Mebendazole/trichlorfon combination: a new anthelmintic for removing monogenetic trematodes from fish

Mebendazole, trichlorfon, and a combination of these two drugs were evaluated for anthelmintic properties against the external monogenetic trematodes of fish, Gyrodactylus elegans and Dactylogyrus vastator . Mebendazole effectively removed G. elegans after a 24-h. exposure to 0·01 mg l^-1, but it had no effect on D. vastator up to 2·0 mg l^-1. Trichlorfon was 95% effective on D. vastator between 0·4 and 1·6 mg l^-1 after a 24-h exposure, but it had no effect on G. elegans up to 2·0 mg l^-1. A combination of mebendazole at 0·4 mg l^-1 and trichlorfon at 1·8mgl^-1 was 100% effective on both parasites. Trichlorfon appeared to inhibit the action of mebendazole on G. elegans , but mebendazole had no apparent inhibition on the action of trichlorfon to D. vastator . The minimum effective exposure time was 24 h and shorter exposure times, even at high dose levels, were not effective. The combination had no apparent toxic effect on fish, except possibly catfish, and field tests in various geographical areas of the United States showed that the combination was effective in all cases.     

The effect of dissolved oxygen and salinity on the toxicity of ammonia to smolts of salmon, Salmo salar L.

The survival of Atlantic salmon smolts on exposure to constant concentrations of ammonia has been measured under laboratory conditions. At concentrations of dissolved oxygen close to the air-saturation value, the 24-h LC50 of un-ionised ammonia is 0.15 mg NH₃1⁻¹ in fresh water (hardness 264 mg 1⁻¹ as CaCO₃) and 0.3 mg NH₃1⁻¹ in 30% sea water; at concentrations of dissolved oxygen of 3.5 mg 1⁻¹ in fresh water and 3.1 mg 1⁻¹ in 30% sea water, the 24-h LC50 is 0.09 mg NH₃ 1⁻¹ and 0.12 mg NH₃ 1⁻¹ respectively; for fish acclimated for 1 day to a concentration of ammonia close to the 24-h median for un-acclimated fish, the median is increased between 38 and 79%, depending on test conditions.     

Effects of pollutants in fresh waters on European non-salmonid fish I: Non-metals

As part of a programme of acquiring data for preparing standards to safeguard European, nonsalmonid, freshwater fish from pollution, toxicity tests were carried out in hard, well-aerated water. Asymptotic median lethal concentrations (LC50s) of undissociated ammonia, cyanide, nitrite and phenol to one or more of three species were determined. The LC50s were as follows: to common carp 16mg1^-1 as NO₂–N; to perch 0.1 mg1^-1 as HCN; to roach 0.35 mg1^-1 as NH₃-N, 0-11mg1^-1 as HCN, 10.1 mg1^-1 asNO₂-Nand 10mg^-1 as phenol. In order to define these LC50s, exposure periods within the range 0.3 days (phenol) to 14 days (nitrite) were required. Comparisons are made with other data and the tentative water quality 'criteria' proposed by the European Inland Fisheries Advisory Commission.     

Toxicity versus avoidance response of golden shiner, Notemigonus crysoleucas, to five metals

Avoidance thresholds and 96-h LC50 values were determined for golden shiners, Noiemigonus crysoleucas , for five individual elements: chromium, Cr; copper, Cu; cadmium, Cd; arsenic, As; selenium, Se. The avoidance concentrations were 73, 26 and 28 μgl^-1 for Cr-VI, Cu and As-III, respectively. Cadmium and Se were not avoided at experimental concentrations up to 68 and 3489 μg1^-1, respectively. Acute flow-through 96-h LC50 values were Cr-VI 55·0, Cu 84·6, and As-III 12·5 mg 1^-1, which were more than two orders of magnitude above avoidance concentrations. The acute flow-through 96-h LC50 values for Cd and Se were 2·8 and 11·2 mg 1^-1, respectively. These concentrations are 31 and 2·2 times the highest concentration employed in the avoidance tests, neither of which were avoided by the test organisms. Thus, simple toxicity tests do not identify the environmental hazard of some elements, and the most toxic elements may not elicit a behavioural response. When used in concert with tests of organism function, more realistic indicators of environmental hazard or safety may be determined.     

