Upper Columbia Spring Chinook Salmon, Steelhead, and Bull Trout Recovery
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- 3.12.1Ocean Productivity and Natural Variation
- 3.12.2Global Climate Change
- 3.12.3Hatchery Effectiveness
- 3.12.4Density Independence
- 3.12.5Differential Delayed Mortality of Transported Chinook and Steelhead (D Value)
- 3.12.7Independent Populations
- 3.12.8Effects of Dams on Bull Trout
- 3.12.9Interaction between Resident and Migrant Bull Trout Life-History Types
- 3.12.10Effects of Harvest, Hatchery, Hydropower, and Habitat Actions
- 3.12.11Effects of Human Population Growth
3.12UncertaintiesThe preceding sections described many of the important factors that have, and continue to, reduce the abundance, productivity, spatial structure, and diversity of spring Chinook, steelhead, and bull trout in the Upper Columbia Basin. It is clear that actions must be taken in all Hs (not just habitat) in order to recover listed populations. However, there are “key” areas of uncertainty66 identified in Biological Opinions (BiOp), PATH (Plan for Analyzing and Testing Hypotheses), QAR analyses, USFWS Bull Trout Draft Recovery Plan, and Northwest Power and Conservation Council documents that can affect the success of actions implemented within each of the Hs. Resolution of uncertainties will greatly improve chances of attaining recovery goals outlined in this plan. These “key” uncertainties are highlighted below. 3.12.1Ocean Productivity and Natural VariationGlobal-scale processes in the ocean and atmosphere can regulate the productivity of marine, estuarine, and freshwater habitats of Chinook salmon and steelhead. Although managers cannot control these processes, natural variability must be understood to correctly interpret the response of salmon to management actions. For example, assessing needed survival improvements based on spawner returns from 1980-1999, during periods of below average climatic and other background conditions (Coronado and Hilborn 1998), has the effect of projecting these generally poor ocean conditions into the future. In the QAR assessment, results for Upper Columbia spring Chinook showed the survival improvement required to avoid the risk of extinction criteria was either 95, 47, or 2% depending on whether a historical time period back to 1980, 1970, or 1960 was used, respectively. If one were to add recent years (2000-2004, representing better ocean conditions) to the analysis, estimated required survival increases would decrease by about one third or more. Additional research is needed to help understand the mechanisms of ocean and climatic survival conditions, and to help improve forecasting and relating fisheries management capabilities and ensure that Upper Columbia populations persist over the full range of environmental conditions they are likely to encounter. 3.12.2Global Climate ChangeThe potential impacts of global climate change are recognized at national and international levels (Scott and Counts 1990; Beamish 1995; McGinn 2002). Many climate models project changes in regional snowpack and stream flows with global climate change. The effects of these changes could have significant effects on the success of recovery actions and the status of listed fish populations in the Upper Columbia Basin. The risks of global climate change are potentially great for Upper Columbia stocks because of the sensitivity of salmon stocks to climate-related shifts in the position of the sub-arctic boundary, the strength of the California Current, the intensity of coastal upwelling, and the frequency and intensity of El Nino events (NPCC 2004). Bull trout are particularly sensitive to water temperatures and it is uncertain how global climate change will affect their habitat. More research is needed to address the effects of climate change on ocean circulation patterns, freshwater habitat, and salmon and trout productivity. 3.12.3Hatchery EffectivenessUncertainties exist regarding the potential for both benefits and harm of hatchery-produced fish on naturally spawning populations (see Section 5.3). A major uncertainty is whether it is possible to integrate natural and artificial production systems in the same subbasin to achieve sustainable long-term productivity. There is also uncertainty about the reproductive success of hatchery fish spawning in the wild. NOAA Fisheries evaluated survival requirements using a broad range of 20 to 80% historical effectiveness of hatchery-origin spawners to cover this uncertainty.67 There is currently little data available and experimental methods for obtaining this information will take several years to get initial results and much longer before conclusions can be inferred from the empirical information. NOAA Fisheries and WDFW have initiated some of these studies in the Upper Columbia Basin and it is important that these experiments continue. Although supplementation is considered a potential benefit to recovery, it carries risks as noted here. 3.12.4Density IndependenceNOAA Fisheries analysis (2000 FCRPS BiOp) of needed survival improvements for spring Chinook and steelhead assumes that fish survival is independent of population density at all life stages. While density dependence is not apparent in single-stock models of population dynamics using only 1980-present data, PATH and others have found strong evidence of compensatory mortality (higher survival rates at lower population levels) and carrying capacity limits in Upper Columbia populations using data from the late 1950s to present. If the survival rates of Upper Columbia populations are density dependent at certain life stages (i.e., egg-to-smolt survival), then the analysis would tend to be pessimistic about extinction risks and optimistic with regard to survival increases necessary to achieve recovery levels. Incorporating density dependence would therefore tend to support lower risk for management actions that may not have immediate survival benefits, but require higher overall survival improvements to meet longer-term recovery goals. WDFW and the ICBTRT are currently drafting an approach for measuring tributary habitat performance that includes an evaluation of tributary density-dependence. They have identified density-dependence in smolt production for Wenatchee spring Chinook (Figure 3 .30). Additional research on density dependence (independence) is needed to provide a better understanding of the potential benefit of actions over time. 3.12.5Differential Delayed Mortality of Transported Chinook and Steelhead (D Value)The differential delayed mortality of transported spring Chinook and steelhead (D value) is the estimated ratio of the post-Bonneville survival of transported fish relative to in-river migrating fish. This differential mortality can occur during any time from release downstream from Bonneville Dam, through the estuary and ocean life stage, and during adult upriver migration to the specific dam from which they were transported. The factors determining D are complex and poorly understood. Little information is available on potential D values for Upper Columbia spring Chinook and steelhead. Historical data when fish were transported from McNary indicate a D ranging from 0.8 to 1.0. This uncertainty has little effect under current conditions because few Upper Columbia stocks are currently transported. However, an improved understanding of D will be necessary to determine the appropriate role of McNary transportation in the future. Furthermore, the future role of transportation and the potential benefit of major hydro-system configurations are highly sensitive to this uncertainty. 