The Effects of Different Types of Stress on Blood Glucose in the Giant Tiger Prawn Penaeus monodon

Abstract— Juvenile Penaeus monodon prawns were exposed to a variety of putative stressom and blood glucose concentrations monitored as an index of metabolic stress. Prawns were held under controlled conditions and food deprived for 12–18 h before blood sampling. Juvenile prawns maintained in tanks at densities of 9, 23, 36 and 50 prawns/m² for 4 wk did not have significantly different baseline levels of blood glucose, with mean concentrations varying from 1.1 to 1.3 mmol/L. In contrast, as an index of overall condition, antennal length and rostral spine length were significantly degraded in the 36 and 50 prawns/m² groups compared to the 9 and 23 prawns/m² groups ( P < 0.05). Blood glucose levels were significantly elevated after prawns were exposed to air for 10 min and also increased Significantly when dissolved oxygen was decreased from 6.5 mg/L to 2.1 mg/L. ( P < 0.05). Gassing of water from pH 8.5 to 5.9 with carbon dioxide, with a corresponding decrease of dissolved oxygen from 6.6 to 5.9 mg/ L, induced a rapid and significant rise in blood glucose levels from 1.1 to 2.3 mmol/L. In contrast, a decrease of water pH from 8.3 to 5.9 with sulfuric acid, did not result in a significant change in blood glucose concentrations. These findings are discussed in relation to pond management for maintaining prawns in a low stress environment.     

Effects of different bronopol treatments on final survival rates in the artificial incubation of crayfish eggs (Pacifastacus leniusculus,Astacidae)

Two experiments were conducted on the effects of bronopol in the artificial incubation of crayfish eggs (Pacifastacus leniusculus) with the aim to search an alternative to formaldehyde. In the first experiment, 50, 250, 500 and 1000 ppm bronopol and 3000 ppm formaldehyde (control) in periodical administrations were tested on a density of 6.6 eggs cm^?2. After 44 days of incubation, the highest survival was obtained with 1000 ppm bronopol (81.9% to stage 2 juvenile, with no significant difference from formaldehyde), whereas lower bronopol concentrations resulted in significantly lower survival. In the second experiment, 1000, 3000 and 5000 ppm bronopol and 3000 ppm formaldehyde (control) administered for 15 min every second day were tested on eggs at a density of 20 eggs cm^?2. After 78 days of incubation, bronopol at 3000 ppm allowed for a stage 2 juvenile survival rate of 65.0% (with no significant difference from formaldehyde), whereas significantly lower survival was obtained with 1000 ppm or 5000 ppm. This study shows that bronopol may constitute an alternative to formaldehyde in the artificial incubation of crayfish eggs. A concentration of 3000 ppm administered for 15 min every second day may be adequate even on long incubations at high densities (at least 20 eggs cm^?2, one complete layer).     

Suppression of Stress Responses in Siberian Sturgeon,Acipenser baeri,Juveniles by the Dietary Administration of Bovine Lactoferrin

A study was performed to investigate the influence of dietary lactoferrin (LF) on growth and stress responses of juvenile Siberian sturgeon. Fish were fed six experimental diets (0, 100, 200, 400, 800, and 1600 mg LF/kg diet) for 10 wk. At the end of the experiment, fish were exposed to an acute stressor of 2‐min air exposure. The levels of cortisol, glucose, and lactate were measured before and at 1, 3, 6, 9, 12, and 24 h after stress. LF supplementation did not influence the fish growth. Cortisol and lactate, but not glucose level, were significantly affected by dietary LF. Cortisol levels in the control group rose twofold 1 h after stress and were significantly higher than that in LF groups. Moreover, the lowest level of cortisol at all sampling times (prestress and poststress) was observed in fish fed 400 mg LF/kg diet. Lactate concentrations in sturgeon fed 400 mg LF/kg markedly rose 1 h after stress, albeit changes in other LF groups were not significant. Results of this study show that dietary LF can suppress the stress responses in Siberian sturgeon, while 400 mg LF/kg diet appears to be an effective dietary level for this species to reduce stress.     

