Fish Length and Swim Speeds


Swimming speeds found in the FishXing Literature Swim Speed tables are directly related to fish length.  Fish length is one of the most influential factors affecting the swimming speed of fish (Beamish 1978).

Absolute Swim Speed

For most fish species, absolute swimming speed (distance per time) and fish length are positively related through all swimming categories: sustained, prolonged and burst. For example, large juvenile pallid sturgeon (fork length, 17 cm to 20.5 cm) could swim faster than small pallid sturgeon (fork length, 13 cm to 16.9 cm) in all swimming categories tested:

Swim Speed

Large Juvenile Pallid Sturgeon

Small Pallid Sturgeon


25 cm/s

10 cm/s


30 cm/s

15 cm/s


55 cm/s

40 cm/s


 Relative Swim Speed

On the other hand, when relative swim speeds (body lengths per time) are studied for some species the relationship between length and speed is reversed. Smaller fish generally have higher relative swim speeds than larger fish; but this relationship can be affected by temperature. For example, smaller largemouth bass were found to have higher relative prolonged swimming speeds than larger fish of this species when temperatures were near their physiological optimum, but when temperatures were lower this relationship was not apparent (Beamish 1970). Both biological processes (such as, muscle and fin size, or respiration) and the hydrodynamic properties (such as various components of drag) underlie the relationship between fish swim speed and size. Informative discussions of these topics can be found in Beamish (1978), Grey (1998), Videler (1993), and Webb (1975, 1977, 1994).

Total Length

Knowing the total length of your Analysis Species is essential for selecting an appropriate swim speed.  Total fish length is one of the key parameters presented in the FishXing Literature Swim Speeds Tables and is a variable in many swim speed equations.    

In certain situations, total fish length is also used in the determination of when the fish is able to swim rather than leap into a culvert outlet.

See also: Measures of Fish Length, Converting Fish Lengths, Swim Speed Equations, Entering the Culvert: Leap or Swim

See an illustration of fish length measurement.