3.12.6Invasive SpeciesAnother critical uncertainty is the effect of invasive species on the viability of listed populations in the Upper Columbia Basin. One such species, American shad, may affect the abundance and survival of spring Chinook and steelhead in the lower Columbia River. It is possible that the growing population of shad is competing directly with juvenile Chinook and steelhead by cropping food sources important to salmonids in the lower Columbia River. It is also possible that the large numbers of shad in the lower river contribute to the growth of northern pikeminnow, smallmouth bass, and walleye, which are important predators of salmon and steelhead. Shad may be sustaining large populations of predators during periods when salmon and steelhead are not available to the predators, and, as a result, more and larger predators are present during periods when salmon and steelhead are moving through the lower Columbia River. Brook trout is an invasive species within the Upper Columbia Basin that competes with bull trout for food and space. Brook trout can hybridize with bull trout and adult brook trout are known to feed on juvenile bull trout. Research is needed to assess the direct and indirect effects of invasive species (including invasive plants)68 on the abundance and survival of spring Chinook, steelhead, and bull trout in the Upper Columbia Basin. 3.12.7Independent PopulationsICBTRT and QAR identified independent spring Chinook and steelhead populations within the Upper Columbia Basin. QAR and PATH assessments assumed that spawning aggregations of an ESU or a DPS behaved as independent populations in isolation. Likewise, the Bull Trout Draft Recovery Plan (USFWS 2002) identified independent “core” bull trout populations, which are made up of several “local” populations. Given the geographic proximity and genetic similarity of many of these sub-groups, the assumption of independence is questionable and may lead to pessimistic assessments of needed survival improvements. Research regarding population structures, natural straying and movement among aggregations, and improvements to the assessment methods to include meta-population dynamics may be warranted. The monitoring program outlined in this plan and detailed in the Upper Columbia Monitoring Strategy (Hillman 2004), completed watershed plans, and subbasin plans will contribute substantially to resolving this uncertainty. 3.12.8Effects of Dams on Bull TroutThe Bull Trout Draft Recovery Plan (USFWS 2002) has identified dams as an important factor for the decline of bull trout in the Upper Columbia Basin. Although it is true that dams can affect salmonids by delaying or impeding migration of adults and by injuring or killing juveniles that pass downstream, there is currently little information on the effects of dams on bull trout in the Upper Columbia River. Recent research by BioAnalysts (2002, 2003) indicates that adult bull trout passed through mainstem PUD dams with no loss and arrived on spawning grounds within their spawning window. In contrast, there is virtually no information on the effects of mainstem dams on juvenile (or subadult) bull trout. Additional work is needed to assess the effects of dams on the viability of bull trout in the Upper Columbia Basin. Dams and other passage barriers in the Upper Columbia may affect bull trout. For example, in the Wenatchee River basin, Tumwater Dam, Dryden Dam, Dam 5 on Icicle Creek, and the weir on the Chiwawa River may affect bull trout spatial structure and diversity. 3.12.9Interaction between Resident and Migrant Bull Trout Life-History TypesThe Bull Trout Draft Recovery Plan (USFWS 2002) proposes recovery criteria for bull trout based on connectivity, abundance, productivity, and spatial structure of migrant (fluvial and adfluvial) life-history types. A critical uncertainty is the role of resident life-history types in maintaining viable populations of bull trout. Little is known about the abundance and spatial structure of resident forms in the Upper Columbia Basin, and even less is known about their contribution to migrant life-history types. Research is needed to assess the spatial structure and importance of resident types in maintaining viable populations of bull trout in the Upper Columbia Basin. 3.12.10Effects of Harvest, Hatchery, Hydropower, and Habitat ActionsA critical uncertainty associated with the implementation of this recovery plan will be the effect of management actions or strategies on the environment and on life-stage specific survival rate and population level responses. It is unclear how strategies implemented within each of the Hs (Harvest, Hatcheries, Hydropower, and Habitat) will interact and contribute to recovery. In particular, a high level of uncertainty exists for the magnitude and response time of habitat actions. Even if all habitat actions could be implemented immediately (which they cannot), there will be delays in the response to actions. Populations will likely respond more quickly to some actions (e.g., diversion screens and barrier removals) than they will to others (e.g., riparian plantings). Although the effects of interacting strategies on population VSP parameters remain unknown, monitoring will contribute substantially to resolving this uncertainty. 3.12.11Effects of Human Population GrowthHuman population growth in the Upper Columbia Basin and its effects on recovery of listed species is a critical uncertainty. The size of the human population within the Upper Columbia region is expected to nearly double in the next two decades (may not apply equally across all subbasins).69 Projected development will probably expand along streams and rivers at a greater rate than in upland areas. At the time this plan was written, critical area ordinances and comprehensive plans are being updated. A high degree of coordination among agencies, tribes, and counties will be needed to maximize recovery efforts.
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