Comparative effects of long-term hypoxia on growth, feeding and oxygen consumption in juvenile turbot and European sea bass

When juvenile turbot Scophthalmus maximus and sea bass Dicentrarchus labrax were fed to satiation, growth and food intake were depressed under hypoxia (3·2±0·3 and 4·5±0·2 mg O₂ l^-1). However, no significant difference in growth was observed between fishes maintained in hypoxia and fed to satiation and fishes reared in normoxia (7·4±0·3 mg O₂ l^-1) and fed restricted rations (same food intake of fishes at 3·2 mg O₂ l^-1). Routine oxygen consumption of fishes fed to satiation was higher in normoxia than in hypoxia due to the decrease in food intake in the latter. Of the physiological parameters measured, no significant changes were observed in the two species maintained in hypoxia. This study confirms the significant interaction between environmental oxygen concentrations, feeding and growth in fishes. Decrease in food intake could be an indirect mechanism by which prolonged hypoxia reduces growth in turbot and sea bass, and may be a way to reduce energy and thus oxygen demand.     

Physiological stress effects of continuous- and pulsed-DC electroshock on juvenile bull trout

Juvenile bull trout Salvelinus confluentus exposed to continuous- or pulsed-DC electroshock exhibited rapid elevations in plasma cortisol and glucose, but plasma chloride did not change. In a 1-h experiment using 240 V at 1·4 A of 60-Hz pulsed DC (voltage gradient 0·81 V cm⁻¹), which proved lethal, plasma cortisol and glucose rose significantly within 15 min of a 10-s electroshock. Plasma cortisol reached a peak level of 156 ± 18 ng ml⁻¹ at 45 min and then decreased, whereas plasma glucose reached its highest level of 179 ± 7·5mg dl⁻¹ at 1 h. In a 24-h experiment using lower dosages, plasma cortisol increased from 6·1-16 ng ml⁻¹ to peak levels of 155–161 ng ml⁻¹ in 1 h in response to a 10-s electroshock of continuous (130 V, 0·5 A, 1·45 V cm⁻¹) or pulsed (120 V, 0·5 A, 60 Hz, 0·55 V cm⁻¹) DC. Although plasma concentrations declined thereafter, levels remained above control values at 24 h. Plasma glucose was elevated from 60–65 to 120–134 mg dl⁻¹ after 1h by both electroshock treatments and remained near or above those levels for the 24-h duration. Plasma cortisol and glucose levels were much higher in electroshocked bull trout at 1 h compared with those in fish 1 h after receiving a 30-s handling stressor (cortisol, 90 ± 12 ng ml⁻¹; glucose, 82 ± 6·1 mg dl⁻¹). The results indicate that both continuous and pulsed DC were more stressful to juvenile bull trout than handling and that recovery, at least for pulsed DC, may take longer than 24 h.     

Effect of acute and chronic ammonia and nitrite exposure on oxygen consumption and growth of juvenile big bellied seahorse

Juvenile big bellied seahorse Hippocampus abdominalis were exposed acutely and chronically to elevated ammonia and nitrite {24 h exposure: 0·01, 5·0, 10·1, 14·8 and 19·9 mg l⁻¹ total ammonia-nitrogen [TA-N] and <0·001, 74·4, 99·2 and 123·6 mg l⁻¹ [NO₂-N] nitrite-nitrogen and 35 days exposure: 0·11, 0·55, 1·67 and 3·07 mg l⁻¹ TAN and <0·001, 0·92, 4·67 and 9·10 mg NO₂-N l⁻¹}. Significant ( P <0·001) increases in oxygen consumption rate and ventilation frequency occurred at 14·8, 19·9 mg l⁻¹ TA-N and 99·2, 123·6 mg l⁻¹ NO₂-N for acutely exposed fish. Oxygen consumption rate was significantly ( P <0·05) elevated at 1·67 and 3·07 mg l⁻¹ TA-N in chronically treated fish and ventilation frequency increased significantly ( P <0·05) at 0·55, 1·67, 3·07 mg l⁻¹ TA-N and 4·59, 9·10 mg l⁻¹ NO₂-N. There were no significant differences in growth between controls and ammonia exposed fish. Mortalities occurred at 14·8, 19·9 mg l⁻¹ TA-N.     

