Morphology

Fish morphological characters used in taxonomy include meristics (countable structures: fin ray counts, vertebral counts, scale row counts, gill raker counts) and morphometrics (measurable proportions: body depth, head length, snout length). Meristic characters are generally more taxonomically reliable than morphometrics, which can vary with age and condition. Geometric morphometrics — using landmark-based analyses of body shape in two or three dimensions — provides a more sophisticated quantitative approach. Comparative anatomy of internal structures (pharyngeal teeth, swim bladder anatomy, skull bones) provides additional characters less subject to environmental modification.