The response was very thorough and well organized. Each issue raised in the previous ISRP review was explicitly addressed. The additional information on previous studies that have been conducted as part of the effort to restore the focal fish species in Lake Pend Oreille was especially helpful in clarifying the questions raised by the ISRP in the previous review.

The ISRP agrees that working in this large natural lake poses many difficult challenges, but the responses indicate that IDFG is making a good faith effort to incorporate the latest information into their studies and have enlisted the help of very qualified specialists. The ISRP appreciates that additional details about the results of previous investigations have been incorporated into the proposal. Links to annual reports and other reports summarizing data are useful, but they do add to the difficulty of assessing scientific merit when a link must be followed. Where possible, concise summaries of main findings, in addition to the links, are very much appreciated and make the review process more efficient. We also appreciate that the field methods pertaining to this study in Monitoringmethods.org have been reclassified so that details are now accessible.

Overall, the ISRP is satisfied that this project will continue to generate useful data on the management of Lake Pend Oreille and its fisheries, and are confident that the sponsors have thought carefully about addressing these issues in this complex lentic ecosystem.

ISRP Retrospective Evaluation of Results

The Lake Pend Oreille Kokanee Mitigation project is a good example of a study where project staff has done an excellent job of seeking outside assistance in tackling a very tough scientific problem. While the project title suggests that it focuses on kokanee, it is clear that the project's scope has broadened to other fishes as well as the limnological dynamics of the Pend Oreille ecosystem itself. This project is almost 20 years old, and a publication summarizing what has been learned over the last two decades would be a valuable contribution, as well as useful in informing fishery managers in other large lake systems.

The Lake Pend Oreille fishery has received a lot of attention because it focuses on the historically large non-native kokanee population, which is in decline although apparently recovering slowly, as well as a trophy rainbow and bull trout fishery, which is also depressed. Many restoration actions are occurring simultaneously, and it will be difficult to determine the efficacy of individual program elements on both the harvest and conservation objectives. Nevertheless, this project has contributed valuable information on the ecosystem processes supporting the lake's salmonid populations over the last decade, and it is likely to provide useful data in the future.

The ISRP requests clarification on several points before providing a final recommendation.

1. What is the likely role of lake whitefish in reducing abundance of Mysis?
2. Additional justification is requested for adding spawning gravel to select shorelines to increase kokanee spawning.
3. A summary of what has been learned over the past 15 years of management actions in the context of the overall objective of increasing harvest is needed.
4. What has been learned from Lake Pend Oreille research that has helped IDFG balance conservation and harvest objectives?
5. What are likely reasons why rainbow trout have increased in abundance by 50% from 2009 to 2010?
6. Other questions and concern are embedded in the comments provided below. The ISRP suggests the sponsors examine these items as a response is prepared.

Apart from specific questions, the ISRP feels the restoration of native resident bull trout and westslope cutthroat trout in Lake Pend Oreille deserves additional attention. This proposal devotes little attention to these species, even though other proposals in the region do. For example, there may be adfluvial populations of cutthroat trout that could or do provide important sport fisheries, and management could consider restoration actions in Lake Pend Oreille’s tributary habitats. Ongoing lake trout suppression would also benefit these other native species, but increased kokanee production would not likely benefit whitefish or most cutthroat trout

See the ISRP’s programmatic comments on fish stocking.

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

This project has been in place for a long time, and the plan of work was reviewed by the ISRP in 2006, when it was given a favorable assessment. It is important to note that Lake Pend Oreille represents a large natural lake with a highly altered fish community. Of the three primary focal species, two are not native (kokanee and Gerrard stock rainbow trout) and the third (bull trout) is primarily of interest from a conservation standpoint, not a harvest standpoint. Additionally, the food web in Lake Pend Oreille has been strongly affected by the invasion of a non-native zooplankton (Mysis diluviana), which has acted as a competitor with kokanee and also helped to fuel the expansion of the non-native lake trout population, a significant predator on mysids as well as kokanee and juveniles of other salmonid species. As with many large lakes with increasing human development in the watershed, management challenges in Lake Pend Oreille are complex.

The project sponsors have done a good job of describing the relationship of this project to other regional resident fish management efforts, and their description of the technical background was also well done.

The proposal makes clear that recovery of the Pend Oreille fishery is the project's primary goal. Conservation of the two native salmonid species, bull trout and westslope cutthroat trout, is acknowledged in the work, but the primary emphasis is either research that addresses factors limiting kokanee and trophy trout recovery or habitat improvements that benefit kokanee reproductive success, such as addition of spawning gravel. Reduction of the lake's population of lake trout, generally viewed as a negative influence in the Pend Oreille ecosystem, also figures prominently in the work.

As mentioned above, management challenges are complex and restoring a desired balance of species, that is a balance that favors angler harvest of kokanee and trophy trout, will require that a number of potential limiting factors be addressed simultaneously. This will essentially mean a trial and error approach, and that is what IDFW have been doing for the last 15 years. A strong monitoring program will be essential for detecting the signal of programs such as lake trout reduction, winter lake level manipulation, kokanee stocking adjustments, and possible nutrient additions.

