Search

Copyright of Revista de Investigaciones Veterinarias del Peru is the property of Universidad Nacional Mayor de San Marcos (UNMSM) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tricaine methanesulfonate (MS-222) solutions are used routinely for clinical and experimental anesthesia of a variety of aquatic organisms. It is commonly accepted that MS-222 alters pH when added to freshwater, and buffering freshwater anesthetic solutions is considered to be the standard of care. However, buffering saltwater solutions is considered by many to be unnecessary; some individuals question whether any water with high natural mineral hardness needs to be buffered when MS-222 is added. To assess the need for buffering, we studied the dynamics of pH change when adding clinically relevant amounts of MS-222 to artificial seawater and to freshwater of varying hardness. We found that artificial seawater does not possess adequate buffering capacity to prevent a physiologically significant drop in pH when MS-222 is added, and hardness does not accurately predict the reaction of water pH to the addition of MS-222 in clinically relevant concentrations. Our data for salt water suggest that MS-222 solutions should be buffered to saturation with sodium bicarbonate and in freshwater should be titrated to the particular water source to satisfy the optimal pH of the species being anesthetized. Received September 18, 2012; accepted March 4, 2013 [ABSTRACT FROM PUBLISHER]

Objective--To determine whether repeated exposure to clinically relevant concentrations of tricaine methanesulfonate (MS-222) would alter retinal function or induce histologically detectable retinal lesions in koi carp (Cyprinus carpio). Design--Prospective, controlled, experimental study. Animals--18 healthy koi carp. Procedures--2 fish were euthanized at the start of the study, and eyes were submitted for histologic evaluation as untreated controls. Anesthesia was induced in the remaining fish with 200 mg of MS-222/L and maintained with concentrations of 125 to 150 mg/L for a total exposure time of 20 minutes daily on 1 to 13 consecutive days. On days 1, 7, and 13, electro-retinography of both eyes was performed in all fish remaining in the study, and 2 fish were euthanized immediately after each procedure for histologic evaluation of the eyes. Median fa-wave amplitudes were compared among study days for right eyes and for left eyes via 1-way repeated-measures ANOVA with a Bonferroni correction for multiple comparisons. Results--Median b-wave amplitudes on days 1, 7, and 13 were 17.7 20.9, and 17.6 pV, re-spectively, for right eyes and 15.1, 16.9, and 14.3 pV, respectively, for left eyes. No significant differences in b-wave amplitudes were detected among study days. No histopathologic ab-normalities were identified in the retinas of any fish treated with MS-222 or in control fish. Conclusions and Clinical Relevance--Short-term exposure of koi carp to clinically relevant concentrations of MS-222 daily for up to 13 days was not associated with changes in retinal structure or function as measured in this study. [ABSTRACT FROM AUTHOR]

Laparoscopy is a reliable, minimally-invasive technique to obtain reproductive information from wild and captive sturgeon. While generally considered safe, the physiological consequences of laparoscopy in sturgeon are unknown. Therefore clinical pathology changes in juvenile, Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus) following experimental laparoscopy at 10 and 22°C were described. Control fish were anesthetized with MS-222 according to the same protocols as surgical fish, but were not incised. Surgical procedures did not affect heart and ventilation rates, signs of stress (skin redness) or time to recover from anesthesia in comparison to control fish. Anesthesia with MS-222 produced a transient (by 1 h) hemo-concentration (elevated protein and electrolytes), erythrocyte swelling (increased PCV and MCV) and stress response (elevated cortisol and glucose); and a delayed (by 24 h) increase in RBC, leukopenia and increased N : L ratio. Surgical procedures resulted in a delayed (by 24 h) decrease in plasma proteins, electrolytes, RBC and PCV relative to control fish, which may have resulted from surgically-induced hemorrhage. Plasma enzyme activities increased in response to anesthesia and surgery and may indicate general stress and tissue damage. Anesthesia had a greater effect on blood value response than surgery, and the proportion of effect increased with temperature as MS-222 potency and toxicity increases with water temperature. Repeated handling and blood draws within 24 h resulted in a 7% increase in cortisol, 10-14% increase in CK and 9-11% increase in LDH values. Except for plasma enzyme activities, blood values of all fish recovered within 1 week following anesthesia and surgeries. Relative experience of surgeons had no effect on hematology and biochemistry of fish, but healing rates of incisions were improved with better suture technique. Results of this study conclude that the physiological effects of laparoscopy are largely related to the anesthetic, MS-222, and are generally mild and short-lived. Improvements in laparoscopic technique might be gained by exploring alternate anesthetic protocols with faster induction and recovery times and reduced physiological effects. [ABSTRACT FROM AUTHOR]

Anaesthesia is essential to minimize stress and physical damage during handling of fish in captivity. In the present study, induction time in Puntius denisonii (Day, 1865), an endangered aquarium fish exposed to four concentrations of MS-222 (50 mg L-1, 100 mg L-1, 150 mg L-1 and 200 mg L-1) was determined. MS-222 appears to be highly effective as an anaesthetic with no side effects to both fish as well as humans. An induction time of less than or equal to three minutes, and a complete recovery in five minutes was used a basis to record the anaesthesia stages for different doses. The onsets of individual phases of anaesthesia and recovery stages were also studied. Concentration of 150mg L -1 (induction 165±10 seconds and recovery time 112±10 seconds) was determined as the lowest concentration that induces anaesthesia in P. denisonii in less than three minutes. Induction and recovery times were dose-dependent. An inversely proportional relationship was observed between concentrations of anaesthetic and induction time. This is the first study to investigate the efficacy of different concentrations of MS-222 in Puntius denisonii and will be helpful to develop standardised techniques for transportation, captive breeding and other ex-situ conservation plans for this endangered and endemic barb. [ABSTRACT FROM AUTHOR]

