Abstract

Objective: To determine the effectiveness of the anaesthetic agents 2-phenoxyethanol, MS- 222, clove oil and metomidate in attenuating acute handling stress in juvenile specimens of Solea senegalensis subjected to two routine stressful events specific to aquaculture and/or fish research. Methods: The stress-preventing effects of four anaesthetic agents (2-phenoxyethanol, 600 mg/L; metomidate, 5 mg/L; clove oil, 30 mg/L and MS-222, 75 mg/L) were evaluated in juvenile specimens of Senegalase sole (Solea senegalensis) subjected to two different types of acute (handling-related) stress: air exposure and net handling (chasing). To assess the stress-preventing effects of the four anaesthetic agents, diverse blood and plasma parameters (haematocrit, haemoglobin, glucose, lactate and cortisol levels) were determined as stress indicators. Fish were treated with the anaesthetic agents before being subjected to the different types of acute stress, and they were sacrificed 30 min, 2 and 24 h later. Control fish were processed in the same way without pretreatment with the anaesthetic agents. Results: The net handling stress was of sufficient intensity to cause a significant increase in the levels of most of the stress indicators considered. By contrast, air exposure stress only induced significant increases in cortisol and haemoglobin levels. Conclusions: The stress-preventing effects of the anaesthetic agents tested were ranked on the basis of their capacity to prevent increases in the haematocrit, haemoglobin, glucose, lactate and cortisol levels, as follows: metomidate (5 mg/L) > clove oil (30 mg/L) > MS-222 (75 mg/L) > 2-phenoxyethanol (600 mg/L).

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