Standardised Protocols for Taxonomic Measurements for Pleuronectiform Fishes

Study of fish morphometrics has been the primary source of information for taxonomic and evolutionary studies. Despite the value and availability of genetic, physiological, behavioural, and ecological data for such studies, systematic ichthyologists continue to depend heavily on morphology for taxonomic characters. Morphometric data is important in that it can be used as taxonomic characters to examine evolutionary relationships among species; they have the advantage that size effects can be removed before the data are recoded so that inferred evolutionary relationships are based on body-form rather than body-size differences. Identification of stocks of fish has been the mainstay of morphologists. Large data sets have been collected for a diverse array of commercially important fish (Winans,1985). For over 30 years, most morphometric investigations have based the selection of characters on the set of measurements described by Hubbs and Lagler (1947). Most species of fishes have characteristic shapes, sizes, pigmentation patterns, fin disposition and other external features that aid in recognition, identification, and classification that can be examined by dissection or other means of internal examination. Structural measurements sometimes are used directly as characters if they are sufficiently discrete among taxa or if a tree-building procedure is used that allows the use of continuous characters (Farris 1970; Farris et al. 1970). Standard references for taxonomic study of bony fishes are Hubbs and Lagler (1958), Miller and Lea (1972), Lagler et al., 1977, Bond (1979), Moyle and Cech (1981), and Trautman (1981). The general parameters taken into account are those on the left side for bony fishes unless otherwise mentioned or right side when that side is damaged. In the case of elasmobranchs, a glance through any well-illustrated guide to chondrichthyans (e.g. Compagno 1984; Last and Stevens 1994; Compagno et al., 2005) reveals a huge diversity of body morphology. In odd shaped teleost fishes like box fishes also the basic measurement pattern was based on Hubbs and Lagler (1958) with slight modifications. Compared to the other teleosts, measurements are necessary on both sides for the flatfishes due to the flattened nature of the body like in the ray fishes