The first objective of the current proposal is to validate VTG as an indicator of exposure to EDCs in male fishes, first in lake trout and then in other fishes. The second objective is to develop and implement a quantitative method for accurate analysis of VTG. The third objective is to develop antibodies against VTG and use them to develop an economical and easy-to-use detection device/sensor (i.e. COVID-like or pregnancy-like device) that allows one to test the blood of fish in the field, and to accurately determine whether the fish is exposed to EDCs or not, based on the positive detection of VTG in the blood.