Columbia River Basin Food Webs

Developing a Broader Scientific Foundation for Fish and Wildlife Restoration

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The Independent Scientific Advisory Board (ISAB) is pleased to submit its report “Columbia River Food Webs: Developing a Broader Scientific Foundation for Fish and Wildlife Restoration” to the Council, the Columbia River Basin Indian Tribes, and NOAA Fisheries.

Food webs relate directly to the Council’s Columbia River Basin Fish and Wildlife Program, which seeks to establish and maintain an ecosystem that sustains an abundant, productive and diverse community of fish and wildlife. Furthermore, food webs reveal insights into basic properties underpinning productivity and resilience that cannot be obtained from an exclusive focus on hydrosystem, habitat, hatcheries and harvest (the four H’s). Food webs fuel the ecosystem, providing the theme for this review. The ISAB suggests that incorporating a food web perspective into management efforts will help sustain the ecological system, provide for more productive and resilient fisheries, and would complement other approaches – such as the focus on habitat restoration – and thereby enhance our collective ability to meet the Council’s vision.

Food webs describe pathways by which energy, nutrients and other materials make their way to species of cultural and economic interest. While food webs are often thought of as reflections of habitat, many other factors shape their internal organization, linkages, productivity and resilience. Species diversity, the mix of native and non-native species, chemical contaminants, habitat carrying capacity, nutrient delivery and cycling, competition, predation, parasites, disease and associated system-scale processes are all deeply involved in shaping food webs. Nevertheless, highly complex food webs have been successfully manipulated at large scales to improve water conditions as well as recreational fisheries while, at the same time, ill-advised manipulations have resulted in serious environmental issues.

In February 2009, the ISAB Administrative Oversight Panel asked that the ISAB provide a fundamental understanding of aquatic food webs in the Columbia River Basin and their effects on native fish restoration efforts. The scope of the review includes tributaries, riparian zones, impoundments and the mainstem Columbia and Snake rivers, as well as the estuary and plume. The ISAB notes that the Council’s Fish and Wildlife Program and the NOAA Fisheries’ recovery strategies only tangentially consider impacts of changes to food webs and implicitly assume stable conditions. Moreover, substantial changes in physical conditions and in biotic communities, combined with the ongoing proliferation of non-native species and hatchery-reared fish, have resulted in hybrid assemblages of organisms and environmental conditions. Together, these changes have reverberated throughout the Columbia Basin affecting the aggregate carrying capacity of the river to produce wild fish. Further, abundant and widespread use and discharge of chemical contaminants have further affected the ability of food webs to drive biotic production in unknown ways. Collectively, these and other findings detailed in the report suggest that food web processes have been profoundly altered with largely un-quantified impacts on the success of restoration efforts and the status of Columbia River Basin fish and wildlife populations.

The report has five complementary sections:

  1. General concepts and applications related to food webs are examined initially (Section A),
  2. A brief description of the physical setting (Section B),
  3. A detailed discussion of key environmental processes affecting food web characteristics (Section C),
  4. An examination of food webs in typical habitats (Section D), and
  5. A system perspective integrating our findings with contemporary and emerging issues (Section E).

The four appendices describe a variety of methods used in food web investigations (Appendix A), the legal and policy web surrounding restoration activities in the Basin (Appendix B), pesticides used in the Basin (Appendix C), and give a list of common and scientific names used in the report (Appendix D).

The food web-related issues addressed in the report are numerous and complex, more so than initially imagined. Therefore, the ISAB felt that suggesting a time-prioritized action plan would be important. The ISAB proposes that the Council consider a 12-year plan with an estimated total cost of at least $20-25 M. The estimate is given only to provide an initial sense of the scope and scale of food web issues. Specific activities could be nested within the existing Fish and Wildlife Program, representing ~1% of annual budget. Some suggested projects fall naturally under Monitoring, as they involve determination of the state of the system, both in advance of intervention and for progressive monitoring as the effort unfolds. Some fall under Habitat, as they involve efforts at habitat manipulation and/or restoration/reclamation. Some fall under Production, as they involve adjustments to rearing and releasing fish, in what numbers, and where. The rest of the suggested activities fall under Research, particularly those aimed at filling information gaps.

Consideration of food web processes in fish and wildlife planning will help frame recovery actions that have a higher probability of achieving stated objectives over the coming decades. The identification of the types, location, and intensity of potential food web impacts on fish and wildlife should help ensure the long-term success of projects supported by the Fish and Wildlife Program. The ISAB is optimistic that this report will be used to inform the Council’s efforts in selecting projects, implementing the research plan, providing monitoring and evaluation guidance, and continuing the development of subbasin plans and provincial objectives.

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