| Summary: | 1. The kinematics of labriform and subcarangiform swimming have been investigated for juvenile (7–8 cm) and adult (27–30 cm) stages of the antarctic teleost Notothenia neglecta Nybelin at 1–2 °C 2. Upper threshold speeds using the pectoral fins alone (labriform swimming) were 0.8LS−1 in adult fish and 1.4Ls−1 in juveniles, where L is body length 3. In adult fish, steady subcarangiform swimming is only used at speeds of 3.6-5.4Ls−1 (tail-beat frequencies of 5.0-8.3Hz). Intermediate speeds involve unsteady swimming. In contrast, juvenile fish employ subcarangiform swimming at a range of intermediate velocities between the maximum labriform and burst speeds (2.3-8.4Ls−1 at tail-beat frequencies of 4.0-12.5 Hz). These differences in swimming behaviour are discussed in relation to changes in life-style and muscle fibre type composition between juvenile and adult fish 4. Burst swimming speeds in N. neglecta have been compared with equivalent data from temperate species. It seems likely that low temperature limits swimming performance in antarctic fish. This is more noticeable in juvenile stages, which normally have much higher tail-beat frequencies than adult fish
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