Avoidance behaviour of freshwater fish and shrimp exposed to ammonia and low dissolved oxygen separately and in combination

The responses of common smelt (Retropinna retropinna Richardson), inanga (G alaxias maculatus Jenyns), common bully (Gobiomorphus cotidianus McDowall), and shrimp (Paratya curvirostris Heller) to ammonia and low dissolved oxyg en (DO), separately and in combination, were measured in a fluvarium. Only common smelt avoided high or low ammonia (c. 8.5 and 2.0 g m(-3) NH3, respe ctively) and low DO (c. 2 g m(-3)) alone and in combination. Shrimp avoided high ammonia and low DO+ammonia but not low DO on its own. Inanga and bull ies showed no significant negative response to either contaminant; rather, inanga were strongly attracted to low ammonia and bullies to low DO. These results parallel those from toxicity experiments that show common smelt and shrimp are usually among the most sensitive native species to various cont aminants. The consistent and appropriate avoidance behaviour shown by commo n smelt, in particular, suggests this species would be a good indicator org anism for assessing the health of lowland waterways.