Preprint volume - SIBM

Pre-print Volume –Posters
Topic 4: THE ELASMOBRANCHS
C. PORCU, A. MULAS, S. CABIDDU, A. GASTONI, M.C. FOLLESA
Department of Animal Biology and Ecology, University of Cagliari, Via T. Fiorelli, 1 - 09126 Cagliari, Italia.
cporcu@unica.it
REPRODUCTIVE BIOLOGY OF THE BLONDE RAY RAJA BRACHYURA
(CHONDRICHTHYES: RAJIDAE) IN SARDINIAN SEAS
BIOLOGIA RIPRODUTTIVA DI RAJA BRACHYURA
(CHONDRICHTHYES: RAJIDAE) NEI MARI SARDI
Abstract – The reproductive biology of Raja brachyura (Chondrichthyes: Rajidae) in Sardinian waters was
analysed. A total of 839 specimens (431 males and 408 females) were collected at depth of 30-175 m in
2005-2009. Females ranged from 131 to 1055 mm in Total Length and males from 156 to 965 mm. No
significant differences in size distribution among sexes were detected. Mature females and males were
found during spring and summer and from winter to summer respectively. Spent specimens were found in
all seasons except in autumn for females and spring for males.
Key-words: Rajidae, Raja brachyura, reproduction, Sardinian seas.
Introduction - The typical low fecundity and late maturity of rajid species make them
particularly vulnerable to fishing pressure and over exploitation. However, little is
known about their reproductive biology. The blonde ray Raja brachyura Lafont, 1873
shows a clear preference for sandy sea bottoms in the upper continental shelf (Serena,
2005). Generally, it is considered an uncommon species in the Mediterranean (Serena,
2005), but the observations from Follesa et al. (2003, 2010), Catalano et al. (2007) and
Ragonese et al. (2003) indicate that the Sardinian coasts and the western Sicily
represent a zone of the basin where R. brachyura is relatively abundant.
In the last years, few reproductive data were collected (Catalano et al., 2007). This
paper provides new and more complete information about the reproductive biology of
the blonde ray in the Sardinian seas (central western Mediterranean).
Materials and methods - Specimens of R. brachyura were caught during experimental
trawl surveys MEDITS and GRUND carried out between 30 and 175 m depth in 2005-
2009 in Sardinian waters. Each specimen was identified, measured (Total Length, TL
and Disc Width, DW, mm), and weighted (TW, g). The fishes were sexed following
the maturity scales of elasmobranchs reported in Relini et al., 2008. In males, the
length of the claspers (CL, mm) were recorded.
Results – The length distribution of the blonde ray showed a range in size between 131
and 1055 mm TL. The females (N=408) ranged between 131 and 1055 mm (329±147,
mean±SD), while the males (N=431) between156 and 965 mm TL (323±124,
mean±SD). No significant differences in size distribution among sexes were found
(Kolmogorov Smirnov, P>0.05).
The slope of the logarithmic relationship TW-TL among sexes was not significantly
different (t-test, P>0.01) (Tab. 1). At the same TL, females had higher DW than males
(linear relationship among sexes was found statistically different (t-test, P