Effects of formalin on haematological and blood chemistry in olive flounder, Paralichthys olivaceus (Temminck et Schlegel)

Erythrocytes of olive flounder, Paralichthys olivaceus (Temminck et Schlegel), were treated with serial concentrations of formalin (37% formaldehyde) to investigate in vitro haemolysis and methaemoglobin formation. In addition, the short‐term toxicity of formalin concentrations of 0, 100, 212 and 300 ppm was also studied by clinical tests in which fish were subjected to 3‐h bath exposure. There was no haemolysis of fish erythrocytes exposed to formalin concentrations ranging from 31.3 to 2000 ppm. Methaemoglobin formation, however, was induced at concentrations greater than 500 ppm. Red blood cell count, haemoglobin, haematocrit, mean corpuscular haemoglobin concentration and percentage of immature erythrocytes were also markedly elevated in all formalin‐exposed groups (P<0.05). Formalin exposure also caused significant increases in alkaline phosphatase, aspartate aminotransferase, lactate dehydrogenase, potassium, chloride, magnesium and inorganic phosphorus (P<0.05). However, total protein decreased significantly in the formalin‐exposed groups (P<0.05). No significant differences in white blood cell count, mean corpuscular volume, mean corpuscular haemoglobin, albumin, glucose, total cholesterol, high‐density lipoprotein cholesterol, free cholesterol, alanine aminotransferase, calcium, creatinine and total bilirubin were observed in the formalin‐exposed groups (P>0.05).     

The response of coral trout (Plectropomus leopardus) to capture, handling and transport and shallow water stress

The stress response of coral trout (Plectropomus leopardus ) to wild capture or controlled shallow water stressors was investigated. Stress associated with capture from the wild, handling and transport and shallow water evoked significant changes in circulating levels of cortisol, glucose, lactate, haemoglobin (Hb) and haematocrit (Hct) in coral trout. Plasma glucose, Hb and Hct increased over 30 to 60 min in response to the controlled stressor and then returned toward unstressed levels, even if the stressor persisted. Cortisol increased to maximum levels over the 60 min following the onset of the stressor and remained elevated for 4 h in the case of a single 30 min shallow water event or 3 d in response to the capture, handling and transport. The difference between the responses of blood glucose and cortisol suggests that cortisol does not maintain blood glucose during stress in coral trout. The concentrations of circulating thrombocytes, lymphocytes and granulocytes were also significantly affected by shallow water stress. As lymphocytes and granulocytes are important immune components, reduced concentrations of these cells may explain the increases in disease susceptibility, commonly observed in stressed fish during live transport.     

Streptococcus agalactiae Vaccination and Infection Stress in Nile Tilapia,Oreochromis niloticus

Abstract

The stress response following intraperitoneal (IP) injection of a non-adjuvant Streptococcus agalactiae vaccine in cultured warmwater Nile tilapia, Oreochromis niloticus, has not been investigated. Further, little or no information is available on stress following S. agalactiae infection and what effect, if any, vaccination has on susceptibility to infection. The objective of this study was to develop preliminary information on the associations between vaccination, stress, and infection. Blood glucose levels were used to evaluate stress in the fish at different time intervals following vaccination and challenge with S. agalactiae. Blood glucose levels were measured in vaccinates and controls at 0, 2, 6, 24 hours, and 28 days post-immunization (0 hours pre-challenge), and at 2,6, 24,48,72, and 312 hours following challenge with 1.5 × 10⁴ colony forming units (CFU) of S. agalactiae/fish. Significant increases in blood glucose levels were observed only in association with the injection of the vaccine and at 2 hours after injection. After S. agalactiae challenge, both controls and vaccinates had significantly (P < 0.05) higher blood glucose values at 2, 24,48, and 72 hours than at 0 hours. However, blood glucose levels in vaccinates were significantly (P < 0.05) lower than the controls at 24, 48, and 312 hours. Blood glucose levels and mortality of the infected controls were significantly correlated (r² = 0.9236, P = 0.0134). The cumulative mortality of the vaccinates and controls was 10% and 60% after 13 days post-challenge, respectively. The relative percent survival (RPS) was 83.4. Our results indicate that the vaccine was efficacious against S. agalactiae and induced short-term stress in tilapia. These preliminary results also suggested, for the first time, that vaccination may significantly reduce the infection stress associated with S. agalactiae infection in tilapia.     

