Opercular Beat Research Articles

EVALUATION OF MEDIAN LETHAL CONCENTRATION (LC ) 50 OF MYSTUS VITTATUS (BLOCH) FOR COPPER SULPHATE

The toxic effect of Copper on freshwater catfish Mystus vittatus was studied. The LC values of copper in Mystus 50 vittatus for 24, 48, 72 and 96 hours were 20.589, 16.497, 11.815 and 8.665 mg/L respectively. The cat fish was silvery grey in body in the control group throughout the experiment. The body colour changed from original silvery grey to dark colour in heavy metal treated fish. The fish maintained in freshwater behaved normal as usual. But when the fish was exposed to copper, erratic swimming, abnormal posture, dis-balance, sluggishness, imbalance in posture, increase in surface activity, opercular beating, and gradual loss of equilibrium and spreading of excess of mucus all over the surface of the body were observed.

Condition-dependent responses of fish to motorboats.

Anthropogenic noise is a pollutant of global concern that has been shown to have a wide range of detrimental effects on multiple taxa. However, most noise studies to-date consider only overall population means, ignoring the potential for intraspecific variation in responses. Here, we used field experiments on Australia's Great Barrier Reef to assess condition-dependent responses of blue-green damselfish (Chromis viridis) to real motorboats. Despite finding no effect of motorboats on a physiological measure (opercular beat rate; OBR), we found a condition-dependent effect on anti-predator behaviour. In ambient conditions, startle responses to a looming stimulus were equivalent for relatively poor- and good-condition fish, but when motorboats were passing, poorer-condition fish startled at significantly shorter distances to the looming stimulus than better-condition fish. This greater susceptibility to motorboats in poorer-condition fish may be the result of generally more elevated stress levels, as poorer-condition fish had a higher pre-testing OBR than those in better condition. Considering intraspecific variation in responses is important to avoid misrepresenting potential effects of anthropogenic noise and to ensure the best management and mitigation of this pervasive pollutant.

Effect of environmental enrichment on the stress response of juvenile black rockfish Sebastes schlegelii

The stress response is one of the most important aspects of fish welfare in aquaculture. However, relatively few studies focusing on the effect of environmental enrichment on the fish stress response have been conducted, and their limited results were considerably contradictory. The present study aimed to investigate whether the enrichment type and amount had significant effects on the basal stress level and physiological and behavioral responses to acute stress of juvenile black rockfish Sebastes schlegelii. Fish were reared for eight weeks in environments with two enrichment types and three enrichment amounts (i.e., no environmental enrichment control (C), low-amount plant enrichment (PL), medium-amount plant enrichment (PM), high-amount plant enrichment (PH), low-amount structure enrichment (SL), medium-amount structure enrichment (SM), and high-amount structure enrichment (SH)), and subsequently, they were successively subjected to two common acute stressors (i.e., air exposure and confinement) and sampled at 0, 0.5, 1, 3 and 6 h after stress. In general, the plant enrichment groups experienced significantly higher basal stress (indicated by cortisol level and opercular beat rate) than the structure enrichment groups. Meanwhile, no enrichment control group and low-amount enrichment groups experienced significantly higher basal stress than the other two enrichment amount groups. After being subjected to acute stress, the peak cortisol levels of the high-amount enrichment groups were significantly higher than that of the other three enrichment amount groups. The PM, PH and SL fish recovered to basal stress levels at 1 h, the C and PL fish recovered at 3 h, and the SM and SH fish recovered at 6 h after the stress. Moreover, their basal cortisol levels showed strong correlations with peak cortisol levels and recovery time from stress. The correlation between cortisol level and opercular beat rate was also strong. Taken together, these results provide the first evidence to show that enrichment type and amount had significant effects on the fish stress response and might have important applications in fish husbandry and welfare. Based on these results, we suggest that it may be optimal for fish basal stress level and development of an adaptive capacity to provide a medium-amount (approximately 50% floor space coverage) of mixed enrichment in aquaculture.

