20 research outputs found
Assessing hydrosystem influence on delayed mortality of Snake River stream-type Chinook salmon.
Abstract.-Snake River stream-type Chinook salmon Oncorhynchus tshawytscha exhibited substantial delayed mortality despite recent improvements in oceanic and climatic conditions. These salmon declined sharply with the completion of the Columbia River hydrosystem in addition to other anthropogenic impacts and changes in oceanic conditions. Previous analytical approaches have compared management options for halting the population decline. The predicted benefits of these options on salmon recovery hinged on whether the source of the mortality that takes place in the estuary and during early ocean residence is related to earlier hydrosystem experience during downstream migration (i.e., delayed hydrosystem mortality). We analyzed the spatial and temporal patterns of mortality for Chinook salmon populations to determine whether delayed mortality for the Snake River populations decreased during the recent period of favorable oceanic and climatic conditions. We found that Snake River stream-type Chinook salmon populations continued to exhibit survival patterns similar to those of their downriver counterparts but survived only one-fourth to one-third as well. The hypothesis that delayed mortality decreased and became negligible with more favorable oceanic conditions appears inconsistent with the patterns we observed for the common year effect and our estimates of delayed mortality of in-river migrants. A plausible explanation for this persistent pattern of delayed mortality for Snake River populations is that it is related to the construction and operation of the hydrosystem
An Analysis of Differential Delayed Mortality Experienced by Stream-type Chinook Salmon of the Snake River
In the Anadromous Fish Appendix of the US Army Corp of Engineers (USACE) Environmental Impact Statement on the Lower Snake River Hydrosystem Alternatives for recovery of Snake River salmon and steelhead (hereafter referred to as A-Fish ), the National Marine Fisheries Service (NMFS) suggested that transportation effectiveness of spring/summer chinook may have improved markedly in recent years. The NMFS conclusion was based on estimates of \u27D\u27-values (the differential delayed survival rate between transported fish and fish that migrated in-river) for 1994-1995 (NMFS, 1999). NMFS suggested, if \u27D\u27 is high (estimated in A-Fish at 0.8) and extra mortality of in-river and transported smolts is unrelated to the hydropower system, transportation options may meet recovery standards as well or better than natural river options. NMFS also suggested that further studies could reduce the uncertainty about true values of \u27D\u27 and provide greater confidence to make a decision on the alternative management action needed to recover listed Snake River salmon and steelhead. In this analysis, we demonstrate that the evidence is compatible with a wide range of ‘D’ values, but only a small portion of this distribution is as high as the A-Fish estimate. We also present evidence that the extra mortality of in-river fish is related to the hydrosystem.
We analyzed a suite of plausible assumptions used in the calculation of \u27D\u27. Based on our analysis of the 1994-1996 PIT-tag data, there is a wide range of possible \u27D\u27-values. The NMFS\u27 estimate falls at the upper end of this distribution (90th – 95th percentiles). Alternative \u27D\u27-values, based on what we believe to be more reasonable assumptions, were closer to 0.48. Because \u27D\u27 is a modeled value (and not a measurement, as implied in the A-Fish), it is very sensitive to the suite of assumptions made and how the data are grouped. \u27D\u27 estimates were most sensitive to: (1) whether or not fish that were transported from downstream collection/transport sites (Lower Monumental (LMO) and McNary (MCN) dams) were included in the group of fish used to estimate transport smolt to adult return rates (SAR); and (2) how reach survival rate estimates were extrapolated down to Bonneville Dam (BON). In 1994 the ‘D’-value estimated using four collection projects was much lower than two collection projects. However, in 1995 and 1996 the difference in ‘D’ using two and four collection projects was not as dramatic as in 1994. Therefore, the estimated high ‘D’-values are mainly driven by this single assumption for one year. Based on past and proposed future transportation operations, it is unclear why fish transported at the lower two projects were excluded from the NMFS analysis.
Transported fish are subjected to stress, injury, and crowding at the collection projects. In addition, the physiological state of fish may be poorly synchronized with the time of saltwater entry for transported fish. These factors could explain the higher delayed mortality experienced by transported fish as suggested by a consistently estimated ‘D’ value that is less than 1.
We disagree with the NMFS assertion that “ongoing direct experiments that contrast the return rates of tagged fish that pass through the hydrosystem versus the return rates of transported fish can resolve this question in a clear and unambiguous manner”. While a few components of the \u27D\u27-value estimate are measurable, the sensitivity analysis highlights differences in assumptionsand uncertainties that are not likely resolvable in the near term. In addition, low numbers of returning adults and small numbers of smolts for wild spring/summer chinook salmon may hamper reducing the uncertainty in estimates for reach survival rates and SARs for a non-detected group. Therefore, data are unlikely to perfect our understanding of \u27D\u27 or eliminate the uncertainty in the most influential assumptions.
