Biologists have found that the reintroduction efforts of a
little known fish – the Oregon chub –resulted in a genetically diverse
population of the fish in the Willamette Valley, according to a recent study.
The Oregon chub plays an important role in the floodplain
ecosystem in the Willamette River Basin as an important food source for predators,
including both birds and mammals, according to corresponding researcher, Pat
DeHaan, fish biologist with the U.S. Fish and Wildlife Service at the Abernathy
Fish Technology Center in Longview, WA.
Once listed as endangered, the Oregon chub became the first
fish species to be removed from the federal Endangered Species list after all
of its recovery goals had been met. It was downlisted to threatened in 2010 and
removed from the list altogether in 2015, all due to the efforts of a number of
Willamette River basin partners.
“Introductions of new populations, such as the ones we
included in our study, were a big part of this conservation success,” DeHaan
said, adding that there were some important findings in the study.
“Overall, we found that the introduction program for Oregon
chub was successful at creating populations with levels of genetic diversity
similar to those observed in natural populations (this isn't always the case
with introduced populations),” he said. “We also found that introduced
populations with multiple sources had greater genetic diversity than
populations introduced from a single source.”
Finally, he said, the study found that there were a number
of genetic and demographic factors leading to the increased genetic diversity
in the introduced populations, including genetic variation in the source
population, the number of source populations and the number of founding
“Influence of Introduction History on Genetic Variation in
Introduced Populations: A Case Study of Oregon Chub,” was published online
October 7, 2016, in the North American Journal of Fisheries Management (http://afs.tandfonline.com/doi/abs/10.1080/02755947.2016.1206641?journalCode=ujfm20).
DeHaan’s co-authors are Brice Adams, fish biologist with the
Service at the Abernathy Fish Technology Center; and Paul Scheerer and Brian
Bangs, both fish biologists with the Oregon Department of Fish and Wildlife’
Native Fish Investigations Program in Corvallis.
Most naturally occurring populations of Oregon chub are
found from the floor of the Willamette Valley up to 445 meters (1,460 feet) in
the Coast and Cascade ranges in ponds, sloughs, oxbow lakes and low velocity
creeks, according to the study. Their population declined in the 1970s and
1980s, mostly due to flood control operations, habitat losses and the
introduction of non-native species. The fish was listed as endangered in 1993.
Population introduction was one of the measures taken for
the chub’s recovery. The introductions, a closely monitored process according
to the study, used hundreds of founding individuals and multiple source
populations. Some 26 introductions have been established since 1988 and 21 are
still viable populations.
Populations introduced from multiple sources had greater
levels of genetic diversity than those populations introduced from single
source, according to the study.
“If increasing genetic diversity for a threatened species is
a goal of population introduction programs, these data suggest using multiple
source populations will provide a means to achieve this goal,” the study says.
There is a danger to combining multiple sources, however, and that is the “loss
of co-adapting gene complexes through outbreeding depression.”
For future introduction programs, the authors suggest using
multiple introduction strategies.
“We found that it’s important to consider a number of
different factors such as genetic diversity in potential source populations,
the number of donor individuals, and the number of source populations, when
planning successful introductions,” DeHaan said. “We also demonstrated the
usefulness of collecting genetic data before initiating population introduction
Although some introduction programs avoid combining source
populations because of genetic or logistical reasons, it could be a way to
increase genetic diversity, the study concludes.
“This study provides a good example of how some of our
lesser known fish species like Oregon chub can teach us conservation lessons
that are pertinent to a number of threatened and endangered fishes and other
species,” DeHaan said. “Introductions and re-introductions of threatened and
endangered species are becoming more and more commonplace and this study helps
provide information for biologists and managers planning future introduction