The use of Ocimum gratissimum L. essential oil during the transport of Lophiosilurus alexandri: Water quality, hematology, blood biochemistry and oxidative stress

This study evaluated the effects of the essential oil of Ocimum gratissimum L. (EOOG) on water quality, blood characteristics and tissue damage during transport of Lophiosilurus alexandri. One hundred and sixty juveniles of L. alexandri (123.44 ± 1.95 g and 23.71 ± 1.95 cm) were fasted for 24 h before transportation. Fish were then submitted to one of three treatments of transport water with five replicates each: 0 (control), 5 and 10 mg/L EOOG. The animals were transported for 4 h in plastic bags at a density of 1 juvenile/L and 10 animals per bag. The ventilatory frequency of one fish from each bag was determined after 3 h of transport by direct observation and counting of opercular beats. Blood, brain and liver samples were collected prior to (basal group) and at the end of transport from 10 animals each. Blood aliquots were used to determine hematocrit and hemoglobin, total plasma protein, glucose, aspartate aminotransferase and alanine aminotransferase levels. Samples of liver and brain were used to determine parameters and oxidative stress (reactive oxygen species, glutathione peroxidase, superoxide dismutase, glutathione S-transferase, lipid peroxidation and protein carbonyl formation). No mortality was observed 24 h after transport. The addition of EOOG to transport water appeared to reduce animal metabolism, thus ensuring higher dissolved oxygen and lower ammonia levels. Juveniles transported with 10 mg/L EOOG also had reduced opercular beats, lower levels of hemoglobin and blood aspartate aminotransferase and glucose. This concentration also reduced lipid and protein oxidation levels in tissues, thereby avoiding lipid peroxidation and the formation of carbonyl protein. The use of 10 mg/L EOOG during transport promotes a sedative effect in L. alexandri, with reduced oxygen consumption, ammonia excretion and biochemical changes and enhanced protection against oxidative damage.

Opercular beat: A non-invasive and rapid method to detect stress in seahorses

ABSTRACT Seahorses are commonly used in the aquarium trade and in seahorse-watching ecotourism in Brazil. Their manipulation and transportation may lead to significant stress, compromising their health. Assessing stress response during manipulation is difficult. Thus, the aim of the present study was to identify respiration patterns for these animals, providing baseline data for a health and well-being protocol to be applied during seahorse management. We conducted experiments in captivity and in the wild to evaluate transportation and handling as potential stressors. Significant differences between opercular beat after manipulation and recovery was observed in captivity and in the wild. Seahorses displayed a base opercular beat around 30/min in the wild and 45/min in captivity, increasing to 66 beats/min after manipulation in the wild and 64/min in captivity. No difference between sex or size was noticed. Opercular beat in captivity remained higher than in the wild 24 h after manipulation, suggesting that captivity protocols should include acclimation longer than 24 h.

Sublethal fish responses to short-term food chain transfer of DSP toxins: The role of somatic condition

Toxins synthesized by marine benthic dinoflagellates may be transferred towards higher trophic levels via cell ingestion. Okadaic acid (OA) and other compounds produced by benthic Prorocentrum species are associated with acute and lethal fish responses, but its sublethal effects are barely known. The toxicity of low and intermediate P. lima concentrations to the ringneck blenny Parablennius pilicornis was evaluated through short-term food chain transfer experiments using brine shrimps as primary grazers of toxic cells and, subsequently, as fish prey. Fish activity level, opercular beat frequency, feces biomass, condition factor, and hepatosomatic index were used as toxicity proxies. We hypothesized that sub-lethal concentrations of DSP toxins will affect fish responses, but the strength of these effects will be mediated by the initial somatic condition of exposed individuals. Increased opercular beat frequencies were recorded in fish from the treatment with the highest P. lima concentration provided to brine shrimps, contrasting with rather variable and low opercular beat frequencies from the control. Fish fed with brine shrimps exposed to low and intermediate concentrations of P. lima showed a great inter-individual variation in activity level and particularly in opercular beat frequency, wherein the initial condition factor of exposed individuals appeared to have broadly mediated these fish responses. The presence of P. lima all year round in benthic marine systems highlights a possible chronic exposure of fish to OA and fish will likely become more susceptible to predation in natural environments, facilitating, therefore, toxin transfer through marine trophic webs.

