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.

A cost effective, simple, portable hyperbaric chamber was constructed from polyvinyl chloride to aid in the collection of adult rockfishes Sebastes sp. to hold as broodstock. This system was designed to recompress fishes quickly once brought to the surface on hook and line, and to allow for decompression over a period of days. The hyperbaric chamber is capable of continuous stable operation at <1 033 515 N m À2 and can accommodate fishes up to 91Á4 cm in length and 26Á8 cm in diameter. Pressure in the chamber is maintained by a Goulds Booster pump that delivers continuous pressure and supplies sea water at a rate of 3Á8 to 7Á6 l min À1 to as many as four chambers. The hyperbaric chamber operated very effectively and allowed successful decompression of 12 cowcod Sebastes levis captured at depths of 90Á2 to 146Á3 m. # 2007 Hubbs-SeaWorld Research Institute (HSWRI)