Nitrite is toxic to fishes and is often encountered in recirculation aquaculture systems. Accordingly, the nitrite tolerance of potential aquaculture candidates needs to be assessed before the fish can be farmed in land-based recirculation systems. In the present work, we studied the susceptibility of the marbled rabbitfish Siganus rivulatus to nitrite. In the first experiment, we placed fish at 0, 40, 50, 60, 70, 80, 90, 100, 110, 120 and 130 mg l -1 NO 2 -N and evaluated 96 h LC 50 . In the

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... h LC 50 . In the second experiment we measured survival and growth of fish reared at 0, 10, 20, 30, 40, and 50 mg l -1 NO 2 -N for eight weeks. Blood parameters of fish in the various treatments were also measured and gill histology studied. Finally, methemoglobinemia in fish reared at various nitrite conditions was assessed. The NO 2 -N 96 h LC 50 of S. rivulatus juveniles was 105 mg l -1 . In the growth experiment, fish mortality was greater than in the control at NO 2 -N concentrations 30 mg l -1 and greater. Growth in all treatments was less than in the control but there were no significant differences among treatments. Aqueous nitrite affected various hematological parameters such as hematocrit and total hemoglobin. Compared to other aquacultured marine fishes, the marbled rabbitfish is considered tolerant to environmental nitrite.