Comparative Effects of Aqueous and Freeze Dried Leaf Extracts of <i>Tephrosia vogelii</i> on <i>Heterobranchus longifilis</i> Juveniles Val. (Pisces: 1840)

The present study was carried out to evaluate the potential of the aqueous leaf and freeze-dried leaf extracts of Tephrosia vogelii as tranquilizers on an African catfish, Hetetobranchus longifilis post juveniles (mean weight 115.00±25.00g) obtained from wild stock. They were acclimatized under laboratory conditions for two weeks prior to the commencement of the experiment. The fish were fed once a day at 9.00 hours at 4% body weight during the period of acclimatization. Each tank containing acclimatization water was aerated to enhance dissolved oxygen, and water was changed daily to prevent metabolic waste build up. Experimental fish were starved for 24 hours prior to sedation to prevent regurgitation from the gastro-intestinal tract (GIT). Four healthy Hetetobranchus longifilis were selected randomly from both the control and treatment groups. Each fish was weighted and injected 0.05ml of aqueous and freeze-dried leaf extracts at concentrations of 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06g/l using №. 23 needle and a 2ml heparinized syringe. Injection was done intramuscularly (IM) at the dorsal saddle just above the lateral line behind the operculum. Fish in the control group were injected with distilled water. Injected fish were observed for behavioural responses. The result showed that H. longifilis injected with the freeze-dried leaf extract of T. vogelii passed sequentially through the first three stages of anaesthesia but could not attain total loss of equilibrium (stage 4 of anaesthsia). Behavioural responses included mucus secretion, slow and erratic swimming, excrement discharge, increase in opercular beat rate, strong retension of reflex action, partial loss of equilibrium and colour change. The induction time decreased with increasing concentration of the anaesthetic extract. The recovery time followed the reverse order. The opercular beat rates, before and after sedation in the treatment groups showed increase over that in the control group and it increased with increasing concentration. The result of the experiment with aqueous leaf extract showed that there was no significant difference in opercular beat rate after sedation in all centrations used (P>0.05). The result also showed that at higher concentration (0.06g/l) induction was time 44.67 seconds while at concentration 0.02g/l induction time was 83.70 seconds. In the case of the freeze-dried leaf extract of T. vogelii the induction at concentration 0.06g/l was 49.33 seconds while at concentration 0.02g/l induction time 76.67 seconds.

The decolorization effect by Aspergillus sp. 3 on Goldfish opercular beats

Batik effluent had high toxicity to aquatic organisms. Dye decolorization is a process used to reduce color density. Fungi which used for decolorization was Aspergillus sp 3. This study aimed to investigate the ability of fungi on decolorization of 3 kinds of batik effluents (Indigosol Green dye, Indigosol Purple dye, and Naphtol Black dye) and to investigate the ability of fungi on reducing TDS level. The study was also investigated the initial toxicity of batik effluents to Goldfish (Cyprinus carpio). Decolorization was measured by spectrophotometry, the pH value was measured by pH meter, and the TDS value was measured by TDS meter. In addition, the decolorized batik effluent was tested for toxic effect on C. carpio by total opercular beats. Decolorization assay showed that Aspergillus sp. 3 had the ability to decolorized only 2 kinds of batik effluents. The decolorization percentage of Indigosol Purple was 60.015% and Naphtol Black was 56.679%. The pH after treatment decreased from 8.5–9 to 5.3–6. The range of pH value of Indigosol Green, Indigosol Purple, and Naphtol Black 5.3–6. Besides that, Aspergillus sp. 3 also had the ability to reduce the TDS level in the effluent. The TDS level on Indigosol Green, Indigosol Purple, and Naphtol Black as 4,965%, 25,307%, and 15,129%, respectively. Initial toxicity assay of effluent to C. carpio showed that there was a difference of total opercular beats, which exposed by decolorized and before decolorized batik effluent. The total opercular beats of C. carpio on decolorized batik effluents showed high value than before decolorized batik effluents. It can be concluded that Aspergillus sp. 3 had the ability to decolorize and decreasing the initial toxicity of Indigosol Purple batik effluents on C. carpio.

