDTA results in removal of 99% of the zinc and 88% of the copper from plasma proteins.     

A comparison of cadmium-induced metallothionein gene expression and Me2+ distribution in the tissues of cadmiumsensitive (rainbow trout; Salmo gairdneri) and tolerant (stone loach; Noemacheilus barbatulus) species of freshwater fish

1. The accumulation of cadmium in the liver, kidney and gills of rainbow trout and stone loach was measured during exposure of the fish to the metal at 3 smg/l in their aquarium water. The pattern of accumulation of the toxic metal in the individual organs was different between the two species.2. The tissue concentrations of metallothionein-specific mRNA and metallothionein protein were also determined in these organs from the same fish. In rainbow trout, the induction of metallothionein gene expression resulted in a gradual increase in metallothionein concentration in gill over the course of the experiment whereas increases in metallothionein in the liver and kidney were detected only at the later time points of analysis (beyond 19 weeks). By contrast, in the same tissues from stone loach, relatively minor changes were quantified in specific mRNA and metallothionein concentrations.3. Throughout the experimental period, tissue concentrations of zinc and copper were determined in the liver, kidney and gills of the rainbow trout and stone loach. Subtle decreases were observed in the zinc concentration of gills in rainbow trout and substantial increases were observed in the hepatic copper concentrations in both species at the later time points of analysis.4. The ability of cadmium to induce metallothionein gene expression and its subsequent ability to compete for the sequestration sites on the newly-synthesized protein is discussed with regard to the relative levels of cadmium, zinc and copper in the organs studied and differing regimes of cadmium administration.     

Effects of malachite green on leucocyte abundance in rainbow trout, Salmo gairdneri (Richardson)

Blood counts from more than 1000 young-of-the-year rainbow trout, Salmo gairdneri (Richardson), were examined to determine if static exposure to malachite green at 1·35,13·5, or 21·0 mg/1 for 25–30 min or 42·0 or 72·0 mg/1 for 5 min caused chronic leucopaenia. The major changes in fish exposed for 25–30 min came during the first 24 h. After an initial lag of 3·4 h, total leucocyte-thrombocyte counts in both treated and control fish rapidly declined. Recovery was essentially complete 1·4 days after exposure, and no leucopaenia was noted after 14 or 28 days. Thrombocytosis developed during the first 24 h in fish exposed to the higher concentrations. Lymphopaenia and neutrophilia also developed, but abated after the 4th post-treatment day. Leucocyte numbers in control and exposed groups were virtually the same by the 14th day. The total leucocyte-thrombocyte counts in fish exposed for 5 min declined after 24 h, but counts were not as depressed as those in fish exposed for 30 min.
Because leucocyte changes similar to those in exposed fish were evident in the controls in both experiments, we believe that the leucocyte changes in rainbow trout exposed to malachite green were a result of a nonspecific vertebrate stress syndrome, rather than of specific leucocytotoxic effect of this chemical.     

The effect of inorganic and organic pollutants on sperm motility of some freshwater teleosts

Using four different sperm types from brown trout Salmo trutta fario (Salmonidae), chub Leuciscus cephalus (Cyprinidae), burbot Lota lota (Gadidae) and African catfish Clarias gariepinus (Clariidae) the effect of inorganic (cadmium, copper, mercury, lead, zinc and nitrite) and organic (cyclohexane and 2,4‐dichlorophenol) environmental pollutants on sperm motility was investigated. Spermatozoa were activated in double distilled water containing the different test substances and the motility was compared to controls of similar pH. From the investigated motility variables the sperm motility rate and swimming velocity reacted most to the environmental pollutants whereby the changes depended on the species and on the test substance. African catfish spermatozoa were the most resistant, chub and burbot spermatozoa showed medium resistance and brown trout spermatozoa were the most sensitive to the pollutants. With exception of 2,4‐dichlorophenol and zinc the effective concentrations of the tested pollutants exceeded the recommendation for surface waters 100–10·000‐fold and were in a range lethal for the fish themselves. Therefore, it was concluded that fish sperm motility is not a suitable marker for risk assessment of environmental pollutants.     

