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No abstract

Vision is not required in order for fish to school. Five individual saithe, Pollachius virens, were able to join schools of 25 normal saithe swimming in an annular tank, while blinded with opaque eye covers. Test fish maintained position within the school indefinitely and responded to short-term movements of individuals within the school, although quantitative differences in reaction time and schooling behavior were noted. Five fish with lateral lines cut at the opercula were unable to school when wearing opaque eye covers. Although it is unlikely that blind saithe could school in the wild, the constraints of the apparatus permitted a demonstration of a role of the lateral line organ in schooling.

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Endurance and swimming speed were measured in mackerel, herring and saithe when they were induced by the optomotor response to swim at prolonged speeds along a 28-m circular track throughstillwater ina 10-mdiametergantry tank. Themaximumsustainedswimmingspeed(U,,, was measurcd as body lengths per second (H.L.S -') for each species and for saithe of direrent size groups. Hcrring with Lfm% of 4.06 B . L .~ ' (25.3 cm, 13.5' C) were the fastest, mackerel U,, was 3 . 5 1 3 .~~ ' (33cm. I1.7"C) and saithe (14.4"C) showed a size effect where Urn, at 25cm was 3.5 R.L.S ' and at 50cm 2.2 B . L .~ I . When swimming at speeds higher that U,,, all three species showed reduced endurance as speed increased. How thecurved track reduces the swimming speed is discussed.