The hypothesis of extra or delayed mortality due to hydrosystem passage has an empirical basis, as well as biological rationale. Based on recent PIT tag data we also found evidence that delayed mortality of both in-river and transported smolts was related to hydropower. More specifically, the evidence suggests that, at least for collected and bypassed smolts, there is a difference between the patterns of direct passage survival rates and SARs. Smolts first detected and transported from the downstream projects (LMO and MCN) had lower SARs than smolts collected and transported from higher up in the system. Similarly (as reported in the A-Fish), SARs of in-river smolts decreased as the number of times the fish were collected and bypassed increased. These pieces of information provide evidence that the Snake River spring summer chinook extra mortality is related to the juvenile migration hydrosystem experience.
Based on results from life-cycle modeling (Marmorek and Peters 1998b), transport based management options lead to a high likelihood of recovery only when ‘D’ is high and the source of extra mortality is not related to the experience during hydrosystem passage. However, when extra mortality is hydrosystem related (which our analysis supports), the natural river options are still the most likely management action to recover these stocks, even if ‘D’ is high (which our analysis does not support). Simply studying ‘D’, if that were possible, without determining the source of extra mortality, yields little additional insight into effects of the different management actions on Snake River spring/summer chinook recovery. Given the dangerously low level ofthese populations, we do not believe it is prudent to make management decision on the configuration and operation of the Snake and Columbia hydrosystem for the next 5-20 years (i.e. delaying a decision preserves status quo configuration), based solely on one optimistic assumption about the effectiveness of past and current hydrosystem operations
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Idaho Habitat Evaluation for Offsite Mitigation Record : Annual Report FY 1984.
An evaluation of existing and proposed habitat improvement projects for anadromous fish in the Clearwater River and Salmon River drainages was conducted. The Clearwater River and Salmon River drainages account for virtually all of Idaho's wild and natural production of summer steelhead and spring and summer chinook salmon, as well as a remnant run of sockeye salmon. Habitat enhancement projects are intended to either increase the amount of habitat, or increase the carrying capacity of existing (usually, degraded) habitat, or both. Migration barriers, such as waterfalls, culverts, and water diversions, can be modified to make available habitat that is not being used, or is underutilized, by anadromous fish. The objectives of this evaluation are: (1) document physical changes in habitat; (2) measure changes in steelhead and chinook production attributable to habitat enhancement projects; (3) measure changes in standing crops of resident fish species due to enhancement; and (4) determine project effectiveness, including relative costs and benefits, to establish the record of credit for mitigation and to guide future management actions. It was not possible to define the level of enhancement for any BPA project in 1984. Evaluations for all projects except three were in the pre-treatment phase during 1984. Because full benefits cannot be defined at current low seeding levels, projects must be monitored until full-seeding is approached. We obtained post-treatment information for three projects in 1984: Lolo Creek instream structures; upper Lochsa River instream structures; and screening of the irrigation diversion on Pole Creek. Of the three, only the Lolo Creek project exhibited any apparent benefits; these apparent benefits were not conclusively determined in 1984. The Lolo Creek project requires a follow-up evaluation in 1985. The Pole Creek project requires better passage for adult chinook at the irrigation diversion. 36 refs., 71 figs., 50 tabs. (ACR
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Evaluation and Monitoring of Idaho Habitat Enhancement and Anadromous Fish Natural Production : Annual Report 1986.
The Idaho Department of Fish and Game (IDFG) has been conducting an evaluation of existing and proposed habitat improvement projects for anadromous fish in the Clearwater River and Salmon River drainages over the last 3 years. Projects included in the evaluation are funded by or proposed for funding by the Bonneville Power Administration (BPA) under the Northwest Power Planning Act as off-site mitigation for downstream hydropower development on the Snake and Columbia rivers. This evaluation project is also funded under the same authority. A mitigation record is being developed to use increased smolt production (i.e., yield) at full-seeding as the best measure of benefit from a habitat enhancement project. Determination of full benefit from a project depends on completion or maturation of the project and presence of adequate numbers of fish to document actual increases in fish production. The depressed nature of upriver anadromous stocks have precluded measuring full benefits of any habitat enhancement project in Idaho. Partial benefit will be credited to the mitigation record in the interim period of run restoration
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Idaho Habitat Evaluation for Off-Site Mitigation Record : Annual Report 1985.
Evaluation approaches to document a record of credit for mitigation were developed in 1984-1985 for most of the habitat projects. Restoration of upriver anadromous fish runs through increased passage survival at main stem Columbia and Snake River dams is essential to the establishment of an off-site mitigation record, as well as to the success of the entire Fish and Wildlife program. The mitigation record is being developed to use increased smolt production (i.e., yield) at full-seeding as the basic measure of benefit from a habitat project. The IDFG evaluation approach consists of three basic, integrated levels: general monitoring, standing crop evaluations, and intensive studies. Annual general monitoring of anadromous fish densities in a small number of sections for each project will be used to follow population trends and define full-seeding levels. For most projects, smolt production will be estimated indirectly from standing crop estimates by factoring appropriate survival rates from parr to smolt stages. Intensive studies in a few key production streams will be initiated to determine these appropriate survival rates and provide other basic biological information that is needed for evaluation of the Fish and Wildlife program. A common physical habitat and fish population data base is being developed for every BPA habitat project in Idaho to be integrated at each level of evaluation. Compatibility of data is also needed between Idaho and other agencies and tribes in the Columbia River basin. No final determination of mitigation credit for any Idaho habitat enhancement project has been attainable to date
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Idaho Habitat/Natural Production Monitoring, Pt. I: General Monitoring Subproject : Annual Progress Report 1990.
