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An
Evaluation of the Reproductive Success of Natural-Origin, Hatchery-Origin
and Kelt Steelhead in the Columbia Basin
Abstract |
We conducted
a field study to investigate the reproductive success of hatchery,
wild, and artificially reconditioned kelt steelhead. Three sites (Omak
Creek, WA; Section Corner Creek, WA; and Shitike Creek, OR) were chosen
to provide replicates to evaluate reproductive success of Oncorhynchus
mykiss. Potential adults and progeny were sampled in each drainage
and genotyped with 16 microsatellite loci to determine parentage.
In Omak Creek, two of three reconditioned kelts released in fall of
2005 returned in 2006. If they successfully reproduced, their progeny
should be detectable in 2007 and 2008. Genetic evidence supports the
presence of distinct resident and anadromous populations in Omak Creek.
The combination of population and parentage assignment tests showed
that Mission Falls may be a genetic barrier limiting the passage of
adult steelhead. Twelve of the 21 juveniles sampled above Mission
falls in 2005 were assigned to the anadromous population whereas no
fish sampled above the falls in 2006 were assigned to the anadromous
population. This may be the result of a velocity barrier at Mission
Falls resulting from high water flows in 2006 but not in 2005.
In Section Corner Creek, all juveniles sampled were assigned to a
single parental cross based on genetic identity and parentage analysis.
Brood year 2005 juveniles were sampled as both fry in 2005 and parr
in 2006 and matched to adults released in Section Corner Creek in
2005. Six female and five male parents contributed to the progeny
sampled in each year. While the same fish contributed each year, there
was a significant difference between the yearly distribution of progeny
assigned to each individual. This difference was largely due to the
differential survival or migration of progeny between females. Fewer
adults contributed to reproduction in 2006 with only two females and
two males contributing to the fry sampled. None of the kelt females
were identified as parents of juveniles collected in either year,
likely due to problems with rematuration timing during reconditioning.
Further research is being completed to determine environmental cues
and dietary needs of reconditioned kelts.
In Shitike Creek, juveniles collected at the screwtrap were not successfully
assigned to any of the potential anadromous parents. It is apparent
that the sampled juveniles were not progeny of the anadromous population.
Analysis of allele frequencies showed that the juveniles that were
sampled in 2006 are more similar to and likely progeny of, the resident
population in Shitike Creek. However, parentage analysis was not possible
as the resident population is large and the majority of resident adults
were not sampled. Juvenile sampling protocols will be expanded in
2007 to help identify anadromous progeny. |
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