Difference between revisions of "Trout Management Flows"
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==Treatment 4: Increase or Maintain Turbidity in Marble Canyon during Periods of High Trout Recruitment== | ==Treatment 4: Increase or Maintain Turbidity in Marble Canyon during Periods of High Trout Recruitment== | ||
− | + | This treatment is founded on observations from the Natal Origins project which indicate that the abundance of rainbow trout at the LCR can be reduced by limiting the frequency of fall HFEs when trout abundance in Marble Canyon is high. The Natal Origins project found that one of the factor affecting rainbow trout abundance in Marble Canyon is a trout’s ability to maintain a positive condition factor by efficiently finding and consuming food. Because rainbow trout are sight feeders and eat macroinvertebrates drifting in the water column, feeding efficiency can be substantially reduced by a relatively small increase in turbidity. The Natal Origins projects found that rainbow trout in Marble Canyon typically only grow in the winter and spring because turbidity in the summer and fall is too high for them to find food. Modeling has indicated that foregoing a fall HFE in a year with a large sediment input from the Paria River allows enough fine sediment to remain in Marble Canyon to provide a small increase in turbidity (from ~5 NTU to ~35 NTU) over the subsequent winter. The model also predicts this small increase in turbidity reduces the maximum reactive distance of rainbow trout by 20-30% when compared to conditions with a fall HFE. Modeling indicates that a reduction in reactive distance of this magnitude is sufficient to reduce condition factor enough to limit reproduction and survival of rainbow trout below the Paria River. | |
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− | + | This treatment would be most effective during periods of high trout abundance in Marble Canyon and large sediment inputs from the Paria. This treatment could also be considered immediately following a large recruitment event of rainbow trout in the Lees Ferry reach since data from the Natal Origins project suggests that immigration to Marble Canyon increases under these conditions. | |
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*Large fluctuations in daily flows is thought to have limited egg survival and age-0 trout recruitment under pre-ROD conditions. | *Large fluctuations in daily flows is thought to have limited egg survival and age-0 trout recruitment under pre-ROD conditions. | ||
− | ==Scenario 2: | + | ==Scenario 2: Monitoring detects an increase in the abundance of rainbow trout in Marble Canyon== |
− | + | This scenario describes a situation where monitoring is detecting an increasing abundance of rainbow trout in Marble Canyon to the point where mechanical removal may be triggered. This scenario may also apply to a situation where an operation like a spring HFE or equalization creates a large rainbow trout recruitment event and young rainbow trout are expected to immigrate into Marble Canyon. In either of these cases a sediment-triggered fall HFE would be foregone and the sediment input would be allowed to dissipate over the winter thereby increasing turbidity levels and disadvantaging rainbow trout that have already immigrated to below the Paria River. This would continue until the abundance of rainbow trout in Marble Canyon return to acceptable levels. | |
− | ==Scenario 3 | + | ==Scenario 3. Spring HFE == |
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This scenario describes a combination of possible Trout Management Flows that could be implemented during a spring HFE. Conduct a pre-treatment redd count in February and March to get an estimate of trout production. Once every 2-4 weeks beginning in mid-March, reduce releases early in the morning to the lowest allowable minimum release and hold for 10-12 hours to dewater redds. During the day of the treatment when the water levels are low, remove redds located below the minimum flow elevation with a hydraulic pressure washer or a suction dredge (Treatment 1). Repeat every 2-4 weeks until the end of April. Implement the spring HFE at the end of April. At the conclusion of the spring HFE, downramp flows as fast as allowable to the lowest allowable minimum flow for a nighttime stranding treatment lasting 10-12 hours (Treatment 3). Then proceed with age-0 trout displacement flow treatments by increasing daily flow fluctuations to as high of level as allowable (Treatment 2). Continue with these high flow fluctuations until the end of August. During the first week of September, perform a population estimate on the age-0 trout population to determine the effectiveness of this actions. | This scenario describes a combination of possible Trout Management Flows that could be implemented during a spring HFE. Conduct a pre-treatment redd count in February and March to get an estimate of trout production. Once every 2-4 weeks beginning in mid-March, reduce releases early in the morning to the lowest allowable minimum release and hold for 10-12 hours to dewater redds. During the day of the treatment when the water levels are low, remove redds located below the minimum flow elevation with a hydraulic pressure washer or a suction dredge (Treatment 1). Repeat every 2-4 weeks until the end of April. Implement the spring HFE at the end of April. At the conclusion of the spring HFE, downramp flows as fast as allowable to the lowest allowable minimum flow for a nighttime stranding treatment lasting 10-12 hours (Treatment 3). Then proceed with age-0 trout displacement flow treatments by increasing daily flow fluctuations to as high of level as allowable (Treatment 2). Continue with these high flow fluctuations until the end of August. During the first week of September, perform a population estimate on the age-0 trout population to determine the effectiveness of this actions. | ||
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[[File:TroutFryToEggs.jpg|thumb|center|400px|https://pubs.usgs.gov/fs/2011/3002/fs2011-3002.pdf]] | [[File:TroutFryToEggs.jpg|thumb|center|400px|https://pubs.usgs.gov/fs/2011/3002/fs2011-3002.pdf]] | ||
+ | ==Scenario 4. Equalization flows that require full power plant releases for an extended period of time== | ||
+ | This scenario describes a combination of possible Trout Management Flows that could be implemented during equalization flows. Conduct a pre-treatment redd count in February and March to get an estimate of trout production. Once every 2-4 weeks beginning in mid-March, reduce releases early in the morning to the lowest allowable minimum release and hold for 10-12 hours to dewater redds. During the day of the treatment when the water levels are low, remove redds located below the minimum flow elevation with a hydraulic pressure washer or a suction dredge (Treatment 1). Repeat every 2-4 weeks until the end of April. Beginning in May, downramp flows one day every 2-4 weeks as fast as allowable to the lowest allowable minimum flow for a nighttime stranding treatment lasting 10-12 hours (Treatment 3). Repeat every 2-4 weeks until the end of the equalization flow (probably September 30). During the first week of October, perform a population estimate on the age-0 trout population to determine the effectiveness of these actions. | ||
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+ | *The 2012 equalization flow increased survival of YOY trout ultimately leading to an over population of trout in the ferry and a subsequent population crash during the winter of 2014-15. [https://pubs.er.usgs.gov/publication/70187999] | ||
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Revision as of 18:12, 18 July 2018
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Trout Management FlowsThe purpose of implementing Trout Management Flows (TMFs) is to evaluate methods for using releases from Glen Canyon Dam to reduce the production of large numbers of age-0 rainbow trout in order to improve the quality of the Lees Ferry trout fishery and conserve the endangered humpback chub and other native fishes in Grand Canyon. Three objectives were identified for Trout Management Flows:
TMFs under the LTEMP EIS were timed to target rainbow trout and can be scheduled to occur from May to August. The windows for effectiveness for brown trout is thought to be February to April. The drivers for TMFs are relatively untested and and their affects are largely unknown. |
Rainbow Trout | Brown Trout |
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