Effects of metomidate hydrochloride sedation on blood glucose and marketability of transported threespot gourami Trichogaster trichopterus

Our objectives were to determine whether sedation with metomidate hydrochloride (hereafter, "metomidate") during transportation of threespot gourami Trichogaster trichopterus would prevent an increase in blood glucose levels and improve fish marketability (i.e., based on appearance and behavior) in comparison with unsedated controls. Threespot gourami are obligate air-breathers that possess a labyrinth organ, enabling the fish to respire air above the water surface; these fish should be lightly sedated during transport. Fish were transported for approximately 24 h via truck and domestic airline. Blood was sampled at 0, 2, 6, and 12 h posttransport ation, and appearance and behavior were observed at 0, 2, 4, 6, and 12 h and 7 d posttransportation. Metomidate concentrations tested were 0.0 (control), 0.1, 0.2, 0.3, and 0.4 mg/L. At the concentrations tested, metomidate neither inhibited elevations in blood glucose nor improved marketability. Fish that were transported with 0.3-mg/L metomidate were less marketable based on behavioral indices, and fish that were transported with 0.4-mg/L metomidate had higher glucose levels than control fish. Use of metomidate as a transport sedative for threespot gourami should be considered with caution and may be problematic at the concentrations tested; however, further research examining additional indices of stress may clarify metomidate use for this species.     

Investigational Use of Metomidate Hydrochloride as a Shipping Additive for Two Ornamental Fishes

Abstract

During shipping, ornamental fish can be stressed due to handling, high stocking densities, and deteriorating water quality. Adding sedatives, such as metomidate hydrochloride, to shipping water may improve fish survival rates and the percentage of fish in saleable condition. Although the effects of metomidate hydrochloride on the stress response in fish have been studied, its application as a shipping additive has not been well investigated, particularly for tropical ornamental fishes shipped under industry conditions. Convict cichlids Cichlasoma nigrofasciatum and black mollies Poecilia sphenops were evaluated for 7 d after a 24-h period of exposure (including ground and air transport) to one of four metomidate hydrochloride concentrations: 0.0, 0.2, 0.5, and 1.0 mg/L. Immediate posttransport and cumulative mortality data, as well as 12-h and 7-d posttransport appearance and behavior scores, were generated. In convict cichlids, the highest dose of metomidate hydrochloride (1.0 mg/L) reduced mortality (0% compared with cumulative means of 5.5–9.2% in other groups) and increased the percentage of saleable fish (91.7% were immediately saleable compared with 12.5–50% in other groups). No effect was detected in black mollies at any concentration tested. Metomidate hydrochloride showed promise as a shipping additive for convict cichlids, but further studies are warranted to evaluate species-specific responses in other ornamental species.     

Pharmacokinetic and pharmacodynamic properties of metomidate in turbot (Scophthalmus maximus) and halibut (Hippoglossus hippoglossus)

Metomidate was administered to halibut (Hippoglossus hippoglossus) and turbot (Scophthalmus maximus) intravenously at a dose of 3 mg/kg bodyweight, as a bath treatment at a dose of 9 mg/L water for 5 min to study the disposition of metomidate, and as bath treatment (9 mg/L) for 10 min to study the absorption and effect of metomidate on respiration and balance/motor control. Additionally, turbot were given metomidate orally at a dose of 7 mg/kg. The studies were performed in seawater at a temperature of 10.3 +/- 0.4 degrees C (halibut) and 18.0 +/- 0.3 degrees C (turbot). Pharmacokinetic modeling of the data showed that metomidate had shorter elimination half-life and higher plasma concentrations in turbot compared with halibut, both species displaying a rapid uptake, distribution and excretion. Following intravenous administration, the volumes of distribution at steady state (Vd(ss)) were 0.21 L/kg (halibut) and 0.44 L/kg (turbot). Plasma clearances (Cl) were 0.099 L/h.kg in halibut and 0.26 L/h.kg in turbot and the elimination half-lives (t(1/2)lambdaz) were calculated to be 5.8 h and 2.2 h in halibut and turbot, respectively. Mean residence times (MRT) were 2.2 h in halibut and 1.7 h in turbot. Following oral administration, the t(1/2)lambdaz was 3.5 h in turbot. The maximum plasma concentration (Cmax) was 7.8 mg/L in turbot 1 h after administration. The oral bioavailability (F) was calculated to 100% in turbot. Following 5 min bath the maximum plasma concentrations (Cmax), which were observed immediately after end of the bath, were 9.5 mg/L and 13.3 mg/L in halibut and turbot, respectively. Metomidate rapidly immobilized the fish, with respiratory depression, reduced heart rate, and loss of balance/motor control within 1 min (mean). Recovery was slow, with resumed balance/motor control after 26.4 min. Opercular respiration movements were resumed more rapidly with a recorded mean of 1.7 min. Oral administration was demonstrated to be a way of immobilizing fish, for example in large aquariums, without exposing them to unwanted stress.     

