30 



Fishery Bulletin 98(1) 



B 



Figure 2 



Sagitta (specimen OB 764) from a fish tagged and injected in March 1994 at 57 cm FL and recaptured 

 in February 1997 at 111 cm FL. (A) Four increments were counted on the whole, burnt otolith and 

 measured from the primordium (P) to the beginning of each translucent zone apparent on the distal 

 surface along the postrostral axis at 2.2 mm, 3.6 mm, 4.4 mm, and 4.9 mm. (B) The sagitta was sec- 

 tioned through the postrostral axis and viewed in the SEM: the micrograph shows the strontium mark 

 which was located 3.4 mm from the primordium and the positions of the translucent zones measured 

 on the otolith before it was sectioned. Scale bars: 1 mm 



(calcite and celestite for Ca and Sr, respectively), with 

 the "WinEDS" software. 



Recapture rates of orange-tagged fish and recovery 

 of otoliths 



ResuKs 



Of the 20,204 fish injected with SrCl2 between 1990 

 and 1996, 9614 had been recaptured and 616 sets 

 of sagittal otoliths were recovered from these by 1 

 January 1996. Seventy sets of otoliths were chosen 

 for the validation study, selected from the range of 

 size classes in the recaptures — fish of 45 to 102 cm 

 FL at release and 57 to 133 cm FL at recapture — and 

 from the range of times at liberty. Age estimates 

 were made from 67 of the 70 otoliths; three sets of 

 otoliths were excluded from the experiment because 

 the increments on the whole otoliths were either 

 ambiguous or uninterpretable and the reader could 

 not give an age estimate with confidence. 



There were no statistically significant differences be- 

 tween the return rates of yellow tags (from fish not 

 injected with SrCL) and orange tags (from fish in- 

 jected with SrCl2) released in all years of the program 

 (X^=2. 10, P=0.56) nor between the return rates of yellow 

 tags and orange tags for any of the release years (Table 

 1). The number of otoliths recovered, as a percentage 

 of orange tags recaptured, varied between 20%, in the 

 first year of the tagging program, and 88% in the final 

 year (Table 3); overall, otoliths were recovered from 

 65% of the orange-tagged fish that were recaptured. 



Detection of Sr marks In the otoliths of orange-tagged fish 



The otoliths removed from fish injected with stron- 

 tium chloride typically showed a bright band in back- 



