Difference between revisions of "Trout Management Flows"
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− | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3bfb1; text-align:left; color:#000; padding:0.2em 0.4em;"> Trout Management Flow (TMF) Treatments </h2> | + | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3bfb1; text-align:left; color:#000; padding:0.2em 0.4em;">Trout Management Flow (TMF) Treatments</h2> |
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==Treatment 1: Redd stranding flows (with mechanical removal of redds below the minimum flow elevation)== | ==Treatment 1: Redd stranding flows (with mechanical removal of redds below the minimum flow elevation)== | ||
− | This treatment uses flow manipulation at Glen Canyon Dam to periodically dewater redds (nests trout build to lay their eggs in) during the rainbow trout spawning period thereby reducing the number of viable eggs that could hatch and recruit to the age-0 trout population. The objective of this treatment would be to dewater and/or mechanically remove between 50% and 90% of the redds produced over the spawning season. This is one of the mechanisms that is thought to have limited age-0 trout recruitment under pre-ROD conditions. | + | This treatment uses flow manipulation at Glen Canyon Dam to periodically dewater redds (nests trout build to |
+ | lay their eggs in) during the rainbow trout spawning period thereby reducing the number of viable eggs that | ||
+ | could hatch and recruit to the age-0 trout population. The objective of this treatment would be to dewater | ||
+ | and/or mechanically remove between 50% and 90% of the redds produced over the spawning season. This is one | ||
+ | of the mechanisms that is thought to have limited age-0 trout recruitment under pre-ROD conditions. | ||
− | Redd stranding flows could be implemented within current ROD guidelines and would consist of a period of high steady flows for an extended period of time to encourage fish to spawn on higher elevation gravel bars and benches during the peak spawning period (February-April). Flows would then be reduced to the lowest allowable minimum flow for a dewatering treatment lasting 10-12 hours and occurring every 2-4 weeks over the incubation period (mid-March to mid-May). This treatment should occur during the daytime to take advantage of heating the spawning gravels, which is more effective at reducing the survival of eggs and alevins (newly hatched trout) than just dewatering them. Redds below the minimum flow elevation could be mechanically treated using a hydraulic pressure washer in shallow water or a suction dredge in deeper water to increase the effectiveness of this treatment. Mechanical removal of redds would be less labor intensive than mechanical removal of age-0 fish. | + | Redd stranding flows could be implemented within current ROD guidelines and would consist of a period of high |
+ | steady flows for an extended period of time to encourage fish to spawn on higher elevation gravel bars and benches | ||
+ | during the peak spawning period (February-April). Flows would then be reduced to the lowest allowable minimum | ||
+ | flow for a dewatering treatment lasting 10-12 hours and occurring every 2-4 weeks over the incubation period | ||
+ | (mid-March to mid-May). This treatment should occur during the daytime to take advantage of heating the spawning | ||
+ | gravels, which is more effective at reducing the survival of eggs and alevins (newly hatched trout) than just | ||
+ | dewatering them. Redds below the minimum flow elevation could be mechanically treated using a hydraulic pressure | ||
+ | washer in shallow water or a suction dredge in deeper water to increase the effectiveness of this treatment. | ||
+ | Mechanical removal of redds would be less labor intensive than mechanical removal of age-0 fish. | ||
− | This treatment would likely be most effective during periods of extended high flows (i.e. equalization flows) due to the tendency of trout to spawn higher on gravel bars under these flow conditions. The effectiveness of this treatment is limited by how low flows could be reduced without impacting other resources in the canyon, such as aquatic foodbase resources used by adult rainbow trout. The effectiveness of this treatment is also limited by compensatory mechanisms where increased survival of young trout may increase under low density conditions. An initial test of this treatment from 2003-2005 resulted in strong compensatory survival of fry produced from redds located below the minimum flow level and resulted in no observable reduction in the number of age-0 trout later in the year. | + | This treatment would likely be most effective during periods of extended high flows (i.e. equalization flows) due |
+ | to the tendency of trout to spawn higher on gravel bars under these flow conditions. The effectiveness of this treatment | ||
+ | is limited by how low flows could be reduced without impacting other resources in the canyon, such as aquatic foodbase | ||