Hematology and stress physiology of juvenile diploid and triploid shortnose sturgeon (<Emphasis Type="Italic">Acipenser brevirostrum</Emphasis>)

This study examined diploid and triploid shortnose sturgeon hematology and stress physiology through the investigation of various characteristics and components of whole blood and blood plasma. Erythrocytic cellular and nuclear length and width were significantly larger in triploids than in diploids. Hematocrit was depressed in triploid sturgeon in comparison to diploids, but total blood hemoglobin content and mean erythrocytic hemoglobin concentration (MEHC) did not differ between ploidies. The mean erythrocytic hemoglobin (MEH) was elevated in proportion to the increase in erythrocyte size. Taken together, these data suggest that triploids and diploids likely have similar oxygen carrying and aerobic capacities. In response to an acute stressor of 15 min chasing, plasma cortisol and glucose levels did not differ between ploidies. Cortisol levels were significantly depressed at 2 h post-stress with an increase back to 0 h post-stress levels at 6 h into recovery, whereas glucose levels did not change during the recovery period. There was a significant interaction between ploidy and time post-stress for blood hemoglobin concentrations, with diploids demonstrating elevated hemoglobin content at 6 h post-stress. Plasma osmolality, chloride ion concentrations and lactate levels were elevated in triploids. Overall, it does not appear that sturgeon have developed an elaborate stress response and the triploid stress response appears to be slightly reduced in comparison to diploids.     

Retention of formaldehyde in the tissues of two tropical fish species following exposure to therapeutic levels

Abstract. Formalin is an effective fish chemotherapeutant which is used to control certain ectoparasitic and bacterial infections. It is toxic to fish and its pathological and physiological effects have been reported. An experiment was conducted to elucidate the possibility of retention of formaldehyde in the muscles of two tropical food fish species, following exposure to therapeutic levels of formalin. The results indicated that Puntius gonionotus (Bleeker), retained 5·75 ppm formaldehyde following exposure to 50 ppm formalin for 24h. In contrast, Clarias batrachus (L.) retained 14·03 ppm and 18·72 ppm formaldehyde following exposure to formalin at 50 ppm and 100 ppm for 24 h respectively. However, no formaldehyde was detected after keeping the exposed fish in clean running water for 24h.     

Comparison of tricaine methanesulphonate (MS222) and clove oil anaesthesia effects on the physiology of juvenile chinook salmon Oncorhynchus tshawytscha (Walbaum)

This study investigated the feasibility of using clove oil as an alternative to tricaine methanesulphonate as a fish anaesthetic, particularly in fish stress research. The physiological stress responses of juvenile chinook salmon Oncorhynchus tshawytscha (Walbaum) anaesthetized with either tricaine (50 mg L^?1) or clove oil (20 p.p.m.) were compared using unanaesthetized fish as controls. Haematocrit, serum cortisol and serum glucose concentrations, serum lysozyme activity and differential leucocyte counts were measured from blood samples collected before, during and upon recovery from anaesthesia and at specified intervals up to 72 h after recovery. Differences between the two anaesthetic groups were not significant for most of the physiological traits measured. Serum lysozyme activity of control fish, however, was significantly suppressed relative to the treated fish for 72 h after stress. Clove oil may be a safe and cost‐effective alternative to tricaine without significantly affecting study results. Furthermore, clove oil may be more practical for field‐based research, because a withdrawal period is unnecessary, and clove oil does not pose an environmental hazard.     

Shipping studies with juvenile and adult Malaysian prawns Macrobrachium rosenbergii (de Man)

Four studies examined shipping factors of packing technique, density, duration, type of water and use of habitat material for shipping juvenile and adult prawns Macrobrachium rosenbergii. Prawns were shipped in double polyethylene lined 38 × 38 × 20 cm deep styrofoam boxes containing oxygenated water. At temperatures of 19–20°C, 17 g prawns could be shipped safely for 42 h at a density of 10–12 prawns per box (12–15 g liter⁻¹ shipping water). Juveniles, mean size about 6 g, could be shipped at a density of 40 per box (18 g liter⁻¹) for 24 h or 20–25 per box (9–11 g liter⁻¹) for 48 h. Use of mesh material to increase surface area in the box did not appear beneficial nor did shipping in brackish water (salinity8‰). Adults packed unrestricted resulted in survival rates substantially higher than those obtained from immobilized prawns wrapped in mesh.

During the shipment, pH and dissolved oxygen concentrations decreased whereas ammonia concentrations increased. The decreased pH levels may have reduced the ammonia toxicity by decreasing the amount of toxic unionized ammonia (NH₃) in solution. In general, dissolved oxygen concentrations appeared more closely related to survival rates than did other water quality parameters which were measured.     

