The proposal should have provided a better summary of the response of kokanee to the initial addition of nutrients to the lake and have more strongly anticipated the expected future response. The following comments are given as feedback so future analysis might be strengthened.

To understand how the kokanee population responds to nutrient addition, it would seem to be necessary to track each cohort (brood year) separately over its lifespan. Data should have been broken out into growth and abundance by age, and before and after maturation, as that gives a better indication of whether there is a strong year class and how well the fish are growing. Although the sponsors indicated that they would age fish and some objectives addressed specific numbers of fish of a given age, it would have been better if they had set a target density, that is number, of fish of a given growth rate or size.There are many problems with assessing kokanee populations because of their short life and semelparity. Density plays a large role in not only pre-maturation growth rate but maturation schedule, post-maturation-decision growth rate, total survival of fish to an age, and thus on year-class strength. The proposal would have benefited from a clearer description of exactly how the sponsors would monitor kokanee response to better clarify if abundance and growth are actually responses or just observations independent of the nutrient addition. The sponsors simply showed that kokanee biomass went up after the years of nutrient addition, without carefully documenting the exact age-specific response or causal links that may be potentially identifiable in their shorter term plankton responses.

The proposal does not indicate how many age-groups of kokanee are present in Dworshak Reservoir, but from papers by Rieman and others it appears to be three. Table 1 of the response gives data for a variety of age-groups and appears to suggest the age-2 fish might be the oldest the project dealt with. This point needs clarification.

Reviewers were expecting to see creel census data presented in the response, but the response indicates no creel surveys were done because of lack of funds. This is an important oversight, but the sponsors note that some creel census will be incorporated into future efforts.

The sponsors repeated that, “The benefits of N supplementation are cumulative, with benefits reaching higher trophic levels in successive years.” This statement is poorly documented. If many of the phytoplankton responses are rapid and zooplankton consume phytoplankton, then why is it assumed that it takes 4-5 years for a kokanee response? How good are the scientific data from Stockner and the work of others leading to this conclusion and why was it not referenced? Understanding the reality of this lag time seems crucial to their claimed observed kokanee response in the past and crucial to the proposed 5-year time frame in this proposal. Without that understanding, the observed year class of kokanee may have been due to more random and unknown year class events/variations that kokanee are well known to exhibit.

In the response, new information was given on kokanee size and numbers from fall seining of prespawning adults collected at index tributaries of the North Fork Clearwater River. These data, presented with minimal detail, appear to contradict previous conclusions based on trawl and acoustic surveys. Figure 4 shows that the number of adult kokanee gathering to spawn increased sharply in 2010, but that average length was the same as before nutrient addition. This is the opposite of what was observed in summer trawl/acoustic sampling when fish density remained about the same, but biomass increased after nutrient addition as compared to pre-nutrient addition. Also, having this "record number" of spawners indicates a high density of age-0 kokanee might be expected for 2011, which is not a desired outcome, and apparently did not occur.

The ISRP has concerns about the interpretation of Objective 3 and the part of Deliverable 3 that involves this seining of index spawning streams and measurement of spawner length, weight, and fecundity of female spawners. The inference here is that spawner carcasses will increase the productivity of these streams and thus benefit resident fishes. The sponsors make the valid point that nutrient addition to lakes has been shown in other studies to increase kokanee growth and biomass. The sponsors, however, plan to measure neither stream productivity nor the response of lower trophic levels and resident stream fishes. For these reasons, the ISRP does not believe that simply measuring spawner abundance in the index streams and inferring a positive response is scientifically warranted. Without basic measures of stream and lower trophic level biomass productivity, it will be difficult to demonstrate any relationship between the reservoir nutrient enrichment actions with increases in stream food web productivity. If the project moves in that direction, comparisons with adjacent reference streams that are not accessible by Dworshak kokanee spawners would seem an important evaluation element.

A lawsuit stopped lake fertilization in 2011, the fourth year of a five-year test, which although a setback for the project was beneficial in terms of monitoring and evaluation. With a cessation of fertilizer input, the sponsors saw a rapid response with blue green algae returning to pre-nutrient enhancement levels. In a nitrogen-limited system, blue green algae can fix nitrogen, and thus outcompete other species that need nitrogen. However, with adequate nitrogen levels, other algal species and their zooplankters predominate over blue green algae, and support a plankton-based kokanee fishery. 

The proposed food web monitoring is critical to evaluating success or failure of the proposed project and addressing both scientific and political concerns. Nevertheless, the ISRP wonders if the monitoring could be reduced in scale and budget and still meet the political and scientific needs for the project? For example, the enclosure experiment could be deleted, as it seems unnecessary and expensive. 