+ | resources used by adult rainbow trout. The effectiveness of this treatment is also limited by compensatory mechanisms | ||
+ | where increased survival of young trout may increase under low density conditions. An initial test of this treatment | ||
+ | from 2003-2005 resulted in strong compensatory survival of fry produced from redds located below the minimum flow | ||
+ | level and resulted in no observable reduction in the number of age-0 trout later in the year. | ||
*Attempted in January-March 2003-2005 | *Attempted in January-March 2003-2005 | ||
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==Treatment 2: Age-0 Trout Displacement Flows== | ==Treatment 2: Age-0 Trout Displacement Flows== | ||
− | This treatment relies on increased daily flow fluctuations to reduce the habitat availability of age-0 trout (fry and juveniles). This would make age-0 trout more reliant on sub-optimal habitats where they would be subject to poorer growing conditions. Daily flow fluctuations have been shown to negatively impact age-0 trout without affecting larger trout (Makinster et al. 2011). Under this flow regime age-0 trout are more likely to remain in deeper, colder water with higher velocities. This should result in decreased growth rates and lower survival. Habitat limiting flows could be enhanced by increasing the allowable daily fluctuation when age-0 trout are most sensitive to flow fluctuations (May-August). A nighttime minimum flow treatment would be more effective than a daytime treatment because age-0 trout typically come closer into shore at night. Increasing limits on daily fluctuations beyond ROD limits on at least a weekly basis would likely increase the effectiveness of this treatment. A critical component of this treatment would be to ensure that flows drop to the lowest allowable minimum flow for 12-14 hours on at least a weekly basis to dewater shallow gravel bars and benches in the Lees Ferry reach. Fluctuating flows like these are another mechanism that is thought to have limited age-0 trout recruitment under pre-ROD conditions. | + | This treatment relies on increased daily flow fluctuations to reduce the habitat availability of age-0 trout |
+ | (fry and juveniles). This would make age-0 trout more reliant on sub-optimal habitats where they would be subject | ||
+ | to poorer growing conditions. Daily flow fluctuations have been shown to negatively impact age-0 trout without | ||
+ | affecting larger trout (Makinster et al. 2011). Under this flow regime age-0 trout are more likely to remain in | ||
+ | deeper, colder water with higher velocities. This should result in decreased growth rates and lower survival. | ||
+ | Habitat limiting flows could be enhanced by increasing the allowable daily fluctuation when age-0 trout are most | ||
+ | sensitive to flow fluctuations (May-August). A nighttime minimum flow treatment would be more effective than a | ||
+ | daytime treatment because age-0 trout typically come closer into shore at night. Increasing limits on daily | ||
+ | fluctuations beyond ROD limits on at least a weekly basis would likely increase the effectiveness of this treatment. | ||
+ | A critical component of this treatment would be to ensure that flows drop to the lowest allowable minimum flow for | ||
+ | 12-14 hours on at least a weekly basis to dewater shallow gravel bars and benches in the Lees Ferry reach. | ||
+ | Fluctuating flows like these are another mechanism that is thought to have limited age-0 trout recruitment under | ||
+ | pre-ROD conditions. | ||
− | This treatment would likely be most effective during periods of time when releases from Glen Canyon Dam are already fluctuating for power generation. This treatment may be more effective at having a population level response than redd stranding flows because it is targeting an older age class that is less likely exhibit a density-dependent response. | + | This treatment would likely be most effective during periods of time when releases from Glen Canyon Dam are already |
+ | fluctuating for power generation. This treatment may be more effective at having a population level response than | ||
+ | redd stranding flows because it is targeting an older age class that is less likely exhibit a density-dependent response. | ||
*Suppression flow window: May-August [https://www.gcmrc.gov/about/ka/KA%202%20-%2010-19-11/PM%20Talks/Korman_TroutFlowHabUse_PHX_Oct2011.pdf] | *Suppression flow window: May-August [https://www.gcmrc.gov/about/ka/KA%202%20-%2010-19-11/PM%20Talks/Korman_TroutFlowHabUse_PHX_Oct2011.pdf] | ||
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==Treatment 3: Age-0 Trout Stranding Flows== | ==Treatment 3: Age-0 Trout Stranding Flows== | ||