Effect of Dietary Vitamin E on Cortisol and Glucose Responses to Handling Stress in Juvenile Beluga Huso huso

Abstract

An 8-week feeding experiment was conducted to investigate the effect of dietary vitamin E on the physiological response to handling stress in juvenile beluga Huso huso. Fish were fed six experimental diets supplemented with 0, 25, 50, 100, 200, or 400 mg Dl-all-rac-α-tocopherol acetate/kg diet. At the end of the experiment, the fish in each tank were subjected to acute handling and air exposure stress. Cortisol and glucose were measured as the primary hormonal and secondary metabolic responses to the stressors, both before and 3 h after application of the stressors. The growth parameters and feed utilization rates were significantly lower in fish fed the diet not supplemented with vitamin E than in fish fed diets supplemented with vitamin E. Cortisol concentration was not affected by dietary treatment but glucose concentration was. Fish fed vitamin E at 0, 25, 100, and 400 mg/kg diet had higher concentrations of glucose than those fed vitamin E at 50 and 200 mg/kg. However, fish fed diets with 50 and 200 mg/kg exhibited higher growth rates. These results indicate that dietary vitamin E has some effect on plasma glucose but no effect on plasma cortisol. In general, when the stressors were applied to belugas, the glucose and cortisol responses were relatively low. This may be due to higher resistance and lower physiological responses to these types of stressors by this species or by chondrosteans in general.

Received January 10, 2011; accepted August 4, 2011     

Safety of Strontium Chloride as a Skeletal Marking Agent for Pacific Salmon

Abstract

The purpose of this study was to evaluate the biological effects associated with administering strontium chloride as a marking agent to age-0 Chinook Salmon Oncorhynchus tshawytscha fry. Fish were held in a 0× (0 mg/L), 1× (3,000 mg/L; current standard dosage), 3× (9,000 mg/L), or 5× (15,000 mg/L) solution of strontium chloride for 72 h (three times the standard duration of 24 h). The mortality among fish in the 5× strontium chloride exposure group was significantly higher than that observed in the other groups. A dose-related effect on general fish behavior and on feeding behavior was observed. Fish in all test tanks appeared to feed to satiation, except for fish in the 5× tanks during days 2 and 3. Fish in all other test tanks behaved normally. No dose-related effect on fish growth was detected. Histopathological evaluations showed that fish in the 5× exposure group had a significantly higher number of gill lesions than the 0× group. Our mortality, behavioral, and histological assessments suggested that juvenile Chinook Salmon could be safely immersed for three consecutive days in a 9,000-mg/L solution of strontium chloride. This finding potentially expands the present 1,000–3,000-mg/L dosage and 24-h holding period that can be used to mark juvenile fish with strontium chloride solutions. The research also provides necessary target animal safety data for U.S. Food and Drug Administration approval of strontium chloride as an alternative marking method that is suitable for fish with a short holding time.

