Conrath et al : Age and growth of Mustelus cams 



681 



1992; Yamaguchi et al. 1996; Goosen and Smale, 1997). 

 Smooth dogfish growth coefficients are at the high end of 

 this range (A'=0.4399 for males and A'=0.2919 for females). 

 Mean asymptotic length of M canis is at the midrange of 

 reported L^ values for Mustelus species, which range from 

 L^ = 71.4. and 88.6 cm for male and female M. manazo 

 (Tanaka and Mizue, 1979) to L„=155.9 and 233.6 cm for 

 male and female M. antarcticus (Moulton et al., 1992). As 

 in nearly all accounts of age and growth for Mustelis spe- 

 cies, male and female growth in our study was virtually 

 identical in the first few years, and males have a higher 

 growth coefficient (A") than females due to a plateau in 

 growth at a much smaller size (Table 4). However, Fran- 

 cis and Francis (1992) found that female M. lenticulatus 

 grow faster than males but still reach a larger maximum 

 length. Their estimates were based on length-frequency 

 data and they acknowledged that the lack of large females 

 may have affected their estimates of von Bertalanffy 

 growth coefficients. 



Our growth coefficients for male and female smooth 

 dogfish were comparably high for a shark population; 

 previously reported K values ranged from 0.038 for dusky 

 sharks, Carcharhinus obscurus (Natanson et al., 1993) 

 to 1.337 for male Australian sharpnose sharks, Rhizo- 

 prionodon taylori (Simpfendorfer, 1993). Smooth dogfish 

 grow very quickly for a shark species and mature at a 

 relatively young age. These characteristics may make 

 the northwest Atlantic population more productive and 

 possibly more resilient to exploitation than many other 

 shark populations. 



Acknowledgments 



This project was supported by Wallop-Breaux funds 

 administered by the Virginia Marine Resources Commis- 

 sion. We thank the following individuals, organizations, 

 and vessel crews for their assistance in obtaining samples 

 for this project: J. Galbraith, H. McBride, V. Nordahl, N. 

 Shepherd. A. Howe, J. Loefer, G. Skomal, B. Falterman, R. 

 Kraus, D. Grubbs, K. Goldman, J. Romine, D. Ward, the 

 National Marine Fisheries Service Northeast Fisheries 

 Science Center survey crew, Massachusetts State Fisher- 

 ies survey crew, scientists at Grice Marine Laboratory and 

 the Massachusetts Division of Marine Fisheries, and the 

 crews of the RV Albatross IV. RV Gloria Michelle, and the 

 RV Bay Eagle. 



Literature cited 



Bigelow, H. B.. and W. C. Schroeder. 



1948. Sharks. In Fishes of the western North Atlantic, 

 part 1: lancelets, cyclostomes, and sharks (A. E. Parr and 

 Y. H. Olsen. eds. l. p. 244-254. Sears Found. Mar. Res. 

 Memoir 1 Yale Univ, New Haven, CT. 

 Casey, J. G., H. L. Pratt, and C. E. Stillwell. 



1985. Age and growth of the sandbar shark (Carcharhinus 

 plumbeus) from the western North Atlantic. Can. J. Fish. 

 Aquat. Sci. 42:963-975. 

 Castro, J. I. 



1983. The sharks of North American waters. 180 p. Texas 

 A&M Univ. Press. College Station, TX. 