Effect of Fish Density During Transportation on Stress and Mortality of Juvenile Tambaqui Colossoma macropomum

The increased demand for juvenile tambaqui Colossoma macropomum for grow-out ponds and stocking programs in the Amazon state of Brazil has increased the transportation of this species. This study was designed to determine the optimum density of juvenile tambaqui during transportation in closed containers. Fish (51.9 ± 3.3 g and 14.9 ± 0.4 cm) were packed in sealed plastic bags and transported for 10 h at four densities: 78, 156, 234, and 312 kg/m³. After transportation, fish from each density were kept in separate 500-L tanks for 96 h. Mortality, 96-h cumulative mortality, water quality, and blood parameters (hematocrit, plasma cortisol, and glucose) were monitored. Fish mortality after transportation was significantly lower at densities of 78 and 156 kg/m³ than at 234 and 312 kg/m³. Cumulative mortality was significantly lower at a density of 78 kg/m³. Dissolved oxygen after 10 h of transportation remained high at a density of 78 kg/m³, but reached critically low values at all other densities. Ammonia concentration was highest at the lowest density and was lower at higher densities. Carbon dioxide concentration was lowest at the density of 78 kg/m³ but higher in the other treatments. Plasma glucose and cortisol increased significantly immediately after transportation at densities of 156, 234, and 312 kg/m³, returning to control values by 24 h. The best density for juvenile tambaqui during a 10-h transportation haul in a closed container was 78 kg/m³. At this density there was no fish mortality, water quality was kept within acceptable values, and fish were not stressed.     

The ability of clove oil and MS-222 to minimize handling stress in rainbow trout (Oncorhynchus mykiss Walbaum)

The effects of 60‐mg L^?1 clove oil and 60‐mg L^?1 tricaine methanesulphonate (MS‐222) on the blood chemistry of rainbow trout were compared after exposure to handling stress via caudal puncture blood sampling. Fish sampled by caudal puncture and subsequently exposed to anaesthetics showed a typical handling stress response over a 48‐h period. There were no significant differences between the responses of fish exposed to equal concentrations of clove oil and MS‐222, with the following exceptions: the blood glucose at full anaesthesia, and lactate at full recovery increased significantly in the clove oil‐exposed fish. In a subsequent experiment, the stress response observed in fish sampled by caudal puncture and exposed to clove oil and MS‐222 was compared with a non‐anaesthetized control group. The increases in plasma cortisol levels were significantly lower at recovery in fish treated with either anaesthetic compared with the control fish. Fish exposed to MS‐222 had significantly higher cortisol levels at 1 h. These findings show that few differences exist between the anaesthetic effects of clove oil and MS‐222 on the physiological response of fish to stress. However, clove oil is more effective at reducing the short‐term stress response induced by handling and blood sampling, and is recommended as an alternative fish anaesthetic.     

Effects of dietary inclusions of red beet and betaine on the acute stress response and muscle lipid peroxidation in rainbow trout

This study evaluates the effects of red beet (RB) and betaine on rainbow trout submitted to an acute stress challenge. A control diet was compared with four experimental diets in which red beet (14 and 28%) and betaine (0.9 and 1.63%) were incorporated in different concentrations according to a factorial design. Cortisol in plasma and fin, glucose and lactate plasma levels, and malondialdehide (MDA) in muscle were all measured before the stress challenge and 30 min and 6 and 12 h after the stress challenge as parameters to determine the diet effects. RB and betaine had no effect on cortisol, glucose, and MDA basal levels. However, lactate basal levels were significantly lower on fish fed with RB and betaine. Thirty minutes after the stress challenge, there was a significant increase in plasma and fin cortisol, glucose and lactate concentrations, although fish fed with diets containing RB and betaine showed significantly higher plasma cortisol values. MDA values of fish fed with 14% RB and 0.9% betaine were significantly higher than MDA values from fish fed with 28% RB and 1.63% betaine. After 6 and 12 h, plasma and fin cortisol and lactate levels recovered in a similar trend. Glucose plasma levels recovered in almost all groups 12 h after the stress. Also, MDA values recovered basal levels after 6 and 12 h. RB and betaine did not enhance the tolerance to the stress challenge compared to the control group, although the presence of these ingredients had no negative effect on any of the stress indicators.     

