Coeliotomy under general anaesthesia and removal of an enterolith from a sand tiger shark ( Carcharias taurus )

Sporadic feeding over a period of 18 months was observed in a previously healthy adult female sand tiger shark ( Carcharias taurus ) housed in an aquarium. This led to severe weight loss, revealing a mobile rounded bulge in the abdomen of the shark. Due to the failure of non-invasive treatments with antibiotics and NSAIDs, coeliotomy under general anaesthesia was performed in a bespoke anaesthesia/surgery tank. A spherical enterolith (10 cm in diameter) was found in the spiral valve, causing partial obstruction, and constituted from concentrically lamellated calcium hydroxyapatite (the major component of fish scales and skeletons) around an undigested octopus beak. After closing the incision, the shark was returned to the water but died seven hours postsurgery without recovering from the anaesthesia. Factors leading to postsurgical mortality, and the potential for anaesthetic monitoring methods and postsurgical gastric reinflation to improve outcome, are discussed.