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11 Locomotion of Marine Animals
Table 11.1: Typical swimming velocity, approximate size and corresponding
Reynolds number of self-propelled marine organisms (adapted from Videler, 1993)
Marine organism Velocity (m/s) Length (m)
Re
Blue whale
10
30
3 X 10 8
Tuna
10
3
3 X 10 7
Mackerel
3.3
0.3
1 x 10 6
Herring - Adult
1
0.2
2 x 10 5
- Larvae
0.5
0.1
5 x 10 4
- Larvae
0.16
0.04
6 x 10 3
- Larvae
0.06
0.02
1 x 10 3
- Larvae
0.02
0.01
2 x 10 2
Copepods
0.002
0.001
2
Sea urchin sperm
0.0002
0.00015
3 x 10- 2
Bacteria
0.00001
0.000001
1 x 10- 5
Human
1.7
1.8
3 x 10 6
in which /I is the coefficient of kinematic viscosity. Comparison of Eqs. (11.8)
and (11.10) indicates that swimming velocity, U, based on animal length, L, is
consistent with velocity determined using Reynolds number Re.
A similar relationship between swimming velocity, U, and Reynolds number, Re, for a large variety of marine organisms, from bacteria to whales, was
established by Okubo (1981) as:
(11.11)
Thus:
(11.12)
which is comparable with the relationship (11.10).
The relationships from (11.7) to (11.12) are based on a variety of organisms
which use different mechanisms to swim. For example, bacteria or copepoda
are too small to swim independently against ocean currents. Buoyancy is most