Cortisol,glucose and hematocrit changes during acute stress,cohort sampling,and the diel cycle in diploid and triploid brook trout (Salvelinus fontinalis Mitchill)

In this study, groups of diploid (control) and triploid brook trout were subjected to a 5 min acute handling/confinement stress. Blood samples were collected from equal numbers of diploid and triploid fish at regular predetermined intervals, beginning prior to confinement and continuing for up to 3h after confinement. These blood samples were used for the measurement of hematocrit and plasma cortisol and glucose concentrations. The effects of cohort sampling and the diel cycle on these variables were also analysed. Except for minor differences, both groups responded similarly to the acute stress, with short-term elevations in plasma cortisol and hematocrit levels, and a more sustained increase in plasma glucose levels. No significant differences were found between diploid and triploid fish in their reactions to cohort sampling. However, the act of removing an individual from a tank caused significant changes in plasma cortisol levels in cohorts remaining in that tank (p < 0.001). Significant diel effects were observed for both ploidy groups in plasma cortisol (p < 0.05) but not in plasma glucose or hematocrit. To whom correspondence should be addressed     

Effects of dorsal aorta cannulation on the stress response of channel catfish (Ictalurus punctatus)

The stress response to dorsal aorta cannulation and serial blood sampling was examined in the channel catfish Ictalurus punctatus. Channel catfish cannulated and repetitively sampled once a day for 7 days did not exhibit a change in response to surgery or to the 24h sample regime as measured by plasma cortisol, glucose, and chloride. In fish that were either serially bled (0, 1, 3, 6, 9, 12, 24, and 48h) immediately after surgery or allowed to recover 6 days before being serially bled, overall plasma cortisol levels were higher than those of fish bled every 24h. Catfish serially bled immediately after surgery had significantly higher plasma glucose levels compared with catfish allowed to recover from surgery 6 days before serial sampling. Although channel catfish recover from cannulation surgery in 24h, a longer recovery period may be needed prior to serial sampling if the samples are taken more frequently than every 24h.     

The role of dietary L‐ascorbyl‐2‐polyphosphate on the growth and physiological functions of beluga,Huso huso (Linnaeus, 1758)

Effects of dietary ascorbic acid (AA) supplementation were carried out on growth performance and physiological indices in juvenile beluga Huso huso fed different levels of dietary L‐ascorbyl‐2‐polyphosphate as AA source consisting of 0 (control), 100, 200, 400, 800 and 1600 mg AA kg^?1 diet for 16 weeks. No significant differences were found in growth performances between treated groups except for condition factor. Using AA caused significant differences in haemoglobin, number of red blood cells, white blood cells, aspartate aminotranspherase and lactate dehydrogenase, while no significant difference was found in haematocrit, mean corpuscular haemoglobin concentration, differential white blood cells count and alkaline phosphatase activity at the end of the experiment. Lysozyme activity after 8 weeks was significantly affected by dietary treatments with the lowest value in fish fed control diet, but not at completion of 16‐week feeding trial. Liver AA concentration showed a significant increase in correlation with dietary AA increase. Air exposure stress test showed significant differences among the treatments in case of cortisol and glucose concentrations. Also between pre‐ and post stress, significant changes were observed in some of treatments. The lowest and highest levels of cortisol were 9.2 ± 3 (in 200 mg kg^?1) and 16.8 ± 5.1 ng mL^?1 (in control), 6 h post stress (P < 0.05) respectively. Also, the lowest and highest levels of glucose were measured in fish fed 200 and 800 mg AA kg^?1 respectively. The obtained results showed that most growth parameters were not affected by dietary AA, but some physiological and immunological parameters of this species were influenced by this vitamin. We suggest that under rearing conditions, AA should be added to the diet especially during early life stages for improving health status and resistance to stressors.     

Effect of saponin on hematological and immunological parameters of the giant freshwater prawn, Macrobrachium rosenbergii

Giant freshwater prawns, Macrobrachium rosenbergii (17.9 ± 2.7 g), exposed to different concentrations of saponin at 0, 0.3, 0.6, 0.9 and 1.2 mg l^− 1 for 168 h were examined for osmolality, electrolyte levels, oxyhemocyanin, protein levels, acid-base balance status, total hemocyte count (THC), phenoloxidase activity, and respiratory bursts. Hemolymph oxyhemocyanin, protein, and pO₂ were inversely related to the saponin concentration. Hemolymph oxyhemocyanin, protein, pO₂, pCO₂, and pH of prawns exposed to 1.2 mg l^− 1 saponin were significantly lower than those of prawns exposed to 0.3 mg l^− 1 and control solutions. However, no significant difference was observed in osmolality or electrolyte levels of prawns exposed to different concentrations of saponin for 168 h. The THC of prawns following 168 h of exposure to 0.9 and 1.2 mg l^− 1 saponin increased, but the phenoloxidase activity decreased suggesting that the decrease in phenoloxidase activity under saponin stress was not a consequence of the increase in THC. We concluded that saponin at as low as 0.9 mg l^− 1 decreases the respiratory protein level and acid-base balance, and modulates the immune system of M. rosenbergii.     

