Effects of tricaine methanesulfonate, hypno, metomidate, quinaldine, and salt on plasma cortisol levels following acute stress in threespot gourami Trichogaster trichopterus

Blood plasma cortisol concentration is an indicator of stress in fish, and anesthetics may serve to ameliorate stress and reduce the cortisol response. Previous Studies have concentrated on cold- and warmwater species: little information exists for tropical fishes. Mortalities are increased after handling stress of threespot gourami Trichogaster trichopterus (Osphronemidae), a commonly cultured tropical ornamental fish. Plasma cortisol levels were evaluated in threespot gourami after a handling stressor and treatment with one of four anesthetics-tricaine methanesulfonate (TMS: 60 mg/L), metomidate (0.8 mg/L), quinaldine (5 mg/L). and Hypno (0.14 mg/L)-or salt (NaCl: 3 g/L). Fish in all anesthetic treatments had significantly lower cortisol levels than either salt-treated fish or the untreated controls. Therefore, the use of such anesthetics should be beneficial in reducing handling stress. Based on Our data, further studies refining the use of anesthetics, particularly metomidate and quinaldine, with tropical ornamental species are warranted. Although salt did not reduce cortisol. it is beneficial as an osmoregulatory aid; therefore, future studies should investigate combination treatments of an anesthetic with salt.