Qualifications:

The ISRP recommends that the proponents describe their responses to the ISRP's comments and suggestions below in their upcoming annual report covering FY 2019 accomplishments.

1.      This long-running project has fully developed annual objectives and well-established field and analytical tasks. However, project's methods were developed over twenty years ago. Consequently, the proponents should determine (a) if it is possible to use their extensive capture-recapture data in the Barker Model to estimate survival, recruitment, movement, and abundance; (b) if their estimators for abundance based on CPUE are still valid; and (c) how well those approximations align with potential estimates produced from capture-recapture data. Validation of the abundance estimator is important since it is linked to the project's predation index. The proponents should also determine whether current bioenergetic models could provide improved estimates of consumption of juvenile salmonids, instead of indices of consumption.

2.      The ISRP asks the proponents to determine if direct measures of predation due to colonial waterbirds that have been developed can be applied to piscivorous fishes in the Basin. Although results from analyses on a variety of parameters including PSD, W_r, diet composition, and indices of abundance, consumption, and predation failed to detect signs of compensatory responses in northern pikeminnows, smallmouth bass, and walleye, their data suggest that localized compensatory responses may be occurring. The proponents should perform analyses to evaluate trends in locations that exhibit potential compensation by these predators. We also recommend that the proponents work with the Basin's avian researchers to see if their efforts to remove northern pikeminnow have prompted a compensatory effect in colonial waterbirds. Recently, direct measures of predation due to colonial waterbirds have been developed. The data collected by this project appear to be suitable for a similar analysis. We ask the proponents to explore this possibility with the avian researchers.

3.      We encourage the proponents to work with others to publish peer-reviewed papers describing their work and findings. It appears that the most recent work published from this very large effort was published before the turn of the last century.

4.      Although it is clear that the project is using adaptive management to change and refine its actions, a brief description of the process being used is needed. Is it a formal process or an ad hoc one prompted by an apparent need?

Comment:

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

The northern pikeminnow management program (NPMP) has three major goals, to: (1) estimate rates of exploitation of northern pikeminnow and quantify predation reduction, (2) characterize population parameters of northern pikeminnow, smallmouth bass, and walleye in the Columbia and Snake rivers, and (3) assess evidence of intra- and inter-specific compensation due to the sustained removal of northern pikeminnow. These goals are addressed in the project's six overarching implementation objectives which are to (1) conduct a sport-reward fishery; (2) perform fisheries at the John Day and The Dalles dams; (3) evaluate the dam fisheries; (4) examine potential compensatory responses in northern pikeminnow, smallmouth bass, and walleye due to the continuous removal of northern pikeminnow; (5) estimate fishery exploitation rates; and (6) evaluate the overall effects of the NPMP on predation rates. Specific details on the tasks that are performed under each of these implementation objectives are presented in the project's 2017 Annual Report.

Pikeminnow control occurs annually. Quantitative objectives have been established for some objectives (e.g., annual exploitation rate of 10% to 20%), establishment of 19 sport fishery registration, and creel stations situated throughout the Basin. In most cases, however, specific quantitative objectives have not been set. However, they could be established if power analyses were used to help set yearly objectives for the number of diet samples, numbers of fish that should be tagged, and number to be collected for indices. Such objectives would need to be determined for each reservoir reach sampled by the project. For data analysis objectives, quantitative goals are not appropriate, other than their yearly completion.

2. Results and Adaptive Management

The proposal and 2017 Annual Report (Williams et al. 2018) indicate that annual sport-reward and dam fisheries have occurred as planned. Catch, effort, diet, and other biological data have been collected and analyzed. Additionally, a model developed in the 1990's is used to estimate the potential decrease in predation of juvenile salmonids due to the program's removal of northern pikeminnow. The proponents acknowledge that simply saving juvenile salmon from northern pikeminnow predation may not increase their overall survival. Compensatory responses (i.e., changes in abundance, diet, growth, or relative condition) in the northern pikeminnow population and in other potential predator populations may nullify any apparent gains in juvenile salmonid survival. Consequently, a portion of the project's work examines possible compensatory responses in northern pikeminnow, smallmouth bass, and walleye. The project's CPUE estimation of abundance indices, however, should be reviewed and recalibrated. The population estimation methods were developed in 1995 and have not been reassessed or calibrated in more than 20 years. Local increases in smallmouth bass have been documented in several major sites. Compensation could be occurring locally and reducing the effectiveness of the pikeminnow control efforts, but the current averaging of abundance indices across the system will not reveal those impacts.