Short-term thermal acclimation induces adaptive changes in the inner mitochondrial membranes of fish skeletal muscle

In the oxidative muscles (musculi laterales superficiales) of crucian carp Carassius carassius acclimated for 6 weeks to either 5 or 25° C, the volume density and the surface density of fibres per tissue did not differ significantly between the control and experimental groups. The correlation ratio (μ²) for these values was below 50, 39·3 and 43·9 respectively. After acclimation to 5° C, the surface density of outer mitochondrial membrane per fibre increased significantly from 0·93 to 1·23m² cm⁻³ in the summer population but dropped from 0·94 to 0·67 m² cm⁻³ in the winter population. The surface density of outer mitochondrial membrane per mitochondrion increased from 3·24 to 4·52 m² cm⁻³ in summer fish. After acclimation to 25° C, the surface density of inner mitochondrial membranes per muscle fibre decreased from 4·04 to 1·79 m² cm⁻³ in summer fish and from 3·86 to 1·07 m² cm⁻³ in winter fish. The surface density of inner mitochondrial membranes per mitochondrion increased from 14·17 to 15·60 m²cm⁻³ in summer fish but dropped from 13·91 to 10·67 m² cm⁻³ in winter fish. Correlation matrices demonstrate a negative correlation of the surface density of outer mitochondrial membrane per mitochondrion with the volume density of mitochondria per fibre and temperature, suggesting cold-induced proliferation of small mitochondria. It was concluded that short-term cold acclimation increased surface area of the inner mitochondrial membranes in summer fish.     

Changes in hypoxia tolerance during metamorphosis of bonefish leptocephali

Survival times of metamorphosing leptocephali of the bonefish Albula sp. placed in hypoxic sea water (0·68 mg O₂ l^-1) decreased by about three-fold (from c. 15 to 5 min) over the 10 day metamorphic period. Increased sensitivity to hypoxia coincided with increased larval oxygen demand during metamorphosis. Plots of hypoxic survival time against standard length or wet mass suggested that metamorphosis (phase II of larval development) could be divided into subphases (IIa and IIb). American Public Health Association.     

Protein synthesis, nitrogen excretion and long-term growth of juvenile Pleuronectes flesus

This study aimed to measure protein synthesis using a stable isotope method, investigate protein-nitrogen flux in a flatfish Pleuronectes flesus , and use the data to test the hypothesis that individual differences in growth efficiency were related to individual differences in protein-nitrogen flux mediated through differences in protein synthesis and degradation. Three measurements of protein-nitrogen flux via consumption, protein synthesis and nitrogenous excretion were made for individual flounder during a 212-day period and fractional rates of protein-nitrogen flux were scaled for a 50–g flounder to provide mean values for protein consumption (2·11 ± 0·21% day⁻¹), protein synthesis (2·08±0·23% day⁻¹), protein growth (0·71±0·06% day⁻¹) and protein degradation (1·37±0·24% day⁻¹). Mean rates of nitrogenous excretion were 0·142 mg N g⁻¹ day⁻¹ and 0·047 mg N g⁻¹ day⁻¹ for ammonia and urea, respectively. Individual flounder had different protein growth efficiencies and this was correlated negatively and significantly with mean rates of protein synthesis ( r - 0·70; P <0·05) and degradation ( r - 0·67; P < 0·05) and correlated positively and significantly with the efficiency of retaining synthesized protein ( r +0·63, P <0·05). This supported the proposed hypothesis that flounder which grow more efficiently achieve this through adopting a low protein turnover strategy.     

