This is the original proposal (Dr. Jason Dunham, June 2009) to produce a review of the literature
on effects of barrier removal on aquatic populations and recommendations on methods for
effectiveness monitoring at road-stream crossings replaced or modified for aquatic organism
passage.
Aquatic Organism Passage: Systematic Evidence Review and Guidelines for an
Effectiveness Monitoring Protocol
Background – Restoration of aquatic organism passage through culverts is a major focus of
improving aquatic ecosystems in the United States. The cost of restoration has totaled hundreds
of millions of dollars, with potential work to be done on hundreds of thousands of structures that
may act as barriers to aquatic organism movements. This massive investment has been
motivated by the potential benefits of restoring passage, which seem obvious for native species.
Measurable responses to restoration of passage include 1) increased probability of use of habitats
upstream of reaches with passage restoration, 2) increased genetic diversity with and reduced
variability among locations after passage restoration, 3) increased rate of movement after
restoration, and 4) changes in population density or expression of life histories. Whereas passage
restoration is generally thought to be beneficial for native species, tradeoffs between isolation
and invasion may emerge if restoration would be likely to increase invasion by nonnatives that
threaten native species. From this brief consideration of the issues, it is clear that there is a
diverse range of responses of aquatic organisms for passage restoration, and that passage
restoration may often, but not always provide benefits to native species.
Problem statement – The actual impacts of restoration for aquatic organisms have not been
summarized for diverse native and nonnative aquatic species across the United States. A review
of the evidence is needed to provide an assessment of our current understanding of biotic
impacts, and for identifying responses to measure for effectiveness monitoring of aquatic
organism passage.
Objectives – 1) Identify a series of critical questions to frame a systematic evidence review of
impacts of aquatic organism passage impairment and restoration, representing diverse species
across the United States; 2) Acquire relevant literature; 3) Provide a systematic review of
evidence; and 4) Summarize results with recommendations for response designs to be used for an
aquatic organism passage effectiveness monitoring protocol.
Products – Peer-reviewed USGS Open-File Report to include: 1) An overview of relevant
questions addressed; 2) Review of existing literature; and 3) Synthesis with recommendations for
effectiveness monitoring of aquatic organism passage
Timelines – Project would be initiated in October 2009 with completion scheduled for October
2010, with preliminary guidelines available to inform pilot development of an effectiveness
monitoring protocol in the summer of 2010 (draft guidelines available by 31 March 2010).