Abstract

The superfamily Tetraodontoidae includes the Tetraodontidae (puffers) and Diodontidae (porcupinefish and burrfish). Members of this iconic group are commonly displayed in public aquaria. A retrospective review was conducted to examine health issues in the Tetraodontoidae at the National Aquarium, Baltimore between January 1, 2000 and December 31, 2010. Computerized husbandry and medical records were used to assess the numbers of each species, the time each individual spent in the collection, and morbidity and mortality information.

The records showed that 46 individual animals comprising six species were held during this period: 13 Canthigaster rostrata (sharpnose puffer), 9 Sphoeroides maculatus (northern puffer), 2 Sphoeroides spengleri (bandtail puffer), 5 Diodon hystrix (spotfin porcupinefish), 4 Diodon holocanthus (freckled porcupinefish), and 13 Chilomycterus schoepfii (striped burrfish). The 46 individuals included 10 animals still in residence (21.7%), 6 dispositions to other facilities (13%), and 30 mortalities (65.2%). Longevity (including resident animals and dispositions) was greatest for spotfin porcupinefish (mean > 1732 +/- 847 days) and shortest for northern puffers (mean > 417 +/- 252 days). The sharpnose puffers showed high mortalities within 90 days of arrival (4 of 9 mortalities, 44.4%). Conspecifics that made it through the initial 90 days subsequently did well (mean > 819 +/- 641 days).

Twenty-seven medical cases were recorded, involving 17 animals, predominantly porcupinefish and burrfish. The most common problems identified were skin and fin erosions (48% of cases), ocular lesions (33%, primarily keratitis), inappetance (22%), lethargy (19%), coelomic distension (11%), positive buoyancy (7%), skin nodules (7%, papillomas and lymphocystis), and dental plate overgrowth or pitting (7%, spotfin porcupinefish only). Medical and surgical management were well tolerated. The case resolution rate was 85.2%. Sharpnose puffers rarely presented with clinical signs and were typically found dead.

Causes of mortality were often unidentified. A life support system failure that caused 8 mortalities was the greatest single contributor to mortality (26.7% of 30). Gross necropsies were carried out on all porcupinefish but on few puffers and burrfish due to their small size and rapid autolysis. Histopathology was limited to 4 individuals: 1 northern puffer, 1 striped burrfish, and 2 spotfin porcupinefish. Findings included hepatic lipidosis (100%), granulomatous nephritis and splenitis due to Mycobacterium sp. (75%), granulomatous oophoritis and coelomitis due to Edwardsiella tarda (25%), and phaehyphomycotic nephritis (25%).

While postmortem diagnostics were limited, this study does show the value of tracking fish as individuals. The information gained can help guide management decisions for these species.