The project summary indicates the project has a long history of using adaptive management to change its methods and management actions. For example, changes were made on: (a) the lower size limit of the northern pikeminnow that should be harvested, (b) how sport fishers should be paid for harvested fish, (c) whether dam fisheries should occur and where these fisheries should take place, (d) where registration and creel check stations should be established, (e) tagging methods used to estimate tag loss, and (f) the number of agencies involved in program oversight. The results and lessons learned are largely applicable to the project. The overall approach of assessing potential survival benefits of predator removal on prey species, however, may have applicability beyond the Basin.

The project has consistently provided annual reports, helped organize a basinwide conference on predation, and made presentations to the Council. All these are useful for management. The project also produced peer reviewed journal articles before 2000, but the proposal does not report the publication of any journal articles in 20 years.

Since its inception in 1991, the program has harvested ~ 4.9 million northern pikeminnow, reached its desired exploitation rate of 10%-20% on northern pikeminnow > 25 cm in 24 out of 28 years, reduced potential consumption on juvenile salmonids (estimated from indices) by an average of 32% (range 17% - 49%), and detected no system-wide compensatory responses in sampled piscivores. There are several opportunities for the project to further its investigations on the effectiveness of its actions on juvenile salmon survival. For instance, the project could integrate its data with others (e.g., projects 1996-020-00 Comparative Survival Study and 1993-029-00 Survival estimates for passage through Snake and Columbia River dams and reservoirs) to estimate survival rates from one reservoir to the next. These rates could be correlated with exploitation and possibly SAR values. The project should also use its plentiful capture-recapture data to estimate abundance, survival, recruitment, and movement of fish throughout the river system. These estimates could be made by reservoir or location and compared to those the project makes on a systemwide basis.

Additionally, the project should investigate the possibility of using currently available DNA methods (including eDNA; see Sethi et al. 2018, Krehenwinkel et al. 2019) to help determine the diets of harvested northern pikeminnow by size, area, and time strata. Also, the current model to evaluate improvements in survival of juvenile salmonids estimates how the removal of northern pikeminnow in year "n" has enhanced survival in the following year (year "n + 1"). Juvenile salmonid survival is also expected to increase during the year of removal (i.e., year "n"). The proponents collect data that could be used to estimate the number of juvenile salmonids "spared" due to the operation of their fisheries in the same year the fisheries are taking place.

The project's proposal and annual reports conclude that compensatory responses in northern pikeminnow and other predatory resident fish have not been detected. This conclusion needs to be investigated further. Currently, abundance indices for northern pikeminnow, smallmouth bass, and walleye are based on catch-per-unit effort (CPUE) data. CPUE data have apparently not been calibrated with the project's capture-recapture data since the early 1990s. Such an evaluation should be done as CPUE estimates of relative abundance likely vary among years and seasons. Also, the proposal reports that smallmouth bass have increased in several Snake River reservoirs and locations in the mainstem. This suggests that compensatory responses may be occurring in specific locations. This possibility should be investigated.

Finally, efforts to evaluate compensatory responses among predators has been restricted to fish species. The proponents should explore working closely with avian researchers in the Basin to see if see if reductions in northern pikeminnow abundance have led to compensatory responses in bird populations (e.g., numerical and migratory responses in gulls, pelicans, terns, cormorants, seabirds in the plume, etc.). Recently, for example, Real-Time Research scientists have developed methods that directly measure the predatory impacts of colonial waterbirds on juvenile salmonids. They discovered that bird predation was likely additive and varied from week to week. When asked, these scientists were confident that the data being collected by the northern pikeminnow project would be amenable to their approach. This would allow the project to make more robust assessments of additive or compensatory responses.

