32 



Fishery Bulletin 98(1) 



B 



Figure 4 



SEM micrographs of a carbon-coated whole etched otolith of specimen OB 127, showing 

 the position of the strontium mark and the check associated with tagging and injection. 

 The dotted line (B) indicates the axis along which the position of the strontium mark was 

 measured in relation to the primordium and the postrostrum. Scale bars: 1 mm (A and B), 



0.1 mm(C). 



features on the whole otolith when increments were 

 counted. We could not identify Sr marks on vertebral 

 sections from fish injected with SrCl2. 



The presence of strontium in the bright bands was 

 demonstrated by EDS spectra, which showed a strong 

 peak of strontium Lor x-rays when, the electron beam 



was directed to the Sr mark, in contrast with very low 

 (background) levels in the regions of the otolith pre- 

 ceding the mark (Fig. 5). The relative levels of stron- 

 tium and calcium in the bright band were further con- 

 firmed by inspection of the difference spectrum ob- 

 tained by subtracting a spectrum acquired in the area 



