Using Pedigree Analysis to Evaluate a Reintroduced Chinook Salmon Population in Newsome Creek, Idaho

The Clearwater River in the Snake River Basin historically supported large spawning populations of Chinook salmon (Oncorhynchus tshawytscha); however, extirpation occurred throughout the basin following construction of the Lewiston Dam in 1927.  Hatchery reared spring Chinook salmon have been released in many Clearwater tributaries since 1971.  These populations are not considered wild because they were derived from reintroduction efforts, but progeny of fish spawning in the natural environment (instream) are designated as natural-origin. The Nez Perce Tribe is conducting an extensive monitoring and evaluation effort throughout the Clearwater River Sub-basin, with specific long term goals that include estimating the genetic effects of interactions between natural- and hatchery-origin populations, and evaluating demographic effects such as naturalization resulting from supplementation. The NPT Hatchery employs a Natural Rearing System technique designed to produce fish behaviorally, physiologically and genetically similar to natural populations.  Newsome Creek, a tributary to the South Fork Clearwater River, receives hatchery outplanted fish (directed supplementation).  A proportion of both marked and unmarked fish returning to Newsome Creek are collected for broodstock with the remainder passed upstream of an exclusionary weir.  We conducted a preliminary evaluation in 2009 using genetic pedigree analysis to assess relative reproductive success (RRS) in Newsome Creek.  We observed similar productivity between hatchery and natural-origin (or naturalized) fish.  Our current efforts are directed at expanding this evaluation and verifying preliminary findings across multiple generations.  This will include genetic detection of returning adult progeny and potential RRS in the F2 generation. Fish have been sampled from among adult returns (n= 654) and juvenile outmigrants (n=747) between brood years 2002-2010.  All collections have been genotyped at a suite of 15 microsatellite loci.  Parent-progeny trios will be assigned using full exclusion and likelihood based procedures.  Managers will be provided with the RRS results as part of ongoing M&E that may infer local adaptation and naturalization of a reintroduced species into its former historic range.