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Serra-Pereira B.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Moura T.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Griffiths A.M.,Marine Biological Association of The United Kingdom | Figueiredo I.,Instituto Nacional Of Recursos Biologicos Ip Ipimar
Zoologica Scripta | Year: 2011

Due to their vulnerability to fishing pressure, many species of skate (Rajidae) in the Northeast Atlantic are undergoing declines in abundance. The assessment of stock status and subsequent proposal of management measures are often complicated by high levels of species diversity and endemism, coupled with morphological and ecological conservatism, which makes distinguishing between species difficult. To improve the identification of skates and investigate the phylogenetic position of endemic species the cytochrome c oxidase subunit I (COI) was sequenced in 12 species (Dipturus oxyrinchus, Leucoraja naevus, Leucoraja circularis, Neoraja iberica, Raja brachyura, Raja clavata, Raja maderensis, Raja microocellata, Raja miraletus, Raja montagui, Raja undulata, Rostroraja alba) inhabiting the Portuguese waters. Based on sequence divergence R. maderensis and R. clavata only differ by 1% of the 652 bp COI sequence, questioning the recognition of R. maderensis (considered to be endemic to Madeira and the Azores), as a reproductively isolated species. Otherwise, there was clear phylogenetic support for the different genera and all the remaining species, although the genetic divergence was low compared to other chordates. In particular, COI analysis allowed clear identification of the morphologically similar species R. brachyura and R. montagui. © 2010 The Authors. Zoologica Scripta © 2010 The Norwegian Academy of Science and Letters. Source


Serra-Pereira B.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Farias I.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Moura T.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Santos M.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Figueiredo I.,Instituto Nacional Of Recursos Biologicos Ip Ipimar
ICES Journal of Marine Science | Year: 2010

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. Source


Serra-Pereira B.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Figueiredo I.,Instituto Nacional Of Recursos Biologicos Ip Ipimar
Marine Biology | Year: 2011

In Portuguese waters, thornback ray Raja clavata spawns mainly between May and January, although females and males in spawning condition are found throughout the year. The maturation process can be divided into three main phases by using information on gonad weight, oviducal gland and uterus width in females and on gonad weight, clasper length and sperm duct width in males. Females attain length-at-first-maturity at 784 mm and males at 676 mm, at ages of 7. 5 and 5. 8 years, respectively. In females larger than length-at-first-maturity, a resting stage was identified characterized by low gonadosomatic index and well-developed oviducal glands and uteri. These results along with the low proportion of adult females that are effectively reproducing per month demonstrated that the thornback ray cannot be considered a continuous spawner as described in other studies. Fecundity was determinate with about 35 eggs released per batch. During the spawning season, a total of four batch episodes occur indicating that the total fecundity was approximately 136 eggs per female. Regional differences may exist in the reproductive strategy of the species, namely on the duration of the spawning season, length-at-first-maturity, and fecundity, which can be related to a more intense fishing pressure in northern European waters. © 2011 Springer-Verlag. Source


Maia C.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Erzini K.,University of Algarve | Serra-Pereira B.,Instituto Nacional Of Recursos Biologicos Ip Ipimar | Figueiredo I.,Instituto Nacional Of Recursos Biologicos Ip Ipimar
Journal of Fish Biology | Year: 2012

The present study is the first to provide data on the reproductive biology of cuckoo ray Leucoraja naevus in Portuguese continental waters. No difference in size at maturity was detected between sexes, which was estimated as 56 cm total length. Spawning occurs all year round, but maximum activity was during winter months. Maximum fecundity is c. 63 eggs female-1 year-1. Encapsulated eggs are released in batches, nine in total with a mean number of seven extruded eggs in each batch. © 2012 The Fisheries Society of the British Isles. Source

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