Fish Sedation and Anesthesia

Righting response and electrocardiographic evaluation of juvenile tambaqui (Colossoma macropomum) (Cuvier, 1818) exposed to immersion baths with different concentrations of bushy lippia essential oil (Lippia alba)

In recent years, the use of natural products as alternatives to synthetic anesthetic agents has gained notoriety in aquaculture. Among the essential oils studied, Lippia alba has attracted attention due to its diverse pharmacological properties, including sedative and anesthetic effects. This study aims to evaluate the anesthetic activity of Lippia alba essential oil (LAEO) to propose a therapeutic window for its use in tambaqui (C. macropomum). In this research, juvenile tambaqui (10.9 ± 5.9g, n = 90) were submitted to anesthetic baths with LAEO at concentrations of 80-140 μL.L-1 for behavioral assessment and electrophysiological recordings. The findings showed that all concentrations were effective in inducing the loss of posture reflex and its subsequent reversible return. However, electrocardiographic recordings at concentrations of 120 and 140 μL.L-1 revealed alterations in the graph elements, indicating more intense bradycardia and atrioventricular block during anesthetic induction. Nevertheless, during the anesthetic recovery period, cardiac normality was restored at all tested concentrations, although more slowly at the highest concentration (140 μL.L-1). Thus, we conclude that this oil is safe for providing short-term anesthesia at concentrations between 80 and 100 μL.L-1 in C. macropomum specimens.

Etomidate as an anesthetic in Colossoma macropomum: Behavioral and electrophysiological data complement each other as a tool to assess anesthetic safety

The use of anesthetic agents in the management of fish in fish farming or ornamental fish breeding aims to minimize stress and promote animal welfare. Therefore, this study aims to investigate behavioral, electrocardiographic, and ventilatory characteristics of tambaquis exposed to anesthetic baths with etomidate. The study was conducted with juvenile tambaquis (27.38 ± 3.5g) n = 99, at etomidate concentrations of 2-4 mg.L -1, analyzing induction and anesthetic recovery behavior (experiment I), electrocardiogram (experiment II), and opercular movement (experiment III). Fish exposed to high concentrations of etomidate reached the stage of general anesthesia faster, however, the recovery time was longer, characterizing a dose-dependent relationship. Cardiorespiratory analyzes demonstrated a reduction in heart rate (69.19%) and respiratory rate (40.70%) depending on the concentration of etomidate used during anesthetic induction. During the recovery period, there was cardiorespiratory reversibility to normality. Therefore, etomidate proved to be safe as an anesthetic agent for this species at concentrations of 2 to 3 mg.L -1 for short-term anesthesia, but at higher doses the animals showed slow reversibility of anesthesia in a gradual manner and without excitability. The hemodynamic effect due to the rapid decrease in heart rate includes a negative factor of using higher concentrations of etomidate for Colossome macropomum anesthesia.

Behavioral and electrophysiological study in Colossoma macropomum treated with different concentrations of Nepeta cataria oil in an immersion bath revealed a therapeutic window for anesthesia

The purpose of this study was to characterize the activity of essential oils from Nepeta Cataria (EON) at concentrations of 125 μ L  L-1, 150 μ L  L-1, 175 μ L  L-1, and 200 μ L  L-1 on the behavior of loss of the posture reflex and recovery of the posture reflex and electrocardiographic activity and recording of the opercular beat of Colossoma macropomum during immersion bathing for a period of 5 min, in order to obtain a window for safe use during anesthesia. The fish (23.38 ± 3.5 g) were assigned to the following experiments: experiment 1 (latency to loss and recovery of the posture reflex): (a) 125 μ L  L-1, (b) 150 μ L  L-1, (c) 175 μ L  L-1, and (d) 200 μ L  L-1 (n = 9) per group. Experiment 2 (electrocardiographic and heartbeat recordings): (a) control group; (b) vehicle control group (2 ml of alcohol per liter of water), (c) 125 μ L  L-1, (d) 150 μ L  L-1, (e) 175 μ L  L-1, and (f) 200 μ L  L-1 (n = 9), per group. All the concentrations used showed efficacy in inducing loss of the posture reflex and reversibility with recovery of the posture reflex, but the electrocardiographic recordings indicated morphographic changes such as bradycardia during induction and p wave apiculation during recovery at the highest concentrations tested. In this way, we suggest a safe use window for short-term anesthesia with EON in the concentration range of 125 to 150 μ L  L-1 for juvenile Colossoma macropomum.