− | This treatment relies on a period of high steady flows to draw age-0 trout (fry and juveniles) onto high elevation gravel bars and benches and then stranding those fish by rapidly decreasing releases from Glen Canyon Dam. Age-0 trout stranding flows could be provided within ROD guidelines with the treatment consisting of a period of high steady flows for an extended period of time to encourage age-0 trout to inhabit high elevation gravel bars and benches. Flows would then be rapidly reduced to the lowest allowable minimum flow for a dewatering treatment lasting 10-12 hours and occurring every 2-4 weeks. This treatment would take place from May to August when age-0 trout are most likely to be in these near-shore habitats. A nighttime minimum flow treatment may be more effective than a daytime treatment because age-0 trout typically come closer into shore at night. Increasing downramp rates and reducing flows below ROD guidelines may make this treatment more effective. The ROD currently limits downramp rates to 2,500 cfs/hr to reduce the probability of stranding young fish in nearshore habitats. Operationally, down ramping from 33,200 cfs (maximum power plant capacity at Glen Canyon Dam) to the daily minimum could occur nearly instantaneously. | + | This treatment relies on a period of high steady flows to draw age-0 trout (fry and juveniles) onto high |
+ | elevation gravel bars and benches and then stranding those fish by rapidly decreasing releases from Glen | ||
+ | Canyon Dam. Age-0 trout stranding flows could be provided within ROD guidelines with the treatment consisting | ||
+ | of a period of high steady flows for an extended period of time to encourage age-0 trout to inhabit high | ||
+ | elevation gravel bars and benches. Flows would then be rapidly reduced to the lowest allowable minimum flow | ||
+ | for a dewatering treatment lasting 10-12 hours and occurring every 2-4 weeks. This treatment would take | ||
+ | place from May to August when age-0 trout are most likely to be in these near-shore habitats. A nighttime | ||
+ | minimum flow treatment may be more effective than a daytime treatment because age-0 trout typically come | ||
+ | closer into shore at night. Increasing downramp rates and reducing flows below ROD guidelines may make this | ||
+ | treatment more effective. The ROD currently limits downramp rates to 2,500 cfs/hr to reduce the probability | ||
+ | of stranding young fish in nearshore habitats. Operationally, down ramping from 33,200 cfs (maximum power | ||
+ | plant capacity at Glen Canyon Dam) to the daily minimum could occur nearly instantaneously. | ||
− | This treatment would be most effective during periods of extended high flows (i.e. equalization flows) due to the likelihood of age-0 fish of utilizing high elevation gravel bars and benches when flows are held high and steady for an expanded period of time. As with Treatment 2, this treatment may be more effective at having a population level response than redd stranding flows because it is targeting an older age class that is less likely to exhibit a density-dependent response. This treatment, however, may also strand larger, more desirable trout occupying nearshore habitat during the night as well. Any larger fish caught in the nearshore during a stranding event would likely be more susceptible to mortality than smaller, age-0 fish because they would not be able to escape or endure the stranding as readily as a smaller fish. | + | This treatment would be most effective during periods of extended high flows (i.e. equalization flows) due to |
+ | the likelihood of age-0 fish of utilizing high elevation gravel bars and benches when flows are held high and | ||
+ | steady for an expanded period of time. As with Treatment 2, this treatment may be more effective at having a | ||
+ | population level response than redd stranding flows because it is targeting an older age class that is less | ||
+ | likely to exhibit a density-dependent response. This treatment, however, may also strand larger, more desirable | ||
+ | trout occupying nearshore habitat during the night as well. Any larger fish caught in the nearshore during a | ||
+ | stranding event would likely be more susceptible to mortality than smaller, age-0 fish because they would not | ||
+ | be able to escape or endure the stranding as readily as a smaller fish. | ||
[[File:LTEMPtmf.jpg|thumb|center|400px|LTEMP FEIS]] | [[File:LTEMPtmf.jpg|thumb|center|400px|LTEMP FEIS]] | ||
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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 number 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 factors 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 if a fall HFE was implemented. Modeling indicates that a reduction in reactive distance of this magnitude is sufficient to reduce condition factor enough to limit reproduction and abundance of rainbow trout below the Paria River. [https://www.usbr.gov/uc/progact/amp/twg/2018-01-25-twg-meeting/AR12.pdf] | + | This treatment is founded on observations from the Natal Origins project which indicate that the number |
+ | 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 factors 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 if a fall HFE was | ||
+ | implemented. Modeling indicates that a reduction in reactive distance of this magnitude is sufficient | ||
+ | to reduce condition factor enough to limit reproduction and abundance of rainbow trout below the Paria River. | ||
