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African Journal of Marine Science

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Life history and diet of two southern African smoothhound sharks, mustelus mustelus (linnaeus, 1758) And mustelus palumbes smith, 1957

MJ Smale, lJV Compagno

Abstract


Aspects of the life history and biology of two sympatric coastal shark species (Mustelus mustelus and M. palumbes) off southern Africa are described and compared. Free-swimming male M. mustelus measured
390–1 450 mm total length (TL), whereas females were recorded up to 1 650 mm TL. Most specimens of both sexes were found at depths shallower than 100 m. Males mature at 950–1 300 mm TL and females at
1 250–1 400 mm TL. Reproduction is seasonal, and each cycle may take one year or longer, if there is a resting period between pregnancies. Litter size was correlated with female size and varied between 2 and 23. The
largest embryo measured 425 mm TL. The hepatosomatic indices were negatively correlated to embryo length in both species. Prey was dominated by crustaceans, although cephalopods became important in larger M. mustelus. There was a good relationship between prey size and fish size. Free swimming male M. palumbes measured 275–1 008 mm TL, whereas females were recorded up to 1 126 mm TL. M. palumbes males were most often taken from 100–180 m deep and females from 60–140 m. Males mature at 750–850 mm TL and females at 800–100 mm TL. Reproduction appears to be aseasonal in M. palumbes and litters of 3–15 young were recorded, with larger females having larger litters. The largest embryo recorded measured 340 mm TL.The timing of reproductive cycles could not be established, but a high proportion of non-pregnant females
suggests that there may be a resting period following pregnancy. Crustaceans were the dominant prey type recorded, although larger predators ate a wider variety of prey types than smaller individuals. Although there was overlap in the prey taken by the two shark species, the composition of the diet was strongly influenced by the prey available in different habitats.



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