Meristics is an area of zoology and botany which relates to counting quantitative features of animals and plants, such as the number of fins or scales in fish.
Meristic characters are the countable structures occurring in series (e.g. myomeres, vertebrae, fin rays).
In rainbow and steelhead trout the most notable differences among populations occur in counts of scales.
Ichthyologists follow a basic set of rules when performing a meristic analysis, to remove as much ambiguity as possible.
A meristic formula is a shorthand method of describing the way the bones (rays) of a bony fish's fins are arranged.
Vertebral counts may be split into abdominal (those associated with the body cavity) and caudal (tail) vertebrae.