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Our conservation efforts on the South Fork in 2008 begin with a number of
research projects to better understand the ecosystem such as the situation
with trout spawning behavior, habitat assessments and a genetic
study to determine where the origins of the resident fish during the fishing
season. Click the links below to be taken to
a more detailed description of our 2008 projects:
Genetic Study
The centerpiece of
the 2008 conservation research will be a genetic study to
understand the origins of the fish the make up the South Fork
fishery. We will sample fish from the South Fork Boise below
Anderson Dam, and the (non-lethal) tissue samples will be used to
profile the local rainbow trout population and compare it to an
existing library of genetic profiles for wild rainbow trout
populations throughout the headwaters of the North, Middle and
South Fork of the Boise River.
Analyses of genetic
diversity and genetic population structure have become important
tools for the recovery and management of recreational species and
species of conservation concern. Genetic data can be used to make
inferences about populations including extinction risks, migration
routes and effective population sizes. Recent advances in
analytical approaches also make it possible to address questions
focused on the individual. For instance, it is now possible to
characterize the Ôgenetic fingerprintÕ of an individual and
determine the population from which that individual most likely
originated by Òindividual assignmentÓ.
Individual assignment
is well suited for addressing the conservation effortÕs need to
determine likely sources of the large, potentially migratory,
individuals observed in the SFB. It is an efficient method for
tracking movement in that it does not require actually following
the physical movement of individuals, an effort which is often
both time and cost-prohibitive. Using individual assignments
effectively, however, requires the genetic characterization of all
or most potential source populations, and for this foundation we
are fortunate to draw from other genetic work already completed
within the basin.
For illustrative
purposes we show below an example of a color-coded display of
genetic information on five different subpopulations of cutthroat
trout in northern Nevada.
Scientists with the
US Forest Service and Idaho Fish and Game, along with Trout
Unlimited have analyzed genetic samples from dozens of rainbow
trout populations in the Boise River basin. Other Boise River
basin populations have yet to be analyzed. Collectively, this work
provides genetic samples from approximately 50 populations in the
Boise River (North and Middle Fork), covering a large portion of
populations expected as sources of migratory rainbow trout.
The Summer sampling
of the South Fork Boise between Arrowrock and Anderson Ranch
Reservoirs, and use of the established laboratory protocols and
genetic information previously obtained will help determine the
likely source populations for the South Fork Boise River fishery.
Future sampling from approximately twelve Boise River Basin sites
will provide additional SFB population information as to redband
migrant recruitment to the river.
Participating local
fishing clubs will coordinate a South Fork Boise fishing outing on
Saturday, July 12 to collect tissue samples for genetic analysis
based on hook & line methods. Volunteers are needed to contribute
their angling skills or driftboat use in the name of science!
A base camp for this
fish sampling day is planned to be setup at the Reclamation
Village area. Participants are welcome to camp in this area
and make it a weekend long outing if desired. Look for the
TU and BVFF banners to locate the base camp.
Biologists from TU
and IDFG will be on hand to instruct anglers how to sample tissue
from caught fish, a small fin clip about the size of a spilt shot
that is harmless to the fish. Marked envelopes will be
provided to anglers to hold the tissue samples and later return to
the biologists at the base camp. Measure boards and photo's
will also be used to record statistics of each fish.
Supporters and
Anglers are encouraged to participate in our "Adopt-a-Fish"
program for $25 per fish. Each contributor may name the fish and receive a
simple genetic report about the origins of that fish. Photos
and the report will be posted on the Gallery pages later this year
or early 2009.
Tributary Survey
A number of small
tributaries drain directly into the South Fork Boise River, but
their contribution for spawning and rearing habitat is poorly
understood. Potential tributary enhancement projects could be
effective, but the first step is learning whether fish are
presently using the tributaries and the water conditions, whether
the culverts inhibit or prevent fish passage, and habitat present
in those tributaries.