Received February 19, 2017; accepted July 16, 2017 Published online September 22, 2017     

Preliminary investigations of hydrogen peroxide treatment of selected ornamental fishes and efficacy against external bacteria and parasites in green swordtails

The objectives of these preliminary studies were to evaluate the use of hydrogen peroxide (H2O2) for the treatment of selected species of ornamental fishes and its efficacy in treating external bacteria and parasites. In the first part of the study, fish of five species (serpae tetra Hyphessobrycon eques (also known as Serpa tetra H. serpae), tiger barb Puntius tetrazona, blue gourami Trichogaster trichopterus, suckermouth catfish Hypostomus plecostomus, and green swordtail Xiphophorus hellerii) were exposed to H2O2 for 1 h at concentrations between 6 and 34 mg/L or for 24 h at concentrations between 1 and 6 mg/L. The results were species specific: green swordtails tolerated all of the treatments, serpae tetras and tiger barbs were sensitive only to the highest concentration, and mortalities of suckermouth catfish and blue gourami were recorded in every treatment. In the second part of the study, clinically healthy green swordtails and fish infested with external motile rod-shaped bacteria (i.e., Ichthyobodo spp., Trichodina spp., and Gyrodactylus spp.) were treated with several concentrations of H2O2. A single H2O2 treatment of 3.1 mg/L or more for 1 h effectively eliminated external bacteria, concentrations of 6.5 mg/L or more appeared to effectively kill Ichthyobodo spp., and none of the treatments tested was effective against Trichodina spp. or Gyrodactylus spp. These preliminary findings suggest that H2O2 is effective for treating certain external bacterial infections and flagellate infestations in some species of ornamental fish at the dosages tested. Other treatment regimens may need to be tested for effectiveness against Trichodina spp. and Dactylogyrus spp.     

Analysis of Short-Term Cortisol Stress Response in Channel Catfish by Anesthetization with Metomidate Hydrochloride and Tricaine Methanesulfonate

The ability of the anesthetics metomidate hydrochloride and tricaine methanesulfonate (MS-222) to mitigate the cortisol stress response of Channel Catfish Ictalurus punctatus was evaluated during a 10-min confinement stress. The cortisol concentrations of Channel Catfish anesthetized in metomidate hydrochloride remained consistent throughout the 10-min exposure; however, for fish anesthetized with MS-222 and nonanesthetized fish, cortisol concentrations were approximately 7- and 22-fold higher, respectively, than the baseline concentrations. While both anesthetics reduced cortisol concentrations relative to those of nonanesthetized fish, these results suggest that MS-222 is an appropriate anesthetic to use during the initial 5 min of sedation and that metomidate hydrochloride is appropriate for longer periods of sedation.

Received November 18, 2014; accepted April 9, 2015     

Effect of posttransportation grazing on the physiological condition and meat quality traits of Black Bengal goats

This study was designed to reveal the role of posttransportation grazing on the physiological condition and meat quality traits of Black Bengal goats. Twenty‐four castrated male Black Bengal goats were divided into a control (untransported) group and three treated groups: Walking and Transportation with Human Interference group (WTHI) (30 min walking before 6 hr transport and then 30 min walking with human interference), posttransportation grazing for 48 hr (PTG1), and posttransportation grazing for 72 hr (PTG2). The WTHI and PTG1 groups had a significant reduction in their blood concentrations of tri‐iodothyronine (T₃) and thyroxine (T₄), and a significantly higher neutrophil and lymphocyte (N:L) ratio compared with those of the control group. Blood concentrations of T₃ and T₄ and the N:L ratio of PTG2 returned to the control level after 72 hr of grazing. The final pH and water‐holding capacity values of meat were significantly higher in the WTHI group than in the control group, but those in the PTG2 group returned to the control level after 72 hr of grazing. These results demonstrate that posttransportation grazing for 72 hr is effective for recovering from damage induced by transportation stress.     

