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Turkish Journal of Fisheries and Aquatic Sciences 2014, Vol 14, Num, 1     (Pages: 193-204)

Age, Growth, Mortality, Longevity and Reproductive Biology of the White Skate, Rostroraja alba (Chondrichthyes: Rajidae) of the Gulf of Gabès (Southern Tunisia, Central Mediterranean)

Hasna Kadri 1 ,Sondes Marouani 1 ,Mohamed Nejmeddine Bradai 1 ,Abderrahmen Bouaïn 2 ,Eric Morize 3

1 Institut National des Sciences et Technologies de la Mer, Centre de Sfax, B.P. 1035, Sfax 3018, Tunisie
2 Faculté des Sciences de Sfax, Sfax, Tunisia
3 Lemar/ IRD 230 Broennou, 29870 Landéda France
DOI : 10.4194/1303-2712-v14_1_21 Viewed : 1304 - Downloaded : 1313 The Age, growth, mortality, longevity and reproductive parameters were studied for Rostroraja alba from the Gulf of Gabès (Southern Tunisia, central Mediterranean Sea), collected monthly during 2007 from commercial fisheries. 43.75% of the composition was females and 56.25% males. A total of 140 females (44.5-160 cm TL) and 180 males (39.5-150 cm TL) were examined to study the reproductive cycle. A subsample of 115 specimens (65 females and 50 males, ranging from 39.5 to 160 cm TL) was used for age and growth estimation derived from vertebral centra.

The oldest female was 35 years and 160 cm TL, whereas the oldest male was 32 years and 150 cm TL. The von Bertalanffy growth parameters were L∞= 177.6±3.61 cm, k= 0.06±3.08 year-1 and t0= -1.28±1.97 10-1 year for females and L∞= 199.6±3.66 cm, k= 0.04±1.9610-3 year-1 and t0= -1.47±0.35 10-1 year for males. Growth was not significantly different between sexes.

The maturity size (TL 50%) was 119.3 cm (94.20 cm DW) for males and 129.4 cm (95.77 cm DW) for females. The maturity age (A50%) was estimated to 19.69 and 23.47 years respectively for males and females. Size and age maturity were not significantly different between sexes. Keywords : Rostroraja alba, age, growth, reproduction, Gulf of Gabès, Mediterranean Sea