The aquarium industry contributes to hundreds of millions of dollars of marine ornamental fish sales per year in the United States.1 The majority of fish which are used in this industry are captured from the wild, but large strides are being made in the commercial aquaculture of these species with the goal of reducing the impact on wild populations and ecosystems. Two genera of fish which are extremely popular in the aquarium industry and which have been successfully aquacultured for many years are the clownfish (Amphiprion spp.) and seahorse (Hippocampus spp.).
The objective of this study was to determine the common causes of morbidity and mortality in these genera when raised in commercial aquaculture facilities. For this purpose, the records of sick animals submitted to the University of Florida Tropical Aquaculture Laboratory in Ruskin, Florida, over the past 5 years were reviewed. Sixty-four cases of clownfish and 24 cases of seahorses were found that fit these criteria. The most common findings in the clownfish were husbandry (n = 11), parasitic infection (n = 13), bacterial infection (n = 21), or viral infection (n = 11). External parasites found on the clownfish were flagellates (n = 4), monogeneans (n = 4), Amyloodinium (n = 3), Cryptocaryon (n = 2), other motile ciliates (n = 1), and amoeba-like protists (n = 1). Bacteria isolated and identified were Vibrio spp. (n = 8), Aliivibrio sp.(n = 1), and Bacillus sp.(n = 1); 12 other aerobic bacteria were isolated but not identified. Epitheliocystis (n = 3) and an unidentified filamentous hair-like bacteria (n = 1) were visualized under microscopy. Viral pathogens included alloherpesvirus (n = 4), lymphocystis (n = 1), and a suspected viral disease which we are currently attempting to identify (n = 6). In the seahorses, the most common findings were husbandry-related (n = 3), parasitic infection (n = 16), and bacterial infection (n = 15). Parasites observed were flagellates (n = 8), Cryptocaryon (n = 1), other motile ciliates (n = 12), sessile ciliates (n = 5), external nematodes (n = 2), Cryptosporidium (n = 1), and copepods (n = 1). Bacteria cultured and identified included Vibrio spp.(n = 2), Pseudomonas sp.(n = 1), and Bacillus sp.(n = 1). Leucothrix (n = 8) and marine Columnaris (n = 1) were visualized microscopically, and Mycobacterium spp. (n = 3) were identified by positive bench-top acid-fast staining. While all pathogens mentioned were identified during examination, not all were determined to be the primary cause of disease.
This investigation is important both as a guideline for ornamental fish producers and for the creation of quarantine protocols for hobbyists and public aquaria. While antiparasitic treatments such as hyposalinity, copper, formalin, chloroquine, and praziquantel are common prophylactics utilized during marine fish quarantine in public zoos and aquaria,2 these will have no effect on bacterial or viral pathogens. In the clownfish in particular, diagnostics such as aerobic bacterial culture and histopathology were necessary to identify possible causes of morbidity and mortality in 23 cases (36%), indicating their importance in this species. In the cases reviewed, histopathology helped to implicate associated viral diseases, but histopathology is often not utilized in the quarantine process.2 Diagnosis of viral diseases in particular is critical during quarantine to prevent spread of disease to resident animals. For this reason, routine use of histopathology as part of clownfish disease diagnostics is recommended.
The authors thank Drs. Jeff Wolf and Scott Terrell for their help with reading histology slides for many of these cases, and Dr. Tom Waltzek for his help with virus identification. The authors also thank Drs. Mark Flint, Trevor Gerlach, Elizabeth Arnett Chinn, and Lauren Smith for their time working on these cases. Finally, we thank the many students and veterinarians who have spent time working on these cases at the University of Florida Tropical Aquaculture Lab.
* Presenting author
+ Student presenter
1. Larkin S, Degner R. The US wholesale market for marine ornamentals. Aqua Sci Conserv. 2001;3:13–24.
2. Hadfield CA, Clayton LA. Fish quarantine: current practices in public zoos and aquaria. J Zoo Wildl Med. 2011;42:641–650.