Abstract

Nearly a quarter of all elasmobranch (shark and ray) species are listed in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (Version 2015-3).¹ Sharks are an important part of many public aquarium collections and it is vital to develop breeding programs to create self-sustaining captive populations and reduce collection pressure on wild populations, as well as to understand barriers to natural reproduction. For larger species where moving animals for breeding purposes may not be feasible, the development of assisted reproductive techniques and methods for moving gametes would enable the maintenance of a healthy and genetically diverse population.

The sand tiger shark, Carcharias taurus, is a large and docile shark species popular for display because of their size, menacing appearance, and longevity. Multiple US aquaria are collaborating on a holistic approach to achieve propagation of sharks under managed care, using the sand tiger as a model species. This approach includes the development of artificial insemination techniques, including semen collection. Using either tonic immobilization or anesthesia, spermic ejaculates have been successfully collected from whitespotted bamboo, Chyloscyllium plagiosum (n = 16), brownbanded bamboo, Chyloscyllium punctatum (n = 10), sand tiger (n = 10), leopard, Triakis semifasciata (n = 1), and blacktip, Carcharhinus limbatus (n = 1) sharks under managed care and from free-ranging sand tiger (n = 2) and dusky smoothhound, Mustelus canis (n = 1) sharks. Shark semen is collected from the paired ampullae or terminus of the epididymis. Semen includes fluid produced by accessory reproductive glands along the length of the epididymis. Semen collection can be accomplished via 2 methods: internal catheterization of the ampullae via the urogenital papilla (brownbanded and whitespotted bamboo and sand tiger sharks) or through external pressure on the ampullae resulting in semen liberated into the urogenital sinus and out the urogenital papilla (brownbanded and whitespotted bamboo, blacktip, dusky smoothhound, leopard and sand tiger sharks). In agreement with published literature, preliminary data indicates that species such as the bamboo sharks produce semen all year while other species, such as the sand tiger, produce semen seasonally. Characteristic spiral shaped, filiform heads have been observed in all species studied to date. Continued efforts, made possible by wide engagement of aquaria, will focus on defining the best time of year for semen collection in sand tiger sharks and on development of cryopreservation techniques. This study is part of a large, holistic, multi-institutional collaboration also investigating in situ sand tiger shark movements to locate breeding and pupping grounds, advancing the development of safe and effective handling techniques as well as more coordinated efforts to move animals for optimal breeding, and which hopes to establish itself as a model for other shark species in managed care.

Acknowledgements

The authors acknowledge the help and expertise of curatorial and aquarist professionals that assist with handling and collection efforts, and the National Aquarium and National Marine Fisheries Service Northeast Fisheries Science Center Apex Predators Program for access to wild shark populations.

* Presenting author

Literature Cited

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