Influence of water aeration levels on the opercular respiratory beats and selected water quality parameters of <i>heteroclarias</i> fingerlings under laboratory conditions in Minna, Nigeria

A twelve (12) week experiment was carried out to determine the influence of water aeration on the Opercular Respiratory Beats (ORB) and selected water quality parameters of 1,800 Heteroclarias fingerlings of average weight of 1.40 g under laboratory conditions. One hundred and fifty fingerlings were allotted in a complete randomized design into water aeration levels: 0.00(control), 6.00, 12.00 and 24.00 hours respectively as treatments and replicated thrice. The ORB and water quality parameters were determined weekly based on standard procedures .Water quality parameters investigated were not influenced by water aeration except the Dissolved Oxygen (DO) concentration in the control that was significantly (p 0.05) different at the end of the 12th week. At the 2nd, 8th and 10th weeks, respiratory beats of the Heteroclarias fingerlings were not significantly (P>0.05) different among the treatments. However, in the 1st and 7th weeks respiratory beats were significantly (P<0.05) higher among the fishes not aerated (131.63±8.35operculum beats per minute) and those aerated (76.33±10.75 operculum beats per minute) for 6.00 hours. The ORB decreased with increase in fish size from week 1 to the end of the study. The research also showed that water aeration had no influence on the water quality parameters except DO of the controlled fingerlings. Water aeration had influence on ORB only at the 1st and 7th weeks of the experiment but no significant influence was recorded during the greater period of investigation. As a recommendation, fish farmers are advised to monitor the dissolved oxygen concentration daily in their ponds to ascertain when aeration is necessary. Findings of this research also remove the fears of maintenance cost of using Air pump.Keywords: water aeration, Heteroclarias, water quality, operculum respiratory beats, fish size

Propofol and essential oil of Nepeta cataria induce anaesthesia and marked myorelaxation in tambaqui Colossoma macropomum: Implications on cardiorespiratory responses

This study aimed at characterizing the modulation of skeletal muscle contraction and cardiorespiratory response of tambaqui, Colossoma macropomum submitted to baths using anaesthetic concentrations (capable of inducing fast, i.e. < 5 min, and full body immobilization) of propofol (PRP) and essential oil of Nepeta cataria (EON). For the evaluation of electromyography, electrocardiographic data, and opercular beat intensity (OBI) and rate (OBR), fish (5.6 ± 1.8 g, 8.0 ± 0.3 cm, total length) were assigned to the following groups: a) control (basal recording), b) ethanol-exposed fish (vehicle control), c) fish submitted to induction with EON at 175 μL L−1 and subsequent recovery, and d) fish submitted to induction with PRP at 4 μL L−1 and subsequent recovery. Eight fish (n = 8) per group were used. Both products induced full body immobilization and suppressed (99.9%) dorsal muscle contraction power, determining a general anaesthesia-like state. During exposure to either anaesthetic, cardiac function was transiently affected, with decreased heart rates (42–43%) and a mild arrhythmia in PRP recovering fish. Moreover, ventilatory capacity was reduced with this drug (85.3% and 59.6% decrease in OBI and OBR, respectively), yet without mortality. On the other hand, EON did not alter ECG tracings, allowing for the maintenance of normal ventilation intensity during exposure, albeit a slight increment in OBR occurred during deep anaesthesia. This study confirms propofol anaesthesia in fish and presents N. cataria essential oil as a novel and safe natural anaesthetic for juvenile Colossoma macropomum and potentially for other teleost species.

