Effect of analytical conditions in wavelength dispersive electron microprobe analysis on the measurement of strontium-to-calcium (Sr/Ca) ratios in otoliths of anadromous salmonids udud

摘要

The use of strontium-to-calcium (Sr/Ca) ratios in otoliths is becoming a standard method to describe life history type and the chronology of migrations between freshwater and seawater habitats in teleosts (e.g. Kalish, 1990; Radtke et al., 1990; Secor, 1992; Rieman et al., 1994; Radtke, 1995; Limburg, 1995; Tzeng et al. 1997; Volk et al., 2000; Zimmerman, 2000; Zimmerman and Reeves, 2000, 2002). This method provides critical information concerning the relationship and ecology of species exhibiting phenotypic variation in migratory behavior (Kalish, 1990; Secor, 1999).udMethods and procedures, however, vary among laboratories because a standard method or protocol for measurement ofudSr in otoliths does not exist. In this note, we examine the variations in analytical conditions in an effort to increase precision of Sr/Ca measurements. From these findings we argue that precision can be maximized withudhigher beam current (although there is specimen damage) than previously recommended by Gunn et al. (1992).