The role of lake whitefish in reducing abundance of Mysis is mentioned once but is not addressed again. Could this be important?

The objective to increase kokanee spawning success by adding spawning gravel to select shorelines needs additional scientific justification. When gravel is added in streams or lakes without addressing the hydrogeomorphic factors that create clean spawning gravel, for example upwelling and wave action, the usual result is that the gravel simply becomes unsuitable, requiring either more gravel or manual cleaning, all at great expense. Additionally, we wonder whether studies of kokanee egg survival in the laboratory and in boxes buried in lake substrate will answer the question of interest: what conditions are necessary for high survival, and how does survival vary with sediment deposition? It is clear that survival should be low when sediment is high, but at moderate levels of sediment, it is not clear whether human-placed egg boxes or eggs monitored in the laboratory will mimic those from egg pockets placed by female fish sufficiently to generate useful data. 

2. History: Accomplishments, Results, and Adaptive Management (ISRP Review of Results)

The proposal does a good job of summarizing the administrative accomplishments of the project. More details could have been given on results to date. A single graph was presented showing lake trout abundance from 1999 to 2008 but with only 5 years sampling data, while it would have been helpful to have seen similar summaries as graphs or tabular data for the other salmonid species. Over the last 15 years a variety of management actions have been implemented such as lake trout netting, experimental winter drawdowns, hatchery operations, and angler programs. A summary of what has been learned from these actions in the context of the overall objective of increasing harvest is needed. It does appear that predator control has had some success, but what about other efforts? Also, there was little mention of warm-water fishes. Have these introduced fishes had negligible impact on focal species in other areas of the lake?

More information is also needed on how the results of the Lake Pend Oreille research have been incorporated into management changes. In particular, the potential for conflict between conservation and harvest objectives needs additional clarification. What has been learned from the research that has helped IDFG balance these two important objectives?

Other questions on accomplishments include:

Why have rainbow trout increased in abundance by 50% from 2009 to 2010? Is this difference significant, or are the confidence intervals around these estimates wide? If the difference is real, and not owing to high variability, then what is the explanation – high recruitment rates of small fish?

Lake trout marking – lake trout are reported as being marked in 2011 to estimate abundance by mark-recapture, but in the rest of the proposal all the lake trout were removed. When and where were these lake trout marked, how many, and of what sizes?

Management changes have focused on better targeting lake trout removal efforts in response to new data, and thereby reducing bull trout bycatch. The project sponsors acknowledge pressure from kokanee and rainbow trout anglers to increase abundance of these fishes and expand the fisheries, but how has this pressure driven management decisions as opposed to a focus on conservation and restoration of resident native fishes?

ISRP Retrospective Evaluation of Results

It is clear that the food web dynamics in the lake are changing, but it also seems clear that the primary focal species have not returned to a level of abundance that support harvest objectives. There is no question that the studies proposed here will help address some of the most important problems; however, the proposal itself did not supply very many details about the results of previous management experiments, with the possible exception of the lake trout netting program. Sorting out the benefits of the various initiatives including predator control, habitat improvements, hatchery releases, and nutrient manipulations will be very difficult when they are all happening at the same time and will require very creative field experiments and analyses.

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

Because this project has a long history and Lake Pend Oreille has been intensively studied, the suite of potentially limiting factors has been adequately characterized. The project also seems to be well integrated into other work taking place in the Pend Oreille watershed.

The questions being asked specific to kokanee restoration seem appropriate, for example, where do lake trout spawn and at what locations in their daily or seasonal movements will they be particularly vulnerable to capture? Additional work is needed on understanding the role of winter drawdown in regulating kokanee reproductive success, whether physical addition of gravel along shoreline spawning areas can be cost-effective, and whether deliberate nutrient supplementation can achieve desired food web benefits. Fortunately, the proposal contains elements that address these matters.

The proposal did not supply much detail regarding how salmonid releases from hatcheries would be carried out to maximize learning opportunities nor did it give many details about existing or planned monitoring efforts except for the acoustic tracking work on lake trout, which was adequately covered. It was also unclear how project staffs are exchanging information with other RME practitioners in the region, although the explicit call for an annual science review meeting to discuss results is an excellent idea.

4. Deliverables, Work Elements, Metrics, and Methods

The ISRP had several questions relative to project deliverables:

The proposal did not specify metrics and indicators in very much detail for some of the deliverables. Often the metrics were described in general terms, but not in a way that particular measurement protocols could be identified or assumed. Many of the protocols and methods in MonitoringMethods.org were in draft form and did not contain sufficient detail for scientific review.

The proposal also lacked information on what would be considered reference conditions for some of the deliverables. For example, if gravel is added to a kokanee spawning area, what would the reference condition be, pre-gravel enhancement egg survival or egg survival in an adjacent spawning area without gravel addition?

Can annual exploitation rates be accurately determined if only 30 lake trout are tagged with acoustic tags per year?

We were unsure why a gear efficiency study is necessary. Would it be more cost effective to buy a bigger boat and trawl and simply increase efficiency this way?