Acute toxicity of nitrite in fat snook (Centropomus parallelus)

Oxidative stress and hypoxia responses in Centropomus parallelus exposed to three different concentrations of nitrite (0, 0.5, and 10 mg L−1) were evaluated. To determinate toxicity, we used enzymatic analyses and quantifications of oxygen consumption and opercular beats under conditions of normoxia and hypoxia. There was no significant difference in GST, CAT, or GPx enzymes in the liver or in GPx in the gills. Levels of GST were altered at a concentration of 10 mg L−1 in experiment I. Experiment II displayed alterations for GST and CAT in the liver at the same concentration, indicating that exposure to nitrite does not generate differentiated activation in the body’s defense system by the production of oxidative stress enzymes. When nitrite was associated with hypoxia, there was a significant increase in both enzymatic activity and opercular beating under hypoxia in the group exposed to 10 mg L−1 nitrite compared to the control.

Physiological and behavioural evaluation of common anaesthesia practices in the rainbow trout

Anaesthetic drugs are commonly administered to fish in aquaculture, research and veterinary contexts. Anaesthesia causes temporary absence of consciousness and may reduce the stress and/or pain associated with handling and certain invasive procedures. The rainbow trout (Oncorhynchus mykiss) is a widely-used model species with relevance to both aquaculture and natural ecosystems. This study sought to establish the relative acute impact of commonly used anaesthetics on rainbow trout when used for anaesthesia or euthanasia by exploring their effects on aversion behaviour and stress physiology. Five widely used anaesthetics were investigated at two concentrations reflective of common laboratory practises: MS-222, benzocaine, 2-phenoxyethanol, etomidate and eugenol. The anaesthetics were administered via immersion and fish were: 1) euthanised with anaesthetic; or 2) allowed to recover from deep plane anaesthesia; or 3) subjected to a conditioned place avoidance paradigm. Behaviour, opercular beat rate and plasma cortisol concentrations and cortisol release rates to water were quantified to investigate the effects of the five drugs. Based upon longer induction to deep plane anaesthesia, and increased plasma cortisol levels post-anaesthesia the widely-used and recommended anaesthetic MS-222 may be relatively stressful for rainbow trout. Whereas 2-phenoxyethanol, due to a combination of quicker induction, reduced aversive behavioural response during anaesthesia and lower post-anaesthesia plasma cortisol levels may be a more advisable alternative. It is crucial for the welfare of fish that the use of anaesthetics is as humane as possible and thus these findings have important implications for the welfare and husbandry of captive rainbow trout.

Essential oil of citronella modulates electrophysiological responses in tambaqui Colossoma macropomum: A new anaesthetic for use in fish

The aim of this study was to evaluate the efficacy of essential oil of citronella, Cymbopogon nardus (EOC) as an anaesthetic for fish, using juvenile tambaqui Colossoma macropomum as a model. The times to induction and recovery after short-term anaesthesia were evaluated by concentration-response trials. Moreover, electrophysiological responses in muscle (EMG), electrocardiographic data (ECG), opercular beat intensity (OBI) and rate (OBR) were also evaluated. Juveniles were placed in aquaria containing six concentrations of EOC (200, 400, 600, 800, 1000 and 1600μLL−1) and the times of anaesthetic induction and recovery were registered. Sham control fish and fish exposed to ethanol-added water were used as controls. With the exception of the lowest concentration used (200μLL−1), deep anaesthesia was attained at all other subsequent concentrations, being the use of 600μLL−1 sufficient to promote rapid induction (<3min) and uneventful recovery (<5min) from deep anaesthesia; while the concentration of 200μLL−1 was sufficient to induce sedation. EOC elicited a conspicuous depression on muscle contraction power with loss of muscle tonus. Although transient cardiorespiratory depression occurred during deep anaesthesia, gradual increases in the amplitudes of the differences in potential and frequencies in EMG, OBI and ECG, corroborate the reversibility and smooth transition to normal swimming behaviour during recovery from anaesthesia with EOC.

