Abstract
Traditionally, MS-222 has been the anesthesia of choice for sharks. However, there are many drawbacks including large dose, water contamination, and inhibition of nerves used in research. Two injectable anesthetic protocols, propofol and a ketamine / medetomidine combination were administered intravenously or intramuscularly respectively to 15 spiny dogfish (Squalus acanthias) and the depth of anesthesia was determined every 5 minutes for 60 minutes using the protocol described in Miller et al. (2005).2 Three doses of each drug were evaluated. Effects of anesthesia were evaluated using guidelines as described in "Stages of Anesthesia in Fishes".1
Doses of propofol used were 1.5mg/kg, 2.5mg/kg, and 5mg/kg. The mean maximum plane (depth) of anesthesia and mean time at the maximum plane (mean time) for the low and mid level doses were 2.2 (between deep sedation and light narcosis) for 15 minutes and 2.4 for 22 minutes. The highest dose of propofol (5mg/kg) achieved a depth of anesthesia of 5.8 (between light anesthesia and surgical anesthesia) for a mean time of 9 minutes. Doses of ketamine/medetomidine used were 1mg/kg/50µg/kg, 2mg/kg/100µg/kg, or 4mg/kg/200µg/kg. The depths of anesthesia for ketamine+medetomidine were 1.2 (between light and deep sedation), 1.2 and 1.6 for the three doses respectively. The mean times were 34 minutes, 41 minutes and 35 minutes respectively.
This study showed that a minimum dose of 5mg/kg of propofol is needed to achieve a surgical plane of anesthesia in the spiny dogfish and that ketamine/medetomidine is an adequate choice for sedation, but not for surgical anesthesia.
Acknowledgments
The authors would like to thank the NCSU-CVM Support for Aquatic Animal Medicine Research Fund for funding this project and the MBL Animal Resources Department for providing the animals. Also, thanks to Shane Christian, Aquatic Animal Medicine Technician at NCSU-CVM, and the staff and volunteers at the Marine Biological Laboratory for their assistance in the completion of this project.
References
1. Brown LA. 1992. Anesthesia and restraint. In: Fish Medicine. M.K. Stoskopf (ed.). Philadelphia: Saunders Publishing. Pp.79-90.
2. Miller SM, Mitchell MA, Heatley JJ, Wolf A, Lapuz M, Lafortune M, JA Smith. 2005. Clinical and cardiorespiratory effects of propofol in the spotted bamboo shark (Chylloscyllium plagiosum). J. Zoo Wildlife Med. 36(4):673-676.