Dill, P.A., 1971. Perception of polarized light by yearling sockeye salmon (Onchorynchus nerka). Journal of Fisheries Research Board of Canada 28(9):1319-1322.

Region: Canada Species: Sockeye yearlings

Study Objectives: Determine if yearling sockeye salmon can discriminate between different planes of polarized light.

Study Methods: Controlled laboratory experiments in a conditioning tank, an incandescent light source and polaroid filters, one with a vertical plane of polarization and one with a horizontal plane of polarization. Two experiments were performed: one using intact fish and one using fish with their adipose eyelids removed.

Results: Juvenile sockeye salmon discriminate between filter boxes containing vertical and horizontal polarizers. The adipose eyelid does not appear to be involved in the discrimination of horizontal and vertical polaroids. This is believed to support the hypothesis that yearling sockeye salmon may use the plane of polarization of the blue sky for maintenance of direction during their seaward migration in lakes.