A new early life-stage toxicity test using the California grunion ( leuresthes tenuis) and results with chlorpyrifos

Abstract

California grunion were continuously exposed as embryos and fry to technical chlorpyrifos in two toxicity tests conducted in the same exposure apparatus. The first test, a 35-day early life-stage (ELS) test, began with approximately 2.5-day-old embryos that were exposed in flow-through aquaria in darkness until hatching was stimulated on Day 9 of exposure. The second toxicity test, a fry test, began with newly hatched fry and lasted 26 days. Test water temperature ranged from 23 to 26°C and salinity from 24.5 to 34.0%.. Results of the two tests were similar, indicating that exposure of embryos added little to the overall toxicity of chlorpyrifos to grunions. Percentage hatch of embryos was unaffected by the chlorpyrifos concentrations tested. Fry survival was apparently reduced in nominal concentrations ⩾ 1.0 μg/liter in both tests, but significantly so in concentrations ⩾ 1.0 μg/liter in the ELS test and ⩾2.0 μg/liter in the fry test. When compared with carrier controls, mean fish weights were significantly reduced in nominal chlorpyrifos concentrations ⩾ 0.5 μg/liter in the ELS test and ⩾1.0 μg/liter in the fry exposure. Mean bioconcentration factors were 770× for fish that survived the ELS test and 190× for those that survived the fry test. Results demonstrate the practicality of conducting ELS tests for the first time with a marine fish from the Pacific coastal waters of the United States.