Argyrosomus regius (3.0 AE 0.9 g) were exposed to different concentrations of ammonia in a series of acute toxicity tests by the static renewal method at three temperature levels (18, 22 and 26°C) at a pH of 8.2. Low temperature clearly increased the tolerance of the fish to total ammonia nitrogen (TAN) and unionized ammonia (NH 3 ) (P < 0.05). While the 96-h LC 50 values of TAN were 19.79, 10.39 and 5.06 mg L À1 , the 96-h LC 50 of NH 3 were 1.00, 0.70 and 0.44 mg L À1 at 18, 22 and 26°C respectively. The safe levels of NH 3 for A. regius was estimated to be 0.10, 0.07 and 0.04 mg L À1 at 18, 22 and 26°C respectively (P < 0.05). This study clearly indicates that A. regius is more sensitive to ammonia than other marine fish species cultured on the Mediterranean and Eastern Atlantic coasts.

Meagre, Argyrosomus regius, is a candidate marine fish species for aquaculture diversification, presenting a high economic value in the Mediterranean. Tolerance of juvenile meagre to nitrite (NO 2 -N) was determined relating to temperature. Fish (3.2 ± 0.6 g and 5.4 ± 0.9 cm) were exposed to different NO 2 -N concentrations in a series of acute toxicity tests by the static renewal method at three temperatures (18, 22, and 26 C) at a pH of 8.0. Low temperature clearly increased tolerance to NO 2 -N (P < 0.05). The 96-h median lethal concentration (LC 50 ) values of NO 2 -N were 177.63, 139.55, and 49.61 mg/L, at 18, 22, and 26 C, respectively. The safe levels of NO 2 -N for juvenile meagre were estimated to be 17.7, 13.9, and 4.9 mg/L at 18, 22, and 26 C, respectively (P < 0.05). This study indicates A. regius is more sensitive to nitrite than other marine fish species cultured in the Mediterranean.