The sponsors did food web work, which should be encouraged, but do not identify the criteria they are going to use for evaluating success nor do they commit to much detail on their fishery goals, in spite of some recent positive results. For example, what kokanee population response is needed to indicate success? The sponsors need a more rigorous presentation of their analysis methods and of existing data to date, including how annual variation in kokanee abundance can be sorted out from treatment response. 

The proposal needs to be more sharply focused on a testable hypothesis. The sponsors argue that fertilization must be repeated, for an additional five years, because four years of data are apparently inconclusive (yet almost no detail regarding results is given to review). A critical question is whether four years of study shows significant enhancement of kokanee. When the population biomass "doubled" at the end of four seasons, were the IDFG management goals for kokanee met? Is it not possible that four years of fertilization were indeed adequate to evaluate a fishery response?

Alternatively, would simply monitoring the kokanee population in summer 2012 answer the question? Further, what really is the question – what kokanee population response is needed to indicate success? The sponsors need to discuss their results (especially kokanee) in light of what has been found in other water bodies. Is the Dworshak work really pioneering?

A response is requested on the following issues: 

1. Provide justification that the duration of the second phase of the study (five years) is long enough to yield conclusive results, given the inevitability of natural variation in kokanee abundance, catch, and spawner counts, and the likelihood that a response of kokanee to the treatment will only be observed in the last one or two years of the study. In their response the sponsors should consider providing a more comprehensive analysis of variability in kokanee abundance and spawner counts prior to the first treatment. In addition it would be helpful if the sponsors provided information on the response of lake biota following cessation of the first set of treatments in 2010.
2. Provide data indicating that pre-treatment kokanee population abundance, angler catch, and fish size did not meet IDFG’s management objectives for the reservoir, and how the objectives were derived.
3. Provide better justification for how the enclosure experiments will directly contribute to understanding kokanee response to nutrient additions in the reservoir. Granted these experiments will shed light on limnological responses over a range of nitrogen concentrations and perhaps assuage public concerns, but what else will they do? For example, will these experiments provide information on trends in lake chemistry, phytoplankton, and zooplankton that cannot be reliably obtained from reservoir samples? Will the experiments provide greater understanding of mechanisms underlying biotic responses to nutrient addition? Will the experiments provide information on kokanee response that is not already known from the fisheries literature? Finally, could the enclosure experiment be reduced in scope or eliminated without compromising the project’s biological goals? 

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

The proposal identifies three stated objectives: to enhance reservoir productivity, to enhance the kokanee population and to improve nutrient cycling in the river upstream from the reservoir.

The proposed work is to determine if the addition of nitrogen fertilizer to Dworshak Reservoir will enhance the kokanee population and improve the reservoir and upstream fishery. The U.S. Fish and Wildlife Service established a goal of stocking 100,000 lbs of trout annually in Dworshak as mitigation for the loss of resident fisheries (Ecovista et al. 2003, pg 327). However, this goal has only been met three times in the history of the project (IDWR 2000) and recently stocking has been approximately 20,000 pounds annually. Fisheries for non-native kokanee and smallmouth bass have since supplanted trout as the primary fisheries in the reservoir. However, these fisheries continue to be severely limited by reservoir operations. There are no present efforts to mitigate for the loss of historically abundant anadromous fish and marine derived nutrients to the fish and wildlife populations of the North Fork Clearwater ecosystem.

The sponsors present some evidence that the productivity of Dworshak Reservoir has declined, possibly due to operation of the dam, natural aging of the lake, and loss of marine-derived nutrients due to extinction of the salmon run in the North Fork Clearwater River. A five-year pilot nutrient enrichment project was funded in 2007 by BPA. After four years of nutrient addition and data collection the project was suspended in 2010 due to a permitting issue. A positive response in kokanee abundance was seen only in the fourth or last year of the study prior to its cessation. The sponsors are proposing another five year study to more conclusively determine whether nutrient additions to the reservoir will improve kokanee abundance, angler catch, and number of spawners. 

The work is consistent with the Fish and Wildlife Program and the North Fork Clearwater Subbasin Plan where one goal is “assessing where nutrient additions or reductions would be beneficial to focal species.” 

The proposed work would be better justified if the sponsors provided data indicating that pre-treatment kokanee population abundance, angler catch, and fish size did not meet IDFG’s management objectives for the reservoir, and how the objectives were derived. The project introduction states that it "seeks to improve resident fisheries in Dworshak Reservoir through the careful addition of a nitrogen-based fertilizer to the reservoir. In particular, the kokanee population should benefit from improved reservoir productivity and provide a better fishery for anglers. Further, fish and wildlife species in the North Fork Clearwater Subbasin will benefit from nutrients that kokanee transport to spawning tributaries where marine derived nutrients were historically abundant." However, it appears to reviewers that a more accurate description of the current goal is, or should be, to assess if fertilization is sufficiently cost-effective to adopt as regular, annual management.

