Using Oxygen Isotope Fractionation (delta-18O) in Otoliths to Characterize the Temperature History of Fall Chinook Salmon
EMSL Project ID
47394
Abstract
Fall Chinook salmon in the Snake River are listed as threatened under the Endangered Species Act. A potential factor limiting their recovery is the impact from hydropower generation on river temperature during adult migration and spawning. Evidence suggests that higher river temperatures arising from anthropogenic effects can reduce reproductive success in salmon, but the upper thermal tolerance for final maturation and spawning in this population has not been determined, in part because the actual temperatures experienced by these fish from freshwater entry to spawning have not been documented. We propose to address these questions by measuring the abundance of naturally occurring isotopes of oxygen in otoliths (ear bones) obtained adult fall Chinook salmon in the Snake River. Otoliths are composed of primarily of calcium carbonate and incorporate elements such as oxygen during growth that provide a permanent record of the water chemistry history of the fish. Oxygen is a useful measure of temperature history because it precipitates in calcium carbonate structures at or near equilibrium with the oxygen isotope ratio of the ambient water, which is temperature dependent. Thus, if the temperature dependent fractionation of oxygen isotope ratios in both the otolith and water are known, oxygen can be used to describe temperature history. We will characterize the temperature history of adult fall Chinook salmon by measuring oxygen isotope ratios (?18O) that accrete on a daily basis in juvenile and adult Chinook salmon using secondary ion mass spectrometry (SIM). Daily otolith increment width will also be measured by electron microscopy (FIB-SEM) to determine the spatial-temporal resolution of the SIM instrument. Analysis of ?18O fractionation in otoliths from juvenile fish reared at known constant temperatures will allow us to construct a species specific temperature– ?18O fractionation relationship for use on otoliths from adult fall Chinook salmon, which were collected in 2011. The temperature history for these fish from passage at Bonneville Dam through spawning will be determined using their otolith ?18O values and the temperature– ?18O fractionation relationship developed from the laboratory study. The estimated adult temperatures will be confirmed from tag data for known passage dates at Columbia and Snake River dams where river temperatures were recorded and by back-calculation from the daily growth increments in the otoliths.
Project Details
Project type
Exploratory Research
Start Date
2012-03-15
End Date
2013-03-24
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Linley, T., E. Krogstad, K. Carter, and M. Nims. 2014. Geochemical Analysis of Fin Rays to Identify Spring-Run Chinook Salmon Populations in the Wenatchee Basin Using Inductively Coupled-Mass Spectrometry. Final Report to the Priest Rapids Coordinating Committee. Report No. PNWD-4412. 32 p.