Influence of temperature on the respiratory rate of Nile Tilapia, Oreochromis niloticus (Pisces: Cichlidae) in the laboratory

Tilapia, Oreochromis niloticus, (Linneaus, 1758) is an important aquaculture species in Nigeria and other parts of the world. We obtained specimens (3,5-13,00 cm total length; 1,7 to 49 g) from Jabi Reservoir, Nigeria, and exposed them to 18-38o C. The frequency of opercular beats (i.e.respiratory rate) was determined from videos. At room temperature (28o C), the average frequency of opercular beats per minute for the weight groups of 1, 7 – 3,3; 4,0 – 7,0; 11,0 – 20 and 40 – 49g were 218, 190, 167 and 119 respectively. It decreased to 153, 137, 94 and 77 beats respectively when the water temperature was lowered to 18o C. It subsequently increased to 283, 267, 209 and 136 beats respectively when water temperature was raised to 38o C (p&lt;0, 05).

EFFECTIVENESS OF THE ANESTHETIC AQUI-S® 20E IN MARINE FINFISH AND ELASMOBRANCHS.

Immersion anesthetics are used in hatchery settings by veterinarians, field biologists, and laboratory researchers to aid in handling finfish for medical procedures, research purposes, and moderating perceived stress responses. The only Food and Drug Administration- (FDA) approved anesthetic for food fish, tricaine methanesulfonate, requires a 21-d withdrawal period prior to harvest. Ten percent eugenol (AQUI-S® 20E) has been gaining momentum for FDA approval because of its 0-d withdrawal time if fish are not of harvestable size within 72 h of exposure. We performed two trials to determine appropriate anesthetic doses for two cultured marine finfish: Atractoscion nobilis (white seabass, WSB) and Seriola lalandi (California yellowtail, YT). Fish were held in a treated water bath for 10 min or until opercular beat rate slowed to a rate of <2 beats/min. Based on these results, we conducted a field trial with wild Paralabrax maculatofasciatus (spotted bay bass), Paralabrax nebulifer (barred sand bass), Paralichthys californicus (California halibut), Triakis semifasciata (leopard shark), and Mustelus californicus (grey smooth-hound) at a single dosing regime, with animals held 5-10 min in anesthetic baths. Anesthetic dosing of 35-55 mg L(-1) provided relatively fast induction and good anesthetic maintenance in cultured and wild finfish. Anesthetic induction times were comparable among S. lalandi and A. nobilis at 35-mg L(-1) to 75-mg L(-1) doses, but recovery times were variable. Mortality rates of 20-90% were observed at higher doses (75 mg L(-1) and 100 mg L(-1), A. nobilis; 55 mg L(-1) and 75 mg L(-1), S. lalandi). The apparent increase in sensitivity of S. lalandi may have been associated with nutritional stress in the fish tested. There were no differences in time to anesthesia or recovery among wild finfish species tested at a single dose. Anesthetic induction, maintenance, and recovery were less predictable in the elasmobranch species tested and additional trials are needed to determine optimal dosing.

Does environmental enrichment promote recovery from stress in rainbow trout?

The EU Directive on animal experimentation suggests that all protected animals should have enrichment to improve welfare yet relatively little research has been conducted on the impact of enrichment in fish. Studies employing enrichment in zebrafish have been contradictory and all fish species should be provided with species-specific enrichments relevant to their ecology. Salmonids are important experimental models in studies within aquaculture, toxicology and natural ecosystems. This study therefore sought to establish whether an enriched environment in an experimental aquarium may promote improved welfare in rainbow trout (Oncorhynchus mykiss) by enhancing their recovery from invasive procedures. Trout were held individually in either barren (no tank ornamentation) or enriched (gravel, plants and an area of cover) conditions. Recovery rates after a noxious stimulus and a standard stressor were investigated by monitoring behaviour, opercular beat rate and plasma cortisol concentrations. Fish were randomly assigned to one of four treatment groups: Control (undisturbed), Sham (handled but not manipulated), Stress (air emersion) and Pain (subcutaneous injection of acetic acid). The results suggest that for rainbow trout environmental enrichment appears to promote recovery and ameliorate adverse effects following a stressor. However, recovery rate did not differ between environments in the pain treatment groups. Thus environmental enrichment may not be an important factor when the fish is responding to a painful stimulus. These results have important implications for the husbandry and welfare of captive rainbow trout and possibly other salmonids and suggest that enriched environments may be preferable to barren environments in experimental studies.

