Species specific anaesthetics for fish anaesthesia and euthanasia

Abstract

There is a need to ensure that the care and welfare for fish maintained in the laboratory are to the highest standards. This extends to the use of anaesthetics for both scientific study, humane killing and euthanasia at end of life. An anaesthetic should not induce negative behaviours and fish should not seek to avoid the anaesthetic. Surprisingly little information is available to facilitate a humane choice of anaesthetic agent for fish despite over 100 years of use and the millions of fish currently held in thousands of laboratories worldwide. Using a chemotaxic choice chamber we found different species specific behavioural responses among four closely related fish species commonly held in the laboratory, exposed to three widely used anaesthetic agents. As previously found for zebrafish (Danio rerio), the use of MS-222 and benzocaine also appears to induce avoidance behaviours in medaka (Oryzias latipes); but etomidate could provide an alternative choice. Carp (Cyprinus carpio), although closely related to zebrafish showed avoidance behaviours to etomidate, but not benzocaine or MS-222; and rainbow trout (Oncorhynchus mykiss) showed no avoidance to the three agents tested. We were unable to ascertain avoidance responses in fathead minnows (Pimephales promelas) and suggest different test paradigms are required for that species.

Ethical considerations in fish research

“…Readman et al . () argue that in addition to assessing the ease of delivery and rate and stability of anaesthesia, researchers should also consider the way a fish responds to anaesthesia when initially exposed to the chemical. Danio rerio demonstrate a negative behavioural response when exposed to benzocaine and MS‐222 (Readman et al ., ) and appear to remember exposure to some anaesthetics (Wong et al ., ).…”

“…Danio rerio demonstrate a negative behavioural response when exposed to benzocaine and MS‐222 (Readman et al ., ) and appear to remember exposure to some anaesthetics (Wong et al ., ). Medaka Oryzias latipes (Temminck & Schlegel 1846) also show a negative behavioural response to these chemicals, whereas carp Cyprinus carpio L. 1758 and O. mykiss do not (Readman et al ., ). Clearly, further research is warranted on the welfare of anaesthesia practices in fishes, along with discussions at regulatory levels to ensure that chemicals with the greatest welfare potential are accessible.…”

“…Recent work has highlighted that the way fishes respond behaviourally to anaesthetic exposure is species-specific. Readman et al (2017) argue that in addition to assessing the ease of delivery and rate and stability of anaesthesia, researchers should also consider the way a fish responds to anaesthesia when initially exposed to the chemical. Danio rerio demonstrate a negative behavioural response when exposed to benzocaine and MS-222 (Readman et al, 2013) and appear to remember exposure to some anaesthetics (Wong et al, 2014) Mettam et al, 2011;Newby et al, 2006Newby et al, , 2009Nordgreen et al, 2009;Rizzo et al, 2017;Schroeder & Sneddon, 2017;Sneddon, 2003b;Taylor et al, 2017).…”

Practices for Drawing Blood Samples from Teleost Fish: Response to Comment

“…; Readman et al. ). For example, as seen in our video, Gilthead Bream were removed from the cage without any anesthetics and their blood was drawn in only 20 s (see the video link provided in the original article).…”

“…; Readman et al. ). According to the American Fisheries Society's “Guidelines for the Use of Fishes in Research,” anesthetics can be used by considering fish health status (Use of Fishes in Research Committee ).…”