Migration and rearing histories of chinook salmon (Oncorhynchus tshawytscha) determined by ion microprobe Sr isotope and Sr/Ca transects of otoliths

• Published in: Canadian journal of fisheries and aquatic sciences 2004-12, Vol.61 (12), p.2425-2439
• Main Authors: Bacon, Charles R, Weber, Peter K, Larsen, Kimberly A, Reisenbichler, Reginald, Fitzpatrick, John A, Wooden, Joseph L
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Animal and plant ecology; Animal migration; Animal, plant and microbial ecology; Animals; Applied ecology; Autoecology; Biological and medical sciences; Brackish; Chemical analysis; Downstream; Estuaries; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fish; Fresh water; Freshwater; Fundamental and applied biological sciences. Psychology; Geology; Isotopes; Marine; Oncorhynchus tshawytscha; Otoliths; Rivers; Saline water; Salmon; Salts; Seasonal variations; Seawater; Spring; Strontium; Vertebrata; Water analysis; Watersheds
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f04-167

Strontium isotope and Sr/Ca ratios measured in situ by ion microprobe along radial transects of otoliths of juvenile chinook salmon (Oncorhynchus tshawytscha) vary between watersheds with contrasting geology. Otoliths from ocean-type chinook from Skagit River estuary, Washington, had prehatch regions with 87 Sr/ 86 Sr ratios of ~0.709, suggesting a maternally inherited marine signature, extensive fresh water growth zones with 87 Sr/ 86 Sr ratios similar to those of the Skagit River at ~0.705, and marine-like 87 Sr/ 86 Sr ratios near their edges. Otoliths from stream-type chinook from central Idaho had prehatch 87 Sr/ 86 Sr ratios ≥0.711, indicating that a maternal marine Sr isotopic signature is not preserved after the ~1000- to 1400-km migration from the Pacific Ocean. 87 Sr/ 86 Sr ratios in the outer portions of otoliths from these Idaho juveniles were similar to those of their respective streams (~0.708–0.722). For Skagit juveniles, fresh water growth was marked by small decreases in otolith Sr/Ca, with increases in Sr/Ca corresponding to increases in 87 Sr/ 86 Sr with migration into salt water. Otoliths of Idaho fish had Sr/Ca radial variation patterns that record seasonal fluctuation in ambient water Sr/Ca ratios. The ion microprobe's ability to measure both 87 Sr/ 86 Sr and Sr/Ca ratios of otoliths at high spatial resolution in situ provides a new tool for studies of fish rearing and migration.