The Reaction of Fish to Moving Backgrounds

Abstract

1. An apparatus is described to study the response of fish to moving backgrounds. 2. Observations were made on pike, three-spined sticklebacks, trout, perch and roach; cod, whiting, whiting-pout, smelt, herring, armed bullhead, lesser weaver, plaice, dabs, soles and dogfish. 3. Pike followed a moving background equivalent to a water current of 0.03 cm./sec. Pike were the best and most consistent performers among the freshwater species, followed by the three-spined stickleback, trout, roach and perch. 4. The marine species fell into two groups. The cod, whiting, whiting-pout, smelt, and herring responded to background movements equivalent to water currents of 1-2 cm./sec. The other fish failed to respond to movements equivalent to currents up to 24 cm./sec. and it is thought that this may have been due to contact with the bottom. 5. The fish that orientated to a moving background also responded kinetically. Cod, whiting, and whiting-pout gained on the background (swam upstream) at rotational speeds equivalent to water currents less than 1 fish lengthlsec., but started to lag behind at speeds equivalent to currents faster than 1-2 L/sec., although the fish were shown to be capable of swimming fast enough to keep pace with the background. Herring gained on the background up to rotational speeds equivalent to water currents of 3-4 fish lengths/sec. 6. The results are discussed in relation to the contranatant theory of fish migration.