Some aspects of sustained training of rainbow trout, Salmo gairdneri Richardson

Groups of 6-7 cm length rainbow trout, Salmo gairdneri Richardson, were simultaneously trained at four water velocities (0, 1·4, 2·2 and 3·5 Ls^-1) for a period of 46 days. Oxygen consumption and swimming ability (fatigue time) were then measured. Only training at 3·5 Ls^-1 increased the swimming ability of the fish. A study of the relative proportion of the white and red muscles indicated that the white muscle was increasing its mass at velocities in excess of 2·2 Ls^-1. The oxygen consumption rate of the trained fish was lower than that of the untrained fish when considered over the whole velocity range.     

The acute lethal toxicity of mixtures of cyanide and ammonia to smolts of salmon, Salmo salar L. at low concentrations of dissolved oxygen

The survival of Atlantic salmon smolts on exposure to constant concentrations of cyanide and ammonia, singly and together, has been measured under laboratory conditions at a concentration of 5 mgl^-1 of carbon dioxide. The 24-h LC50 values of cyanide and of un-ionised ammonia, in fresh water, were 0·073 mg HCN l^-1 and 0·20 mg NH₃l^-1 respectively at a concentration of dissolved oxygen of 10 mg l^-1, and 0·024 mg HCN l^-1 and 0·08 mgNH₃l^-1 respectively at a concentration of dissolved oxygen of 3·5 mg l^-1. In 30% sea water the corresponding values were similar for cyanide but markedly higher for ammonioa. In 80% sea water the values were intermediate between those of fresh water and 30% sea water. Prior acclimation of the fish to the respective toxicant increased the resistance of the fish only slightly to cyanide, but with ammonia the 24-h LC50 was increased between 1·4 and 2-fold after acclimation for 1–3 days to between 0·2 and 0·5 of the 24-h LC50 value. Mixtures of cyanide and ammonia were between 0·6 and 1·25 times as toxic as expected, assuming simple additivity of toxicity.     

The feeding response of diploid and triploid Atlantic salmon and brook trout

Pair and group experiments were conducted to determine whether differences exist in feeding success between juvenile diploid and triploid salmonids in a competitive situation. In the pair experiments, 22 pairs (one diploid and one triploid) of size-matched Quebec-strain brook trout Salvelinus fontinalis (7·2–46·3 g) were fed an unlimited number of pellets three times a day for 5 days. Dominance was assigned to the fish which ate the most pellets within each pair. In the group experiments, groups of three diploid and three triploid size-matched fish were fed a restricted ration three times a day for 5 days. Hierarchical rank within the group was assigned based on the number of pellets consumed by each fish. The group experiment was repeated 10 times with Atlantic salmon Salmo salar (5·1–62·7 g), Quebec-strain brook trout (11·8-110·8 g), and large UNB-strain brook trout (18·2–33·0 g), and 12 times with smaller UNB-strain brook trout (0·6–2·0 g). A statistically significant difference in rank between ploidies was found only for the smaller UNB-strain brook trout in the group experiments, with diploids dominant over triploids. This suggests that there may be a difference in competitive feeding success between diploid and triploid brook trout early in development, but that this difference diminishes as the fish grow.     

The trout (Salmo trutta) population of the Afon Cwm, a small tributary of the Afon Dyfi, mid-Wales

Data are presented from a 10-year (1984 to 1993) study of a Salmo trutta population in the Afon Cwm, a small tributary of the Afon Dyfi, mid-Wales. The stream is a spawning and nursery area for sea trout. Growth of trout within the stream can be summarized by a von Bertalanffy growth coefficient ( K ) of 0·310, with asymptotic length (1∞) 21·6 cm and with length at age 1 of 7·6 cm. Mean population density in the whole stream varied from year to year between 0·05 and 0·60 0-group trout m⁻² and between 0·05 and 0·70 older trout m⁻². Mean biomass varied, between years, from 0·1 to 3·5 g m⁻² for 0-group and from 1·3 to 10·4g m⁻² for older trout. Loss between 3 and 5 months of age appeared to be proportionate at about 50 to 60% and instantaneous loss rate from 5 to 53 months of age varied from 0·04 to 0·10 month⁻¹ and was positively correlated with cohort number at 3 months of age. Production between 3 and 53 months of age varied between cohorts from 3 to 8 g m ⁻² live weight.     

The effect of acid water on the hatching of salmonid eggs

The survival of salmon Salmo salar , sea trout and brown trout Salmo trutta eggs in acid water in the range pH 3·5±7·0 was investigated over a period of three winters. The effects of fertilising the eggs in acid water at pH 4·0, 4·5 and 5·0, and dilution of the test media were also studied. There was considerable yearly variation in the numbers of eggs which hatched, but there were no marked differences between the three species in the tolerances of the eggs to acid water; pH 3·5 was lethal within 10 days to all the eggs, but at pH 4·5 and higher pH levels there was no obvious difference in hatching attributable to acidity.     