Anaesthetics are used in aquaculture and fisheries to facilitate routine procedures, such as capture, handling, transportation, tagging, grading and measurements that can often cause injury or induce physiological stress. Two experiments were performed to assess the efficacies of four anaesthetic agents, clove oil, benzocaine, 2-phenoxyethanol and MS-222 on juvenile marbled spinefoot rabbitfish ( S iganus rivulatus). In the first experiment we tested the lowest effective doses that produced induction and recovery times in 3 min or less and 5 min or less respectively. Dosages were 70 mg L−1 for clove oil, 60-70 mg L−1 for benzocaine, 400 μL L−1 for 2-phenoxyethanol and 100-125 mg L−1 for MS-222. In the second experiment, we determined optimal concentrations of the four anaesthetics if they were to be used to transport rabbitfish fry. Anaesthetic concentrations suitable for handling and transport were: 10-15 mg L−1 of MS-222, 5-10 mg L−1 of benzocaine, 5 mg L−1 of clove oil and 50-100 μL L−1 of 2-phenoxyethanol. All anaesthetic agents are acceptable for use on S . rivulatus, however, 2-phenoxyethanol, MS-222 and clove oil appear to be more suitable than benzocaine. Further studies need to be conducted on effects of high and low doses of anaesthetic agents on physiology of marbled spinefoot. [ABSTRACT FROM AUTHOR]

The notochord is an important organ involved in embryonic patterning and locomotion. In zebrafish, the mature notochord consists of a single stack of fully differentiated, large vacuolated cells called chordocytes, surrounded by a single layer of less differentiated notochordal epithelial cells called chordoblasts. Through genetic analysis of zebrafish lines carrying pseudotyped retroviral insertions, a mutant exhibiting a defective notochord with a granular appearance was isolated, and the corresponding gene was identified as ngs (notochord granular surface), which was specifically expressed in the notochord. In the mutants, the notochord started to degenerate from 32 hours post-fertilization, and the chordocytes were then gradually replaced by smaller cells derived from chordoblasts. The granular notochord phenotype was alleviated by anesthetizing the mutant embryos with tricaine to prevent muscle contraction and locomotion. Phylogenetic analysis showed that ngs encodes a new type of intermediate filament (IF) family protein, which we named chordostatin based on its function. Under the transmission electron microcopy, bundles of 10-nm-thick IF-like filaments were enriched in the chordocytes of wild-type zebrafish embryos, whereas the chordocytes in ngs mutants lacked IF-like structures. Furthermore, chordostatin-enhanced GFP (EGFP) fusion protein assembled into a filamentous network specifically in chordocytes. Taken together, our work demonstrates that ngs encodes a novel type of IF protein and functions to maintain notochord integrity for larval development and locomotion. Our work sheds light on the mechanisms of notochord structural maintenance, as well as the evolution and biological function of IF family proteins. [ABSTRACT FROM AUTHOR]

The design of anesthetic protocols for frogs is commonly hindered by lack of information. Results from fishes and rodents do not always apply to frogs, and the literature in anurans is concentrated on a few species. We report on the response of treefrogs (Hyla chrysoscelis and H. versicolor) to tricaine methanesulfonate. Body mass did not differ significantly between the species or between sexes. In the first exposure of a frog to TMS, variation in induction time was best explained by species (H. chrysoscelis resisted longer) and body mass (larger animals resisted longer). Multiple exposures revealed a strong effect of individual variation on induction time and a significant increase of induction time with number of previous anesthesia events within the same day. Recovery time was mostly explained by individual variation, but it increased with total time in anesthetic and decreased with induction time. It also increased with number of days since the last series of anesthesias and decreased with number of previous uses of the anesthetic bath. This is one of the first studies of anesthesia in hylids and also one of the first assessments of the factors that influence the variability of the response to anesthesia within a species. [ABSTRACT FROM AUTHOR]

The efficacy of immersion anaesthesia with tricaine methanesulphonate (MS222) or propofol on albino and grey silver catfish Rhamdia quelen was assessed through induction and recovery times and observation of mortality. Besides reporting a novel, efficient and practical use of propofol as an immersion anaesthetic, the study shows that it is essential to consider size and strain when anaesthetizing R. quelen with MS222 or propofol bath solution in order to minimize physiological impact. [ABSTRACT FROM AUTHOR]

Tricaine methane-sulfonate (MS-222) is one of the most widely used anaesthetics for poikilotherms worldwide. This paper outlines its anaesthetic efficacy and dosage in fish and legislation for its use, fish stress responses to MS-222 anaesthesia and its effect on fish physiology and blood properties, pharmacokinetics, genotoxicity, immune response, potential interference with fish hepatic cytochrome P450 spectra, and its impact on nerve sensitivity. Key questions arising from the available data are analysed, such as regulatory constraints on its use, the need for the standardization of buffering protocols, and interdependencies of the factors impacting the specific applicative efficacy of MS-222. Current research has provided an abundance of data on MS-222 use in fish, although the applications within these studies are often impractical at the farming level. Specific emphasis is therefore placed on highlighting application strategies on a practical basis, presenting potential future research on topics that require in-depth analysis (preparation and storage of anaesthetic solutions, pre-anaesthetic sedation and stress reduction, cortisol response in aquarium fish, toxicity of MS-222 metabolites, and possible immunodepressive properties). Additionally, both from a scientific and practical perspective, it is necessary to have a better understanding of safety margins, induction, immersion and recovery times for many (marine and freshwater, farmed and ornamental) fish species in order to achieve optimal utilization. [ABSTRACT FROM AUTHOR]

Abstract: The frog Xenopus laevis is a model species for developmental biology but is also of significant interest to comparative immunologists. Amphibians are the oldest group of organisms in which both the B lymphocytes of some species undergo immunoglobulin (Ig) class switch recombination and also have a dedicated mucosal Ig isotype. The purpose of this study was to test the hypothesis that frog IgX would be produced in response to oral immunization. In order to facilitate studies of humoral, and especially mucosal immunity, in this model species, we developed a gavage technique for oral immunization. The result of this oral administration of antigen to frogs was assayed by the induction of the mucosal antibody isotype, IgX, in plasma by enzyme linked immunosorbant assay (ELISA), and a significant IgX upregulation was detected compared to frogs receiving systemic immunization into the coelom. These data are consistent with the view that IgX is the functional analog of mammalian IgA and mandate further studies of the relationship between IgX and IgA. Additionally, the gavage technique should be adaptable for functional studies of gut-associated immunology in other small aquatic vertebrates. [Copyright &y& Elsevier]