Effectiveness of Praziquantel Bath Treatments against Bothriocephalus acheilognathi in Grass Carp

Abstract

Many states ban the importation of fish infected with the Asian tapeworm Bothriocephalus acheilognathi. Treatment with an effective tapeworm parasiticide prior to shipment would allow fish to be imported that might otherwise be rejected. In this study, extended praziquantel bath treatments of infected grass carp Ctenopharyngodon idella were tested to determine their efficacy against Asian tapeworms. Preliminary praziquantel treatments of 0.7 mg/L or more for an exposure period of 24 h at grass carp densities of 69 g/L were effective in eliminating all tapeworms from 22-g fish. When the treatment duration was lowered to 12 h, a praziquantel concentration of 2.8 mg/L was required for effective treatment. In replicated studies, significantly reduced tapeworm numbers (0–5 tapeworms per treated fish compared with 30+ tapeworms per control fish) were observed following 24-h exposures to praziquantel at 0.5, 0.7, 1.0, and 1.5 mg/ L. Tapeworm elimination occurred only at the maximum concentration of 1.5 mg/L when 88-g grass carp were stocked at a density of approximately 6 g/L. When fish density was raised to 60 g/L, the 1.5-mg/L treatment did not eliminate all tapeworms: 4 of 30 fish contained a single tapeworm.     

Preliminary Morphometrics of Spleen and Kidney Macrophage Aggregates in Clinically Normal Blue Gourami Trichogaster trichopterus and Freshwater Angelfish Pterophyllum scalare

Abstract

Macrophage aggregate (MA) morphometry and pigment composition are believed to be dependent on the species, age, and health status of the fish. The aim of this study was to characterize a “normal” morphometry baseline of spleen and kidney MAs in blue gourami Trichogaster trichopterus and freshwater angelfish Pterophyllum scalare. Three size-classes of clinically normal fish were analyzed. Blue gourami and freshwater angelfish were obtained from three local ornamental fish farms; for each size-class, 10 fish from each farm were analyzed. Hematoxylin- and eosin-stained tissue sections were analyzed by light microscopy at 100× magnification and an image analysis program. The percentage of tissue occupied by MAs, MA size, and MA number were calculated on three arbitrarily selected fields of view from each spleen and kidney. In clinically normal blue gourami, increases in the percentage of tissue occupied by MAs and in MA size were associated with an increase in fish size, but in clinically normal angelfish no correlation was observed. Furthermore, in angelfish, a high variability in MA morphometry was observed, even among fish from the same sample group. In both species, a significant difference in the value of the morphometric parameters was observed among farms. Because iridoviruses inhibit macrophage activity and (possibly) proliferation, MAs in 25 clinical cases of iridovirus-infected blue gourami were analyzed. Preliminary data indicate that in iridovirus-infected blue gourami, there is a decrease in MA size and MA number compared with those of healthy fish.     

Efficacy of benzocaine as an anaesthetic for Crucian carp (Carassius carassius)

ObjectiveTo investigate the anaesthetic induction time and concentrations of stress markers in Crucian carp (Carassius carassius) subjected to different concentrations of benzocaine.Study designProspective experimental study.AnimalsThirty-six Crucian carp [body weight 368.3 ± 22.7 g and length 28.1 ± 1.9 cm (mean ± SD)].MethodsFish were divided into four groups, initially with nine fish per group. Each group was subjected to one of four final concentrations [0, 25, 50 and 100 parts per million (p.p.m.)] of benzocaine. The times to induction of sedation, to pre-anaesthesia and to anaesthesia were recorded according to the behavioural events observed after exposing the fish to benzocaine. At each stage, blood was collected from the caudal vein of three fish of the group, and these three fish were then euthanized. Plasma cortisol and glucose concentrations in the blood samples were measured as indices of stress response.ResultsInduction times for all stages of anaesthesia decreased significantly with increasing concentrations of benzocaine (1678 ± 103, 475 ± 73 and 251 ± 2 seconds for anaesthesia in 25, 50 and 100 p.p.m., respectively). Plasma cortisol and glucose concentrations were significantly lower in the anaesthetized groups than the control group (p < 0.05), and tended to decrease with an increasing dose of benzocaine. The cortisol concentrations (36.1 ± 5.8 ng dL^?1) at the anaesthetic stage for the 100 p.p.m. group were significantly decreased compared with the other groups (67.3 ± 14.9 ng dL^?1 in 25 p.p.m. and 47.6 ± 2.6 ng dL^?1 in 50 p.p.m.). Differences in glucose concentrations between benzocaine-treated groups were not significant.Conclusions and clinical relevanceIn this study, the fish group exposed to 100 p.p.m. benzocaine had a fast induction time for all monitored stages, low circulating cortisol and glucose concentrations and no immediate mortality.     