The Idaho Department of Fish and Game (IDFG) has been monitoring and evaluating proposed and existing habitat improvement projects for rainbow-steelhead trout Oncorhynchus mykiss, hereafter called steelhead, and chinook salmon O. tshawytscha, hereafter called chinook, in the Clearwater and Salmon River drainages for the past seven years. Projects included in the evaluation are funded by, or proposed for funding by, the Bonneville Power Administration (BPA) under the Northwest Power Planning Act as off-site mitigation for downstream hydropower development on the Snake and Columbia rivers. This evaluation project is also funded under the same authority (Fish and Wildlife Program, Northwest Power Planning Council). A mitigation record is being developed using increased carrying capacity and/or survival as the best measure of benefit from a habitat enhancement project. Determination of full benefit from a project depends on completion or maturation of the project and presence of adequate numbers of fish to document actual increases in fish production. The depressed status of upriver anadromous stocks has precluded measuring full benefits of any habitat project in Idaho. Partial benefit is credited to the mitigation record in the interim period of run restoration
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Idaho Habitat Evaluation for Off-Site Mitigation Record : Annual Report 1987.
The Idaho Department of Fish and Game has been monitoring and evaluating existing and proposed habitat improvement projects for steelhead (Salmo gairdneri) and chinook salmon (Oncorhynchus tshawytscha) in the Clearwater and Salmon River drainages over the last four years. Projects included in the evaluation are funded by, or proposed for funding by, the Bonneville Power Administration (BPA) under the Northwest Power Planning Act as off-site mitigation for downstream hydropower development on the Snake and Columbia rivers. A mitigation record is being developed to use increased smolt production at full seeding as the best measure of benefit from a habitat enhancement project. Determination of full benefit from a project depends on presence of adequate numbers of fish to document actual increases in fish production. The depressed nature of upriver anadromous stocks have precluded attainment of full benefit of any habitat project in Idaho. Partial benefit will be credited to the mitigation record in the interim period of run restoration. According to the BPA Work Plan, project implementors have the primary responsibility for measuring physical habitat and estimating habitat change. To date, Idaho habitat projects have been implemented primarily by the US Forest Service (USFS). The Shoshone-Bannock Tribes (SBT) have sponsored three projects (Bear Valley Mine, Yankee Fork, and the proposed East Fork Salmon River projects). IDFG implemented two barrier-removal projects (Johnson Creek and Boulder Creek) that the USFS was unable to sponsor at that time. The role of IDFG in physical habitat monitoring is primarily to link habitat quality and habitat change to changes in actual, or potential, fish production. Individual papers were processed separately for the data base
A review of potential conservation and fisheries benefits of breaching four dams in the Lower Snake River (Washington, USA)
Abundances of important and imperiled fishes of the Snake River Basin continue to decline. We assessed the rationale for breaching the four lower Snake River Basin dams to prevent complete loss of these fishes, and to maximize their likelihood of recovery. We summarize the science surrounding Sockeye Salmon (Oncorhynchus nerka), Chinook Salmon (O. tshawytscha), steelhead (O. mykiss), Bull Trout (Salvelinus confluentus), White Sturgeon (Acipenser transmontanus), and Pacific Lamprey (Entosphenus tridentatus). From this, we drew ten conclusions: (1) development of the Columbia River System (including the Snake River Basin) has converted mainstem rivers into reservoirs, altering fish behavior and survival; (2) most populations currently record their lowest abundance; (3) the Columbia River System dams reduce productivity of diadromous fishes in the highest-quality spawning grounds that could buffer against future climate dynamics; (4) past actions have done little to reduce impacts or precipitate recovery; (5) the Columbia River System constrains survival and productivity of salmon, steelhead and Bull Trout; (6) Snake River Basin salmon and steelhead remain at high extinction risk; (7) eliminating migration impediments and improving mainstem habitats are essential for maintaining genetic diversity and improving Bull Trout persistence; (8) the lower Snake River Basin dams preclude passage of adult White Sturgeon, constraining gene flow and recruitment; (9) the lower Snake River Basin dams impede dramatically passage of adult and juvenile Pacific Lamprey, and (10) Snake River Basin Pacific Lamprey is at high risk of extirpation. Breaching the four lower Snake River Basin dams is an action likely to prevent extirpation and extinction of these fishes. Lessons from the Columbia River System can inform conservation in other impounded rivers