Abstract

Three sandtiger sharks (Odontaspsis taurus) were chemically immobilized for examination of progressive spinal deformities that had occurred during captivity. Each shark was given an intramuscular (IM) injection of medetomidine combined with ketamine (med./ket.), administered by pole syringe directed at the base of the dorsal fin. One shark was immobilized twice and the others once, for a total of four anesthetic events using this drug combination. Three of the events were with the shark separated in a holding tank in shallow water with easy access to the animal. In the remaining case, the shark was free swimming in a large mixed exhibit tank and was approached by a diver for injection. Water temperatures were 21-22 C. The doses of med./ket. (based on actual body weights) varied from 80 mcg/kg medetomidine combined with 10 mg/kg ketamine to 60 mcg/kg med. combined with 5 mg/kg ket. The lower dose was the initial target dose and was as effective as the high dose although the induction time was longer. In each event the shark developed smooth deep narcosis within 4-18 minutes following injection. There was no response to manipulations during brief periods out of water (2-3 minutes at a time) for weighing, radiography and tank shifts, or for other procedures with the shark partially submerged such as blood sampling and intravenous (IV) injections using the caudal tail vein. The work time during these procedures varied from 30-45 minutes. Gilling rates were 12-18 per minute without supplemental oxygen compared to 16 per minute in one unanesthetized shark. Euthanasia was performed on one shark 35 minutes after immobilization without attempting recovery. Reversal drugs were given at the completion of procedures in the other three immobilization events and the sharks swam away within 12-20 minutes. A different drug regimen was used for each reversal. One shark was given atipamezole IM (5 times med. dose) followed in 15 minutes with doxapram IV (100 mg). The second shark was given only doxapram IV (100 mg). Although both sharks resumed swimming, they appeared to have incomplete reversal in that each remained sedated for several days and did not eat for 8-18 days following the immobilization. The second shark was re-anesthetized 1 month later with the lower dose med./ket. and was reversed with atipamezole (dosed at 5 times the med. dose) given half IV and half IM. The shark swam away 18 minutes after reversal, had no obvious post-immobilization sedation and it resumed feeding within 24 hours of recovery. The variation in recovery times could be due to relatively high ketamine doses given in some of the sharks. IV doxapram has been anecdotally associated with immediate hyperexcitement and should be used with caution. The results of these limited trials seem to warrant further investigation of med./ket. and reversal with atipamezole as a method for immobilization and handling of sharks.

Acknowledgements

The authors wish to thank the following aquarium staff whose support was essential in handling the sharks and in conducting these studies:

 Holly Lane, Aquarium Manager; Rich Lerner, Head Aquarist; Eric Jones and Scott Wimmer, Senior Aquarists at the Albuquerque Biological Park.

 Marj Awai and Steve Vogel, Assistant Curators; Karla Jeselson and Tom Fenske, Senior Biologists; and Erik Hovland and Alex Slater, Biologists at The Florida Aquarium.