Distinguishing between natural and hatchery Snake River fall Chinook salmon subyearlings in the field using body morphology

Transactions of the American Fisheries Society
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Abstract

We used body morphology to distinguish between natural- and hatchery-origin subyearling fall Chinook salmon Oncorhynchus tshawytscha in rearing areas of the Snake River and at a downstream dam during seaward migration. Using subjective eye and body shape characteristics, field personnel correctly classified 88.9–100% of natural subyearlings (N = 626) and 90.0–100% of hatchery subyearlings (N = 867) in rearing areas from 2001 to 2008. The morphological characteristics used by these personnel proved to have a quantitative basis, as was shown by digital photography and principal components analysis. Natural subyearlings had smaller eyes and pupils, smaller heads, deeper bodies, and shorter caudal peduncles than their hatchery counterparts during rearing and at the dam. A discriminant function fitted from this set of morphological characteristics classified the origin of fish during rearing and at the dam with over 97% accuracy. We hypothesize that these morphological differences were primarily due to environmental influences during incubation and rearing because it is highly probable that a large portion of the natural juveniles we studied were the offspring of hatchery × hatchery mating in the wild. The findings in this paper might provide guidance for others seeking to differentiate between natural and hatchery fish.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Distinguishing between natural and hatchery Snake River fall Chinook salmon subyearlings in the field using body morphology
Series title Transactions of the American Fisheries Society
DOI 10.1080/00028487.2011.545003
Volume 140
Issue 1
Year Published 2011
Language English
Publisher Taylor & Francis
Contributing office(s) Western Fisheries Research Center
Description 10 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Transactions of the American Fisheries Society
First page 21
Last page 30