Objective 3, “Improve nutrient cycling to the North Fork Clearwater River and its tributaries,” is based on the supposition that decomposition of the carcasses of larger runs of kokanee will increase nutrient levels in spawning streams and so benefit stream biota such as bull trout. They also surmise that kokanee fry will provide a food source for bull trout. While possible, this assumption seems at this point to be largely conjecture because no direct evidence was presented that the spawning streams were nutrient limited or that bull trout growth and survival were food limited. Furthermore, the sponsors do not propose to measure nutrient concentrations in the tributaries or determine if any changes in stream biota, including bull trout growth and abundance, have occurred following nutrient addition to the reservoir. Without this information Objective 3 cannot be accomplished. Consequently, either the sponsors should provide an adequate plan to accomplish this objective or the objective should be deleted from the proposed work at this time. 

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

In the spring of 2007, the U.S. Army Corps of Engineers (USACE) began applying liquid fertilizer weekly to the reservoir while IDFG monitored the response of the reservoir and kokanee population. Results from the first four years of nutrient supplementation indicated an immediate increase in densities of picoplankton, followed by a reduction in N₂ fixing cyanobacteria concurrent with an increase in the proportion of edible phytoplankton taxa, and an increase in the density and biomass of Daphnia, the preferred forage of kokanee (Scofield et al. 2011). By the fourth year of the project, kokanee were larger than they were in a pre-supplementation year with similar fish densities, and kokanee biomass was twice as high as it had been in recent years for which the sponsors were able to estimate biomass (Wilson et al. in prep). In addition, spawner counts in index streams were the highest on record (Wilson et al. in prep). How much confidence can be placed on the "biomass being twice as high" statistic? Is that likely to be a real, meaningful increase when considering the extent of normal interannual variability? 

A positive response by kokanee was seen only in the last, or fourth, year of the first set of treatments. The sponsors expect the lake to return to pre-treatment conditions following cessation of the first round of nutrient supplementation in 2010. If this occurs and a kokanee response is observed only in the fourth or fifth year of the second set of treatments, as it was in the first set, it could be difficult to determine, with only one or two years of data, whether the response was due to the treatment or to natural variability in lake chemistry, phytoplankton, zooplankton abundance, and kokanee abundance. Given this variability, there is no certainty that a clear, scientifically valid, kokanee response will be evident in a five-year time frame. It seems that a study of much longer duration would be needed to account for natural variability and to provide conclusive results.

ISRP Retrospective Evaluation of Results

The lack of detail given in the proposal on results to date, especially regarding kokanee, made the proposal more difficult to review adequately. The sponsors need to provide more results and discussion than a table and two figures. Data and discussion about creel results including fish size, and catch rates, would have been informative.

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

The sponsors will work in collaboration with the USACE’s Dworshak Resident Fish Mitigation Project. The proposed work also is relevant to two BPA funded projects: the Lake Pend Oreille Fishery Recovery Project (199404700) and IDFG’s nutrient restoration project on the Kootenai River that is part of the Kootenai River Resident Fish Mitigation Project (198806500). Relationships with USACE are described, with the USACE covering the cost of the fertilizer and its application, $181K annually, as before.

4. Deliverables, Work Elements, Metrics, and Methods

Most Deliverables are accomplishable and relate directly to the stated Objectives. Standard limnological methods will be used to collect data on lake chemistry, phytoplankton, and zooplankton. Data on the kokanee population will be collected using protocols developed by IDFG. These methods appear sound.

There are six deliverables, including badly-needed public outreach.

Deliverable 1: Monitor limnological conditions of the reservoir – Some monitoring is clearly appropriate but needs to be described in more detail and better justified. Monitoring accounts for nearly half of the annual budget for the proposal. 

The ISRP has commented in its retrospective reports and other reports on the importance of monitoring to evaluate responses to actions; however, the ISRP has also noted that monitoring needs to be targeted so it can answer the needed questions but not consume a disproportionate portion of the project’s budget. We wonder if a scaled down monitoring plan for the food web could adequately provide the project’s M&E needs and increase cost-effectiveness for the project. 

Deliverable 2 is the experimental enclosure experiments. Although interesting, the need for enclosure experiments (Deliverable 2) is uncertain. The central question this proposal addresses is whether the kokanee population will respond positively to nutrient additions and the enclosure experiments will shed little light on this question. Reviewers are not convinced of the need for this task, suggesting it is redundant with work done elsewhere.