Assessment of the suitability of the black-striped rainbowfish (Melanotaenia nigrans) as a laboratory toxicity testing organism, January 1998


Internal Report 272
Williams SJ, Camilleri C & van Dam RA
Supervising Scientist Division
Department of the Environment

About the report

The suitability of the black-striped rainbowfish, Melanotaenia nigrans, as a laboratory organism for toxicity testing was investigated, primarily as a tool for assessing mining wastewaters and developing water quality guidelines in the wet-dry tropics of northern Australia. M. nigrans was found to be a prolific and reliable breeder if fed a varied but specific diet, and if well maintained in clean aquaria. In addition, survival of M. nigrans larvae over 96 h was high when the brood stock were maintained in good condition. Test water water type (artificial or natural) and volume did not appear to affect larval survival over 96 h. When larval survival was poor, the addition of the exogenous food source, Aquasonic® freshwater fry starter (one of three food types tested), greatly enhanced the survival of larvae, although the ration administered (ie 0.5, 1 or 2 µl/ml) had no effect. Having demonstrated adequate survival of larval M. nigrans, the acute toxicity of copper (Cu), and the effect of feeding on Cu toxicity were assessed. Both Cu and feeding had a , significant effect on mean survival of M. nigrans larvae. In the presence of a food source (Aquasonic®), Cu had no effect on larval survival up to the highest concentration tested, of 100 µ/L. In the absence of a food source the survival of larvae decreased with increasing Cu concentration, with the effect being significant at 100 µ/L.

M. nigrans has the potential to be a suitable laboratory toxicity testing organism, due to the successful survival of larvae, unfed, over a 96 h test period. A comparison of the sensitivity of M. nigrans and the currently used fish species, Mogurnda mogurnda, to toxicants relevant to northern Australia is required before adopting M. nigrans as a standard laboratory toxicity testing organism. However, it is recommended that a laboratory acute toxicity test using larval M. nigrans be adopted for use in the Alligator Rivers Region, to complement the established in situ (creekside) toxicity test using the same species.