Abstract: The neuroplasticity and regenerative properties of the olfactory system make it a useful model for studying the ability of the nervous system to recover from damage. We have developed a novel method for examining the effects of long-term deafferentation and regeneration of the olfactory organ and resulting influence on the olfactory bulb in adult zebrafish. To test the hypothesis that repeated damage to the olfactory epithelium causes reduced olfactory bulb afferent input and cessation of treatment allows recovery, we chronically ablated the olfactory organ every 2–3 days for 3 weeks with the detergent Triton X-100 while another group was allowed 3 weeks of recovery following treatment. Animals receiving chronic treatment showed severe morphological disruption of the olfactory organ, although small pockets of epithelium remained. These pockets were labeled by anti-calretinin, indicating the presence of mature olfactory sensory neurons (OSNs). Following a recovery period, the epithelium was more extensive and neuronal labeling increased, with three different morphologies of sensory neurons observed. Repeated peripheral exposure to Triton X-100 also affected the olfactory bulb. Bulb volumes and anti-tyrosine hydroxylase-like immunoreactivity, which is an indicator of afferent activity, were diminished in the olfactory bulb of the chronically treated group compared to the control side. In the recovery group, there was little difference in bulb volume or antibody staining. These results suggest that repeated, long-term nasal irrigation with Triton X-100 eliminates a substantial number of mature OSNs and reduces afferent input to the olfactory bulb. It also appears that these effects are reversible and regeneration will occur in both the peripheral olfactory organ and the olfactory bulb when given time to recover following cessation of treatment. We report here a new method that allows observation not only of the effects of deafferentation on the olfactory bulb but also the effects of reinnervation. [Copyright &y& Elsevier]

Abstract: Tricaine methanesulfonate, a sedative for temporarily immobilizing fish, has a 21-day withdrawal time. Benzocaine has been proposed as an alternative sedative because a withdrawal period may not be required. Since benzocaine is known to induce methemoglobinemia, the potential for orally administered benzocaine to induce methemoglobin was assessed in rats. Sprague–Dawley rats were given a single gavage administration of 64mg benzocaine hydrochloride per kg bw and then euthanized at intervals up to 120min. Plasma levels of benzocaine were relatively low at all times, whereas methemoglobin peaked at 24min. Additional rats were orally gavaged with 0–1024mg benzocaine hydrochloride per kg bw and euthanized after 24min. Plasma levels of benzocaine increased from 0.01μM at 2mg per kg bw to 2.9μM at 1024mg per kg bw. Methemoglobin levels did not differ from controls at doses up to 32mg per kg bw in females and 64mg per kg bw in males, whereupon the value increased to ∼80% at 1024mg per kg bw. These data were used to estimate the potential impact of benzocaine residues in fish and suggest that the consumption of fish treated with benzocaine hydrochloride will not cause methemoglobinemia in humans. [Copyright &y& Elsevier]

Three anaesthetic agents were tested in sturgeon hybrid Acipenser naccarii female × Acipenser baerii male: clove oil at 100 mg L (CLO); tricaine methanesulfonate at 150 mg L (MS-222); combined medetomidine and ketamine hydrochloride (MK) administered by intravenous injection at 0.04 mg kg + 4 mg kg, respectively. Efficacy of the anaesthetics was evaluated as well as physiological effects on blood gas status, acid-base balance and stress response by measuring blood PCO, PO, pH, haematocrit and serum cortisol, glucose, NEFA, lactate, Na, K, Cl concentration. Anaesthetic dosages were safe and effective in order to rapidly anaesthetize the sturgeons: induction time was significantly shorter with MS-222 (3.2 min) compared with CLO (4.7 min) and MK (5.4 min). Recovery time was significantly longer in MK anaesthetized fish (16 min) in comparison with CLO (5.8 min) and MS-222 (3.8 min). Anaesthesia induced blood hypercapnia, respiratory acidosis and stress response, with differences among anaesthetics. Blood PCO and cortisol levels were significantly higher in MS-222 (11 mmHg; 97.0 ng ml) and CLO (9.6 mmHg; 65.3 ng ml) anaesthetized groups compared to MK (7.8 mmHg; 39.6 ng ml) and control (7.0 mmHg; 10 ng ml). Overall results indicated that anaesthesia with MS-222 produced a greater physiological impact in sturgeons compared to the other anaesthetics. The effects were slightly attenuated in fish anaesthetized with clove oil, indicating that the use of this chemical was better than MS-222 in reducing handling stress. MK anaesthesia affected physiological parameters to a lesser extent. Intravascular administration of medetomidine at a dose of 0.04 mg kg in combination with ketamine at a dose of 4 mg kg proved to be a safe and effective anaesthetic protocol in this hybrid sturgeon, suitable for experimental studies and diagnostic procedures related to broodstock management and artificial reproduction. [ABSTRACT FROM AUTHOR]

Tricaine methanesulfonate (TMS) is an anesthetic that is approved for provisional use in some jurisdictions such as the United States, Canada, and the United Kingdom (UK). Many hatcheries and research studies use TMS to immobilize fish for marking or transport and to suppress sensory systems during invasive procedures. Improper TMS use can decrease fish viability, distort physiological data, or result in mortalities. Because animals may be anesthetized by junior staff or students who may have little experience in fish anesthesia, training in the proper use of TMS may decrease variability in recovery, experimental results and increase fish survival. This document acts as a primer on the use of TMS for anesthetizing juvenile salmonids, with an emphasis on its use in surgical applications. Within, we briefly describe many aspects of TMS including the legal uses for TMS, and what is currently known about the proper storage and preparation of the anesthetic. We outline methods and precautions for administration and changes in fish behavior during progressively deeper anesthesia and discuss the physiological effects of TMS and its potential for compromising fish health. Despite the challenges of working with TMS, it is currently one of the few legal options available in the USA and in other countries until other anesthetics are approved and is an important tool for the intracoelomic implantation of electronic tags in fish. [ABSTRACT FROM AUTHOR]

Abstract: The feasibility of using clove oil, 2-phenoxyethanol, or Propiscin as an alternative to tricaine methane sulphonate (MS 222) for anaesthetizing fish was studied, particularly with respect to reducing stress. The blood biochemical and antioxidant profiles of rainbow trout Oncorhynchus mykiss anaesthetized with MS 222 (100mgl−1), clove oil (30mgl−1), 2-phenoxyethanol (0.40mll−1), or Propiscin (1.0mll−1), and a non-anaesthetized control group, were compared. Biochemical and antioxidant profiles were determined from blood samples collected prior to treatment in controls. For each anaesthetic tested, fish were divided into two groups, one sampled immediately after 10min anaesthesia and a second, sampled 24h after 10min anaesthesia. Our results suggest that internal organs and tissues of rainbow trout were slightly altered by all tested anaesthetics and resulted in increased reactive oxygen species formation, leading to oxidative damage to lipids and proteins and inhibition of antioxidant capacities. In short, a low level of oxidative stress could induce the adaptive responses of antioxidant enzymes. On the basis of this experiment, it appears that Propiscin was associated with the lowest effects in rainbow trout and therefore would be recommended as an alternative to MS 222. [Copyright &y& Elsevier]

The article offers information on the attempted surgical correction of egg stasis in Irish lords Hemilepidotus jordani (Bean) and Hemilepidotus hemilepidotus (Tilesius). A technique called modified ovariosalpingectomy was used in the surgical procedure to treat the reproductive problem of the fish after it was immersed in tricaine methanesulfonate anesthesia in sea water. It says that surgery must be performed less than one year of egg stasis to prevent accumulation of eggs in the coelom.

