Acute Effects of Gas Supersaturation on Juvenile Cultured White Seabass

Abstract

White seabass Atractoscion nobilis reared at a production and research hatchery have been observed to occasionally suffer from ocular emphysemas. To identify a possible cause of these lesions, cultured juvenile white seabass were exposed to five gas saturation levels between 98% and 122% total gas pressure (TGP). Experiments were run for 96 h using fish weighing 3 and 22 g at water temperatures of 17.9 ± 0.3°C or 23.0 ± 0.3°C. Fish were observed every 8 h for symptoms of gas bubble disease. Throughout the trial, no fish died when exposed to 98, 102, or 109% TGP and only one fish died at 116% TGP. When fish were exposed to 122% TGP, however, mortality was 5 percentage points greater for both small and large fish in 23°C water than for those at 18°C and 20 percentage points greater for the large than for the small fish at both temperatures. The most prevalent and severe lesions were in large fish exposed at 23°C, followed by small fish exposed at 23°C, large fish exposed at 18°C, and small fish exposed at 18°C. Corneal emphysemas were the most common lesion, affecting even the control group of large fish in 23°C seawater. For fin emphysemas, only the large fish at 18°C were affected at both 116% and 122% TGP. These fish also had the highest incidence of fin emphysemas (50%), followed by the large fish at 23°C (38.3%), small fish at 18°C (6.7%), and small fish at 23°C (1.7%). These results indicate that temperature, size, and gas supersaturation all play roles in the onset of gas bubble disease for white seabass. These factors should be investigated in any hatchery setting when ocular emphysemas arise.

Received September 8, 2010; accepted March 9, 2011