Response requested comment:

This project has been changed and has made significant progress since its inception. The proponents appear poised to develop better methods to determine sea lion predation using accelerometer tags and to collect useful data on distribution and abundance of sea lions using boat surveys. Estimation of sea lion abundances admittedly is a challenging task, but additional efforts to characterize the variance of these estimates would strengthen the research. More information is needed about the statistical analyses of the functional responses and abundance estimates from the tandem boat surveys. Additionally, better goals and criteria are needed for the lethal removal effort. The ISRP requests responses to the following:

1.      More detail is needed about the statistical methods used for the conditional Lincoln-Peterson estimators of sea lion abundance from the tandem boat surveys. How would abundance estimates differ if a sequence of additional observation boats were used (e.g., 2, 3, 4 or more) for a reach? Might drones be used?

2.      The estimation of abundance, distribution, and predation of sea lions is described as a continuation of the previous measurements with tandem boat observation and accelerometers. Additional information should be provided to describe how these two measurements or their analyses will be changed or improved by the proposed research. How will these results be synthesized and reported? How will they evaluate their methods with comparisons to measures by other research groups or modifications of their protocols? More detail is needed about the functional responses fit to the predation data.

3.      How will culling of sea lions be evaluated? What criteria will be used to assess whether it is effective at reducing sea lion abundance and predation on adult salmonids? What factors will be considered when determining how many animals will be culled?

4.      Although lethal removal has been controversial to date, it is likely going to get much more so with increased culling. Is there a CRITFC or NOAA public relations plan in place to address a public response to the culling program?

5.      What are the culling techniques and what do they plan to do with the carcasses? Will the meat, hides, and bones be used? If so, is there concern about possible contaminants in the meat?

6.      A brief description of how adaptive management occurs is needed.

Comment:

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

The proposal identifies three objectives: (1) continue boat-based hazing below Bonneville Dam, (2) estimate abundance, distribution, and predation of salmon by sea lions in the lower Columbia River, and (3) remove nuisance sea lions from the Columbia River. The only objective that is quantifiable is the second objective. The boat hazing and lethal removal objectives describe only implementation of the measures and do not provide quantifiable outcomes of anticipated results. The proposal simply indicates that these activities will occur. The ISRP has questioned the continuation of boat hazing in previous reviews because the proponent's studies indicated it was not effective. The hazing objective will be discontinued if CRITFC is authorized to lethally remove sea lions from the lower Columbia River, assuming that hazing is not a condition for removal under a new NOAA authorization.

The investigators propose to continue surveying sea lion occurrences below Bonneville Dam using tandem boat observation. These observations will be used to estimate abundance of sea lions from Bonneville Dam to Astoria (RM 12) and estimate predation based on a functional response model. They also will use accelerometer tags attached to the heads of sea lions to estimate individual predation rates, but this method is still in the early stages of development and has been applied successfully to only seven individual sea lions.

2. Results and Adaptive Management

The description of objectives, deliverables, and timelines is brief and largely a continuation of previous work. Overall, the project objectives were met in most cases. Non-lethal hazing is not that effective and only temporary. Tandem boat surveys are relatively efficient for estimating abundance and distribution. Acoustic telemetry of individual sea lions gives information on differences in behavior of California versus Stellar sea lions in the lower river. Functional responses give estimates of predation by California sea lions below Bonneville. No obvious trend of increasing or decreasing predation was observed.

It appears that the main benefit of non-lethal hazing is deterring sea lions from areas around the entrance to the Bonneville fish ladder (Tidwell et al. 2019). The estimates of sea lion abundance from 2013-2016 were reported in a table, but the results were not discussed or interpreted. Abundances tended to be greatest in mid to late March but varied greatly between years and zones with no obvious trends.

The section on adaptive management identifies only changes that have been made over the course of the project. It does not identify a decision-making process for adaptive management of the overall project.

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

The field observation methods and statistical analyses are described only briefly in the proposal but were described in more detail in their 2017 Annual Report to BPA. The estimates are based on observed animals only but do not include sea lions in areas that are not surveyed. The researchers plan to develop spatial analyses to adjust their estimates for areas surveyed, but the proposal does not describe these plans.

The proponents state the project is complementary to other sea lion interaction work that is currently being conducted, but they only described hazing or lethal removal activities of USACE and the states of Oregon, Washington, and Idaho. No collaborations on estimation of sea lion abundance and predation rates with other agencies or researchers are described. Such collaboration would be beneficial and improve synthesis of the results of these different studies. It is possible such collaborations are occurring, but the proposal provides no information about them. No information was presented on how lethal removals will be evaluated, in terms of whether they are effective at reducing sea lion abundance and predation on adult salmonids. It should be determined if the project's actions led to shifts in sea lion distribution patterns (numerical responses) and feeding habits. For example, will remaining sea lions switch to eating more salmon per capita?

The description of data management does not indicate the project provides open or online access to the summary data and research products. QA/QC appears to be limited to proofed field data sheets prior to entry into Excel spreadsheets. Data potentially are shared if requested, but policies and criteria for sharing are not described. Key findings were shared via project reports, but peer-reviewed publications reporting results of boat surveys of abundance and functional response models have not been completed yet would be highly useful to other investigators and managers.

Literature cited:

Tidwell, K.S., B.A. Carrothers, K.N. Bayley, L.N. Magill, and B.K. van der Leeuw 2019. Evaluation of Pinniped Predation on Adult Salmonids and other Fish in the Bonneville Dam Tailrace, 2018. U.S. Army Corps of Engineers, Portland District, Fisheries Field Unit. Cascade Locks, OR. 65pp.

The proposal is insufficient for technical review. The ISRP finds that none of the proposed project objectives have been technically justified (see comments in sections B-D, below). The ISRP recommends the elimination of the proposed non-lethal hazing of sea lions (Objective 1) as a stand-alone objective. The ongoing cooperative hazing activities have not been justified by any documented positive results of reducing predation on salmonids. However, the effects of non-lethal hazing on feeding behavior of sea lions could be studied through responses of acoustic tagged individuals and therefore, could be incorporated as an element of Objective 3 – see below. The ISRP also recommends eliminating the video monitoring portion of the proposal (Objective 2). The rationale for the proposed video monitoring to estimate sea lion predation is weak (i.e., the study design is incomplete and metrics undefined), and to attempt estimates outside the current observation area below Bonneville Dam (~150 river km) may take years to develop with a high risk of failure in collecting quantitative data. However, the proposed acoustic telemetry project (Objective 3) is a good idea, and the ISRP encourages further development of this part of the proposal. To accomplish this, a much more detailed study design is needed, including methods and monitoring protocols for acoustic tagged sea lions, and some specific statements of how the resulting data will be applied towards management of this predation problem (see comments in section F, below).