Meristics

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. A meristic (countable trait) can be used to describe a particular species, or used to identify an unknown species. Meristic traits are often described in a shorthand notation called a meristic formula.

Meristic characters are the countable structures occurring in series (e.g. myomeres, vertebrae, fin rays). These characters are among the characters most commonly used for differentiation of species and populations. In the salmonids, scale counts have been most widely used for the differentiation of populations within species. In rainbow and steelhead trout the most notable differences among populations occur in counts of scales. Meristic comparison is used in phenetic and cladistic analysis.