COPPER TOXICITY TO SPERM, EMBRYOS AND LARVAE OF TOPSMELT ATHERINOPS-AFFINIS, WITH NOTES ON INDUCED SPAWNING

Topsmelt, Atherinops affins, were induced to spawn repeatedly in the laboratory using a combination of environmental cues. Temperature 'spikes' appeared to be the most important factor to induce spawning. Egg production peaked four days after a 2-degrees-C increase in water temperature, and declined thereafter. A series of static toxicity tests compared the r relative sensitivity of topsmelt sperm, embroyos, and larvae to copper chloride. Of the three developmental stages compared, sperm were more sensitive than embryos, and embryos were more sensitive than larvae. The mean EC50 from four separate 48-h fertilization experiments was 109-mu-g copper liter-1. The mean EC50 from three, 12-day embryo development tests was 142-147-mu-g copper liter-1, depending on the endpoint used. The mean LC50 from three, 96-h larval mortality tests was 238-mu-g copper liter-1. Topsmelt are amendable to laboratory culture and are a promising eastern Pacific toxicity test species.