Hypoxia tolerance of European sturgeon (Acipenser sturioL., 1758) young stages at two temperatures

Summary European sturgeon sensitivity to oxygen depletion at two different temperatures was evaluated with embryos from fertilization to hatching time that were exposed to 90% O2 saturation (% O2 sat), 50% O2 sat and 30% O2 sat at 20 and 26°C; and three-month-old juveniles (12 cm length, 7.3 g width) exposed to oxygen challenge from 70% O2 sat to 10% O2 sat at 20 and 25°C. Parameters measured included embryonic survival rate (ESR) and hatch rate (HR); in juveniles the opercular beat frequency (OBF), altered swimming behavior, loss of equilibrium (LOE), and death were recorded. ESR did not differ between oxygen saturation levels for a single temperature but decreased between 20 and 26°C from 60.7 to 21.4% mean survival, respectively. No hatching was observed in embryos exposed to oxygen depletion at 50 and 30% O2 sat, regardless of temperature. The HR was lower at 26°C (15.4% mean) than at 20°C (75.8%) at 90% O2 sat. In embryos, all three oxygen concentrations allowed embryonic survival at the tested temperatures but were insufficient for increased activity such as hatching except at 20°C and 90% O2 sat. In juveniles, OBF peaked at 40% O2 sat at 212 beats per minute at 25°C and at 40–30% O2 sat at 182–183 beats per minute at 20°C. For LOE and death no significant differences were observed with regard to oxygen saturation at 20 and 25°C. Altered swimming behavior appeared at a significantly higher oxygen saturation at 25°C (43.5%) compared to 20°C (34.5%). Anaerobic metabolism was initiated after the OBF peak, which would represent a PO2crit for European sturgeon juveniles under 30 and 40% at 20°C and 25°C, respectively. Temperature increase also adversely affected the threshold of altered swimming behavior, which could be considered as a behavioral indicator of metabolic stress. The probability that the sturgeon embryos are being exposed to harmful temperatures and hypoxic conditions remains a true threat in the Gironde catchment basin.

Physiological and behavioural responses to noxious stimuli in the Atlantic cod (Gadus morhua).

In the present study, our aim was to compare physiological and behavioural responses to different noxious stimuli to those of a standardized innocuous stimulus, to possibly identify aversive responses indicative of injury detection in a commercially important marine teleost fish, the Atlantic cod. Individual fish were administered with a noxious stimulus to the lip under short-term general anaesthesia (MS-222). The noxious treatments included injection of 0.1% or 2% acetic acid, 0.005% or 0.1% capsaicin, or piercing the lip with a commercial fishing hook. Counts of opercular beat rate (OBR) at 10, 30, 60, 90 and 120 min and observations of behaviour at 30 and 90 min post-treatment were compared with pre-treatment values and with control fish injected with physiological saline, an innocuous stimulus. Circulatory levels of physiological stress indicators were determined in all fish at 120 minutes post-treatment. All treatments evoked temporarily increased OBR that returned to pre-treatment levels at 60 minutes (saline, 0.005% capsaicin, hook), 90 minutes (0.1% acetic acid, 0.1% capsaicin), or 120 minutes (2% acetic acid), but with no significant differences from the control group at any time point. Fish treated with 0.1% and 2% acetic acid and 0.1% capsaicin displayed increased hovering close to the bottom of the aquaria and fish given 2% acetic acid and 0.1% capsaicin also displayed a reduced use of shelter. The only effect seen in hooked fish was brief episodes of lateral head shaking which were not seen pre-treatment or in the other groups, possibly reflecting a resiliency to tissue damage in the mouth area related to the tough nature of the Atlantic cod diet. There were no differences between groups in circulatory stress indicators two hours after treatment. This study provides novel data on behavioural indicators that could be used to assess potentially aversive events in Atlantic cod.

