No abstract

No abstract

Small groups of fish of a schooling species were trained in successive discrimination reversals with an avoidance paddle. In this method, fish are transitorily swept out of the water by a moving paddle passing through their tank if they fail to swim through an opening, which is shifted rightleft in successive reversals. Errors declined significantly through reversals. This is an unusual result for fish, which generally fail in reversal learning problems.

No abstract

Two groups each of approximately 100 Moenkhausia dichroura, a schooling characid, showed a long-lasting, constant-oriented swimming when placed in a light-centred circular channel. This apparatus consists of a I-m diameter circular channel illuminated by either a central or a peripheral light system, so that the light angle is constant all around the channel. With the central light at a fixed angle, fish swam for several months in one direction and reversed direction at a certain date. When the light angle was increased by 10" every other day between 0" (horizontal) and 90" (vertical), swimming direction was reversed at a particular angle in each experiment. This response to artificial light suggests that this small schooling fish uses the sun as an orientation clue in its seasonal migrations.