Body composition and energy allocation in life-history stages of brown trout

Energy contents of immature parr and smolts, and mature resident and anadromous brown trout Salmo trutta sampled from a small stream in southern Norway were estimated from lipid, protein and carbohydrate concentrations. In immatures the lipid concentrations were highest in parr in the autumn. Mean lipid concentrations increased significantly with age in parr sampled in autumn (1·3% in age 0+ to 3·4% in age 3+), whereas they did not in smolts. The lipid concentrations of parr in spring were not significantly different from those of similarly aged smolts. By contrast, the relative water content (%) decreased with age in parr in the autumn and increased with age in smolts, mean values being slightly higher in smolts (78%) than in parr (77%). Protein and carbohydrate concentrations did not vary with age in the immature fish, mean protein concentrations being 18·0, 17·5 and 16·8% in parr in the autumn and spring, and in smolts, respectively. In residents, the concentrations of lipids were lower and of water higher, in age group 1 than in older fish, whereas there was no significant variation with age amongst anadromous trout. The energy concentration of 2+ smolts (349 kJ 100 g^-1) was similar to that of 0+ parr in the autumn. Mean somatic energy density in autumn was 1·1 times higher in freshwater residents than in parr at age 1+ (407 and 387 kJ 100 g^-1) and marginally different at age 2+ (462 and 426 kJ 100 g^-1, respectively). The energy contents per unit mass of residents were 1·3–1·6 times that of similar aged smolts. Mean somatic energy density of anadromous trout (504 kJ 100 g^-1) was higher than that of residents (455 kJ 100 g^-1). Somatic energy, lipid and protein concentrations were correlated highly with water contents of all life stages, age and sex groups.     

Changes in tissue adenylates and water content of bluegill, Lepomis macrochirus, exposed to copper

Bluegill were exposed to copper (2–0 mg/1⁻¹ unfiltered) for 24, 48, 72 or 96 h at 24° C. This concentration approximated the 96 h LC20. Water content of liver increased 4–8% after 24 h exposure and muscle 4–6% by 48 h. These changes persisted throughout the 96 h experiments. Copper exposed fish exhibited decreases in muscle ATP, ADP, total adenylates, and energy charge by 48 h. There was a trend toward recovery of ATP with further exposure. Liver ATP of exposed fish was lower than controls at all intervals with the greatest difference evident at 48 h. No significant changes in brain adenylates were observed. Muscle and liver lactic acid was unchanged at 48 h exposure, therefore tissue hypoxia was not the cause of the adenylate changes. It was concluded that copper causes decreases in muscle and liver ATP several days before probable death of copper exposed fish and the changes seen are the result of dilution by increased tissue water, and the copper acting on certain cellular enzymes involved in detoxification and energy metabolism.     

Influence of available dietary carbohydrate content on tolerance of waterborne copper by rainbow trout,Salmo gairdneri Richardson*

The effect of increased available dietary carbohydrate on the tolerance of waterborne copper by rainbow trout was investigated. Trout were reared for six to eight weeks on one of four isocaloric and isonitrogenous diets which varied in available carbohydrate content due to either processing (extrusion v. steam-pelleting) or supplementation with cerelose (0 or 21%). The incipient lethal level (ILL) of copper for trout reared on the low-available-carbohydrate steam-pelleted diet was 350 μg I^?1, significantly higher than the 276 μg I^?1 shown for trout reared on the high-available-carbohydrate extruded diet. The ILL of copper for the low-carbohydrate group (0% cerelose) was 408 μg I^?1, significantly higher than the ILL of 246 μg I^?1 of trout reared on the high-carbohydrate diet (21% cerelose). Increased available dietary carbohydrate resulted in increased liver glycogen content and liver-body weight ratios and decreased liver protein content. Significant correlations were evident between waterborne copper tolerance and liver glycogen, liver-body weight ratios and liver protein. Relative to those on high carbohydrate diets, livers of fish on low-carbohydrate diets contained higher concentrations of copper after seven days of exposure to 0 or 196 μg I^?1 of copper. The elevated liver glycogen levels, resulting from increased dietary carbohydrate, are thought to have impaired liver function, thus reducing copper tolerance.     