Toads in the genus Bufo are commonly kept in pet, research, and zoological settings and may require anesthesia during veterinary care. Limited information is available comparing anesthetic protocols in most amphibian species. The purpose of this study was to evaluate the clinical and cardiopulmonary effects of tricaine methanesulfonate (MS-222) and propofol in Sonoran desert toads (Bufo alvarius). Nine juvenile Sonoran desert toads were anesthetized with an immersion bath of 1 g/L MS-222 and 35 mg/kg intracoelomic propofol with a minimum 2-wk wash-out period between trials. Heart rate, respiratory rate, and reflexes (righting, escape, corneal, superficial pain, and deep pain) were monitored every 5 min for the first 90 min and then every 10 min for the next 90 min during both anesthetic trials. Surgical anesthesia was defined as complete loss of all measured reflexes. MS-222 produced surgical anesthesia in 100% (9/9) of toads, whereas propofol produced surgical anesthesia in 11.1% (1/9). Mean induction time for the MS-222 trial was 19.9 min (SD: 5.4, Min-Max: 13-30), with mean duration of surgical anesthesia 23.9 min (SD: 10.8, Min-Max: 10-42). Mean recovery time after removal from the MS-222 bath was 85.3 min (SD: 18.5, Min-Max: 60-110). Righting reflex was lost in all animals in the propofol trial at a mean of 23.9 min (SD: 5.5, Min-Max: 20-35) following administration. A single animal in the propofol trial reached a surgical plane of anesthesia at 25 min post-administration, with surgical anesthesia lasting for 50 min. Mean time to recovery following administration of propofol was 145 min (SD: 47.2, Min-Max: 60-180); one toad was not fully recovered at the end of the monitoring period. Heart rate was not found to significantly (P < 0.05) change from baseline at any monitoring point for either anesthetic protocol. Respiratory rate was found to decrease significantly (P > 0.05) at all time points between 5 and 65 min in the MS-222 trial and between 10 and 130 min in the propofol trial. MS-222 at 1 g/L immersion was found to reliably produce surgical anesthesia in Sonoran desert toads with a faster onset of action and recovery when compared to propofol administered intracoelomically at 35 mg/kg. [ABSTRACT FROM AUTHOR]

Six experiments were designed to determine the optimal anaesthetic dosage of tricaine methanesulphonate (TMS) and clove oil that could be used safely on juvenile cobia Rachycentron canadum of two sizes [G1=4.9±0.8 g; G2=13.9±3.1 g]. We documented the stage of anaesthesia and the acute toxicity as 96 h LC50 (lethal concentration 50% population) at various exposure times of the two anaesthetics. At 10 min induction time, the TMS 96 h LC50 was 93.9 mg L−1 in G1 and 97.0 mg L−1 in G2. Compared with clove oil, the 96 h LC50 was 60.0 mg L−1 in G1 and 69.8 mg L−1 in G2. The difference between the two groups (G1, G2) did not influence anaesthesia safety ( P>0.05). Rachycentron canadum achieved stage 3 anaesthesia more rapidly at a lower clove oil concentration level (40 mg L−1, 10 min) than TMS (60 mg L−1, 10 min), but the recovery period of clove oil, was significantly longer. Clove oil was the most effective in reducing the short-term stress induced by routine biometry (20 mg L−1, 10 min) and also by transporting (1 mg L−1, 8 h). Whereas, for long-term exposure, 40 mg L−1 TMS was found to be safe. [ABSTRACT FROM AUTHOR]

This study investigated the feasibility of using clove oil, 2-phenoxyethanol, or Propiscin as an alternative to tricaine methane sulphonate (MS 222) as a fish anaesthetic, particularly in regard to reducing fish stress. The biochemical blood profiles of perch Perca fluviatilis L. anaesthetized with either MS 222 (100 mg L−1), clove oil (33 mg L−1), 2-phenoxyethanol (0.40 mL L−1) or Propiscin (1.0 mL L−1), and a non-anaesthetized control group were compared. Biochemical profiles were determined from blood samples collected before treatment in controls. For each anaesthetic tested, fish were divided into two groups, one sampled immediately after 10-min anaesthesia and a second, sampled 24 h after 10-min anaesthesia. The values determined in the present study suggested that internal organs and tissues of perch were slightly altered by MS 222, clove oil and 2-phenoxyethanol anaesthesia, but not by Propiscin anaesthesia. [ABSTRACT FROM AUTHOR]

Simple Summary: Although zebrafish are used in vast numbers in laboratories all over the world, no consensus has been reached in the scientific community on a humane, consistent, and effective method for euthanasia of this species. Here, we screened commonly used anaesthetic drugs to see if an overdose could induce loss of reflexes of adult zebrafish in a rapid and reliable manner, and without causing distress. The tested anaesthetics were isoeugenol, clove oil, 2-phenoxyethanol, tricaine, benzocaine, lidocaine hydrochloride, and etomidate. We found that lidocaine hydrochloride, buffered with sodium bicarbonate and ethanol to increase its efficacy, induces loss of reflexes in a fast, predictable, and relatively peaceful manner. We recommend its use for adult zebrafish euthanasia. Zebrafish are often euthanized by overdose of anaesthesia. However, fish may have aversion towards some anaesthetics, and protocol efficacy varies between species. Using wild type adult Danio rerio, we assessed time to loss of opercular beat, righting, and startle reflexes during induction of anaesthetic overdose by either tricaine (0.5 g/L or 1 g/L), benzocaine (1 g/L), 2-phenoxyethanol (3 mL/L), clove oil (0.1%), isoeugenol (540 mg/L), lidocaine hydrochloride (1 g/L), or etomidate (50 mg/L). Initial screening demonstrated that benzocaine and buffered lidocaine hydrochloride achieved the fastest loss of reflexes. The rapid induction times were confirmed when retesting using larger batches of fish. The fastest induction was obtained with 1 g/L lidocaine hydrochloride buffered with 2 g/L NaHCO3, in which all adult zebrafish lost reflexes in less than 2 min. Next, we monitored signs of distress during benzocaine or buffered lidocaine hydrochloride overdose induction. The results indicated that buffered lidocaine hydrochloride caused significantly less aversive behaviors than benzocaine. Finally, we tested several buffers to refine the lidocaine hydrochloride immersion. The most efficient buffer for euthanasia induction using 1g/L lidocaine hydrochloride was 2 g/L NaHCO3 with 50 mL/L 96% ethanol, inducing immobility in less than 10 s and with only 2% of adult zebrafish displaying aversive behaviors during treatment. [ABSTRACT FROM AUTHOR]