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

The NPMP has developed and implemented its program based on sound scientific principles and initial empirical studies that modeled northern pikeminnow predation and produced indices of abundance, predation, and consumption. This foundational work continues to be the basis for the program and its continued focus on exploitation rates of northern pikeminnow. The approaches being used are appropriate. However, after more than 28 years, there are opportunities to:

·         Re-evaluate estimators of abundance and predation rates. For instance, in 2017 more than 1400 northern pikeminnow were tagged with individual tags. About 170 were recaptured and used to estimate exploitation rates. It seems like much more could be done with these data. The Barker model, for analyzing capture-recapture data (an extension of the CJS open-population model), could be used to estimate the survival of northern pikeminnow by size class and perhaps estimate their abundance (see Conner et al. 2015; Bouwes et al. 2016). If these estimates were calculated for different years, they may also provide information about compensatory responses of northern pikeminnow to the project's consistent removal program.

·         Take advantage of the PIT-tagging program to create alternative estimates of abundance as well as measure the distribution and habitat use of northern pikeminnow across seasons.

·         Conduct focused northern pikeminnow population estimates in the upper Columbia and use the survival studies of the PUDs and CSS study to evaluate the effects of pikeminnow predation on juvenile salmonid survival.

·         Examine to what degree is the project's systemwide sport fishing harvest more efficient than focused intensive harvest activities by state and federal agencies or contractors in areas where elevated predation is likely occurring. For instance, dams, tailraces, and habitats upstream and downstream of passage routes are areas where predators can congregate. Salmonid prey are concentrated, and may be injured or impaired, as they pass through these locations. Predator management is warranted in such areas as it may increase the survival of juvenile salmonids as they navigate through the mainstem.

·         Perform power analyses to determine appropriate numbers of tagged fish to release in each of the reservoirs being evaluated by the project.

·         Use current bioenergetic models to estimate total consumption of salmonids by pikeminnow across reservoirs.

·         Develop local and systemwide assessments of compensation to see if patchy compensatory responses are occurring, increasing, or simply represent interannual variation.

The NPMP has a long record of timely reporting to BPA and the states and has developed a public website where its reports and data on fishing results can be found. After more than 20 years of sampling and analysis, publication of their findings in peer-reviewed journals would increase their education and technical transfer efforts.

Literature cited:

Bouwes, N., N. Weber, C.E. Jordan, W.C. Saunders, I.A. Tattam, C. Volk, J.M. Wheaton, and M.M. Pollock. 2016. Ecosystem experiment reveals benefits of natural and simulated beaver dams to a threatened population of steelhead (Oncorhynchus mykiss). Nature Scientific Reports 6:28581.

Conner, M.M., S.N. Bennett, W.C. Saunders, and N. Bouwes. 2015. Comparison of tributary survival estimates of steelhead using Cormack-Jolly-Seber and Barker models: implications for sampling efforts and designs. Transactions of the American Fisheries Society 144:34-47.

Krehenwinkel, H., S.R. Kennedy, S.A. Adams, G.T. Stephenson, K. Roy, R.G. Gillespie. 2019. Multiplex PCR targeting lineage specific SNPs - a highly efficient and simple approach to block out predator sequences in molecular gut content analysis. Methods in Ecology and Evolution https://doi.org/10.1111/2041-210X.13183.

Sethi S.A., W. Larson, K. Turnquist, and D. Isermann. 2018. Estimating the number of contributors to DNA mixtures provides a novel tool for ecology. Methods in Ecology and Evolution. 00:1-11. https://doi.org/10.1111/2041-210X.13079.

This proposal describes a successful ongoing program to encourage anglers to exploit a native nuisance predator, the northern pikeminnow (NPM), and to evaluate the effectiveness of this exploitation for reducing predation on outmigrating salmonids. After 20 years of modifications and fine-tuning, the program has achieved 10-20% exploitation rates on large northern pikeminnow, which are the most predaceous, and an estimated 40% reduction in predation on out-migrating smolts.

