Most populations
of anadromous salmonids in the Snake River have been listed as threatened
under the Endangered Species Act (ESA) by the National Marine Fisheries
Service, including steelhead (Oncorhynchus mykiss) and spring/summer
Chinook salmon (O. tshawytscha). Bull trout (Salvelinus
confluentus) has been listed as threatened by the U.S. Fish and
Wildlife Service. Historically, Asotin Creek is known to have supported
summer steelhead, spring Chinook salmon, fall Chinook salmon, bull
trout, and lamprey sp. (Petromyzontidae) populations. The Washington
Department of Fish and Wildlife (WDFW) designated the Asotin Creek
Subbasin a wild steelhead refuge in 1997, and no hatchery fish have
been planted in Asotin Creek since 1998. Limited, but continuous,
efforts have been made to assess salmonid populations in the subbasin
since 1984 (M. Schuck, pers. comm.).
Critical uncertainties
must be answered if salmonid populations are to be rebuilt and de-listed.
Such uncertainties may include habitat/life history stage relationships,
causal relationships between degraded habitats and depressed or extirpated
populations, and understanding the relationship between resident and
anadromous O. mykiss subpopulations (ASP 204, p. 173). Critical uncertainties
for the Asotin Creek Subbasin include: 1) Is the steelhead population
parent-to-progeny ratio above the replacement [>1.0]? 2) How can
fisheries managers intervene to rebuild steelhead populations that
may be at marginally successful productivity above eight Federal Columbia
River Power System (FCRPS) dams, if necessary? (Asotin Subbasin Plan
(ASP) 2004). Moreover, measuring the effects of recovery actions on
these populations is extremely difficult due to out-of-subbasin-effects
on anadromous salmonids (e.g. hydrosystem operational changes, ocean
survival, and between year environmental conditions).
The genetic nature
of naturally produced (presumed wild origin) salmonids in the Snake
River Basin is a critical concern under the ESA. This project provides
the opportunity to contribute tissue samples to regional efforts to
better describe steelhead and bull trout population structure, and
potentially to determine the origin of spring Chinook salmon that
may be spawning in Asotin Creek opportunistically. Samples from this
project, coupled with genetic sampling in adjacent subbasins, will
aid in understanding the effect of lower Snake River hatchery supplementation
and describe population genetic similarities and differences for recovery
planning efforts.
Prior to this
project, there were consistent, but limited efforts to determine adult
abundance, collect data on population dynamics and estimate life stage
survival (smolt-to-adult, adult-to-adult survival, and smolt production
by brood year), and obtain life history diversity information on Asotin
Creek steelhead by sampling juveniles in the summer.
This project was
implemented under reasonable and prudent alternative (RPA) 180 in
the NMFS 2000 and Action 180 in the 2004 FCRPS Biological Opinions
(BiOp) for hierarchical basin-wide measurement. This program is expected
to determine population and environmental status (including assessment
of performance measures and standards), and review of status change
over time. The Asotin Creek Assessment project was selected for implementation
in 2002 and was fully funded beginning in 2004.
The WDFW and the
NOAA Fisheries Interior Columbia Technical Recovery Team (TRT) considers
the population of spring Chinook salmon to be functionally extinct
in Asotin Creek. However, 1,884 and 219 juvenile Chinook salmon were
captured in 2004 and 2005, respectively, providing estimates of 4,145
and 349 juvenile Chinook, emigrating from Asotin Creek (Mayer and
Schuck 2004; Mayer, et al., 2005). This suggests that spring Chinook
salmon can spawn successfully in Asotin Creek, but there is insufficient
information to infer population status.
Bull trout populations
in the Columbia River Basin were listed as threatened in June 1998.
The Asotin Creek population is part of the Columbia Basin Distinct
Population Segment (DPS) for bull trout. Although once believed to
be nearly extinct in the basin, redd surveys conducted by the U.S.
Forest Service (USFS) found bull trout spawning in the upper North
Fork Asotin Creek in 1996 (D. Groat, USFS, pers. comm.). Since that
time, the USFS and WDFW have conducted bull trout spawning surveys
in portions of the upper North and South Forks of Asotin Creek. Four
juvenile bull trout were captured in 2004 and eleven were captured
in 2005.
Despite the extirpation
of spring Chinook salmon and depressed status of bull trout, there
is currently a significant population of naturally producing steelhead
in Asotin Creek. We captured 8,506 juvenile steelhead in 2004 and
7,214 in 2005 (Mayer and Schuck 2004; 2005). The estimated population
of juvenile steelhead for the 2004 calendar year out-migration was
43,327 (95% CI = 38,009 – 50,796 juveniles) and 26,462 (95%
CI = 22,443 – 32,746 juveniles) in 2005, which is about 742
juveniles per rkm (1,220 juveniles/mile) above the trapping site at
rkm 7.0.
The goal of this
project is to determine the abundance and current productivity of
anadromous adult and juvenile salmonids in Asotin Creek (primarily
summer steelhead) above George Creek, and to estimate life stage survival
rates. This project implements the research, monitoring and evaluation
(RM&E) criteria specified in the Asotin Subbasin Plan (ASP 2004),
by establishing a baseline of the salmonid population in Asotin Creek
to provide estimates of abundance, productivity, survival rates, and
additional information on temporal and spatial distribution of ESA-listed
species, primarily summer steelhead, and secondarily spring Chinook
salmon. In addition, this project will document the abundance of bull
trout captured at the trapping locations. Estimates of smolt-to-adult
and adult-to-adult survival for the natural steelhead population in
Asotin Creek will provide the data necessary to help determine if
salmonid production in the subbasin is being limited by within- or
out-of-basin factors.
The objectives
for this project are:
- Objective
1: Estimate escapement of wild and hatchery steelhead and Chinook
salmon into Asotin Creek.
- Objective
2: Estimate spawner abundance and adults per redd.
- Objective
3: Document juvenile steelhead life history patterns, survival rates
and estimate juvenile emigrant production.
- Objective
4: Collect DNA samples for future genetic characterization of the
focal species.
- Objective
5: Report and disseminate Asotin Creek salmonid assessment data.
The expanded
population baseline data collected for each focal species in the Asotin
Creek Subbasin under this project is needed to refine fish return
and management goals, and to assist in the establishment of future
numeric fish population goals as outlined in the Asotin Subbasin Plan
(ASP 2004, p. 160). In addition, assessing the Asotin Creek steelhead
population may provide a better understanding of limiting factors
that affect similar or adjacent populations. Moreover, data from this
project could be used to help determine if regional recovery efforts
to stabilize and rebuild steelhead populations would be best spent
on within-subbasin projects or out-of subbasin actions (i.e., FCRPS
modifications).
We received a
national Conservation Partnership Award from the U.S. Department of
Agriculture for our work with the Asotin Conservation District to
restore and protect the Asotin Creek watershed in 2006. The award
was presented on October 26 in Walla Walla, Washington, by the USDA
Under Secretary for Natural Resources and Environment, Mark Rey, who
oversees the U.S. Forest Service and Natural Resources Conservation
Service.