Abstract  The fish extoparasite Ichthyophthirius multifiliis was subjected to tricaine methanesulfonate (TM) exposure while fish were anesthetized for parasite collection. No information is available on the effects of TM exposure to I. multifiliis. This study evaluated the effects of TM on the survival and reproduction of I. multifiliis. Significant differences were not observed in survival and reproduction of tomonts collected from fish anesthetized using unbuffered or buffered TM or in control fish not exposed to TM. Results of the current study demonstrated that TM had no adverse effect on I. multifiliis survival and reproduction when used at concentrations and exposure times required for fish anesthetization. [ABSTRACT FROM AUTHOR]

Abstract: Ethylbenzene and para-xylene (p-xylene), but not the chemically closely related organic solvents ortho-xylene (o-xylene) and meta-xylene (m-xylene), are known to cause ototoxicity and irreversible hearing loss, though the underlying mechanisms are still unknown. In this study, effects of ethylbenzene and of p-, o-, and m-xylene on human heteromeric α9α10 nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes were investigated using the two-electrode voltage clamp technique. ACh dose-dependently evoked an α9α10 nAChR-mediated ion current with an EC50 of 137μM. When ACh is applied at a low concentration (10μM), the nAChR-mediated ion current is inhibited by a low concentration (10μM) of ethylbenzene and p-xylene, but not by the same concentration of the non-ototoxic solvents. At a high solvent concentration (300μM), all solvents cause inhibition of the ion currents evoked by 10μM ACh. Ion currents evoked by a near maximum-effective concentration ACh (1mM) are inhibited by the selected organic solvents only at 300μM. These results demonstrate that low concentrations of the known ototoxic solvents ethylbenzene and p-xylene inhibit α9α10 nAChR-mediated ion currents, whereas the structurally related, non-ototoxic solvents m-xylene and o-xylene do not, indicating that the α9α10 nAChR is a potential target for solvent-induced ototoxicity. [Copyright &y& Elsevier]

Tricaine methanesulfonate (MS-222) and CO2 are anesthetics that can be legally used in fisheries work in the United States, but they are limited in their field applications. A mandatory 21-d withdrawal period is required for fish exposed to MS-222. Carbon dioxide is not approved by the U.S. Food and Drug Administration, but it is a "low regulatory priority drug" that can be used legally for fish anesthesia. However, stressful induction and lengthy recovery times have been associated with CO2. AQUI-S is a clove oil derivative that has the potential to become an approved anesthetic without the limitations of MS-222 or CO2. We compared the efficacy of CO2 with that of AQUI-S when surgically implanting radio transmitters into cutthroat trout Oncorhynchus clarkii. A 20% survival rate was observed when CO2 was used in combination with silk sutures, but a 100% survival rate was observed when CO2 was used in combination with surgical staples to shorten the duration of the surgical procedure. A 100% survival rate was observed when AQUI-S was used in combination with either silk sutures or surgical staples. Carbon dioxide in combination with surgical staples seemed to provide a reasonable option when surgically implanting radio transmitters into cutthroat trout, but AQUI-S may be the preferred anesthesia because high pH and dissolved oxygen levels and low free-CO2 concentrations are maintained during surgical procedures. [ABSTRACT FROM AUTHOR]

In-situ caged rainbow trout ( Oncorhynchus mykiss) studies reveal significant fish toxicity and fish stress in a river impacted by headwater acid rock drainage (ARD). Stocked trout survival and aqueous water chemistry were monitored for 10 days at 3 study sites in the Snake River watershed, Colorado, U.S.A. Trout mortality was positively correlated with concentrations of metals calculated to be approaching or exceeding conservative toxicity thresholds (Zn, Mn, Cu, Cd). Significant metal accumulation on the gills of fish stocked at ARD impacted study sites support an association between elevated metals and fish mortality. Observations of feeding behavior and significant differences in fish relative weights between study site and feeding treatment indicate feeding and metals-related fish stress. Together, these results demonstrate the utility of in-situ exposure studies for stream stakeholders in quantifying the relative role of aqueous contaminant exposures in limiting stocked fish survival. [ABSTRACT FROM AUTHOR]

Abstract  The genotoxicity of the anaesthetic MS222 (tricaine) was analysed in fish under both in vivo and in vitro conditions. Based on results of the single cell gel/Comet assay, MS222 had no direct genotoxic effect on the experimental fish, indicating that MS222 does not induce primary DNA damage. These results suggest that the use of this important anaesthetic in aquaculture can be considered to be safe in terms of genotoxicity. [ABSTRACT FROM AUTHOR]

Abstract: A liquid chromatography tandem mass spectrometry (LC–MS/MS) method for the determination of residues of the anaesthetic tricaine mesilate (MS222) in fish tissues is described. Residues were extracted from homogenized tissues with McIllvaine buffer/methanol and purified over a C18 solid-phase extraction column followed by LC–MS/MS analysis. In the multiple-reaction monitoring mode of the mass spectrometer, chromatograms were recorded by monitoring the m/z 166→ m/z 138 and m/z 166→ m/z 94 transitions for quantification and confirmation of the residues in the finfish matrix, respectively. Recoveries were in the range of 67%±10% (n =6) for tilapia at 2μgkg−1, 95%±7% (n =6) at 2μgkg−1 in salmon and 92%±3% (n =5) for trout at 2.5μgkg−1. The limits of detection were 0.5, 0.6 and 0.6μgkg−1 in trout, salmon and tilapia, respectively. No residues of tricaine were found in eight sampled aquacultured fish (salmon and trout) bought from the local market. [Copyright &y& Elsevier]

