Before flow patterns were modified at an Ice Harbor style fish ladder in the Connecticut River, counts of American shad (Alosa sapidissima) successfully negotiating the entire Turners Falls, Massachusetts powerhouse fishway were only 687 in 1980 and 219 in 1981, compared with 367,000 and 377,000 for the same years at Holyoke, a mechanical elevator 36 miles downstream. Before the 1983 run, a zigzag flow pattern was established and ikncluded a change from plunging to streaming flow over the weir crests. American shad passage in 1983 was 26,697, of 528,000 that passed the downstream fish elevator. Peak daily passage was 4,540 and the maximum hourly rate was 780. A second Ice Harbor style ladder without flow modifications passed only 263 shad during the 1983 season, but passed 4,563 in 1984 following similar changes.