Exposure to permethrin or chlorpyrifos causes differential dose- and time-dependent behavioral effects at early larval stages of an endangered teleost species

Pyrethroid and organophosphate pesticides are two of the most commonly used classes insecticide worldwide. At sublethal concentrations, permethrin (a pyrethroid) chlorpyrifos (an organophosphate) impact behavior in model fish species. We investigated behavioral effects environmentally relevant concentrations or on early larval delta smelt Hypomesus transpacificus , a Critically Endangered teleost species endemic to San Francisco Bay Delta, California, USA. Using photomotor assay oscillating light dark periods, we measured distance moved, turn angle, meander, angular velocity, rotations, thigmotaxis (time spent border versus center), swim speed duration frequency. The lowest tests (0.05 0.5 µg l -1 ) caused significant increases moved at 72 96 h, respectively. 48, 72, h exposure, 5 hyperactive state which larvae significantly decreased thigmotaxis, quickly turning short bouts activity, characterized by rotations freezing events. Larvae exposed 0.05 increased h. In response chlorpyrifos, velocity events Behavioral data contaminants present their limited habitat have potential aid evaluations suitability spawning rearing habitats for this endangered species, thus improving conservation management strategies focused sensitive life stage.