Coniath et al Age and growth of Mustelus cams 



675 



Year 



Figure 1 



Reported smooth dogfish landings from National Marine Fisheries Service com- 

 mercial catch statistics for the Atlantic and Gulf states, from 1981 to 2000. 



eries (MDMF). Total length (TL), precaudal length 

 (PCL), and male clasper length (CD were measured, 

 and sex was recorded at the time of collection. A 

 section of the vertebral column containing eight to 

 twelve vertebrae was removed from directly under 

 the first dorsal fin and stored frozen. Reproductive 

 samples were taken from smooth dogfish at this time 

 and maturity state was assessed from these samples. 



Vertebral samples were cleaned, soaked in 70% 

 ETOH for 24 hours, and air-dried for 24 hours. 

 Dried vertebrae were sagitally sectioned through 

 the focus with an Isomet rotary diamond saw ( Bue- 

 hler. Lake Bluff, IL). Afterwards, vertebral sections 

 were affixed to microscope slides with mounting 

 medium and polished with wet fine-grit sand paper 

 to a thickness of about 0.5 mm. The vertebrae were 

 viewed under a binocular dissecting microscope with 

 transmitted light. 



Vertebral radius was measured from the focus of 

 the vertebra along the axis of the corpus calcarium 

 to the edge of the vertebra (Fig. 2). Total length (TL) 

 was plotted against vertebral radius (VR) to deter- 

 mine if the growth of the vertebra was proportional 

 to somatic growth of the animal and whether the 

 structure was appropriate for estimating growth 

 rate of the animal. 



Growth patterns of the vertebrae consisted of wide 

 translucent bands separated by narrow opaque bands that 

 extended from the intermedialia to the corpus calcareum 

 (Fig. 2). An angle change — the result of a change in growth 

 rates at this time — was present in the intermedialia ap- 



Figure 2 



An age-.3■^ Mustelus canis vertebra, VR = vertebral radius, AC = 

 angle change denoting birthmark, 1, 2, 3 = age 1, 2, and 3 growth 

 bands, CC = corpus calcareum, and I = intermedialia. 



proximately 2 mm from the focus of each vertebra and 

 was considered to be a birthmark. Age was estimated by 

 enumerating the narrow opaque bands, which were con- 

 sidered to form annually owing to a slowing or stopping of 



