Ecosystem Impact-Nutrient Enrichment by Kokanee in Williston
Williston Reservoir and its tributaries are highly nutrient-limited. Previous attempts to increase productivity through fertilization had only limited success. The introduction of Kokanee, however, has the potential to greatly change nutrient dynamics. From 1990 to 1998, over 3,000,000 Kokanee were stocked into rivers that flow into Williston Reservoir. Aerial counts a decade later showed major runs in the Finlay, Ingenika, Omineca, Ossilinka, and Germanson Rivers.
Kokanee in these rivers can potentially provide a major new source of nutrients, impacting other fish species, stream-living macroinvertebrates, and the adjacent riparian zone. An evaluation of these nutrient transfers will be an important first step to understanding changes in the Williston Reservoir Watershed.
Final Report: Executive Summary
The Williston Reservoir and its tributaries are highly nutrient limited. From 1990 to 1998 over 3,000,000 Kokanee were stocked into rivers that flow into the Williston Reservoir in an attempt to increase the productivity of the reservoir ecosystem, and to also create a potential sport fishery for Kokanee and the fish that eat them. Aerial counts a decade later showed major runs of Kokanee in the Finlay, Ingenika, Omineca, Ossilinka, and Germanson Rivers. Kokanee in these rivers potentially can provide a major new source of nutrients, impacting other fish species, stream-living macroinvertebrates, and the adjacent riparian zone. The goal of the project is to determine the impact of the introduction of Kokanee into the Williston Reservoir on the nutrient dynamics and the complex web of interactions between Kokanee, stream-living macroinvertebrates (aquatic insects), and the surrounding riparian zone (lichen communities). This project aligns with the Peace Fish and Wildlife Compensation Program’s Stream Action Plan Objective 2a – “Understand the effects of Kokanee introductions on the aquatic food web”, and Objective 2a-1 – “Undertake a Kokanee assessment study to summarize status, trends, and aquatic and terrestrial ecosystem impacts and potential risks of Kokanee introductions – Develop appropriate recommendations for actions, as needed.”
Our survey questionnaire provided a qualitative assessment of Kokanee presence / absence and relative abundance and informed our selection of the specific stream reaches for data collection activities. The historic pattern of distribution in tributaries to the Williston Reservoir is extensive – but it is clear that one of the few watersheds where Kokanee have not colonized is the Parsnip River system, although there are reports of Kokanee spawning in tributaries to the system that are close to the reservoir.
We used stable isotope analysis to track the potential delivery of nutrients from the reservoir to tributary streams and their riparian ecosystems. Data from samples collected in 2016 revealstwo patterns; pelagic stream resident species such as salmonids and minnows showed much more variability in stable isotope signature than benthic species such as slimy sculpin, and there was more variability in larger rivers than smaller streams. Although there was variation in the stable isotope signatures within each system, signatures from stream resident fish collected in systems with high numbers of Kokanee spawners showed significant separation from signatures of fish collected from streams with no Kokanee. Our findings are strongly suggestive that Kokanee provide a significant source of nutrients to tributary streams where they spawn.
We surveyed seven streams and rivers in the Williston system for aquatic macroinvertebrates and used DNA barcoding to obtain putative identifications, often to a species level. We sent 667 specimens for barcoding and received back 601 useful sequences from which we were able to discern approximately 115 species – 28 Ephemeroptera, 32 Plecoptera, 16 Trichoptera, 37 Diptera, and two Coleoptera. One of the Trichoptera may represent a new species record for Ecosystem impact of nutrient enrichment by Kokanee in the Williston Reservoir Watershed. 3 Canada. This checklist representsthe most comprehensive listing ofspeciesfound in the Williston system that we are aware of. We also surveyed museum and other collection records from 10 different institutions and databases and developed a combined geographically-labeled database of 17,879 specimens covering most of western Canada and some of the adjacent US. Of those 6,989 records were from BC, including 620 Ephemeroptera, 1,716 Plecoptera, and 4,653 Trichoptera. The specimens – now vouchered in a curated collection – and the database provide an excellent foundation for further research in the region and will also be a useful resource for others.
Our 2016 lichen surveys on non-Kokanee-run rivers reveal a rich lichen flora in east-side riparian habitats of the Table, Hominka, and Parsnip Rivers, including several significant rare species. The abundance of 2 key groups of lichens, the Teloschistaceae and Physciaceae, often regarded as indicators of nitrogen enriched habitats, will be a key part of comparisons with Kokanee-run rivers in 2017.
Click the provincial database link below to read the full final report for this project.