Short-term stress and mortality of juvenile school prawns, Metapenaeus macleayi, discarded from seines and trawls

Abstract  Two experiments were carried out to assess the short-term impacts to juvenile school prawns, Metapenaeus macleayi (Haswell) discarded from commercial seining and trawling in New South Wales, Australia, and the potential utility of modifications to operational and/or onboard handling practices designed to improve survival. For both gears, discards were handled according to two general categories of treatment (termed mild and extreme) chosen to represent the plausible limits of severity during existing commercial operations. A total of 600 trawled and 480 seined school prawns (from both treatments), along with appropriate numbers of controls (previously collected and housed in acclimation tanks), were placed into cages (in groups of 10). Subsets of each of these groups were then destructively sampled over periods of up to 5 days and examined for their mortality and physiological response (measured as levels of l -lactate in the haemolymph). In both experiments, the temporal mortalities in the treatment groups ranged between 0% and 15% and, for the most part, were not significantly different to controls. Prawns in the treatment groups had similar, significantly elevated levels of l -lactate approximately 40 min after being caught, but these returned to levels approaching baseline estimates within 48 h. Under the conditions examined, juvenile school prawns appear capable of withstanding a range of stressors associated with being discarded from active gears, and their fate is not greatly influenced by the duration of gear deployment and subsequent air exposure. However, further work is required to quantify other sources of unaccounted fishing mortality and, ultimately, the impacts that discarding has on stocks.     

Low stress response exhibited by juvenile yellowtail kingfish (Seriola lalandi Valenciennes) exposed to hypercapnic conditions associated with transportation

Transportation of yellowtail kingfish (Seriola lalandi Valenciennes) juveniles from hatchery to on‐growing operations in New Zealand exposes the fish to significantly elevated carbon dioxide (CO₂) concentrations. Experiments were undertaken to assess metabolic and haematological stress responses after a 5‐h period of hypercapnia, followed by recovery in normocapnia. Mortality was low (0.5%) and secondary stress indices (blood glucose, blood lactate, muscle pH and muscle lactate) remained largely unchanged during a simulated transportation and recovery, despite juveniles being exposed to CO₂ concentrations as high as 75 mg CO₂ L^?1 (38 mm Hg partial pressure). There was some haematological disturbance midway through simulated transports, where water was maintained at fixed CO₂ concentrations of 8 and 50 mg CO₂ L^?1 (4 and 26 mm Hg respectively). Persistent erythrocyte swelling continued during transport at 50 mg CO₂ L^?1, whereas at 8 mg CO₂ L^?1, haematological variables had returned to control levels. There was no mortality recorded for any of the treatments, and haematological variables were restored to pre‐manipulation levels after 31 h. The results indicated that juvenile yellowtail kingfish have a robust physiology and can cope with the stressors imposed by acute exposure to moderate to high levels of CO₂ associated with live transport.     

Changes of Non-Specific Immune Parameters in Rainbow Trout,Oncorhynchus mykiss,After Exposure to Antimicrobial Agents Used in Aquaculture

Changes of plasma lysozyme and serum bactericidal activity, ceruloplasmin, total plasma protein, serum glucose, hematocrit and leucocrit levels in rainbow trout (Oncorhynchus mykiss) were studied after exposure to formalin and chloramine-T, which are used in aquaculture as anti-ectoparasitic and antibacterial agents. Fish were exposed to formalin at a concentration of 250 ppm for 60 min and exposed to chloramine-T for 5 ppm for 3 h. The parameters were analyzed for rainbow trout exposed to formalin and chloramine-T soon after treatments and rainbow trout exposed to freshwater after 24 h (return) following the treatments. Plasma lysozyme activity decreased after exposure to formalin; however, it was not affected by chloramine-T exposure. Serum bactericidal activity reduced after both formalin and chloramine-T exposure and did not change after returning to freshwater. Ceruloplasmin and total plasma protein were not affected by both treatments. Serum glucose levels of exposed fish elevated and remained at higher levels during recovery period when compared to control values. Hematocrit values of fish exposed to formalin increased; however, no significant change was observed in fish exposed to chloramine-T. Leucocrit levels of fish treated with both formalin and chloramine-T were higher than that of controls.