Abstract

Ling cod Ophiodon elongatus, white sturgeon Acipenser transmontanus, green sturgeon A. medirostris and harbor seal Phoca vitulina were remotely injected with amino acid/vitamin B complex or gentamycin sulfate without prior capture, using a laser aimed dart gun. Ling cod and sturgeon receiving B complex resumed feeding and territorial behavior shortly after injection/implantation and maintained the increased level of activity for 1-3 weeks. A single captive harbor seat was similarly administered gentamycin sulfate (0.75 ml/kg) and resumed feeding the next day.

Introduction

Captive fish and marine mammals frequently suffer from identifiable diseases yet go untreated due to the effort and physiological stress involved in capturing the animals. Bath treatments are often appropriate for epizootics affecting a group of animals in a common aquarium, yet there are many instances where large valuable specimens require individual treatment. In cases where feeding has ceased, oral or bath application of antibiotics is ineffectve.

Use of a laser-aimed underwater dart gun for immobilization and capture of large display fish in aquaria has been described (Harvey et al 1987). In the present paper we report the use of this device for remote application of liquid and solid formulations of vitamins and antibiotics into freely swimming specimens of ling cod Ophiodon elongatus, white sturgeon Acipenser transmontanus, green sturgeon A. medirostris and harbor seal Phoca vitulina.

Methods

Drugs were applied using the Aquadart (Marine Technology Ltd), a device consisting of a small pneumatic speargun equipped with a battery-powered laser sight that affords highly accurate placement of darts whether the operator is outside the water or in it. Gentamycin sulfate (Gentacin, Schering) and Aminocid (Hoechst) were administered using the small 3 ml pneumatic dart supplied with the gun; for ling cod the standard 16 guage, 2 cm, barbless needle was used, while for injection into harbor seals this needle was replaced with a 5 cm. long 16 gauge needle to ensure penetration past the blubber. For treatment of sturgeon, Vitamin B complex (Novo-B, Novopharm) was mixed with a biodegradable thermoplastic and extrusion molded into 20 x 1.5 mm rods that were implanted using the solid drug implantation system (SDIS) attachment for the Aquadart.

Ten ling cod and three sturgeons were shot in the dorsal musculature from a distance of approximately five feet by a diver swimming in the display tank at Pacific Undersea Gardens, Victoria, B.C. The animals were selected on the basis of chronic sluggishness and loss of appetite; ling cod received a single dose of 2 ml Aminocid (approximately 0.2 ml/kg in a 15 kg fish), while sturgeon received either a single implantation of solid formulated B complex (approximately 4 mg/kg) or two implantations one month apart. Darts that did not fall out of the ling cod within a few minutes were easily pulled out by the diver.

The harbor seal treated with gentamycin was held in a display aquarium at Sealand (Victoria, B.C.) along with 10 other specimens; it had been anorexic for 7 days and was circling repetitively apart from the other animals. Another animal in the same enclosure had recently died after displaying identical symptoms. A diver entering their enclosure was able to select the affected animal using the laser sight and place the dart accurately on the shoulder. Two ml gentamycin sulfate (approximately 0.75 mg/kg were administered in a single dose; the dart fell out and floated to the surface after 5 min.

Results and Discussion

There was no difficulty on placing the darts or plastic rods in the fish or in the actively swimming harbor seal. Fish reacted to implantation or injection with several seconds of slow circling, and then settled into their former positions. The seal appeared aware of the presence of the dart in its side yet continued normal swimming. The only outward sign of implantation or injection was a small puncture wound that was no longer visible the next day.

Feeding and swimming activity in the 3 sturgeon, minimal before treatment, improved dramatically within hours of implantation of the solid-formulated B complex and was maintained for approximately 3 weeks. Repeat implantation after one month had a similar effect. Complete dissolution of the thermoplastic binder requires approximately 30 min in seawater at 10°C, and post-implantation dissection of live dogfish Squalus acanddas implanted with the pellets has shown dissolution in vivo to be complete within 1 h.

The 10 large ling cod injected with Aminocid showed a similar dramatic increase in swimming and feeding activity as well as in territorial behaviour, soon after injection. This improvement lasted approximately one week.

The single harbor seal treated with gentamycin rejoined the other animals in the enclosure after 24 h and resumed feeding the following day. It received tetracycline 10 mg/kg mixed with its food for 2 weeks thereafter.

Although the number of animals treated in the present study is small, the results demonstrate that remote injection of vitamins and antibiotics is an easily performed mode of treatment. The treatments themselves appear to be effective, although more closely controlled studies are necessary to rule out any the possibility that the act of implantation or injection caused the change in swimming and feeding behaviours. Netting the ling cod or sturgeon, each of which weighed over 15 kg, would have required at least two divers and would probably have complicated the outcome of treatment by provoking capture-related physiological stress. If the treated fish had been large, active swimmers, netting would have been impossible, yet Harvey et al have reported sedation of large (over 30 kg) active teleosts and elasmobranchs at Sea Life Park and the Vancouver Aquarium using the same laser-aimed equipment. In the case of the harbor seal at Sealand, the dimensions of the enclosure and the number of other seals sharing it made netting impossible; without remote injection of antibiotics this animal would likely have died.

Acknowledgernents

The authors thank the management and staff of Pacific Undersea Gardens and Sealand of the Pacific for contribution of experimental animals. This study was supported by the Science Council of British Columbia.

References

1.  Harvey, B., Denny, C., Kaiser, S., and Young, J. 1987. Remote intramuscular injection of immobilizing drugs into fish using a laser-aimed underwater dart gun. Proceedings, International Association of Aquatic Animal Medicine, 18th Annual Conference and Workshop, Monterey, 1987.

2.  Tytler, P., and Hawkins, A.D. 1981, Vivisection, anesthetics and major surgery. In: Aquarium Systems, Ed. Hawkins, A.D. Academic Press, London, pp 247-279.