Comment:

This proposal describes impressive progress since 2010 in developing, testing, and refining alternative methods to achieve the lamprey abundance estimation objectives. A power analysis (requested by the ISRP in a previous review) determined that at least 2,000 Pacific lamprey must be tagged to obtain reliable estimates of abundance with the Lincoln-Peterson mark-recapture model. Fieldwork confirmed that PIT-tagged Pacific lamprey could be detected reliably, and that Pacific lamprey could be counted reliably from video recordings; both uncertainties had been identified by the ISRP in a previous review. Based on these results, the proponents expanded the PIT-tag antenna arrays and contracted Oregon State University statisticians to develop an alternative Bayesian model for estimating abundance that does not require tagged fish; this model can be used when low abundance makes it difficult to catch and mark enough fish for capture-recapture estimation. Thus, despite some recent challenges with low abundance, the project remains on track and continues to provide important data for assessing the status of Pacific lamprey. 

1. Objectives, Significance to Regional Programs, and Technical Background

The objectives are clearly stated and justified. The proposal clearly explains why this project was initiated and how it addresses biological objectives identified in the Pacific Lamprey Restoration Initiative, as well as critical uncertainties identified in the Fish and Wildlife Program. Anticipated benefits and opportunities for further research are described, but they are not expressed quantitatively. This is primarily a monitoring project that will require long-term continuity to fully describe escapement trends. 

Obtaining and tracking changes in the abundance and status of Pacific Lamprey returning to the Willamette River is an important conservation task. Additionally, genetic samples collected by the project and analyzed by CRITFC have shown that regional differences occur in the Basin's Pacific lamprey populations. This information is particularly important because it will help inform ongoing translocation efforts. 

2. Results and Adaptive Management

Good progress has been made since 2010 in developing, testing, and refining alternative methods to achieve the abundance estimation objectives. 

The major challenge is that declining catches in the fish ladder (HDX pool) since 2016 have compromised the precision (and feasibility in 2018) of capture-recapture estimates of Pacific lamprey escapement passing the falls through the fish ladders. An additional challenge is that these escapement estimates are expanded further to determine the total abundance that arrive at Willamette Falls in a given year. The expansion factor is the estimated proportion of fish (marked and unmarked) that do not pass the falls, which in turn is inferred from the proportion of marked fish that return through the fish ladders after being collected in the HDX pool, anesthetized, sampled, PIT-tagged, and released below the falls. One concern is error propagation—the percentage of marked fish returning to the fish ladder is low (averaging only 33%) and quite variable. A larger concern is bias because the return rate of marked fish appears to be estimated reliably from detections of PIT tags, but it remains unclear if the return rate for the marked fish accurately represents the passage rate of unmarked fish. Moreover, the fate of the fish that do not return is unknown. The proponents hypothesize that Pacific lamprey have been increasingly deterred from entering the fish ladders by a growing presence of California sea lions. This hypothesis could also explain the greatly reduced (since 2015) correlation between Willamette and Bonneville abundance indices for Pacific lamprey. If the proponents are correct, efforts in 2019 to reduce California sea lion presence should ameliorate these issues. 

Other project objectives, such as obtaining genetic samples, determining harvest rates, collecting biological data (length, weight), and ascertaining use of various passage routes over the falls have largely been met. Progress in assessing the fate of Pacific lamprey that remain below the falls is difficult to evaluate because not enough detail is provided in the proposal about the objectives and methods. Similarly, the genetics component of the project is not described in enough detail to evaluate results to date. This limitation arises partly because results for 2018 were not available for this review.

The proponents are to be commended for their continuing efforts to develop, test, and refine alternative technological and analytical procedures in the face of daunting challenges posed by physical logistics at Willamette Falls and the paucity of knowledge about Pacific lamprey. The credibility of the project has been greatly enhanced by comparing and validating results obtained by alternative approaches. Examples include the corroboration of capture-recapture estimates by video counts in 2011 and development of different statistical models (with OSU) that are less reliant on having access to an adequate sample of marked fish.

The proposal also indicates that the project's objectives are evolving steadily and creatively as information is gained, challenges are discovered, and new hypotheses are developed. However, neither the proposal nor the annual report describes an adaptive management process (i.e., review cycles) by which adjustments are made. For example, it is not clear who within or outside the project evaluates data and makes decisions to alter course. For completeness, the adaptive management process being used by the project will need to be described in the project's next annual report.

The monitoring data from the project are specific to the Willamette River and Falls. However, the project is also providing new knowledge on methodological issues and status and trends that are broadly applicable throughout the Columbia Basin. The genetic sampling in this project is directly linked to a study of population structure, adaptation, and migration that spans the lower Columbia and Snake rivers.

Results for 2018 were not available for this review. The proposal referred to "Other Project Documents on the web" but these documents were not apparent in Taurus. Moreover, the (draft?) 2018 Annual Report seemed to be the 2017 Annual Report with an updated title page. That said, the 2017 and earlier annual reports provide appropriately detailed discussion of objectives, methods, and results.

Findings have been shared as summary data in annual reports and similar documents. No peer-reviewed publications are listed. 

The proponents mention that they may collect samples of juvenile and adult Pacific lamprey for contaminant evaluation by USGS scientists. They note that Pacific lamprey appear to be accumulating high levels of flame retardants, pesticides, and mercury. Such levels may be harmful to the fish and could represent a health threat to human consumers. The ISRP feels strongly that this partnership should be established as soon as possible. It is critically important to ascertain whether contaminants are hampering lamprey recovery. If contaminants are a major issue, then no amount of habitat restoration or other measures will restore populations until their effects can be ameliorated.

The conceptual approach is logically valid for estimating the escapement passing the Falls through the fish ladders and for expanding that estimate to determine the total abundance arriving at the Falls, but it seems quite susceptible to errors in estimating the passage rate for unmarked fish. Confidence in the expansion procedure would be increased if it were possible to demonstrate that the low return rate of marked fish is mostly unrelated to factors associated with their capture and tagging.

3. Methods: Project Relationships, Work Types, and Deliverables

The proposal describes activities and methods in appropriate detail and makes good use of the published literature to justify assertions and to support procedures. Unfortunately, the online file in "Other Project Documents" with tables and figures that was cited to explain the 2018 methods and results could not be found for this review. Previous methods and results are documented clearly and adequately in the 2017 Annual Report. Many of their protocols have been posted on the PNAMP web site.

This project primarily serves a long-term monitoring and data sharing function. The proposal generally provides appropriate detail about the types of monitoring activities that have been conducted or planned. An exception is the discussion on page 10 of how "the sensitivity analysis of sea lions on lamprey indicated dramatic negative effect on below-falls estimates causing them to be unreliable." This discussion is difficult to understand and warrants more explanation. The genetics research component of the proposal lacks clear hypotheses; plans for future sampling are not described in the documents provided.

Meets Scientific Criteria (in part): • Objective 3 meets criteria • Response requested for Objectives 1 and 2 The project proponents initially should undertake the work at one or two passage locations to resolve uncertainties, as detailed below, unless they can present a good rationale for implementing a full-scale project (five locations) at this time. Specifically, more details are requested on the methods that will be employed to investigate the feasibility of the half-duplex PIT tag census technique and the development of a protocol for monitoring and indexing abundance. This should include a statistical estimate of how many lampreys would have to be tagged to obtain a valid escapement estimate.