Abstract

Few aquariums have successfully displayed blacknose sharks (Carcharhinus acronotus) for extended periods. Over four years, New England Aquarium acquired ten wild-caught blacknose sharks. Individuals survived 5 months to 2.5 years. The blacknose, like most pelagic sharks, is sensitive to confined space trauma and handling stress. Based on past experiences and consultations with colleagues, an initial "hands-off" approach was attempted. However, several circumstances required examinations and treatments, including repeated skin erythema and raised nodules of unknown origin, a novel coccidian parasite found on fecal examination, and repeated ocular, rostral, or fin trauma. Originally, sharks were corralled into a large vinyl "bag" and anesthetized with concentrated tricaine methanesulfonate (MS-222; 5 g/L, sodium bicarbonate 20 g/L) via directed spray while swimming. This technique required several people, took significant time, and was very disruptive to tank-mates. Over time, a procedure was nearly perfected. Sharks are now captured in nets by divers and moved to inflatable pools at 120–130 ppm MS-222 (240–260 ppm sodium bicarbonate). Sharks are then transferred to an exam cart and continuously ventilated with 70–90 ppm MS-222 (140–180 ppm sodium bicarbonate). Recovery occurs with mechanical ventilation in a second pool floating in the holding tank allowing for minimal handling during release. This protocol has been used for procedures such as routine examinations, wound treatments, radiographs, endoscopy, and laparoscopy, lasting more than one hour.

Another challenging aspect of care was the transport between the quarantine facility and the aquarium. Initially two sharks were transported in individual padded containers out of water sedated with buffered MS-222 via continuous flow ventilation. Both animals were undesirably alert during 75-minute transport, requiring sedation increases and intermittent direct application of concentrated MS-222 directly into the mouth or gills. Despite initial signs of anesthetic recovery, neither shark fully recovered, and both were euthanized. This procedure was chosen based on previous success for examinations; however, it was clear that a different technique was necessary for subsequent transports. A 4-m ovoid tank was constructed that allowed for natural swimming during transports. The sharks are now carried to and from the transport truck in vinyl stretchers or plastic bags supported by nets, and transported without sedation. This procedure has been successful numerous times with multiple species.

Upon arrival, all groups received quarantine consisting minimally of oral Drontal +/- praziquantel immersion (Table 1). No animals experienced clinical signs during quarantine other than a decreased appetite. Several other medications were administered to the sharks with either beneficial or no ill effects noted (Table 1). A trial of chloroquine immersion, with unexpected increased environmental ammonia concentration, resulted in increased swim speed and wall rubbing; however, fair to good appetites remained. Two blacknose sharks were recently subjected to hyposalinity treatment (17.0 ppt) for Cryptocaryon infection of exhibit teleosts. Both sharks declined rapidly, displaying erratic swimming and generalized subcutaneous edema, and were deceased within four days despite transfer to full salinity and emergency treatments.

The pathological findings of the ten sharks were often remarkable, including bacterial and nematode meningoencephalitis (5), and severe liver atrophy despite fair to good appetite.

Table 1. Medications utilized during the medical care of ten blacknose sharks over four years

Acknowledgements

The authors would like to thank the New England Aquarium Animal Health Department for assistance with the diagnostic procedures, treatments, clinical pathology, environmental quality and pathological examinations. Also thank you to the NEAq Husbandry and Fishes Departments for their tireless hours of feeding, training, monitoring and transporting of the sharks and to all those involved with the design and construction of the procedure and transport equipment. Finally, we greatly appreciate all of our colleagues for responding to the many requests for personal experiences and suggestions.

* Presenting author