Example of conversions based on morphometric data:

In this example, we will use humpback chub, Gila cypha. These conversion factors are only valid for fish that have achieved their adult body form; very young fish have different body morphologies. Notice that the conversion factors are dimensionless so you can use any units of measure (Examples: feet, inches, centimeters).

Excerpt from the Morphometric Data Table: 

Where:   BD = Body Depth,  TL = Total Length,  SL = Standard Length,  FL = Fork Length

1.       There are three possibilities:

a.       If you need body depth and you have total length, then use the column BD/TL (body depth/total length) and the row - humpback chub = 0.224.

b.       If you have fork length and you need total length, then use the column TL/FL (total length/fork length) and the humbback chub row = 1.134.

c.       If you have standard length and you need total length, then use the column SL/TL (total length/standard length) and the humpback chub row = 1.252. 

2.       Multiply the length you have by the conversion factor as follows.  

a.       For a humpback chub with a total length of 8.5 inches to estimate body depth: 

BD/TL x TL = BD

0.224 x 8.5 inches = 1.9 inches body depth

b.     For a humpback chub with a fork length of 21.6 centimeters to estimate total length:

TL/FL x FL = TL

1.134 x 21.6 cm = 24.5 cm total length

c.       For a humpback chum with a standard length of 203 millimeters:

SL/FL x SL = TL

1.252 x 203 mm = 254.2 mm total length

See an illustration of fish length measurement.