Since early 1999 California-based electric-power-research-institute (EPRI) in the US has been trying to determine why the American eel populations have been declining. For years hydro power plant operators have been struggling to ensure that fish pass hydro dams safely, but now they may have to consider eels as well.

According to several resources agencies, the American eel populations appear to be declining and agencies have asked utilities to ensure the passage of eels through hydro plants. However, according to EPRI it is not certain that hydro plants are really the problem as eel passage and protection methods already exist.

Information on the American eel, its life cycle, its decline, and how to protect it is still rather limited. EPRI has been investigating the issue through a detailed study. Its goal is to provide hydroelectric plant operators and regulatory agencies with a sound scientific basis for addressing eel management and protection concerns.

EPRI has found that there have been significant advances in effective upstream passage for the young eels through hydroelectric plants and that practical eel ladders for upstream passage are already in operation in several locations. These include shallow, gently-inclined and zig-zagging water chutes that enable eels to slither around hydro facilities.