Anesthetics are widely used for surgical, field sampling, and experimental procedures in fisheries sciences. Given the high cost and the U.S. Food and Drug Administration's (FDA) mandatory withdrawal time of the only FDA-approved fisheries anesthetic, tricaine methanesulfonate (MS-222), clove oil has emerged as an alternative anesthetic that is generally regarded as safe. However, studies regarding the effectiveness of clove oil in retarding the stress response of fish are contradictory. This study evaluated the effectiveness of MS-222 (60 mg/L), clove oil (30 mg/L) emulsified in ethanol, and clove oil (30 rag/L) mechanically emulsified in water in reducing the stress response of rainbow trout Oncorhynchus mykiss during a 15-min confinement. Clove oil emulsified in ethanol (mean, 56.3 ng cortisol/mL) was nol as effective in reducing the cortisol response as MS-222 (mean, 33.4 ng/mL). Furthermore, clove oil emulsified in ethanol and clove oil mechanically emulsified in water (means, 49.0 and 56.2 ng/mL, respectively) produced a greater cortisol response in undisturbed fish. Our results suggest that clove oil is less effective than MS-222 in reducing cortisol responses in rainbow trout subjected to handling and confinement. Our results also indicate that clove oil can induce stress and possibly lead Io greater release mortality of field-handled fish. [ABSTRACT FROM AUTHOR]

Abstract: We compared electrocardiographic signals in hatchery-reared, non-spinally-transected, immature rainbow trout (Oncorhynchus mykiss Walbaum) under clove oil (25 ppm), tricaine methanesulfonate (tricaine, 60 ppm), and benzocaine (108 ppm) general anesthesia (35 min, 14 °C). For all 3 anesthetics, the mean heart rate (HR) and QRS amplitude did not differ, and QRS duration and QT interval were independent of HR. Heart rate variability (HRV) was significantly (4-fold, P =0.032) higher under benzocaine than under clove oil and tricaine, but did not differ between clove oil and tricaine. QRS duration differed between groups (P <0.001, F =121); benzocaine anesthesia resulted in longer QRS complexes compared to clove oil (P <0.001) and tricaine (P <0.001) anesthesia, and QRS complexes under clove oil were longer than those under tricaine (P <0.001). High HRV and QRS amplitude variation with benzocaine were associated with HR oscillations as anesthetic exposure time increased, and suggest benzocaine toxicity which may influence cardiac function studies. Similar clove oil and tricaine ECG patterns suggest comparable autonomic effects, and maintenance of myocardial excitability. Given its low cost, ease of use, and similar ECG profiles to tricaine, clove oil is a viable alternative for studies of cardiac function in anesthetized rainbow trout. [Copyright &y& Elsevier]

Anaesthetization of Arctic charr Salvelinus alpinus with tricaine methanesulphonate or 2-phenoxyethanol did not alter plasma protein, glucose, free amino acid, non-esterified fatty acid, ion or osmolality levels, suggesting that their use allows for the normal determination of these plasma variables. [ABSTRACT FROM AUTHOR]

Juvenile and adult black sea bass ( Centropristis striata L.) were exposed to various concentrations of four anaesthetics to determine practical dosages for handling as well as for procedures such as bleeding, ovarian biopsy or tag implantation. In experiment 1, juveniles exposed to either 2.0 mg L−1 metomidate, 15 mg L−1 clove oil, 70 mg L−1 tricaine methanesulphonate (TMS) or 200 mg L−1 2-phenoxyethanol (2-PE) reached stage II of anaesthesia in 3–5 min and could be handled for weighing and measuring. All fish had completed recovery to stage III within 6 min. In experiment 2, the established concentrations of each anaesthetic were tested on juveniles to determine their ability to prevent a reflex to a subcutaneous needle puncture. All of the fish exposed to clove oil (20 mg L−1) and 40% of the TMS-treated (70 mg L−1) fish reacted while none of the fish anaesthetized in metomidate (2.0 mg L−1) or 2-PE (200 mg L−1) responded to the needle puncture. In experiment 3, metomidate (5.0 mg L−1), clove oil (30 mg L−1) TMS (125 mg L−1) or 2-PE (300 mg L−1) were all effective for performing an ovarian biopsy or tag implantation on adults. In experiment 4, TMS (125 mg L−1) exacerbated the cortisol response to a short handling stressor during a 30 min exposure. Fish anaesthetized in 2-PE (300 mg L−1), metomidate (5.0 mg L−1) or clove oil (40 mg L−1) had increased cortisol levels associated with the handling stressor but there were no further increases during the remainder of the experimental period. The results demonstrate that these anaesthetics are effective for sedation and anaesthesia of black sea bass and that the best choice is dependant upon the procedures to be performed. [ABSTRACT FROM AUTHOR]

Objective—To develop an easy and safe method for catheterization and determine the pharmacokinetics of a single dose of enrofloxacin after intracoelomic administration in koi. Design—Prospective study. Animal—20 healthy koi. Procedure—6 koi were anesthetized with tricaine methanesulfonate, and a 23-gauge, three-fourths-inch butterfly catheter was inserted into the coelomic cavity and secured. Catheters were flushed daily for 6 days with 0.4 mL of sterile saline (0.9% NaCI) solution containing heparin (100 units of heparin in 250 mL of saline solution) without removing koi from the aquarium. At the end of the sixth day (144 hours), each of the 6 catheterized koi and 6 uncatheterized (control) koi was anesthetized individually Enrofloxacin (10 mg/kg [4.5 mg/lb]) was administered to catheterized koi via the injection port and to control koi via a 23-gauge needle in the same site as the catheter placement. A pharmacokinetics study was performed on multiple plasma samples to validate the efficiency of the catheter. Reliability of the catheterization method was determined in 8 koi. Results—All 6 catheters remained patent and effective for the 6 days prior to the start of the pharmacokinetics study. Results for the 2 routes of administration were comparable, and all koi survived the study without any detectable clinical problems. Conclusions and Clinical Relevance—An intracoelomic catheter was effective and safe when maintained in koi for at least 6 days. This would be highly beneficial for veterinarians, clients, and fish, especially when intracoelomic administration of a drug would require daily or more frequent dosing. [ABSTRACT FROM AUTHOR]

