Chapter 10 - Meristics

Abstract

Meristic characters are enumerable morphological features of fishes. Strictly, meristic features are those that corresponded evolutionarily with body segmentation; however, today, the term is used more broadly. The most commonly enumerated features have been external, including fin spines and fin rays, gill rakers, and scales (along several possible vectors). Internal meristic features that have been analyzed include pterygiophores, vertebrae, branchiostegal rays, and pyloric caeca. Meristic analysis remains a technically simple, inexpensive alternative for the stock identification of fishes. Drawbacks include that in almost all instances, specimens must be sacrificed—it is difficult (although not impossible) to make accurate counts of meristic features on living fish. Also, variation among year-classes as a consequence of environmental effects must be considered. However, there may be instances in which ecophenotypic variation of meristic traits is more effective toward stock identification than are genetic approaches. One instance is where genetic differences are limited because some or all populations to be analyzed are very recent in origin due to natural recolonization or stocking. Another instance is where there is sufficient gene flow among populations to preclude or erode genetic differentiation.