Northwest Fisheries Science Center

Case Examples: Steelhead ID

Salmon eggs found near a dam.

Forensic evidence submitted: Unfertilized salmon eggs recovered near a dam were reported to be endangered steelhead.

Violation: Endangered Species Act (ESA) “take”

Techniques employed: DNA sequencing to identify species and mass spectrometry of stable isotopes to identify life history.

Oncorhynchus mykiss exhibit two distinct life histories: anadromous (steelhead) and fresh water residency (rainbow trout). Although these two life history types often co-occur, only the anadromous or marine-run type is protected under the Endangered Species Act. DNA species identification will verify species, but not life history type, therefore testing in addition to genetic analysis is required to ascertain if the fish (or the fish’s lineage) has a marine signature.

DNA analysis results: The eggs were from the species Oncorhynchus mykiss

Stable isotope results: Elevated carbon and nitrogen ratios are consistent with marine residence.

Stable isotope results Stable isotope results

This genetic database allowed the Forensics Unit to compare the relevant genes from the evidence against the baseline, and revealed that the some of the fish that were killed were indeed protected spring-run Chinook.


Schwenke, P. L., J. G. Rhydderch, M. J. Ford , A. R. Marshall, and L. K. Park. 2006. Forensic identification of endangered Chinook salmon (Oncorhynchus tshawytscha) using a multilocus SNP assay. Conservation Genetics The next link/button will exit from NWFSC web site 7:983–989.