Being a UNESCO-World Heritage Site, the Galápagos harbors the largest global shark biomass in the world’s oceans and a unique marine biodiversity.

In this research, the toxic effects of Cadmium chloride (CdCl2 ), which can seriously pollute aquatic environment and threaten human health, are evaluated based on the behavior responses and the brain Acetylcholinesterase (AChE) activity of zebrafish (Danio rerio). The results showed that Behavior Strength (BS) of test groups (changed from 0.15 to 0.65), which was recorded using an online behavior monitoring system, was lower than the control groups (changed from 0.65 to 0.85). The behavior responses of zebrafish suggested that both dose and time effect relationships existed between Cd2+ stress and zebrafish BS. Meanwhile, the brain Acetylcholinesterase (AChE) activity of zebrafish were strongly inhibited by Cd2+: the AChE activities were lower than 60% after 0.5h Cd2+ exposure in both 1 TU (Toxic Unit) and 2 TU. The AChE activities in 0.1 TU Cd2+ treatment were about 60% in the first 2h and then increased to about 100% in 4h with a decrease tendency in the following exposure time (8h to 48h), which changed from 100% to 70%-80%. Totally, the brain AChE activities of zebrafish showed similar rules with BS after correlation analysis, which might provide an understanding of the ecotoxicological assessment of heavy metal Cd based on zebrafish.