The overall significance of these northern pikeminnow removals on SARs remains unknown, relative to marine survival in particular, as the proponents note:

“Although it is inherently difficult to relate predator removals to smolt survival benefits, it should in theory be relatively easy to estimate the correlation between SARs and NPMP exploitation rates. The NPMP staff plans to complete this evaluation in the next project cycle.”

Qualification 1: The program would be improved if the evaluation was completed (or at least some detailed plans for evaluation completed) in the present project review cycle.

Statistical designs and analyses have been reviewed about 7-10 years ago, and investigators are using estimators that, although valid, might be improved.

Qualification 2: The ISRP recommends investing in an updated review of these methods (before the next review cycle) by scientists with expertise in current capture-recapture methods, to ensure that the best methods are being used.

Previous ISRP comments still apply, “This program is well justified, technically, and the predator removal program seems to have reached its objectives over the years, although better information might be provided on how this has improved smolt-to-adult return rates (SARs).”


Other ISRP comments:

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

This project primarily responds to the 2008 FCRPS BiOp (a number of RPAs referred to for several objectives). The program is important at the regional level, since it measures northern pikeminnow predation throughout >400 miles of the mainstem Columbia and Snake rivers, and addresses predation at the whole-system scale.

The technical background provides good justification for the program and is supported by a large number of peer-reviewed publications detailing the biological parameters of predation, and the models used to estimate both abundance and consumption, all of which are used to estimate system-wide predation and compare it to pre-program levels. However, there may be some potential for further improvements in design and analysis as the statistical sampling design and statistical estimators used have been reviewed about a decade ago (Hankins and Richards 2000 [not listed in the References]; Styer 2003). Moreover, some references listed (e.g., Everhart and Youngs 1981) are nearly 30 years old. Although unbiased statistical estimators do not become out of date, newer methods are constantly being developed that provide improved estimates. For example, capture-recapture methods used for estimating exploitation of waterfowl are an active area of research and analysis. The ISRP believes that a modest investment in review by analysts with expertise in modern capture-recapture theory would be well worth the investment to continue updating methods and deriving the best estimates (e.g., see White and Burnham 1999; Royle and Garrettson 2005, White 2008, Zimmerman et al. 2009).

Royle, J. A., and P. R. Garrettson. 2005. The effect of reward band value on mid-continent mallard band reporting rates. Journal of Wildlife Management 69:800-804.

White, G.C. 2008. Closed population estimation models and their extensions in Program MARK. Environ. Ecol. Stat. 15(1): 89-99.

White, G.C. and K. P. Burnham. 1999. Program MARK: Survival estimation from populations of marked animals. Bird Study 46 Supplement, 120-138.

Zimmerman, G. S., T. J. Moser, W. L. Kendall, P. F. Doherty, G. C. White, and D. F. Caswell. 2009. Factors influencing reporting and harvest probabilities in North American geese. Journal of Wildlife Management 73:710-719.

2. History: Accomplishments, Results, and Adaptive Management

A thorough description of history and accomplishments of the northern pikeminnow program is provided.

Major results are explained in detail in the Problem Statement / Technical Background of the Objectives subsection. Several important ones include:

(1) Fisheries for northern pikeminnow, have resulted in the removal of over 3.3 million northern pikeminnow >250-mm fork length throughout the lower Columbia and Snake rivers, with annual exploitation from 1991-2009 averaging approximately 13%.

(2) Exploitation of northern pikeminnow >250-mm fork length has remained above 10% since 1998, and has increased in recent years. Exploitation rates in 2004 (18.5%), 2005(19.0%), and 2008(19.5%) were the highest observed rates in the history of the program.

(3) Predation index values have generally decreased since the early years of the program (1990-1993), especially above Bonneville Dam. Below Bonneville Dam, predation indices have fluctuated recently (1999, 2004, and 2005), but remain below mean 1990-1996 values.

