A STUDY ON THE OPTOMOTOR REACTION OF SOME YOUNG FISHES

This paper reports the results of the experiment in optomotor reaction about five young fishes, grey mullet (Mugil cephalus), perch (Lateolabrax japonicus), porgy (Sparus latus), carp (Cyprinus carpio) and grass carp (Ctcnopharyngodon idellus).Reaction rate of these fishes decreases as the intensity of illumination weakens or the screen rotary velocity increases. Upper followable stimulus frequency (UFSF) rises with the intensity of illumination. Under 102 Ix, grey mullet's UFSF is as high as 37/sec ; perch's 26/sec ; porgy's, 27/sec ; carp's. 24/sec and grass carp's, 29/sec. Transitional illumination from scotopic to photopic vision is 100—101 Ix for grey mullet; 10-2—10-1 Ix for perch and porgy; 1.0-1—100 Ix for carp and grass carp. The stimulus frequency and illumination have a little influence on latent perirod. Following angular velocity is, on the whole, less than screen rotary velocity, i.e. the following rate is less than 100%, and it decreases as rotation velocity rises. Illumination has little effect on following rate. The reaction of these fishes to moving strips consists of three stages: following, actiwely swimming and no responding.