Mature channel catfish Ictalurus punctatus were exposed to water containing three different concentrations (20, 40, and 60 mg/L) of AQUI-S (50% isoeugenol) during routine handling procedures at a commercial catfish facility. Anesthetic efficacy, recovery time, and the effects of AQUI-S on routine measures of stress were compared with similar measures in a group of fish sampled prior to anesthesia (preanesthesia [PA] group) and a group anesthetized with 100 mg tricaine methanesulfonate (TMS)/L. On average, all the fish lost equilibrium at 8.0, 3.9, and 3.7 rain when anesthetized in 20, 40, and 60 mg AQUI-S/L, respectively. Fish anesthetized with TMS lost equilibrium at 4.5 min. Recovery time in freshwater was 2.1, 2.8, and 5.3 min for fish anesthetized in 20, 40, and 60 mg/L AQUI-S, respectively. Recovery time after TMS anesthesia was 1.7 min. Short-term (24-h) survival was 100% for all treatments, and long-term (21-d) survival ranged from 87.5% for TMS-anesthetized fish to 98.8% for fish anesthetized in 40 mg/L AQUI-S. All anesthetic treatments significantly reduced (P < 0.05) plasma cortisol levels relative to PA fish, and circulating cortisol was lower (P < 0.05) in all AQUI-S-anesthetized fish than in TMS-anesthetized fish. Plasma glucose concentrations were significantly lower (P < 0.05) in fish anesthetized with 40 mg/L AQUI-S than in PA and TMS-treated fish after both anesthetization and recovery. Plasma lactate and chloride concentrations were not reduced (P > 0.05) in any treatment compared with the levels in PA fish. Fish anesthetized with 40 mg/L AQUI-S had lower (P < 0.05) plasma lactate levels after recovery than TMS-anesthetized fish, and plasma chloride levels were significantly lower (P < 0.05) immediately following AQUI-S anesthesia at all concentrations than in fish anesthetized with TMS. Anesthesia did not affect (P > 0.05) postrecovery plasma chloride concentrations. Overall, AQUI-S exhibited efficacy as an anesthetic for... [ABSTRACT FROM AUTHOR]

Inductive neural telemetry was used to record from microwire electrodes chronically implanted into the anterior lateral line nerve of the toadfish, Opsanus tau. Spontaneous neural activity and the response of lateral line fibers to water current were continually monitored from 17 primary afferent fibers before, during, and after the administration of the anesthetic tricaine (MS-222). Significant decrease in spontaneous and evoked activity and increase in interspike interval was noted when anesthetic concentrations were >/=0.010%. Neural activity returned to control levels within approximately 90 min of anesthetic withdrawal. Decreasing the pH of the solution without the anesthetic caused transient heightened sensitivity, indicating that tricaine and not the concurrent drop in pH was responsible for the decrease in sensitivity during anesthesia. During a secondary challenge with the anesthetic 24 h after the first, fibers initially showed faster recovery however overall recovery kinetics were similar. Although high tricaine concentration was correlated with decreased neural sensitivity, the concentrations normally used to maintain anesthesia in the toadfish did not have significant effect on the evoked firing rate. Thus given sufficient time to recover from the induction of surgical anesthesia, it may be possible to maintain the animal under light anesthesia while minimizing the physiological effects of tricaine. [ABSTRACT FROM AUTHOR]

This study examined the direct impact of three commonly used anesthetics--clove oil (86% eugenol), tricaine (tricaine methanesuifonate [MS-222]), and CO2--on egg quality for steelhead Oncorhynchus mykiss and that of clove oil and tricaine on the motility of sperm from both steelhead and white sturgeon Acipenser transrnontanus. Exposure of unfertilized eggs for 6 or 24 h to 150 mg clove oil/L, 225 mg tricaine/L, or less than 100 mm Hg CO2 resulted in no reduction in egg fertility or embryo survival to hatch. However, higher doses (1,500 mg clove oil/L; 2,250 and 22,500 mg tricaine/L; or more than 125 mm Hg CO2) negatively impacted egg quality. Similarly, a 3-h exposure to clove oil (150 mg/L) or tricaine (225 mg/L) produced no significant effect on sperm motility in steelhead. White sturgeon sperm showed a modest decline in motility after incubation in clove oil. Thus, the data suggest that clove oil and tricaine can be used on fish prior to gamete harvesting without significant adverse impacts on gametes. Although CO2 is unlikely to have deleterious effects on eggs, CO2-associated declines in ovarian fluid pH may be of concern when ovarian fluid pH is used as an indicator of egg quality. [ABSTRACT FROM AUTHOR]

The effect of tricaine methanesulfonate (MS222) on rainbow trout liver biotransformation rates was investigated with a microsomal model; an in vitro preparation that can be employed with or without the use of an anaesthetic. Two experimental sets of rainbow trout microsomes were tested; one representing in vivo or surgical tricaine exposures and the other representing in vitro tissue/organ collection tricaine exposures. Microsomal incubations were performed on these two experimental groups with phenol as substrate to assess the effects of tricaine on Phase I (ring-hydroxylation) and II (glucuronidation) liver biotransformation by monitoring production of hydroquinone (HQ), catechol (CAT), and phenylglucuronide (PG). The use of a 2-h 100 mg/l exposure of tricaine for surgical anesthesia with or without 24-h recovery did not significantly (P≤0.05) affect rates of phenol (Phase I and II) biotransformation rates; nor, did the 5-min 300 mg/l tricaine exposure for isolated organ/tissue collection significantly (P≤0.05) affect phenol (Phase I and II) biotransformation rates. There were also no significant statistical differences (P≤0.05) in P450 protein levels, or 7-ethoxyresorufin-O-deethylase (EROD) activity in these microsomal assays between any of the tricaine treated rainbow trout and controls. [Copyright &y& Elsevier]

This study examined the direct effects of tricaine methanesulfonate (MS222), a sodium-channel blocking local anesthetic, on respiratory motor output using an in vitro brain stem preparation of adult North American bullfrogs (Rana catesbeiana). Bullfrogs were anesthetized with halothane, and the brain stem was removed and superfused with artificial cerebrospinal fluid containing MS-222 at concentrations ranging from 0.1 to 1,000 µM. At the lowest concentration of MS-222, respiratory frequency (f[sub R]) increased significantly (P < 0.05), but at higher concentrations, f[sub R] progressively decreased and was abolished in all preparations at 1,000 µM (P < 0.01). Respiratory burst amplitude and burst duration were not affected by MS-222. The frequency of nonrespiratory neural activity did not significantly change with the addition of MS-222 below 1,000 µM. These data indicate that MS-222 has a significant, direct effect on respiratory motor output from the central nervous system, producing both excitation and inhibition of fictive breathing. The results are consistent with other studies demonstrating that low concentrations of anesthetics generally cause excitation followed by depression at higher concentrations. Although the mechanisms underlying the excitatory effects of MS-222 in this study are unclear, they may include increased excitatory neurotransmission and/or disinhibition of inputs to the respiratory central pattern generator. [ABSTRACT FROM AUTHOR]

Reveals the impact of tricaine on the clinical evaluation of skin and gill infections caused by the ectoparasite Ichthyobodo necator. Use a euthanasia agent for fish and amphibians; Effect of varying concentrations of both buffered and unbuffered tricaine; Estimate of parasite load.