Performance and diacetyl production of commercial strains of malolactic bacteria in wine

This study compares 11 commercial cultures of Leuconostoc oenos and Lactobacillus plantarum in Cabernet Sauvignon, Pinot Noir and Chardonnay wines. Performance of the cultures was found to be greatly influenced by wine type. Better survival of the bacteria was observed in Cabernet Sauvignon and Pinot Noir wines. The time necessary to complete malolactic fermentation (MLF) was 65 ± 14 d for Chardonnay, 71 ± 3 d for Cabernet Sauvignon, and 25 ± 8 d for Pinot Noir. The maximal rate of malate utilization was 0·4 g d^-1 for Pinot Noir, and 0·2 g d^-1 for the two other wine types. Final diacetyl concentration was lower in Chardonnay wines (highest 0·58 mg l^-1) compared to the other wines (highest 5·8 mg l^-1). Malic and citric acid were co-metabolized by all strains. None of the strains metabolized glycerol. Significant differences in final diacetyl concentration of wine vinified with the different strains were found. Panelists could reliably differentiate MLF wines from non-MLF wines, irrespective of their diacetyl content, indicating that diacetyl is not the only important MLF flavour.     

The toxicity of iron to brown trout and effects on the gills: a comparison of two grades of iron sulphate

The 96-h LC₅₀ on brown trout Salmo trutta of a commercial iron (III) sulphate liquor, used for treating reservoirs to reduce algal growth, was 28 mg total Fe l⁻¹ (0·05 mg soluble Fe l⁻¹). The 96-h LC₅₀ for analar grade iron (III) sulphate was 47 mg total Fe l⁻¹ (0·24 mg soluble Fe l⁻¹). Lethal and sublethal exposure to both grades of iron resulted in accumulation on the gill, which appears to be the main target for iron toxicity. Greater iron accumulation occurred during exposure to commercial iron sulphate liquor. Physical clogging of gills and gill damage was seen during lethal and sublethal exposure to iron. Gill tissue analysis showed no evidence of iron uptake into gill tissues during lethal or sublethal exposure to iron. Iron did not accumulate in plasma of fish exposed to iron compared to controls. Respiratory disruption due to physical clogging of the gills is suggested as a possible mechanism for iron toxicity.     

Differential survival of juvenile sockeye and coho salmon exposed to low dissolved oxygen during winter

Juvenile sockeye salmon (43–78 mm) survived 100% for 24 h in cages in ice–covered Black Lake, Alaska at oxygen saturations >65% (9 mg l^–1), but only 45% at 24% saturation (3·0–3·3 mg l^–1) and none at <17% saturation (2·3 mg l^–1). All juvenile coho (50–120 mm) survived 100% for 24 h down to 21% oxygen saturation (3·1 mg l^–1), and all 50 coho survived 4–5 days at 23–24% saturation (3·2–3·3 mg l^–1).     

Comparison of field-based and indirect estimates of daily food consumption in larval perch and zander

Since bioenergetics models for 0+ fish have seldom been validated by field consumption estimates, field-based and indirectly estimated daily food rations were compared in larval perch Perca fluviatilis and zander Stizostedion lucioperca. Field-based estimates were calculated with linear and exponential evacuation rates based on gut fullness data during a 24-h cycle, with hourly field samplings instead of the normally recommended 3-h intervals. Indirect calculations used bioenergetics modelling with variable activity multipliers ( A ). Field-based estimates of daily rations ranged between 0·21 and 0·27 g g⁻¹ day⁻¹ in perch (mean L _T 13·1 mm) and 0·31–0·40 g g⁻¹ day⁻¹ in zander (mean L _T 10·6 mm). The higher values were calculated by using the exponential model. Daily rations calculated by bioenergetics modelling with A = 1 were only slightly higher than direct estimates in both species. However, if A values >1 were used, calculated daily rations were substantially higher than direct estimates. Estimates of daily ration based only on every third value ranged between 41 and 72% compared with 1-h intervals, mainly because of lower estimates of evacuation rate.     

