Is there a role for vision in the behaviour of sea lampreys (Petromyzon marinus) during their upstream spawning migration?

Abstract

This study found no evidence to support a role for vision in the behaviour of sea lampreys (Petromyzon marinus) during their spawning migration. Blindness had no affect on the migratory propensity of lampreys, and control and blinded animals moved upstream at the same rate. The diel activity pattern of control and blinded lampreys was identical in both the laboratory and field. Activity was mostly nocturnal, but lampreys in the field did show some daytime activity. Diel activity broke down when lampreys were unable to locate suitable daytime refuge, but blindness did not affect the willingness or ability of lampreys to do so in either the laboratory or field. Laboratory studies indicate that light avoidance is mediated by dermal photoreceptors located in the tail, but the data suggests that refuge sites are sought out before sunrise using tactile and possibly hydraulic cues. Thus, light-induced searching only occurs when the sites chosen at night do not provide adequate concealment after sunrise.