Smale and Goosen: Reproduction and feeding of Trlakls megalopterus 



995 



of a wide range of sizes, and there was a significant 

 linear relation between crab carapace width and to- 

 tal length of sharks (r=0.37, P<0.05, n=39; Fig. lOA). 

 Limited numbers of teleosts made analysis difficult. 

 Combined data for two species (Cheilodactylus pixi 

 and Diplodus sargus) showed a significant relation 

 between the lengths of prey and sharks (r=0.97, 

 P<0.01; n=l; Fig. lOB). The sample size of other prey 

 species was too small to make similar analyses. 



Discussion 



Depth range 



This study confirmed earlier reports that T. mega- 

 lopterus prefers shallow rocky reefs (Bass et al., 1975; 

 Compagno et al., 1989, 1991). They were found very 

 rarely in deep waters, despite extensive sampling in 

 deep waters for a variety of other sharks, including 

 the closely related Mustelus species (Smale, 1991; 

 Smale and Compagno, 1997). The nature of the 

 samples precluded precise determination of intraspe- 

 cific habitat choice, but there were no obvious differ- 

 ences in habitat choice by sharks of different sizes. The 

 skewed sex ratio, which needs further investigation, 

 may be due to sampling bias or social factors. 



Reproduction 



In T. megalopterus, eggs produced by the single func- 

 tional ovary pass through the oviducal gland, where 

 they are probably fertilized before they are enclosed 

 in the membranous egg case. Embryonic development 

 -is ovoviviparous, embryos receiving nourishment 

 from the yolk sac. However, some egg cases were 

 slightly adherent and others intimately connected 



600 



o Juvenile 



800 



1.600 



1,000 1,200 1,400 

 Predator length (mm) 



Adolescent • Mature * Pregnant 



E 



£ 300 



■5 250 



J 200 - 



1 150 - 



i 100 



S 50 



B 



600 



800 



1,000 1.200 1.400 1,600 

 Predator length (mm) 



• Cheilodacn'ltis pixi A Diplodus sargus capensis 



Figure 10 



Relation between prey size and predator length. (A) 

 Plagusia chabrus carapace width (CW) plotted against 

 predator length. CW = 25.1 + 0.014 x TL (r=0.37, f!=39). 

 (B) Total lengths of two teleosts plotted against total length 

 of the predator The linear relation had the form TL (prey) = 

 -41.94 + 0.176  TL (predator) (r=0. 97, n=l). 



to the uterus wall. There was no evidence of the yolk 

 sac forming a placental attachment at later stages 

 of development, supporting Compagno's ( 1984) sum- 

 mary of the genus. 



The size at which 50% of male sharks are mature 

 is equivalent to mean size at maturity (Lenanton et 

 al., 1990). Data from the present study indicated that 

 males mature at approximately 1320 mm. Compagno 

 (1984) estimated that males mature at 1300-1400 

 mm. On the basis of width of the oviducal gland and 

 the diameter of the uterus and eggs, females begin to 

 mature at about 1391 mm, and 507f maturity is 

 achieved at about 1450 mm; all females larger than 

 1500 mm are mature. Compagno ( 1984) estimated that 

 females mature between 1400 and 1500 mm and re- 

 ported mature females of 1400-1740 mm. In this study, 

 50^^ maturity of female sharks is attained at about 1450 

 mm, which represents 70% of the maximum size ob- 

 served, 2075 mm. This size falls within the range of 

 60%-90% noted by Holden and Raitt ( 1974). The small- 

 est pregnant female measured 1465 mm. 



Gestation in sharks is usually 10-12 mo and pro- 

 longed gestation periods are apparently rare, al- 

 though Squalus acanthias has a gestation period of 