The impacts of stress on sodium metabolism and copper accumulation in a freshwater fish

In freshwater fish, stress can often result in significant modifications to Na+ metabolism and may be an important aspect to consider in conservation efforts; as maintaining ion balance is critical to survival and ion transport is also a key determinant of metal toxicity. In order to better quantify the response of stress, Na+ influx, Na+ efflux, and copper accumulation were measured as a result of handling stress in inanga (Galaxias maculatus). This species is a culturally and economically important fish in New Zealand as one of the major species in the local ‘whitebait’ fishery. Na+ influx rates in inanga were found to be 2–3 times greater after handling than in ‘recovered’ fish, and Na+ efflux rates increased in the range of 5–6 times. Both influx and efflux rates quickly returned to resting levels within 24h. Increases in Na+ efflux were strongly correlated with opercular beat frequency. This suggests an increas in ventilation, and subsequent enhanced diffusive loss of Na+, as the mechanism of increased Na+ efflux. Total body copper levels were also measured under similar treatments. Fish had significantly higher levels of copper directly after handling than following a 24h recovery; likely due to a shared Na+/copper uptake pathway. As accumulation is linked to toxicity, fish exposed to elevated copper levels in stressful environments will consequently be more at risk to metal toxicity. In a natural environment, stress can come from many different sources; among which, anthropogenic disturbances can often be a cause. Given that inanga must migrate through metal-contaminated coastal regions to reach breeding habitats, they will be exposed to toxicants under conditions where perfusion and ventilation of the gill is increased. As such, ion loss would be exacerbated, leading to an enhanced compensatory ion uptake and an increase in accumulation of ion-mimicking toxicants such as copper, exacerbating toxicity. This is a concern as conservation efforts in more disruptive environments may not be adequately protected.

Impact of cadmium toxicity on behavioral and haematological biomarkers of freshwater fish, Catla catla

The present work is aimed to evaluate LC 50 values of Cadmium chloride for freshwater and common people edible fish, Catla catla , as well as to observe behavioural alterations treated with Cadmium. The LC 50 values for 24h, 48h, 72h and 96h were found 14.59, 10.76, 8.45 and 5.36 mg/l, respectively. The major behavioural alterations observed during the experiments were erratic swimming, S-jerk movements and burst swimming, restlessness, muscle spasm, fin flickering, profuse mucous secretion, discolouration of the integument in exposed animals. Overall increase in opercular beats in exposed fishes was also recorded throughout the experiments. The above modulations are considered as good bio-markers to access the health status of these valuable and cherished fishes as well as worsening status of aquatic bodies in relation to metallic contaminants, particular Cadmium. Haematological indices are considered to be pathophysiological indicators of the whole body and therefore are important in diagnosing the structural and functional status of animals exposed to pollutants. Exposure of fish to sublethal concentration of cadmium showed a significant decrease in the haemoglobin (Hb) content, total red blood cells (TRBC) and packed cell volume (PCV/Hct) at the end of 30 th day as compared to control, this may impair oxygen supply to various tissues, thus resulting in a slow metabolic rate and low energy production and indicates the worsening of an organism state and developing anaemia. Whereas the total white blood cells (TWBC) increased significantly, with increase in exposure periods, may be attributed to immunological response of the fish to heavy metal. To safeguard these, it is suggested, that the cadmium levels should be monitored and be restricted to release in to the aquatic environment either in any way with heavy metals monitoring devices.