Abstract

Wolffish are regularly housed in aquaria, but few data on their husbandry and health are available for caretakers. High occurrences of xanthomatosis, nephrocalcinosis, and urolithiasis have been observed in Atlantic (Anarhichas lupus) and spotted wolffish (Anarhichas minor). The fish-based diet used by most institutions was suggested as a potential risk factor for these pathological conditions in species of fish that mainly feed on low-fat invertebrates in the wild. To explore the potential link between these diseases and diet, we conducted a 16-month prospective study by randomly dividing 32 juvenile spotted wolffish into four experimental groups fed with different diets: (1) vitamin-supplemented, invertebrate-based diet; (2) vitamin-supplemented, fish-based diet; (3) Skretting® Europa 18 pellets; and (4) Mazuri® LS Aquatic Carni-Blend Diet Formula. Blood analyses were conducted every four months, and urinalysis, radiographs, and complete necropsies were performed at the end of the study. Decreases in the levels of serum cholesterol and free fatty acids were observed in the groups fed with the invertebrate-based and Mazuri® diets. None of the wolffish developed xanthomas, nor uroliths during the study period. All the specimens fed with the fish-based and invertebrate-based diets developed nephrocalcinosis, whereas this condition was seen in 12.5% and 0% of the fish in the Skretting® and Mazuri® groups, respectively. Affected wolffish presented crystalluria and increased radio-opacities in the caudal kidneys. Nutritional analyses suggest that a high gelatin, high vitamin C, and/or low vitamin E dietary contents could be potential risk factors for the development of nephrocalcinosis in wolffish.

Acknowledgements

The authors wish to thank the team of technicians from the Aquarium du Québec for their help with this project. This project was supported by grants from the Fonds du Centenaire—Université de Montréal and from the Zoo de Granby.

*Presenting author