The effects of temperature on muscle pH, adenylate and phosphogen concentrations in Oreochromis alcalicus grahami, a fish adapted to an alkaline hot-spring

The concentrations of phosphorylcreatine (PCr), adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inorganic phosphate (Pi), pyruvate and lactate were determined in freeze-clamped fast muscle samples from Oreochromis alcalicus grahami a fish adapted to extreme alkalinity (∼ pH 10·0) and high temperatures (Lake Magadi, Kenya). Specimens were analysed from both geothermally heated hotsprings (35–37°C) and from isolated cool pools (28°C) and from stocks acclimated to 20°C in the laboratory. The ratios of (ATP)/(ADP) and (ATP)/(ADP) (Pi) decreased with increasing body temperature consistent with an increase in glycolysis and tissue respiration rates, respectively. The apparent equilibrium constant of creatine kinase (K_CK), (creatine) (ATP)/(phosphorylcreatine) (ADP) was found to decrease with increasing temperature: 20·2 (20°C), 13·9 (28°C), 8·0 (37°C). A near constant muscle and blood pH (or slight increase in alkalinity with higher temperatures) was found regardless of body temperature (Blood pH 7·64, 7·74, muscle pH 7·27, 7·51 at 20°C and 35°C, respectively). These results are consistent with an unusual pattern of acid-base regulation in this species.     

Induction of metallothionein gene expression by cadmium and the retention of the toxic metal in the tissues of rainbow trout (Salmo gairdneri)

1. When rainbow trout were exposed to cadmium by intraperitoneal injection, there was a rapid (within 3hr) and significant (approx. 63%) loss of the metal from the whole bodies of the fish.2. Of the metal retained in the bodies of the fish (approx. 37% of the injected dose), more than 98% was accounted for collectively among the liver, kidney and gills.3. Subsequent maintenance of the rainbow trout in fresh water for up to 98 days post-metal administration, indicated that there was no further loss of the cadmium accumulated in the organs studied and that the distribution of the metal among the liver, kidney and gills remained unchanged over that period.4. During this 98-day period of maintenance of the fish, tissue concentrations of metallothionein-specific mRNA and metallothionein protein were quantified using riboprobe and ELISA systems respectively. Metallothionein-specific mRNA concentrations increased rapidly (within 24 hr) before falling back to levels similar to, or slightly greater than, those found in control animals. The concentration of metallothionein protein also increased significantly (within 3 days) then remained elevated thereafter.5. Throughout the experimental period, the concentrations of zinc and copper were also monitored in the liver, kidney and gills of the rainbow trout. The concentrations of each ion differed between each of the organs but did not change during the experiment.6. The induction of metallothionein gene expression by cadmium in the liver, kidney and gill of rainbow trout and the subsequent sequestration of the toxic metal is discussed with regard to the relative levels of these other essential metal ions.     

The relationship between mosaic muscle fibres and size in rainbow trout (Salmo gairdneri)

The dynamics of increase of the mosaic muscle in hatchery reared rainbow trout (2·3 to 61·3 cm fork length) are investigated. In trout <5 cm, all fibres are <40 μm in diameter; from 5 to 20 cm the diameter mode remains in the 0–39·9 μm class and there is some extension in range of diameter, thereby suggesting that mosaic muscle increase up to 20 cm is mainly by recruitment of new (small) fibres. When trout exceed 20 cm, mode of fibre diameter shifts to the 40–79·9 um class and fibres of larger diameter (> 100 μrn) appear but the subsequent overall fibre diameter frequency distribution changes little until 50 cm. Increase in muscle during the phase 20–50 cm seems partly attributable to increase in fibre diameter, but remains largely the result of recruitment of small fibres, although the mechanism of the latter process appears less clear than in fish of <20 cm. The recruitment of new fibres stops at 55 cm and further increase in mosaic muscle evidently depends upon the ability of existing fibres to increase in diameter. Possible means by which increasing muscle fibre diameter may limit the ultimate size which trout may achieve are discussed. A phenomenon of apparent reduction in fibre diameter in winter among fish 20–39·9 cm long is noted and its significance is considered.     