OCCURRENCE OF GERM CELL NEOPLASIA IN MALE STRIPED BASS (MORONE SAXATILIS) UNDER HUMAN CARE IN A PUBLIC AQUARIUM: SURGICAL TREATMENT AND OUTCOME

The striped bass (Morone saxatilis) has been a fish species of special concern in Canada since its marked decline in the early 21st century in the St. Lawrence River. Individuals kept in public aquaria contribute to public education and could support conservation efforts through research. Over a 3-yr period, 12 male striped bass housed in a multispecies exhibit developed coelomic distension. The testes were enlarged (12/12), cystic (2/12), and heterogeneous (3/12) on coelomic ultrasound. Upon coeliotomy, enlarged (12/12), partially (4/12) or totally white discolored (6/12) testes were noted. These were associated with coelomic hemorrhage (8/12), effusion (3/12) or adhesions to surrounding organs (9/12). Orchiectomies were performed in all fish. Among these, seven fish survived 2 mon postsurgery, and four fish were still alive 900 d postsurgery. Germ cell neoplasia was diagnosed on histopathological examination in 9 of 12 individuals, but no abnormalities were found in the three other cases. Preventive orchiectomies were performed on the remaining six male striped bass in this exhibit. Germ cell neoplasms were present in two of these six fish. No anesthetic or surgical complications were noted; all six cases were alive 2 mon postsurgery and four of the fish survived 900 d postsurgery. Survival times were not significantly different between fish that underwent preventive or curative orchiectomy (P = 0.19). Although risk factors associated with the development of these gonadal tumors remain unknown, a genetic or environmental origin is suspected. Orchiectomy should be considered in suspected cases of testicular tumors.

A Post-Operative Follow-Up of an Endangered Saltwater Fish Lensectomy for Cataract Management in a Public Aquarium: A Case Series

Mature cataracts can be a life-threatening condition in fish as it may result in anorexia. Lens extraction has been previously described in fish, but the long-term outcome of this procedure has not been evaluated. Eleven captive-bred adult fish housed in a public aquarium presented with unilateral (n = 3/11) or bilateral (n = 8/11) mature cataracts. All cases belonged to three endangered fish populations: striped bass (Morone saxatilis) originating from the Saint Lawrence River and Atlantic and spotted wolffish (Anarhichas lupus and Anarhichas minor). Pre-operatively, fish presented with anorexia, dark discoloration, abnormal position in the water column, skin abrasions, and/or decreased body condition scores. A lensectomy was performed in eleven fish, including a bilateral procedure in four fish, corresponding to fifteen eyes. Follow-up examinations were performed one to two weeks and one year post surgery. The main complication was self-resolving: corneal edema was present in 67% of eyes, persistent after a week in 47% of eyes, and resolved thereafter. Post-operatively, 73% of fish resumed feeding and regained a good body condition score. Persistent visual impairment post-surgery associated with anorexia required euthanasia in three out of eleven cases. The median time of death was 336 days post surgery (range: 27-1439 days) and three cases were still alive 1334 to 1425 days after the lensectomy. This was considered a favorable outcome for these older individuals with concurrent diseases.

Fluid Therapy in Exotic Animal Emergency and Critical Care

Many new concepts are emerging in the understanding of fluid therapy in human and mammalian medicine, including the role of the glycocalyx, increased understanding of fluid, sodium, and chloride overload, and the advantages of colloid administration in the form of albumin. None of these concepts, however, appear to be directly applicable to non-mammalian exotic patients, and careful consideration of their alternate physiology is required when formulating fluid plans for these patients.