Abstract

Ocular gas bubble disease (GBD) is a pathological process seen in fish where gas or gas bubbles accumulate in or around the ocular tissues. It is most commonly reported in the literature as being caused by gas supersaturation or barotrauma.^1,2 Although reports exist identifying barotrauma in hook-and-line captured Sebastes spp., scientific literature describing cases of gas bubble disease in Sebastes melanops living under human care is limited.³ A retrospective review was conducted in a population of black rockfish (Sebastes melanops) managed at the Vancouver Aquarium between September 2011 and November 2022 to describe medical management and outcome of cases as well as identifying contributing factors to disease development. Medical records were assessed for all individuals showing signs or symptoms of GBD based on the criteria of exophthalmia, buphthalmia, either gas aspirated or gas bubbles observed, recurrence of disease and clinical signs in the same patient, and only microchipped animals were included to ensure accuracy of review. During the 12-year period of study, 30 animals presented with GBD. Twenty animals presented once with GBD while ten animals redeveloped GBD. The mean annual prevalence was 4% with a range of (0–8.8%) with 2015 and 2021 having the highest prevalence at 8.6% and 8.8%, respectively. Medical treatment of cases included ceftazidime (20 mg/kg), acetazolamide (2 mg/kg), and most cases either meloxicam (0.2–0.5 mg/kg) or ketoprofen (3 mg/kg) all given intramuscularly. Duration of treatment and number of injections varied slightly. Treatment often included aspiration of gas under anesthesia. Outcomes for initial single presentation included mild persistent ocular disease requiring no further intervention (45%), full resolution of symptoms (40%), cataract and anterior lens luxation (5%), and euthanasia resulting from trauma and severity of disease (10%). Eighty-five percent of outcomes for animals presenting once were favorable. Outcomes for animals with recurrence of clinical signs included euthanasia (30%), mild persistent ocular disease (30%), full resolution (20%), posterior lens luxation (10%), and enucleation (10%). Fifty percent of these outcomes were considered favorable. Euthanasia was elected in 5/30 cases due to severity of disease. Forty-two separate instances of GBD treatment were evaluated and several factors assessed including habitat (30.9% of cases from Pacific Canada exhibit, 42.8% of cases from Barkley Sound exhibit, and 11.9% from Burnaby Narrows exhibit), location of lesion (47.6% OD, 42.8% OS, 9.5% OU) and presence or absence of visible gas bubbles (42.8% of cases displayed obvious gas bubbles). Based on case review, medical management is more successful for animals presenting once. Patients with recurring lesions were more likely to undergo enucleation or euthanasia as a result of the disease. Additional research is needed to determine the best treatment strategy for patients with chronic symptoms of GBD.

Acknowledgements

The authors wish to thank the aquarists at Vancouver Aquarium for their dedication and care for these animals as well as veterinary technician Sion Cahoon, without whom none of this would be possible.

*Presenting author
+Student presenter

Literature Cited

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2.  Hadfield CA. C1 Noninfectious diseases (environmental). In: Hadfield CA, Clayton LA, eds. Clinical Guide to Fish Medicine. John Wiley and Sons, Inc.; 2021:359–363.

3.  Jarvis ET, Lowe CG. The effects of barotrauma on the catch-and-release survival of southern California nearshore and shelf rockfish (Scorpaenidae, Sebastes spp.). Can J Fish Aquat Sci. 2008;65:1286–1296.