+ | [https://www.usbr.gov/uc/progact/amp/twg/2018-01-25-twg-meeting/AR12.pdf] | ||
− | 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. | + | 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. | ||
− | Increasing turbidity in Marble Canyon to the levels discussed here would likely not impact humpback chub and other native fish since they evolved in a turbid river environment. This treatment has the potential to be able to reduce the Program’s reliance on mechanical removal and other more lethal and expensive approaches to TMFs that some groups (i.e. Tribes, anglers, power users, etc.) find objectionable. Increased turbidity may also reduce direct predation pressure on native fish by nonnative fish like rainbow trout. Predation by other nonnative fish, like brown trout, appear not to be affected by the levels of turbidity being discussed here. Reducing the number of fall HFEs would have a negative impact to sediment-related resources unless the sediment accounting periods in the HFE protocol could be adjusted to allow for fall sediment from the Paria be used for a spring HFE, of which a number of resources would benefit including foodbase, the trout fishery, and recreational beach use. | + | Increasing turbidity in Marble Canyon to the levels discussed here would likely not impact humpback chub |
+ | and other native fish since they evolved in a turbid river environment. This treatment has the potential | ||
+ | to be able to reduce the Program’s reliance on mechanical removal and other more lethal and expensive | ||
+ | approaches to TMFs that some groups (i.e. Tribes, anglers, power users, etc.) find objectionable. Increased | ||
+ | turbidity may also reduce direct predation pressure on native fish by nonnative fish like rainbow trout. | ||
+ | Predation by other nonnative fish, like brown trout, appear not to be affected by the levels of turbidity | ||
+ | being discussed here. Reducing the number of fall HFEs would have a negative impact to sediment-related | ||
+ | resources unless the sediment accounting periods in the HFE protocol could be adjusted to allow for fall | ||
+ | sediment from the Paria be used for a spring HFE, of which a number of resources would benefit including | ||
+ | foodbase, the trout fishery, and recreational beach use. | ||
[[File:HFE Turbidity TMF.jpg|thumb|center|400px|https://www.usbr.gov/uc/progact/amp/twg/2018-01-25-twg-meeting/AR12.pdf]] | [[File:HFE Turbidity TMF.jpg|thumb|center|400px|https://www.usbr.gov/uc/progact/amp/twg/2018-01-25-twg-meeting/AR12.pdf]] | ||
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− | Differences in the efficiency of Trout Management Flows suggest that each of the three treatments discussed above may be more effective under some flow scenarios than others. For example, redd stranding flow and age-0 trout stranding flows would likely be more effective when releases can be held high and steady for an extended period of time (i.e. spring HFEs and equalization flows) whereas age-0 trout habitat limiting flows would likely be more effective at lower flows more typical of normal operations. Releases from Glen Canyon Dam could also be manipulated for short periods of time to where the three treatments outlined above could be used sequentially to target different vulnerabilities of age-0 trout as they age over the course of the year. Several scenarios are presented below for how Trout Management Flows could be incorporated into various release schedules for a range of operations. | + | Differences in the efficiency of Trout Management Flows suggest that each of the three treatments |
+ | discussed above may be more effective under some flow scenarios than others. For example, redd stranding | ||
+ | flow and age-0 trout stranding flows would likely be more effective when releases can be held high and | ||
+ | steady for an extended period of time (i.e. spring HFEs and equalization flows) whereas age-0 trout | ||
+ | habitat limiting flows would likely be more effective at lower flows more typical of normal operations. | ||
+ | Releases from Glen Canyon Dam could also be manipulated for short periods of time to where the three | ||
+ | treatments outlined above could be used sequentially to target different vulnerabilities of age-0 trout | ||
+ | as they age over the course of the year. Several scenarios are presented below for how Trout Management | ||
+ | Flows could be incorporated into various release schedules for a range of operations. | ||
==Scenario 1: Normal Operations== | ==Scenario 1: Normal Operations== | ||
− | This scenario describes a combination of possible Trout Management Flows that could be implemented during normal operations. First, conduct a pre-treatment redd counts 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 flow and hold for 10-12 hours. Remove redds located below the minimum flow elevation with a hydraulic pressure washer or a suction dredge when the water levels are low (Treatment 1). Repeat every 2-4 weeks until May. Beginning in May, proceed with age-0 trout displacement flows (Treatment 2) by increasing daily flow fluctuations to as high of level as allowable. 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 normal operations. First, conduct a pre-treatment redd counts 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 flow and hold for 10-12 hours. Remove redds located below the | ||
