All 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
have 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. Some limited, but continuous,
efforts have been made to assess salmonid populations in the subbasin
since 1984 (M. Schuck, pers. comm.). 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.
Critical uncertainties
must be answered if salmonid populations are to recover and be 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 2004). Critical
uncertainties for the Asotin Creek Subbasin include: 1) Is the steelhead
population parent-to-progeny ratio above replacement? 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 (ASP 2004)? Whether a wild population above
eight mainstem dams can be recovered through habitat and mainstem
actions and without hatchery supplementation is a critical uncertainty
that has basin-wide relevance. 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
are spawning in Asotin Creek. Samples from this project, coupled with
genetic sampling in adjacent subbasins, will aid in understanding
the effect of lower Snake River hatchery supplementation programs
and describe population genetic similarities and differences for recovery
planning efforts.
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. The Asotin Creek Assessment
Project was selected by the Bonneville Power Administration (BPA),
the Northwest Power Planning Council (NPPC) and the Independent Science
Review Panel (ISRP) for implementation in 2002, with full funding
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, 219 and 1,035 juvenile Chinook salmon
were captured in 2004, 2005 and 2006, respectively, providing estimates
of 4,145, 319 and 2,358 juvenile Chinook salmon emigrating from Asotin
Creek (Mayer and Schuck 2004; Mayer, et al., 2005, 2006). The data
suggest that spring Chinook salmon can spawn successfully in Asotin
Creek, but there are currently few adults spawning in Asotin Creek
and their origin is unknown.
Despite the functional
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, 7,214 in 2005 and 5,829 in 2006 (Mayer and Schuck 2004; Mayer,
et al., 2005, 2006). The estimated population of juvenile steelhead
for 2004 was 45,744, 27,287 for 2005 and 36,568 for 2006, which was
an average of 36,533 juveniles, or about 794 juveniles per river kilometer
(rkm) above the trapping site.
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. Under the ESA, the TRT and NOAA Fisheries, have included other
small adjacent Snake River tributaries (Couse, Tenmile, Alpowa and
Almota creeks) as part of the overall Asotin Steelhead population.
There is no effort under this project to sample these small populations.
This project also
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, above George
Creek. The project provides estimates of abundance, productivity,
survival rates, and additional information on temporal and spatial
distribution of ESA-listed species, primarily summer steelhead, and
secondarily on spring Chinook salmon. In addition, this project will
document the abundance of bull trout captured at the trapping locations.
Future 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, above George 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 focal
species.
- Objective
5: Report and disseminate Asotin Creek salmonid assessment data.
The expanded population
baseline data collected for summer-run steelhead in the Asotin Creek
Subbasin under this project are needed to refine fish return and management
goals, and to assist in the establishment of future numeric fish population
goals as outlined in the Subbasin Plan (ASP 2004). Moreover, the relatively
high abundance and productivity of Asotin Creek steelhead is significant
within the Snake and Columbia River basins. As such, this population
can be used as a reference for the evaluation of the effects of hatchery
supplementation on other steelhead populations (Galbreath et al.,
2006). Such evaluations are of great interest to managers in their
attempts to understand how best to recover ESA-listed species, and
will require unsupplemented populations to serve as a control/reference,
if robust supplementation evaluation results are expected (Galbreath
et al., 2007).