The project is continuing to meet goals, but (as indicated above) the ISRP would like to see results and data regarding the question of significance of northern pikeminnow removals for benefiting SARs.

The project is continually practicing adaptive management by adjusting program efforts based on annual results as indicated by exploitation rates.

3. Project Relationships, Emerging Limiting Factors, and Tailored Questions for Type of Work (Hatchery, RME, Tagging)

Although no Project Relationships were listed, it is clear that this effort is a close collaboration among the Pacific States Marine Fisheries Commission, the Oregon Department of Fish and Wildlife, the Washington Department of Fish and Wildlife, and other management agencies.

Northern pikeminnow predation has long been recognized as a limiting factor for salmonid smolt survival. An emerging limiting factor might be the overarching effects of climate change on conditions like temperature, which might foster or reduce populations of northern pikeminnow or non-native predators like walleye and smallmouth bass.

There is scope for value added results from the project such as information on lamprey in northern pikeminnow stomachs. Proponents should collaborate with CRITFC relative to the Columbia River Basin Lamprey plan to see if joint data collection could be conducted.

4. Deliverables, Work Elements, Metrics, and Methods

Deliverables, work elements and metrics are well established and proven to meet their intended purposes (i.e., estimate consumption rate of salmonids by northern pikeminnow). One exception is for Objective 6, which seemed to be a relatively vague statement about using the model and attempts to continually improve it, but with little reference to how these might occur.

Methods were adequately described (with the exception of Objective 6) and references made to peer-reviewed publications where needed.

This proposal describes a successful ongoing program to encourage anglers to exploit a native nuisance predator, the northern pikeminnow (NPM), and to evaluate the effectiveness of this exploitation for reducing predation on outmigrating salmonids. After 20 years of modifications and fine-tuning, the program has achieved 10-20% exploitation rates on large northern pikeminnow, which are the most predaceous, and an estimated 40% reduction in predation on out-migrating smolts.

This is an ongoing project that has proven its worth through repeated technical and economic reviews since its inception. The notion that a major predator on juvenile salmonids could be reduced in numbers and the survival of salmonids improved thereby has been validated by many years of data and analyses. The project has been exemplary on reporting of results and has responded well to external reviews. The sponsors have provided a satisfactory and useful response to the ISRP's questions in the preliminary proposal review.

The predator removal program seems to have reached its objectives over the years, although better information might be provided on how this has improved smolt-to-adult return rates (SARs). The response indicated how difficult this would be and noted that the project has not attempted it. A number of peer-reviewed publications have been prepared and specific reporting has been completed. This history of results is adequately presented in the proposal. The general context is well explained through coverage of the existing regional plans relevant to the project, but linkages with other predator related projects in the Columbia River Basin are only briefly mentioned in the proposal. However, the response provided good amplification regarding other predators. There was also a good outline of work elements. The proposal is slim on methods, although these have been well standardized over the years. An established database and reporting program is in place. The proposal calls for significant increase in effort toward data synthesis and interpretation; this should be supported.

Despite a generally favorable initial review, the ISRP raised several questions that were well addressed in a response by the sponsors.
1) A model for estimating the improved survivorship of smolts is a work in progress.
2) There has been no attempt to relate the predator removals and estimated smolt benefits to SARs because of inherent difficulty.
3) The sponsor clarified what they mean by a systemwide response: "The term "system-wide response" is used in the narrative (2nd paragraph) in reference to possible compensation by remaining pikeminnow and other predators to sustained removal efforts." The sponsors would welcome a wider involvement in Columbia River Basin ecosystem related management. It would be worthwhile to foster this interest. Perhaps an appropriate agency could host a symposium on predation effects on Columbia River salmonids. Predation in all habitats could be discussed and might shed some light on how or if salmon SARs are being influenced by northern pikeminnow.
4) They provided a useful perspective on other predators (smallmouth bass, walleye) that might increase in response to northern pikeminnow reductions, providing both existing knowledge about lack of compensatory effects and current status of these populations. The ISRP appreciates the concise and informative responses.