Rapid Learning of a Constant Course by Travelling Schools of Juvenile Pacific Salmon

Abstract

Either individuals or schools of downstream-migrating chum, sockeye and pink salmon quickly establish a constant course in a circular channel. This clockwise or counter-clockwise course, once established, is not altered by a variety of disturbances including transfer to a channel of different size and shape or, in the case of the chum, removal from the apparatus for almost two days. The schools travel much more frequently in some particular area of a simple maze although, from time to time, they swim through all parts of it. The tendency to swim steadily forward in a winding maze seems to decline as the season of migration comes to an end. Fish trained to swim along one compass direction show no bias for this direction when given a choice of this or an alternate direction at right angles. Fish trained to reverse direction after a definite distance show a tendency to do this when given an opportunity to swim in a channel twice as long. The findings are discussed in relation to simple types of learning such as habituation, insight learning, latent learning and imprinting. The biological significance of the learning is considered in relation to the problem of migration.