Spatial patterns of hybridization between bull trout, <Emphasis Type="Italic">Salvelinus confluentus</Emphasis>, and brook trout, <Emphasis Type="Italic">Salvelinus fontinalis</Emphasis> in an Oregon stream network |
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Authors: | Patrick W DeHaan Lawrence T Schwabe William R Ardren |
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Institution: | (1) U.S. Fish and Wildlife Service, Abernathy Fish Technology Center, 1440 Abernathy Creek Road, Longview, WA 98632, USA;(2) Burns Paiute Tribe, 100 Pasigo St., Burns, OR 97720, USA;(3) Present address: The Confederated Tribes of Grand Ronde, Natural Resources Division, 47010 SW Hebo Rd., P.O. Box 10, Grand Ronde, OR 97347, USA;(4) Present address: U.S. Fish and Wildlife Service, Western New England Complex, 11 Lincoln St., Essex Junction, VT 05452, USA |
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Abstract: | Hybridization with introduced species represents a serious threat to the persistence of many native fish populations. Brook
trout (Salvelinus fontinalis) have been introduced extensively throughout the native range of bull trout (S. confluentus) and hybridization has been documented in several systems where they co-exist and is seen as a significant threat to the
persistence of bull trout populations. We identified a group of diagnostic microsatellite loci to differentiate bull trout
and brook trout and then used these loci to examine the spatial distribution of hybrids in the Malheur River basin, Oregon
USA. In random samples of approximately 100 fish from each of three creeks we identified 181 brook trout, 112 bull trout and
14 hybrids. Although bull trout, brook trout and hybrids were found in all three creeks, they were not evenly distributed;
brook trout were primarily found in the lower sections of the creeks, bull trout further upstream, and hybrids in the areas
of the greatest overlap. One creek with a population of brook trout in a headwater lake provided an exception to this pattern;
brook trout were found distributed throughout the creek downstream of the lake. Several post-F1 hybrids were identified suggesting
that hybrids are reproducing in the Malher River Basin. Mitochondrial DNA analysis indicated that both female bull trout and
brook trout are involved in hybridization events. Analysis of population structure suggested that brook trout have established
multiple spawning populations within the Malheur system. Data presented in this study suggest that relative abundance of brook
trout and habitat quality are important factors to consider when evaluating the threat of hybridization to bull trout populations. |
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