Blood Chemistry Values for Shovelnose and Lake Sturgeon

Abstract

Blood chemistry panels are commonly used for assessing the general health of vertebrate animals. Here, we present novel blood chemistry data for two North American sturgeon species, shovelnose sturgeon Scaphirhynchus platorynchus and lake sturgeon Acipenser fulvescens. Measurements were done using a portable chemistry analyzer (VetScan Analyzer; Abaxis). Among the plasma values measured (mean ± SD for shovelnose and lake sturgeon, respectively) were total proteins (3.7 ± 0.9 and 2.8 ± 0.4 g/dL), albumin (2.0 ± 0.5 and 1.1 ± 0.2 g/dL), globulin (1.7 ± 0.7 and 1.7 ± 0.3 g/dL), glucose (107 ± 46 and 62 ± 9.7 mg/dL), sodium (Na⁺; 132 ± 3.6 and 150 ± 14 mEq/L), potassium (K⁺; 3.5 ± 0.2 and 2.8 ± 1.7 mEq/L), phosphorus (10.4 ± 1.9 and 11.6 ± 3.6 mg/dL), and aspartate aminotransferase (AST; 676 ± 433 and 634 ± 234 IU/L). Higher values for total proteins, albumin, glucose, and Na⁺ in shovelnose sturgeon than in lake sturgeon probably are the result of handling stress. In addition, the plasma of male shovelnose sturgeon had higher concentrations of AST, glucose, and globulin than did that of females, whereas the plasma of females had higher concentrations of albumin and K⁺ than that of males. This study is the first to report blood chemistry data for shovelnose sturgeon. Robust blood chemistry databases can be used by aquaculturists and fish managers for monitoring sturgeon health.

Received July 8, 2011; accepted February 2, 2012     

The Use of Lufenuron to Treat Fish Lice (Argulus sp) in Koi (Cyprinus carpio)

Fish lice can cause significant morbidity and death in heavily infested fish. In addition to being a mechanical irritant when sucking blood, Argulus sp have been shown to be the vector for other fish diseases. Koi carp from a pond environment were presented with multiple raised dark spots on their dorsa and sides. The primary differential disease diagnosis was an Argulus sp. Parasites removed from the affected fish were examined under a dissection microscope, and the definitive diagnosis was determined to be Argulus sp infestation. Treatment with lufenuron (Program; Novartis, Greensboro, NC USA) was initiated with one 409.8-mg tablet per 1,000 US gallons (3,785 L) of water for a concentration of approximately 0.1 mg/L. This treatment was repeated once per week for 5 weeks. The fish have been monitored for 13 months after the initial treatment, and thus far, there has been no reappearance of Argulus sp within the aquatic environment.     

Physiological response of one of South Africa’s premier freshwater sport angling species,the Orange-Vaal smallmouth yellowfish Labeobarbus aeneus,to catch-and-release angling

The practice of catch-and-release fishing has been widely promoted by angling fraternities as a fisheries manage- ment tool. The aim of this investigation was to determine the physiological response of Orange-Vaal smallmouth yellowfish, Labeobarbus aeneus, to catch-and-release angling in the Vaal River, South Africa. Fish were collected using standard fly-fishing techniques, anaesthetised in clove oil and blood was drawn from the caudal vein; thereafter the fish were weighed, measured, revived and released. Blood plasma was analysed for concentra- tions of glucose, cortisol and lactate to determine the effects of angling duration, fish size and water tempera- ture. Larger fish were angled for a longer duration compared with smaller fish. Levels of glucose were affected by water temperature (influenced by time of year). Plasma glucose concentrations decreased with greater angling duration. Few individuals (n = 12) showed increased plasma cortisol concentrations. In extended-capture fish (angled for >1 min), lactate concentrations increased significantly above values for rapid-capture fish (angled for >30 s). These data suggest that catch-and-release causes physiological stress to fish, but nonetheless this practice can be a valuable fisheries management tool to ensure the sustainability of fish populations. Other factors beyond the ‘angling’ time are likely to contribute to physiological disruptions in homeostasis and therefore handling and air exposure of angled fish should be included in future catch-and–release angling studies. In addition, the longer-term impact of angling on fish health should also be determined.     

