Nippon Suisan Gakkaishi 65 (4), 728-731 (1999)

Behavioral Analysis of Feeding Experiment on Visual Axis of Red Sea Bream Pagrus major

Yasushi Shiobara*1,*2 and Takafumi Arimoto*1

Visual axis of red sea bream Pagrus major was analyzed from the laboratory experiment on the feeding behavior in the dome-shaped tank. Feeding time was measured for the food presented at random on the inside wall of the dome, for 33 different directions of equal distance from the starting gate. The fish was observed to approach the food directly toward the front area of 22.5° concentric circle from the center of the dome, which cover the binocular field of red sea bream. This direct approach was also observed in the area of right/left downward in angles of 67.5°, which fit to the previous results on the visual axis of down-forward direction estimated through the retinal morphology. While, at the downward area below the snout, the visual detection of the food was delayed and not approached directly. This confirms the blind area of red sea bream due to the inclined angle of both eyes against the body axis.


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