An experimental site was prepared on Minter Creek above the influence of the Biological Station's weir pond. At this point, the creek was 28 ft wide. The entire flow was screened and the fish caught in four mesh traps. A T-shaped light barrier 40 feet long was pivoted from the center of the stream, and fished on alternate nights to guide fish into the number 1 trap on the right bank, or the number 4 trap on the left bank. The formal experiment was run six nights, thereby permitting duplication of identical light level sequences at the same hours but shining in opposite directions and with guidance to the opposite bank.