Goldfish use the visual angle of a familiar landmark to locate a food source

Three goldfish were trained to search for food buried 20 cm from a perspex tower. In the absence of food, all fish still searched in the correct location, revealing that fish can use a landmark to locate food. Halving either the width or height of the landmark resulted in searches significantly closer to the tower, suggesting that fish determined their position relative to the landmark using its horizontal and vertical visual angles.