Abstract

The Atlantic wolffish (AW) and the spotted wolffish (SW), which are long-lived fish found in the North Atlantic and Arctic oceans, are respectively classified as special concern and threatened species, mainly due to bycatch. To better understand health issues associated with the care of these species, which are occasionally kept in public aquariums, reports from all necropsies performed in two zoological institutions between 2009 and 2018 were reviewed (29 AW and 7 SW). These wolffish were fed with a similar fish-based diet, and kept in multi-species exhibits with comparable environmental parameters. The most frequent necropsy findings were the presence of xanthomas (AW: 38%; SW: 71%), nephrocalcinosis (AW: 39%; SW: 71%) and urinary bladder uroliths (AW: 4%; SW: 71%). Xanthomas, which were mostly (81%) located at the base of pectoral fins, were characterized by an extensive granulomatous inflammation centered on accumulations of partly mineralized degenerate fatty material mainly composed of cholesterol crystals. Nephrocalcinosis was characterized by deposition of calcium salts within the kidneys, especially in the collector tubules, and was commonly associated with tubular necrosis. Even if the etiology of these conditions remains unclear, a nutritional origin is suspected. Indeed, the nutritional composition of the cold-water fish-based diet fed to aquarium-housed wolffish is most likely very different from their natural diet which is mainly composed of invertebrates, such as urchins and crustaceans. These differences in nutrients, such as lipid and mineral content, may explain the high prevalences of xanthoma and nephrocalcinosis/uroliths observed in wolffish housed in these institutions.

Acknowledgement

The authors wish to thank the veterinary residents and veterinarians that performed the necropsies as well as animal health technicians and aquarists that have been involved with the care of these fish.

* Presenting author
+ Student presenter