Acute ammonia toxicity for eight New Zealand indigenous freshwater species

The acute toxicity of un‐ionised ammonia to seven New Zealand indigenous fish and one indigenous crustacean species was established. Shrimp ( Paratya curvirostris ) was the most sensitive species, followed by banded kokopu ( Galaxias fasciatus ), common bully ( Gobiomorphus cotidianus ), common smelt ( Retropinna retropinna ), redfin bully ( G. huttoni ), inanga ( Galaxias maculatus ), and longfin and shortfin eels ( Anguilla dieffenbachii and A. australis ). The 96 h LC 50 at 15°C and pH 7.5 and pH 8.1 ranged from 0.75 to 2.35 mg NH 3 I −1 for these species. Unusually, New Zealand fish were more tolerant to ammonia than some native invertebrate species tested by a similar method. Within the limits of the life stages and species tested here, adequate protection is provided for native fish by adopting US Environmental Protection Agency ammonia criteria.