Maturation, fecundity, and spawning strategy of the thornback ray, Raja clavata: do reproductive characteristics vary regionally?
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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.
KeywordsLarge Follicle Gonad Weight Horn Length Oviducal Gland Portuguese Water
We would like to acknowledge Teresa Moura, Inês Farias, José Lago, Leonor Costa, Emanuel Pombal, and Paulo Castro from IPIMAR, for helping on sampling. We would like to thank Tom Blasdale for revising the English of the manuscript, and to the anonymous reviewers and editor Myron A. Peck for their valued suggestions for improvement. This study was partially supported by project EU Data Collection/, DCR (PNAB). B. Pereira was funded by the Fundação para a Ciência e a Tecnologia, SFRH/BDD/23777/2005 and by the project framework “Desarrollo sostenible de las pesquerías artesanales del Arco Atlántico” (PRESPO) of the INTERREG IVB Programme—Atlantic Arc (co-funded by the EU, ERDF Programme).
- Capapé C, Guélorget O, Siau Y, Vergne Y, Quignard J-P (2007) Reproductive biology of the thornback ray Raja clavata (Chondrichtyes: Rajidae) from the coast of Languedoc (Southern France, Northern Mediterranean). Vie Milieu 57:83–90Google Scholar
- Demirhan SA, Engin S, Seyhan K, Akamca E (2005) Some biological aspects of thornback ray (Raja clavata L., 1758) in the Southeastern Black Sea. Turk J Fish Aquat Sci 5:75–83Google Scholar
- Jardas I (1973) A contribution to our knowledge of the biology and ecology of thornback ray (Raja clavata L.) and brown ray (Raja miraletus L.) in the Adriatic. Acta Adriat 15:1–43Google Scholar
- Richards SW, Merriman D, Calhoun LH (1963) Studies on the marine resources of southern New England IX. The biology of the little skate, Raja erinacea. Bull Bingham Oceanogr Coll 18:5–67Google Scholar
- Serra-Pereira B, Figueiredo I, Gordo LS (2011) Application of a new reproductive terminology for teleosts to the maturation process of oviparous elasmobranchs–the case-study of the thornback ray, Raja clavata. Mar Coast Fish: Dyn Manag Ecosyst Sci 3:160–175. doi: 10.1080/19425120.2011.555707 CrossRefGoogle Scholar
- Sulikowski JA, Kneebone J, Elzey S, Jurek J, Danley PD, Howell WH, Tsang PCW (2005) The reproductive cycle of the thorny skate (Amblyraja radiata) in the western Gulf of Maine. Fish Bull 103:536–543Google Scholar
- Walker PA (1999) Fleeting images—dynamics of North Sea ray populations. PhD. Faculty of Biology, University of AmsterdamGoogle Scholar
- Zar JH (1996) Biostatistical analysis. Prentice-Hall, Englewood CliffsGoogle Scholar