Preliminary Experiments Using Lights and Bubbles to Deflect Migrating Young Spring Salmon

Abstract

Experiments to deflect young spring salmon during their night-time migration by means of a beam of light and/or a "wall" of bubbles were conducted in a canal near Courtenay, B.C. By use of hoop nets it was discovered that under natural conditions no significant difference existed in the respective catches of the spring salmon underyearlings moving downstream on either side of the canal. A significant difference was obtained, however, when a narrow beam of light was directed into the water at a downstream angle in front of one net. A reduction to about one-third the expected catch resulted with either continuous or flashing light. The "wall" of bubbles, in a similar position, did not reduce the catch.Cut-throat trout fry and hatchery-reared Kamloops trout fingerlings were not deflected under these conditions.