Effects of culture conditions on Pectinatus cerevisiiphilus and Pectinatus frisingensis metabolism: a physiological and statistical approach

The genus Pectinatus has been often reported in beer spoilage with off-flavours. The bacteria are strictly anaerobic, Gram-negative rods. Propionate and acetate are the main fermentation products from glucose in the two species belonging to the genus, P. cerevisiiphilus and P. frisingensis. Amino acids routinely present at a high level in beer were not growth substrates for both species, and a significant accumulation of succinate was observed with lactate as growth substrate. Both Pectinatus ssp. showed almost identical fermentation balances on glucose. Growth kinetics of both glucose-grown species were unchanged under a N₂, H₂ or 20% CO₂-containing atmosphere. Combinations of culture medium pH values from pH 3·9 to pH 7·2, of glucose levels between 5 and 55 mmol l^-1, and of lactate concentrations varied from 4 to 40 mmol l^-1 demonstrated that biomass and volatile fatty acids production were proportional to glucose concentration for both Pectinatus species. A significant increase of volatile fatty acid production was measured for both species at the lowest pH values with a lactate or a glucose concentration increase. The maximum biomass production was observed at pH 6·2 for P. cerevisiiphilus , and between pH 4·5 and pH 4·9 for P. frisingensis. Glucose and lactate or pH value were dependent with regard to propionate and acetate production in P. frisingensis. On the other hand, the variations of these three parameters were independent with regard to biomass production for both strains, and to volatile fatty acids production for P. cerevisiiphilus. Addition of ethanol to glucose-grown cultures completely inhibited growth at 1·3 mol l^-1 ethanol for P. cerevisiiphilus , and at 1·8 mol l^-1 for P. frisingensis.     

Body temperature and seawater adaptation in farmed Atlantic salmon and rainbow trout during prolonged chilling

The core temperature of the rainbow trout Oncorhynchus mykiss (3·5 kg) dropped to 1·0° C during the first 6 h of chilling at 0·5° C, remained stable until 24 h, and dropped significantly to 0·7° C after 39 h. Blood plasma osmolality increased and muscle moisture content decreased gradually with increasing chilling time. After 39 h of chilling, the rainbow trout experienced 40 mosmol l^-1 higher blood plasma osmolality and 2·8% less muscle moisture content compared with initial values. In the Atlantic salmon Salmo salar (5·3 kg), core temperature dropped to 1·3° C and blood plasma osmolality increased significantly during the first 6 h of chilling at 0·5° C, but remained relatively stable throughout the rest of the experimental period. After 39 h of chilling, the salmon experienced 20 mosmol l^-1 higher blood plasma osmolality and 0·5% less muscle moisture content compared with initial values. In rainbow trout muscle moisture content was inversely related to blood plasma osmolality indicating reduced seawater adaptation with increasing hours of chilling. No such relationship was observed in the Atlantic salmon. Hence, changes in plasma osmolality and muscle moisture in the Atlantic salmon do not indicate osmoregulatory failure since the new levels, once established, were maintained throughout the chilling time.     

Assessment of microbial involvement in the elevation of copper levels in drinking water

A study of bacterial populations in metropolitan Adelaide domestic reticulation pipes was conducted to investigate a possible link between copper in drinking water and biofilms. Biofilm densities from cold water copper pipes at 10 sample sites were measured by viable cell counts. The range detected was from <2 × 10¹ to 3·25 × 10⁷ cfu cm⁻². Five isolates were selected for further experiments as they represented a range of responses to solvated copper and relative tendency for adhesion on glass slides. Drinking water supplied to the Adelaide Hills is high in total organic carbon (TOC; 22·57 mg C l⁻¹) and has a negative Langelier Index (LI; −1·16), whereas Adelaide metropolitan water undergoes filtration and has both a lower TOC and LI (10·72 mg C l⁻¹, LI, −0·49). Copper coupons were exposed to biofilm isolates (24 h), washed and resuspended in Adelaide metropolitan and Adelaide Hills water. Copper coupons not exposed to biofilm isolates were suspended in respective waters as a control. After 5 d of incubation, the copper content of Adelaide Hills water (4·71 ± 0·87 mg Cu l⁻¹), in which the copper coupons were suspended, consistently exceeded values obtained in the metropolitan Adelaide water (1·17 ± 0·249 mg Cu l⁻¹). The concentration of copper in the Adelaide Hills water was influenced by the bacterial species forming the biofilm on the coupon, with Agrobacterium sp. producing significantly higher levels of soluble copper than the control. The experiments reported here indicate that the suspended organic carbon, the aggressivity of the water and the biofilm may independently or synergistically increase the dissolution of copper from pipes into drinking water.     

