Production, Maturity, Reproductive Cycle and Fecundity of Small-Spotted Catshark, Scyliorhinus canicula (Chondrichthyes: Scyliorhinidae) from the Northern Coast of Tunisia (Central Mediterranean)

摘要

Small-spotted catshark Scyliorhinus canicula (Linnaeus, 1758) is confronted since 2000 to a dras tic decline of captures in Tunisian northern areas where it formerly was quantitatively and qualitatively very abundant A study conducted in the area showed that males and females sexually matured between 400— 478 mm and 364-471 mm total length (7X), respectively The largest male and female were 521 mm and 531 mm TL respectively and weighed 449 and 445.5 g, respectively There was a not significant relationship total mass vs TL between males and females. Conversely, the relationship of liver mass vs. TL significantly differed between sexes. Both HSI and GSI values did not present significant differences between males and females. There was a not significant relationship total mass vs. TL between males and females. Both rnale and female HSI reached high values in adults, significantly higher than those of sub-adults. Both male and female GSI values increased with TL of specimens; additionally, they showed significant differences between juveniles and sub-adults and also between sub-aduhs and adults. The OSI values were significantly different between juvenile and sub-aduh females, and also between sub-adult and adult females. Monthly mean values of adult male and female HSI did not significantly vary throughout the year. Significant monthly changes were recorded in mean values of adult male however no significant changes were observed in monthly mean of GSI and OSI for adult females. Vitellogenic activity and production of egg cases permanently occurred throughout the year. The diameter of largest yolky oocytes ranged from 20.1 to 23.0 (mean = 21.43 ± 1.0^ and weighed from 0.64 to 0.90 g (mean = 0.78 ± 0.09). Some measurements were taken on egg case