84 



Fishery Bulletin 101(1) 



tially in length following the .shift) to reliably fit a second 

 regression line. The back-calculation equation used in our 

 study does not employ the linear regression in its calcula- 

 tions and was minimally affected by the negative bias that 

 this phenomenon had on the slope of the regression. 



Marginal increment analysis in the present study in- 

 dicated that growth increments form in summer. This 

 finding is contrary to that of earlier studies on R. ter- 

 raenovae, which indicated winter deposition (Parsons, 

 1985; Branstetter and McEachran, 1986; Branstetter 

 1987a). However, other species in this genus have been 



shown to deposit increments during the summer months. 

 Simpfendorfer (1993) demonstrated summer (February) 

 increment deposition in R. taylori in Australian waters. 

 He cited stress during the breeding season as a possible 

 cause because hepatosomatic index and condition factor in 

 both sexes were low during the mating season, an indica- 

 tion of probable stress. Furthermore, growth increments 

 in elasmobranchs may reflect periods of slow calcareous 

 accretion that have been compressed by increased growth 

 (Gelsleichter, 1998). This pattern of deposition may result 

 in increments from periods ol' slow growtii not becoming 