The Boise National
Forest has identified the culverts on four South Fork tributaries
as barriers to Aquatic Organism Passage, typically referring to
fish but can be other biologically important species. Culverts
installed typically prior to the 1990Õs like those on the SFB
tributaries, are not designed for fish passage since they
typically move water faster than the stream itself. While
fish swim against a current at higher speed in shallow water,
their passage through the culvert when moving upstream from the
river to the tributary can be restricted due to water velocity,
length of the culvert and depth of water.
Research by Idaho
Fish and Game between 1977-1979 established that rainbow trout
were accessing several tributaries during the spring to spawn. No
recent information exists, however, to determine the role of these
tributaries as contributors to spawning activity.
Volunteers are needed
to survey South Fork Boise tributaries to monitor flows throughout
May and into the summer, and to conduct a redd count on Saturday
June 7 for evidence of spawning activity. Volunteers will be
instructed in redd identification by a USFS Fisheries Biologist.
Instructions for
volunteers working on their own for the flow measurement and fish
activity assessments are available here:
MS Word Doc version and
Adobe PDF version.
Later in the summer,
a Boise National Forest summer work crew will electro-shock
portions of these tributaries to look for evidence of fish
presence and to collect tissue samples to compliment the genetic
study allowing a connection to be drawn between river residents
and any headwater resident populations.
By monitoring the
tributary flows and presence of fish at various locations, an
assessment and prioritization can be made for future remediation
projects such as culvert replacement to improve access for
spawning and rearing habitat.
Main Stem Spawning Survey
Tail water fisheries
experience regular, consistent water flow and temperature compared
to natural streams, allowing fish longer growing seasons and
healthy habitat for invertebrates that the fish eat. At the same
time dams prevent fish from migrating to headwater streams to
spawn. These dams also trap gravels upstream that otherwise
would move through a river during natural flooding and thus
replenish in-stream spawning areas with new gravel that often gets
silted over or scoured to other locations..
It is known that
rainbow trout spawn in some areas of the main stem South Fork
Boise, despite the loss of spawning gravel. Typical spawning areas
are found along braided sections of the river where smaller side
channels carry less water and contain smaller gravel conducive to
fish spawning.
Updating information
on the spawning areas is needed because the main river lacks the
smaller sized gravels commonly found in a natural river. Boise
National Forest biologists have conducted spawning surveys the
past couple of years and have recorded locations -see a map of the
2007 survey at the link below. Volunteers are welcome to assist
and observe this effort which is planned for May12-14. The
survey is also planned to be extended downstream of Danskin Bridge
to the beginning of the canyon reach.
2007 Spawning Redd Survey - map by USFS
Boise National Forest
By understanding the
behavior of in-stream spawning activity and its increasing or
decreasing trends, inference can be made about future populations
as well as areas that should be monitored for affects that would
be detrimental to future spawning or that could be improved with a
variety of improvements encouraging additional spawning behavior.
Canyon Section
Population Survey
In the fall of 2008,
once flows drop to manageable levels, Idaho Fish and Game plans to
survey the fish population in the canyon section of the river from
Danskin Bridge down to Neal Bridge in order to compliment the data
they have taken numerous times in the river above Danskin.
These fish will most likely be included in the genetic survey as
well.
This survey will most
likely be an overnight trip through the canyon section due to the
limited light hours during October. Volunteers are needed to
help capture stunned fish for measure and counting, as well as
ferry gear downstream for an overnight camp. There should be
fishing opportunities available. Persons with river worthy
pontoon craft and experience with some whitewater navigation are
suggested as there will be a limited number of multi-person craft
moving down river. Additional information will be available
as the fall approaches.
Fishing Catch Rate Survey
Idaho Fish and Game gathered extensive catch data through creel
census prior to catch and release regulations went into effect in
the late 70's and for a few years after. Since then, catch
data is fairly scarce as shown on the graph below. By
determining angler success today, we can compare the fishery to
prior years which helps with determining future activities.
If you want to help, please use the
FEEDBACK link above and report for a single angler the
number of hours fished, number fish caught, and lengths of the
fish if recorded.
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