Variation in routine metabolism of juvenile muskellunge: evidence for seasonal metabolic compensation in fishes

Metabolic rate of age 0 muskellunge Esox masquinongy ranged from 0·10 at 5° C to 0·24 mg O₂ g^-1 h^-1 at 25° C and was significantly higher in spring and autumn than during winter months at comparable water temperatures. Reduced metabolic rate in winter was consistent with the metabolic compensation hypothesis, implying that metabolism of muskellunge varies independently of acclimation temperature and gonadogenesis. Moreover, seasonal variation in metabolic rate has important implications for energy budget studies. Single-season estimates of esocid metabolism may be inadequate to describe annual energy requirements; the magnitude of errors will depend on the time of year metabolic rate was measured. As a result, it is suggested that seasonal variation in metabolic rate be incorporated into energy budget determinations for fishes.     

The effect of temperature fluctuations on oxygen consumption and ammonia excretion of underyearling Lake Inari Arctic charr

Underyearling Lake Inari Arctic charr Salvelinus alpinus were acclimated to 11·0) C for 3 weeks, and then one group was maintained at 11·0) C and others were exposed to 14·4) Cconst, 17·7) C_const or a diel fluctuating temperature of 14·3° C ± 1° C (14·3° C_fluc). Routine rates of oxygen consumption and ammonia excretion were measured over 10 days before the temperature change and over 31 days following the change. Measurements were made on fish that were feeding and growing. The temperature increase produced an immediate increase in oxygen consumption. There was then a decline over the next few days, suggesting that thermal acclimation was rapid. For groups exposed to constant temperature there was an increase in oxygen consumption ( M _accl, mg kg⁻¹ h⁻¹) with increasing temperature ( T ), the relationship being approximated by an exponential model: M _accl= 46·53e0·^{086 T} . At 14·3° C_fluc oxygen consumption declined during the 3–4 days following the temperature shift, but remained higher than at 14·4° C_const. This indicates that small temperature fluctuations have some additional influences that increase metabolic rate. Ammonia excretion rates showed diel variations. Excretion was lower at 11° C_const than at other temperatures, and increases in temperature had a significant effect on ammonia excretion rate. Fluctuating (14·3° C_fluc) temperature did not influence ammonia excretion relative to constant temperature (14·4° C_const).     

A 5-h screening and 24-h confirmation procedure for detecting Escherichia coli O157 : H7 in beef using direct epifluorescent microscopy and immunomagnetic separation

An antibody-direct epifluorescent filter technique (Ab-DEFT) detected 100% of the raw ground beef samples inoculated with Escherichia coli O157 : H7 cells (0·15 cells g⁻¹) and incubated in a prewarmed, modified buffered peptone water (mBPW) non-selective enrichment broth for 5 h at 42°C in an orbital shaking water bath (200 rev min⁻¹). Over 50% of the microscopic fields viewed were positive (1–10 fluorescent cells field⁻¹) in the Ab-DEFT. All positive screening results were confirmed within 24 h by subjecting 1 ml of the mBPW to the Dynabeads^® anti- E. coli O157 immunomagnetic separation procedure, followed by plating on MacConkey sorbitol agar containing 5-bromo-4-chloro-3-indolyl-β- D -glucuronide. At this cell concentration, 41·7% of the inoculated samples were detected by the conventional method involving a 24-h selective enrichment. Exposure to viable cells before filtration was minimized by using a 0·58% formaldehyde concentration for 5 min at 50°C (killed >4·00 logs of E. coli O157 : H7 cells) without affecting cell fluorescence.