A number of environmental studies have been conducted in association with therelicensing of the St. Lawrence-FDR Power Project located on the St. Lawrence River nearMassena, New York. Some of these studies have been directed towards determining if there is aneed for additional passage, beyond the existing ladder at the northern end of the MosesSaunders Power Dam, for upstream migrating American eels (Anguilla rostrata). The studiesconducted in 1997-1999 were designed to assess the efficiency of the existing eel ladder and tolearn how and where eels approach the Power Dam. To assess the efficiency of the ladder, 485eels were captured and PIT tagged in 1997, then released immediately downstream of the PowerDam. As of 1999, 34% had entered the ladder and 23% had exited the ladder and passedupstream. Of eels that successfully exited the ladder into Lake St. Lawrence (impoundment),between 6% and 12%, depending upon the year, were recaptured in the tailwaters, indicating thatthey probably returned through the Power Dam turbines. In 1999, eel traps were located alongthe face of the Power Dam and at an adjacent water control structure, Long Sault Dam, to assesswhere and how eels approach the Power Dam. Eels approached the Power Dam unevenly, withsubstantially more eels at the southern end of the Power Dam (43%) than at the middle (23%),northern end (33%), or Long Sault Dam (1%). Recapture of eels following their initial capture andrelease 0.5 km downstream from their capture location indicated that the eels exhibited variablelevels of fidelity for their original capture location. Overall, these studies suggest that another eelladder located on the southern end of the Power Dam would provide additional passageopportunities for upstream migrating eels. Additional studies are being conducted to assess theoptimum ladder entrance and release location.