Methods for Fish Biology

Chapter 4: Taxonomic Methods: Morphology

Richard E. Strauss and Carl E. Bond


The morphology of fishes historically has been the primary source of information for taxonomic and evolutionary studies. Despite the value and availability of genetic, physiological, behavioral, and ecological data for such studies, systematic ichthyologists continue to depend heavily on morphology for taxonomic characters. Species have characteristic shapes, sizes, pigmentation patterns, disposition of fins, and other external features that aid in recognition, identification, and classification. In addition, there are important characters that can be examined by dissection or other means of internal examination. This chapter presents descriptions of important morphological characters and methods of studying them.

Our descriptions are representative of most fish groups. Hagfishes (Myxiniformes) and lampreys (Petromyzontiformes), however, lack such amenities as jaws and paired fins and are not considered to be true fishes. Thus most of the characters described in this chapter are not appropriate for their taxonomy. For a morphological review of lampreys, see Hubbs and Potter (1971); for hagfishes, see Hardisty (1979).

Information on the external morphology of fishes can be found in many standard references, including Hubbs and Lagler (1958), Miller and Lea (1972), Lagler et al. (1977), Bond (1979), Moyle and Cech (1981), and Trautman (1981). We present here a review of basic external features and kinds of variations observed, along with brief definitions of some of the more important morphological terms and conventional measurements.