Carlson and Baremore: Growth dynamics of Corcharhinus brevipmna 



281 



Figure 1 



Map of the sampling area for spinner sharks iCarcharhinus brevipinna) showing areas and locations 

 stated in the text. 



length was measured as a straight line from the tip of 

 the snout to the tip of the tail in a natural position. The 

 weight (kg) of each shark was obtained when sampling 

 conditions permitted. Vertebrae were removed from an 

 area anterior to the first dorsal fin. 



Vertebral sections were placed on ice after collection 

 and frozen upon return to the laboratory. Thawed ver- 

 tebrae were cleaned of excess tissue and soaked in a 5% 

 sodium hypochlorite solution for 5-30 min to remove 

 remaining tissue. After cleaning, vertebrae were soaked 

 in distilled water for 30 minutes and stored in 959f 

 isopropyl alcohol. Prior to examination, one vertebra 

 from each shark was chosen at random, removed from 

 alcohol, and dried. The vertebra was fixed to a clear 

 glass slide with resin and sectioned with a Buehler 82 

 Isomet low-speed saw. 



Sagittal sections of different thicknesses were cut 

 from the vertebral centrum and stained with crystal 

 violet, or alizarin red, or left unstained according to 

 the methods of Carlson et al. (2003). Each vertebral 

 section was mounted on a glass microscope slide with 

 ProTex cytoseal (Lerner Laboratories, Pittsburg, PA) 

 and examined by using a dissecting microscope under 

 transmitted light. The banding pattern was found to 



be most apparent on unstained sagittal sections with a 

 thickness of 0.3 mm. 



Opaque bands representing summer growth and 

 translucent bands representing winter growth were 

 identified following the description and terms in Cail- 

 liet and Goldman (2004) (Fig. 2). Because no validation 

 is available for this species, verification of the annual 

 period of band formation was performed by using the 

 relative marginal increment analysis (Branstetter and 

 Musick, 1994; Natanson et al., 1995): 



MIR = {VR-R n )l{R n -R n _ 1 ), 



where MIR = the marginal increment ratio; 

 VR = the vertebral radius; 

 R n = distance to the outer edge of the last 

 complete band; and 

 R n _i = distance to the outer edge of the next-to-last 

 complete band. 



Mean MIR was plotted against month to determine 

 trends in band formation. A single factor analysis of 

 variance was used to test for differences in arcsine- 

 transformed (Zar, 1984) MIR data among months. 



