680 



Fishery Bulletin 100(4) 



65 

 62.5 



60 

 57.5 • 



55 • 

 525 



50 • 

 47 5 • 



45  

 42 5  



40 

 37.5 



35 

 32 5  



30 



—  — Age 

 n = 150 



n=91 



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80 



78 



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Figure 7 



Seasonal growth for smooth dogfish. M. canis. Solid line and dashed line show mean size by 

 month of age-0 and age-1 animals (error bars are standard errorl, respectively. 



slightly older or younger than the reported maximum of 

 16 years for females and 10 years for males. 



The marginal increment analysis included only animals 

 of length less than or equal to the length of SC'f maturity; 

 therefore the annular nature of the growth bands was 

 verified for these length groups only. Although the mar- 

 ginal widths of the largest animals in the population were 

 too small to discern seasonal differences in these widths, 

 we assumed that these animals follow the same patterns 

 of growth throughout their lifespan. 



Estimates of seasonal growth indicated that animals in 

 this population experience a plateau in growth during the 

 winter months between October and February or March, 

 at least for the first two years of life. Their major period of 

 growth is during the summer, between March and Octo- 

 ber. This finding supports the well established conclusion 

 that an opaque band is deposited annually at the time of 

 slowing or cessation of growth during the winter months. 

 Resuming a faster growth rate after February or March 

 supports the conclusion that a growth band becomes vis- 

 ible in the months of April or May. 



Moss ( 1972) constructed von Bertalanffy growth curves 

 for smooth dogfish by relating tooth width to body length. 

 He estimated that smooth dogfish mature after about one 

 year and reach their maximum size in seven to eight years. 

 He acknowledged that his estimated growth curve did not 

 account for variation in tooth replacement rate and sea- 



sonal differences in body growth rate. Francis ( 1981) esti- 

 mated von Bertalanffy growth rates by extrapolation from 

 embryonic growth rates using Holden's ( 1974) method, but 

 this method has subsequently been discredited for appli- 

 cation to sharks by Pratt and Casey ( 1990). 



Rountree and Able ( 1996) used length-frequency analy- 

 sis to determine growth rates in young of the year (YOY) 

 smooth dogfish in a New Jersey estuary YOY animals born 

 in May at 29-38 cm TL reached 55-70 cm TL by October 

 of the same year. We found a slightly slower growth rate; 

 age-0 animals in October 1999 ranged from 53-60 cm with 

 a mean size of 56.3 cm (7!=6, SE=1.31). We found smooth 

 dogfish grew to a mean of 66.5 cm TL in their first year 

 (size range 61-69 cm, mean size of estimated age-1 May 

 captures, n = 13, SE=0.924). The majority of smooth dogfish 

 used in this study were collected in Virginia and North 

 Carolina; therefore geographical differences in growth or 

 differences in growth between years may have contributed 

 to the small discrepancy between our results and those of 

 Rountree and Able. 



Values of K reported from various Miistelus species 

 (Table 4) ranged from 0.1 for male Mustelus lenticulatus 

 from Pegasus Bay, New Zealand, to 0.695 for male Muste- 

 lus manazo. and from 0.049 for female Mustelus antarcti- 

 cus to 0.42 for female Mustelus lenticulatus from Hauraki 

 Gulf, New Zealand (Tanaka and Mizue, 1979; Yudin and 

 Cailliet, 1990; Francis and Francis, 1992; Moulton et al., 



