Spatial orientation of trout to partially polarized light

Summary The results of this study reveal that rainbow trout (Oncorhyncus mykiss formerly Salmo gairdneri) are capable of orienting to polarized light fields, and that the degree of polarization of the polarized light field affects the accuracy of orientation behavior. As previously shown, rainbow trout can accurately orient to a plane polarized light field after several sessions of food-rewarded training. The present data demonstrate that the accuracy of such orientation decreases the degree of polarization of the plane-polarized light field is lowered. In testing sessions, different concentrations of latex beads were introduced into a cuvette positioned below the light source to degrade the degree of polarization. There was evidence that trout could still detect the evector and use it in making orienting responses when the light was only 65% polarized. However, most of the test trout did not demonstrate orienting ability at levels of polarization below the 75% level.