Experimentally Induced Whirling Disease I. Dose Response of Fry and Adults of Rainbow Trout Exposed to the Triactinomyxon Stage of Myxobolus cerebralis

Abstract

The intensity and prevalence of whirling disease was tested by exposure of 2-monthold fry and 1-, 2-, and 3.5-year-old adults of rainbow trout Oncorhynchus mykiss to a known number of laboratory-produced Myxobolus cerebralis at the actinosporean triactinomyxon stage. Fry exposed to graded concentrations of infectivity (triactinomyxons) for 3 h were individually examined for spores of Myxobolus cerebralis 5 and 6 months later. Exposure of fish to the lowest doses, 1 and 10 triactinomyxons per fish, did not result in detectable myxosporean spores. Fish that became lightly infected by a dose of 100 triactinomyxons per fish experienced a decrease in the incidence of infection between 5 and 6 months after exposure. A linear relationship was found between the numbers of recovered myxosporean spores and doses of 100–10,000 triactinomyxons per fish, and the spore burden appeared to plateau at doses of 10,000–100,000 triactinomyxons per fish. Adult fish continuously exposed to the highest dose of triactinomyxons for 3.5 months were infected and asymptomatic, however, the severity of myxosporean infection decreased with increased age of fish. This information may help in controlling whirling disease in salmonids.     

Remote intramuscular injection of immobilising drugs into fish using a laser-aimed underwater dart gun

Sixty coldwater and warmwater fish ranging in weight from 2 to 35 kg were injected intramuscularly with the hypnotics alphaxalone-alphadolone and metomidate hydrochloride and the non-depolarising muscle relaxant gallamine triethiodide using a laser-aimed underwater dart gun. Alphaxalone-alphadolone produced sufficient sedation for easy netting within five to 20 minutes at doses between 0.3 and 0.5 ml/kg, with induction being somewhat faster in warmwater species. The pattern of induction was similar with metomidate but required doses of 40 to 60 mg/kg. The muscle relaxant gallamine triethiodide showed promise as a practical agent for the capture and handling of large fish by virtue of its smooth induction of paralysis at doses between 1 and 3 mg/kg and its reversible supplementation with orally administered metomidate hydrochloride.     

Journal of Aquatic Animal Health: Guide for Authors 2014

Abstract

Brook trout Salvelinus fontinalis were treated with single 60-min static baths of 250 mg formalin/L, 3% NaCl, and 15 mg Chloramine-T/L to evaluate the efficacy of these compounds against external infections of Aeromonas salmonicida. Prevalence of A. salmonicida was significantly lower in brook trout treated with Chloramine-T than among those treated with formalin or salt. Further laboratory tests substantiated the therapeutic value of a single treatment of ChloramineT (15 mg/L) against A. salmonicida. In two experiments, viable counts of A. salmonicida in mucus did not vary among replicate groups of treated brook trout, but the counts for treated fish were significantly (P < 0.05) lower than those for untreated controls. In vitro tube dilution assays indicated that mean minimum inhibitory concentrations of Chloramine-T for 10 isolates of A. salmonicida were 9.0 mg/L for 1 h and 2.25 mg/L, for 24 h. In field trials at the White River National Fish Hatchery (Bethel, Vermont), the pathogen was detected principally as an external infection of juvenile Atlantic salmon Salmo solar maintained in two culture ponds. In one pond, the bacterium accounted for 100% of the total distribution of tnicroflora isolated from mucus. Seven days after treatment with Chloramine-T, A. sahnonicida accounted for 11% of the total bacterial counts identified from these fish. In the second pond, A. salmonicida composed 3% of the counts of bacteria isolated from the mucus of fish before treatment but was not isolated after treatment.     

