Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 5368
Title: Vulnerability of marked age-0 steelhead to a visual predator
Author: Desmond J. Maynard, D. A. Frost, F. William Waknitz, Earl F. Prentice
Publication Year: 1996
Journal: Transactions of the American Fisheries Society
Volume: 125
Issue: 2
Pages: 330-333

The assumption that marking does not alter the vulnerability of fish to a visual predator was examined.  Equivalent numbers of age-0 steelhead (Oncorhynchus mykiss) were binary coded-wire tagged, PIT-tagged, freeze branded, fingerling-tagged, or left untagged, and all were challenged to survive predation by age-l steelhead.  These challenges were conducted for 24 h in 2.4-m diameter circular tanks filled with clear well water.  Twice as many marked as unmarked age-0 steelhead prey were cannibalized.  There was no significant survival difference among the four marked treatment groups, which suggested that the trauma associated with marking is more important than mark type.  These results, and reviews of previous studies, indicate that researchers should assume marking affects survival until experimentally demonstrated otherwise.   

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Notes: Author's original manuscript available