Peres and Vooren: Sexual maturation, reproductive cycle, and fecundity of Galeorhinus galeus 



657 



Results 



Spatial and 

 temporal distribution 



School sharks were seasonally abun- 

 dant at depths of 40-350 m, be- 

 tween latitudes 32°S and 34°30'S. 

 In this area, mean catch rates per 

 cruise were high from June to Sep- 

 tember, attaining values up to 376 

 kg/hour at depths between 40 and 

 100 m, and 620 kg/hour between 100 

 and 350 m. Figure 1 shows the sam- 

 pling grid and catches for August 

 1983 and 17 July- 17 September 

 1986. Within the study area, the en- 

 tire area of distribution was covered 

 by the sampling grid. 



The species was scarce in April, 

 May, October, and November, and 

 absent in January and February. 

 The school shark is characterized as 

 a seasonal migrant, entering the 

 study area in autumn, attaining 

 peak abundance during winter, and 

 leaving in spring. 



Sexual development and 

 organization of gametes 

 in the male 



Sexual maturation of the male was 

 inferred from the length of the 

 clasper. The relationship between 

 clasper length and total length was 

 sigmoid (Fig. 2). The curve rose 

 steeply between 85 and 117cm TL, 

 and dispersion was greatest in this 

 range. The curve flattened out for 

 clasper lengths greater than 10.5 

 cm. This latter value was taken as 

 the lower limit for sexual maturity. 

 On the basis of this criterion, sex- 

 ual maturation began at 85cm TL. 

 The smallest mature male measured 

 was 107cm TL, 50% maturity oc- 

 curred at 111cm, and all males 

 greater than 117 cm were mature. 

 The clasper of the adult measured, 

 on average, 12.0 cm, ranging from 10.5 to 14.0cm. 

 Potential equations described adequately the rela- 

 tionship of gonad and epigonal organ weight to total 

 length (Fig. 3, Table 1). At total lengths less than 85 



90 100 110 



TOTAL LENGTH(cm) 



Figure 2 



Relationship between total body length and length of clasper in the school shark Galeo- 

 rhinus galeus, from Rio Grande do Sul, Brazil. Points indicate the mean, and ver- 

 tical lines the range for length-class intervals of 1cm. 



cm, gonad weight was similar to the weight of the 

 epigonal organ, and testes were not visually evident. 

 Between 85 and 140 cm TL, epigonal organ increased 

 from 10 to 30 g, and gonad weight increased to an 



