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If you have any questions on the information presented, or require additional report data or attachments, please contact the Report Contact
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Nutrient additions, in the form of liquid agricultural grade fertilizer occurred in Upper Arrow following the same methods as recent years. In total, 40.5 MT of phosphorus and 248.8 MT of nitrogen were added to the Reservoir between early May and end of September.
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Author: Marley Bassett, Steve Arndt and Eva Schindler
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Old Reference Number: COL-F20-F-3006-DCA
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Old Reference System: FWCP - Fish Wildlife Compensation Program Columbia
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Date Published: Mar 2020
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Report ID: 58994
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Audience: Government and Public
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The annual tonnes of phosphorus from fertilizer additions has been around 40 MT since 2016 (this is the fourth year of holding similar loading rates). The 2019 schedule was only adjusted once in mid-August, where the blend was adjusted to only nitrogen, this was due to nitrate levels reported below detection in Lower Arrow water samples.
The April- September daily mean flow for Arrow (total outflow) in 2019 was low compared to the previous eight years. These lower flows were observed in the early summer, from April to June, as well as late August in September. The flows in July and early August were near average. The air temperature in winter of 2018/2019 and spring, summer and fall of 2019 were all below average, as well the lowest temperatures (since 1992) in February were noted in 2019, where the monthly mean temperature was below 5 C.
Secchi depth is a measure of water clarity, where the higher the number, the clearer the water is. In 2019, the Secchi in Upper Arrow was 5.9 m, and in Lower Arrow 5.5 m. These means are slightly lower, i.e. the water was slightly less clear than the long-term Basin means. Total phytoplankton abundance in 2019 was lower than the long term means for all basins. This result is surprising since the Secchi depths were low - i.e. water clarity was less in 2019 which typically is associated with more phytoplankton in the water column. The lower phytoplankton community in addition to lower air temperatures observed in the spring, summer and fall of 2019 may be a contributing factor to the lower Daphnia biomass observed.
Daphnia (the preferred food source to Kokanee) biomass was lower than average in both Upper and Lower Arrow in 2019. This may be attributed to lower than average summer temperatures (Air Temperatures at Castlegar Airport, data on file FLNRORD). These low numbers are likely not due to Kokanee grazing, since in-lake Kokanee estimates and fall spawners were low. Mysid density increased in 2019 from 2018 in both Upper and Lower Arrow basins. In Upper Arrow, the 2019 mean was above the long term 1997-2019 mean, however in the range of mean densities observed over the course of the NRP. In Lower Arrow, the 2019 mean was below the long term mean, a trend since 2015.
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Report Type
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Fish and Aquatic Habitat Information |
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Subject
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Fish Species - Kokanee - Oncorhynchus nerka |
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Region - Kootenay |
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Fish and Fish Habitat - Habitat and Stream Assessment |
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Fish and Fish Habitat - Monitoring |
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Fish and Fish Habitat - Restoration |
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Water Information - Restoration |
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Water Information - Water Quality |
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