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Sea bass (Dicentrarchus labrax, mean start weight 82 g) were exposed to experimental conditions for a period of 84 days. Water supplies with three different levels of gas content (no. 1 — normbaric normoxic, no. 2 — hyperbaric hyperoxic and no. 3 — normbaric hyperoxic) were prepared in three separate header tanks and mixed to the required exposure levels prior to entering the fish tanks. Experimental conditions consisted of three levels of oxygen saturation measured in effluent water and four levels of ΔP. The hyperbaric hyperoxia condition in water no. 2 was obtained by dissolving oxygen under high pressure while the normbaric hyperoxic condition of water no. 3 was obtained by dissolving oxygen under low pressure. The experimental groups consisted of a control group (99% O2, ΔP − 150 mm Hg), two medium hyperoxia groups (mH1: 135% O2, ΔP −160 mm Hg and mH2: 139% O2, ΔP + 29 mm Hg) and one high hyperoxia group (hH: 220% O2, ΔP + 167 mm Hg). Each treatment was performed in triplicate tanks and water was supplied by gravity from the header tanks. As a consequence of the treatment significant increase in mortality rate was observed in the hH group, along with significant reduction in growth, significant increase in food conversion rate and observations of gas bubbles in and around the eyes, at the base of and on the dorsal and pectoral fins. Improved growth was found in both the medium hyperoxia groups, though only the mH1 treatment group showed significant (p |
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