Efficacy of Hydrogen Peroxide to Control Parasitic Infestations on Hatchery-Reared Fish

Abstract

The efficacy of hydrogen peroxide to control external parasitic infestations on juvenile (10–33-g) rainbow trout Oncorhynchus mykiss was evaluated in three clinical field trials. Fish were exposed to hydrogen peroxide concentrations ranging from 0 to 560 mg/L for 30 min once every other day for a total of three treatments. Pre- and posttreatment skin scrapes and gill wet mounts of test fish were microscopically examined to identify and enumerate external parasites. Infestation severity was classified as nonexistent (0 organisms), low (1–10 organisms), moderate (11–20 organisms), or high (?21 organisms). In trial 1, pretreatment skin examinations revealed a severe infestation of the protozoan Ambiphrya on all fish examined. Posttreatment skin examinations conducted within 24 h of the last treatment indicated that all hydrogen peroxide treatments eliminated Ambiphrya, whereas control fish remained severely infested with the protozoan. In trial 2, pretreatment examinations of skin and gill samples indicated a high infestation of the trematode Gyrodactylus (skin) and the protozoan Trichodina (gills) on all fish. Posttreatment examinations conducted within 24 h of the last treatment indicated that Gyrodactylus was eliminated from the skin of all treated fish; however, the high infestation of Trichodina remained on the gills of the test fish. All control fish had high infestation levels of both parasites. A high infestation of Ambiphrya was found on the skin of test fish before treatment (trial 3). Posttreatment examinations conducted 14 d after the last treatment revealed that 56% of the fish were parasite free, whereas the remaining test fish had low infestation levels. Control fish remained severely infested with the parasite. Based on the efficacy data, all hydrogen peroxide treatment regimens were efficacious in the control of Ambiphrya and Gyrodactylus.     

Microbial Pollution in Water and Its Effect on Fish

Abstract

A systematic study of microbial contamination of fish grown in ponds in and around Calcutta was initiated as part of the wetland management project in the city. Ponds were either sewage-fed or conventional (i.e., fed by rain and groundwater). Fish from these ponds are used for human consumption, and therefore a quantitative analysis of their microbial content is necessary. When concentrations of Escherichia coli, Salmonelleae (unidentified species), and Staphylococcus aureus in water and different organs of fish from sewage-fed and conventional ponds were compared, water and fish organs from conventional ponds contained about two orders of magnitude more bacterial cells. We tested for Salmonelleae and S. aureus, in addition to E. coli, because of persistent reports from Calcutta hospitals that most enteric and other infectious diseases in this region are caused by these bacteria. Significant linear correlations were found between concentrations of these bacteria in pond water and their recovery from several tissues of the fish.     

Effect of dietary vitamin E on cortisol and glucose responses to handling stress in juvenile beluga Huso huso

An 8-week feeding experiment was conducted to investigate the effect of dietary vitamin E on the physiological response to handling stress in juvenile beluga Huso huso. Fish were fed six experimental diets supplemented with 0, 25, 50,100, 200, or 400 mg Dl-all-rac-alpha-tocopherol acetate/kg diet. At the end of the experiment, the fish in each tank were subjected to acute handling and air exposure stress. Cortisol and glucose were measured as the primary hormonal and secondary metabolic responses to the stressors, both before and 3 h after application of the stressors. The growth parameters and feed utilization rates were significantly lower in fish fed the diet not supplemented with vitamin E than in fish fed diets supplemented with vitamin E. Cortisol concentration was not affected by dietary treatment but glucose concentration was. Fish fed vitamin E at 0, 25, 100, and 400 mg/kg diet had higher concentrations of glucose than those fed vitamin E at 50 and 200 mg/kg. However, fish fed diets with 50 and 200 mg/kg exhibited higher growth rates. These results indicate that dietary vitamin E has some effect on plasma glucose but no effect on plasma cortisol. In general, when the stressors were applied to belugas, the glucose and cortisol responses were relatively low. This may be due to higher resistance and lower physiological responses to these types of stressors by this species or by chondrosteans in general.