Tricaine, or MS-222, is the most commonly used chemical anesthetic in zebrafish research. It is thought to act via blocking voltage-gated sodium channels, though its mechanism of action, particularly at the neuronal level, is not yet fully understood. Here, we first characterized the effects of tricaine on both body balance and touch responses in freely swimming animals, before determining its effect on the neural activity underlying the optokinetic response at the level of motion perception, sensorimotor signaling and the generation of behavior in immobilized animals. We found that the standard dose for larvae (168 mg/L) induced loss of righting reflex within 30 seconds, which then recovered within 3 minutes. Optokinetic behavior recovered within 15 minutes. Calcium imaging showed that tricaine interferes with optokinetic behavior by interruption of the signals between the pretectum and hindbrain. The motion sensitivity indices of identified sensory neurons were unchanged in larvae exposed to tricaine, though fewer such neurons were detected, leaving a small population of active sensory neurons. We then compared tricaine with gradual cooling, a potential non-chemical alternative method of anesthesia. While neuronal tuning appeared to be affected in a similar manner during gradual cooling, gradual cooling induced a surge in calcium levels in both the pretectum and hindbrain. This calcium surge, alongside a drop in heartrate, is potentially associated with harmful changes in physiology and suggests that tricaine is a better anesthetic agent than gradual cooling for zebrafish laboratory research., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Leyden, Brüggemann, Debinski, Simacek, Dehmelt and Arrenberg.)

[Display omitted] • A novel method for detecting Tricaine is researched. • NPG electrochemical sensor is high sensitive for detection of Tricaine. • Scientific basis provided by the sensor for regulatory system of fishery anesthetics. Tricaine (MS222) is a widely-used compound in fish anesthesia in aquaculture, transportation, and research laboratories, but its use has certain safety risks due to the lack of relevant laws and regulations. Herein, a simple and efficient one-step corrosion method was used to prepare a nanoporous gold (NPG) electrochemical sensor for detecting MS222. Under 0.1 M H 2 SO 4 buffer solution, NPG showed a strong electrocatalytic redox effect on MS222, a wide linear range of 5 μg·mL−1 ~ 100 μg·mL−1, a low detection limit of as low as 0.29 μg·mL−1, and good applicability in actual sample of the recovery rate as 94.89%~107.93%. Thus, this work demonstrates the basic advantages of NPG and provides good application potential for the rapid detection of fishery anesthetic MS222. [ABSTRACT FROM AUTHOR]

The article presents case study of a 9-month-old stocker catfish from the Thad Cochran National Warmwater Aquaculture Center in Stoneville, Mississippi for health assessment and necropsy following euthanasia. It mentions that the fish was euthanized using a immersion method with water containing tricaine methanesulfonate. It also offers information on the genus Henneguya.

Presents information on experiments done on the thermal isomerization of aminoallenes. Methodology used; Results and discussion.

The article investigates on the toxic action of tetrachloroguaiacol (TeCG) and its effect on osmoregulation of adult coho salmon (Oncorhynchus kisutch) in freshwater as well as during seawater challenge. Fish sampling was achieved by terminal anaesthetization with MS222 or tricaine. Anaesthetization prior to sampling has been demonstrated to have no effect on plasma ion concentrations. Blood samples were obtained through the caudal ventral vein. Blood hemoglobin concentrations were determined through analysis of the hemolyzed blood and Drabkin's solution mixture. There were no changes in hematocrit, hemoglobin concentration or mean red cell volume. Overall findings revealed that TeCG can adversely effect the osmoregulation of adult coho salmon in freshwater and during seawater adaptation.

The article presents a study on the hematological profile of cadmium-exposed rainbow trout (Salmo gairdneri). The study used hatchery-reared rainbow trout which were anesthesized with tricaine methane sulphonate after cadmium exposure while analysis of variance (ANOVA) was applied in measuring the leucocyte and erythrocyte counts and the somatic spleen index (SSI). Results showed an unaffected SSI, decreased number of erythrocytes, and higher abundance of leucocytes.

The article presents a case study of a 0.486 kilogram (kg) adult male brook trout, Salvelinus fontinalis, that suffer zinc toxicosis after ingesting s 1995 U.S. penny. The fish was examined and anaesthetized at the North Carolina State University College of Veterinary Medicine (NCSU-CVM). The fish died after overdose of tricaine methanesulfonate.

Presents a letter to the editor in response to the article "Influence of Neutralizing Agents on the Anesthetic Efficacy of Tricaine on Oncorhynchus mykiss (Walbaum) Fry," that was previously published in the journal "Aquaculture Research."

Tricaine methanesulfonate is one of most commonly used anesthetics in fish during blood sampling, artificial propagation and long‐distance transportation. In this study, an accurate method for the quantitative determination of tricaine in fish samples by a stable isotope dilution assay coupled with high‐performance liquid chromatography–triple quadrupole mass spectrometry was developed. Tricaine‐D5 was synthesized and used as an isotopically labeled internal standard for the determination of tricaine. The analytical performance of the method was validated for tricaine determination in marine fish and freshwater fish. The determination of tricaine was linear in the range of 2.0–200.0 μg L−1. The limit of detection and limit of quantitation for fish muscle tissues were 1.0 and 4.0 μg kg−1, respectively. Good recoveries were obtained in the range of 92.08–97.50%. The inter‐ and intra‐assay relative standard deviations (RSD values) were investigated, and the values were 0.39–3.01 and 0.85–2.77%, respectively. The values of CCα and CCβ were 10.21–10.43 and 10.42–10.87 μg kg−1, respectively. The clearance of MS‐222 from grass carp was further studied using our method. The results demonstrate that MS‐222 could be well absorbed and rapidly eliminated after bath administration. [ABSTRACT FROM AUTHOR]