Otolith chemistry reflects migratory characteristics of Pacific salmonids:Using otolith core chemistry to distinguish maternal associations with seaand freshwaters

Experimental crosses with coho, sockeye, and chinook salmon showed that oto lith core strontium concentrations reflected maternal associations with fre sh and sea water. Fry spawned by females maturing in sea water had otolith Sr/Ca values roughly four times greater than those from their freshwater co unterparts, indicating that otolith core strontium is an effective natural marker for captive brood stock programs where fish are raised to maturity i n freshwater. Anadromous and freshwater resident salmonid populations were also distinguishable on the basis of otolith core strontium levels, but cas e studies illustrate that some freshwater systems may have strontium levels high enough to blur the distinction between sympatric progeny from anadrom ous and non-anadromous salmonids. Among a number of wild and hatchery anadr omous salmon populations, a trend in otolith core Sr/Ca reflected the typic al time of entry to freshwater and stage of egg development for migrating f emales. (C) 2000 Elsevier Science B.V. All rights reserved.