Water pH and urinary excretion in silver catfish Rhamdia quelen

The effect of acute exposure to different water pH levels on urinary excretion and plasma ion levels in silver catfish Rhamdia quelen was analysed. Fish were exposed to pH 4·0, 5·0, 7·5, 8·0, and 9·0 for 4 days and urine was collected. Other specimens were also exposed to the experimental pH for 24 h and blood was sampled. Urine flow rate, urine and plasma pH showed a significant trend to increase with the increase of water pH. Urinary Na⁺ excretion rate also increased and ammonia urinary excretion rate decreased with the increase of water pH. There was a significant trend to decrease volume, ammonia, Cl⁻ and Na⁺ urinary excretion rate with increasing mass in fish exposed to all pH levels studied. Plasma ammonia levels showed a slight decrease in fish exposed to water pH from 4·0 to 8·0, but those exposed to water pH 9·0 presented the highest ammonia levels. Most plasma ions and urinary excretion changes observed in silver catfish exposed to acidic or alkaline water were similar to those already detected in rainbow trout Oncorhynchus mykiss . In addition, the kidney and urinary bladder might participate on acid–base balance in silver catfish, since urine pH changed according to plasma pH.     

Evaluation of the contribution of supplemental plantings of brown trout Salmo trutta (L.) to a self-sustaining fishery in the Sydenham River, Ontario, Canada

An autumn planting of 4000 tagged yearling brown trout Salmo trutta (L.) in 1969 resulted in an over-winter survival of 26%, an angler recovery the following year of 8·1 % and made up 22 % of the March, 1970 standing population of the species. August standing populations of brown trout increased from 142 trout/ha (17·6 kg/ha) in 1969 to 360 trout/ha (39·3 kg/ha in 1970 while angler harvest of the species increased from 61 trout/ha (12·7 kg/ha) at a rate of 0·26 fish/h to 89 trout/ha (18·5 kg/ha) at a rate of 0·34/h. Using angler recovery and standing population as criteria the planting contributed substantially to the fishery. Actual contribution of stocked trout however, is questioned after detailed analysis of resident population structure and the potential of natural recruitment. It is suggested that the true benefit of stocked trout may be measured by the presence of those stocked fish in excess of the number of resident trout of that size predictable from a normal length distribution curve in waters with self-sustaining populations. Complexities in evaluating the merits of supplemental plantings of hatchery-reared brown trout to existing stream fisheries are examined.     

The immunoglobulin of the brown trout, Salmo trutta and its concentration in the serum of antigen-stimulated and non-stimulated fish

Immunoglobulin production in the primary and secondary immune response of brown trout to keyhole limpet haemocyanin has been investigated including the effect of dose size, route and number of injections, and the use of adjuvant. Antibody activity was found in the first fraction from Sephadex G200 and in the second from Sepharose 6B. Trout immunoglobulin had β₂—Γ₁ electrophoretic mobility, and S_app of 16·7 and an approximate molecular weight of 670 000 daltons. It was sensitive to dithiothreitol and stable at 56°C for 30 min. Immunoglobulin concentrations were measured by single radial immunodiffusion with a specific rabbit antiserum. Sera from non-injected trout had a mean immunoglobulin level of 7·3 ± 0·3 mg ml⁻¹ which accounted for 10% of the total serum protein. Phosphate buffered saline-injected controls contained 6·7 ± 0·2. In fish given a single injection the mean concentration ranged from 7·5 to 12·9 and in those given more than one injection from 12·6 to 16·8. The use of adjuvant resulted in higher immunoglobulin concentrations. Neither dose nor route had any significant effect on the primary response. However, in the secondary response the intramuscular route resulted in significantly increased immunoglobulin production.     

The interactions of water hardness and pH with the acute toxicity of zinc to the brown trout, Salmo trutta L.

Exposure of brown trout, Salmo trutta , to zinc under continuous flow conditions over 96 h showed that both water hardness and pH exert major influences on the toxicity of the metal. 96-h LC50 values for total zinc ranged from <0.14mg 1⁻¹ in alkaline soft water (pH 8; lOmg 1⁻¹ as CaCO₃) to 3.20 mg 1⁻¹ in acidic hard water (pH 5; 204 mg 1⁻¹ as CaCO₃). A variable reduction in zinc toxicity in hard water compared with soft water over the pH range 4–9 was attributed to high external calcium. Zinc toxicity was positively correlated with decreasing acidity over the pH range 5–7, the metal being most toxic at pH 8–9 where metal complexes predominate. Below pH 5 metal toxicity also increased, irrespective of hardness. Water hardness and pH interacted with zinc toxicity in a complex manner, apparently dependent on physical and chemical transformations of the metal, and as changes in uptake. detoxification and excretion by the fish.