Although differences between selective pressures in hatcheries
and streams have been theorized to cause genetic divergence between
hatchery and wild salmonids, evidence of this is lacking. This study
was initiated to document the presence or absence of genetic change
in hatchery and wild stocks by characterizing genetic traits in fish
of various life history stages within a single generation.
Nine biochemical traits (enzyme loci) and 12 meristic traits
were characterized for adult fall chinook and one or more juvenile
stages of their progeny of the 1984 brood year. Study groups
consisted of hatchery-reared and naturally-reared subunits of
populations in two tributaries of the lower Columbia River: Abernathy
Creek and the Lewis River. Parents of both groups from Abernathy
Creek were primarily of hatchery origin, whereas parents of both
groups from the Lewis River were primarily of wild origin. The
experimental design thus included reciprocal comparisons of hatchery and
wild-reared groups from each of two stocks: one that has been
propagated under hatchery conditions for at least five generations
and one that has evolved in a stream environment.
Both biochemical and meristic traits varied among adult and
juvenile stages within hatchery and wild groups. Changes in some of
these traits appear to have been caused by natural selection. This
was true even for Abernathy hatchery and Lewis wild groups, which
have been in the same environment for many generations. The
direction and/or degree of change in some biochemical and meristic
traits differed between hatchery and wild groups from a given stream,
suggesting that selective pressures of the hatchery and wild
environments differed in those cases. However, it could not be
determined from these data whether the observed divergence of traits
reflects general differences in hatchery and stream environments, or
if it reflects population-specific responses to site-specific
environmental conditions. The extent to which patterns of genetic
change within a single generation might vary among year classes or
generations is likewise unknown.
Evidence of temporal changes in biochemical and meristic traits
of hatchery and wild fish within a single generation has important
implications regarding the use of those traits to characterize
stocks. Assumptions of temporal stability of biochemical or meristic
traits within or between year classes should be applied with caution.
Sampling strategies of studies involving these characters should
account for the possibility of temporal heterogeneity. Finally,
these results suggest that workers using allozymes as genetic tags
should test the assumption of selective neutrality of the particular
allozyme markers being used. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37931 |
| Date | 12 March 1991 |
| Creators | Hulett, Patrick L. |
| Contributors | Schreck, Carl B., Li, Hiram W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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