McCully, S. R., Scott, F., and Ellis, J. R. 2012. Lengths at maturity and conversion factors for skates (Rajidae) around the British Isles, with an analysis of data in the literature. –ICES Journal of Marine Science, 69: 1812–1822. Biological data on skates (Rajidae) from around the British Isles were collected between 1992 and 2010. The relationship between total length and weight for nine species (Amblyraja radiata, Dipturus batis-complex, Leucoraja fullonica, L. naevus, Raja brachyura, R. clavata, R. microocellata, R. montagui, and R. undulata) are provided for each sex and ICES ecoregion (when significantly different). Conversion factors for disc width to total length are provided. The lengths at first maturity and of the largest immature skates are reported for each sex, and the lengths at 50% maturity are estimated. Spatial differences in the length at maturity of R. clavata (females only) and L. naevus (both sexes) were observed. The lengths at maturity are discussed in relation to the results of earlier studies, and methodological differences are considered to have influenced reputed decreases in the length at maturity. A more standardized approach to collecting and reporting maturity information is required if potential spatial differences and temporal changes are to be investigated.

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The undulate ray Raja undulata is one of the lesser-known skates occurring on the continental shelf of the north-east Atlantic Ocean. It is patchily distributed throughout its range, with sites of local abundance in the central English Channel and off the coasts of Ireland, France, Spain and Portugal. Raja undulata is most abundant in coastal waters (<50 m deep) and is often found in proximity to large estuaries, rias and bays. It is a relatively large-bodied species, attaining a maximum total length (L(T) ) of at least 114 cm, with females maturing at an L(T) of c. 84 cm in Portuguese waters. Although infrequently taken in existing trawl surveys, it can be locally abundant in certain areas, where it can be the dominant skate species. Given its large size, patchy distribution and concern over the possibilities of localized depletions, the IUCN listed R. undulata as an endangered species and, since 2009, the European Union has established regulations to prohibit commercial fisheries landing the species. Given the increased interest in the species, a synopsis of current knowledge is provided, and available data from internationally co-ordinated trawl surveys presented.

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