Morphometric ratios of six commercially landed species of skate from the Portuguese continental shelf, and their utility for identification

Abstract

European skate landings have traditionally been reported under a generic landing category, because of problems with species identification. To address this data deficiency, the ICES Working Group on Elasmobranch Fishes compiled conversion factors, including the relationships between different body measurements, for the main elasmobranch species. Size conversion factors for six common NE Atlantic skate species, Leucoraja naevus, Raja brachyura, R. clavata, R. miraletus, R. montagui, and R. undulata are compiled, and the capability of morphometric data to assist species discrimination is evaluated, highlighting the case of similar species such as R. brachyura and R. montagui. The estimated size conversion factors displayed some variability between areas and sexes for most species, the allometric relationship between weight and total length did not differ significantly between sexes, and some morphometric ratios proved adequate in discriminating between rajid species (misclassification error 0.12). Leucoraja naevus was fully discriminated from the remaining species. Species with a similar dorsal colour, e.g. R. brachyura and R. montagui, showed good discrimination based on their morphometry, with just 6-11% misclassification between the two. © 2010 International Council for the Exploration of the Sea.