Abstract

Tricaine methanesulfonate (MS-222) is the current standard of care for fish euthanasia, however, prolonged delivery via immersion has proven ineffective in goldfish.¹ The study objective was evaluation of continuous topical delivery (CTD) of MS-222 for euthanasia of goldfish. Thirty-six goldfish were randomly immersed in buffered MS-222 at the assigned treatment concentration until operculation ceased and then divided into four groups: MS-222 500 mg/L for 30 minutes via immersion (n=6, Group A) or CTD bilaterally over the gills, (n=12, Group B), both followed by placement in anesthetic-free water; MS-222 500 mg/L for 30 minutes via CTD followed by placement in air (n=6, Group C); or MS-222 1000 mg/L for 15 minutes via CTD followed by placement in anesthetic-free water (n=12, Group D). Following MS-222 exposure, serial heart rate assessments via Doppler device were performed until the fish resumed operculation or Doppler sounds ceased. Data were compared with a Kruskal-Wallis rank sum test (p<0.05). Doppler sound cessation occurred in 0/6 (A), 11/12 (B), 6/6 (C), and 12/12 fish (D). Median (range) time to Doppler sound cessation was 6.8 (4.3–9.0), 6.6 (5.5–7.8), and 7.0 (4.3–9.0) hours in B, C, and D, respectively (p=0.9211). Median (range) time to resumption of operculation was 24 (16–46) minutes in A and 133 minutes in B; all fish completely recovered. MS-222 via CTD at 1000 mg/L for 15 minutes was sufficient for euthanasia of goldfish, however, time to Doppler sound cessation was prolonged.

Acknowledgements

The authors wish to thank the North Carolina State University, Veterinary Scholars Program and the Office of the Associate Dean for Research and Graduate Studies, College of Veterinary Medicine for their support of this project.

*Presenting author

Literature Cited

1.  Balko JA, Oda A, Posner LP. 2018. Use of tricaine methanesulfonate or propofol for immersion euthanasia of goldfish (Carassius auratus). J Am Vet Med Assoc 252(12):1555–1561.