+ | minimum flow elevation with a hydraulic pressure washer or a suction dredge when the water levels are | ||
+ | low (Treatment 1). Repeat every 2-4 weeks until May. Beginning in May, proceed with age-0 trout displacement | ||
+ | flows (Treatment 2) by increasing daily flow fluctuations to as high of level as allowable. 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. | ||
*Large fluctuations in daily flows are thought to have limited egg survival and age-0 trout recruitment under pre-ROD conditions. | *Large fluctuations in daily flows are thought to have limited egg survival and age-0 trout recruitment under pre-ROD conditions. | ||
==Scenario 2: Monitoring detects an increasing abundance of rainbow trout in Marble Canyon== | ==Scenario 2: Monitoring detects an increasing abundance of rainbow trout in Marble Canyon== | ||
− | This scenario describes a situation where monitoring detects 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 case, a sediment-triggered fall HFE would be canceled and the sediment input would be allowed to dissipate over the winter thereby increasing turbidity levels below the Paria and disadvantaging rainbow trout that have immigrated into Marble Canyon. This would continue until the abundance of rainbow trout in Marble Canyon returns to acceptable levels. | + | This scenario describes a situation where monitoring detects 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 case, a sediment-triggered fall HFE | ||
+ | would be canceled and the sediment input would be allowed to dissipate over the winter thereby increasing turbidity | ||
+ | levels below the Paria and disadvantaging rainbow trout that have immigrated into Marble Canyon. This would | ||
+ | continue until the abundance of rainbow trout in Marble Canyon returns to acceptable levels. | ||
==Scenario 3. Spring HFE == | ==Scenario 3. Spring HFE == | ||
− | 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. | ||
*Run Spring HFE as late in the window as possible (lower survival before the HFE than after [https://pubs.usgs.gov/fs/2011/3002/fs2011-3002.pdf]) | *Run Spring HFE as late in the window as possible (lower survival before the HFE than after [https://pubs.usgs.gov/fs/2011/3002/fs2011-3002.pdf]) | ||
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==Scenario 4. Equalization flows that require full power plant releases for an extended period of time== | ==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. | + | 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. | ||
− | *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] | + | *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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− | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;"> | + | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Data Needs ([http://ltempeis.anl.gov/documents/final-eis/vol1/Chapter_2-Alternatives.pdf LTEMP FEIS Chapter 2, pages 63-66])</h2> |
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− | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Operational | + | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Operational Constraints</h2> |
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− | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;"> [https://drive.google.com/file/d/0BwY-Z2c3NTUGUmxPbko2dm9URms/view Lees Ferry Anglers Trout Fishery Recommendations ]</h2> | + | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">[https://drive.google.com/file/d/0BwY-Z2c3NTUGUmxPbko2dm9URms/view Lees Ferry Anglers Trout Fishery Recommendations ]</h2> |
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'''Recommendation #5.''' | '''Recommendation #5.''' | ||
− | Under certain conditions, rainbow trout at Lees Ferry have reproduced prolifically. Historically, when there is an over-abundance of young-of-year rainbow trout, the quality and condition of rainbow trout decline. This is likely due to the low quality and low abundance of food sources in Lees Ferry. Trout Management Flows (TMFs) are flow treatments that are hypothesized to reduce the abundance of young-of-year trout by stranding trout shortly after they emerge from their redds (Korman, Ecometric Research, Inc., personal communications, 2015). | + | Under certain conditions, rainbow trout at Lees Ferry have reproduced prolifically. Historically, when |
+ | there is an over-abundance of young-of-year rainbow trout, the quality and condition of rainbow trout decline. | ||
+ | This is likely due to the low quality and low abundance of food sources in Lees Ferry. Trout Management Flows | ||
+ | (TMFs) are flow treatments that are hypothesized to reduce the abundance of young-of-year trout by stranding | ||
+ | trout shortly after they emerge from their redds (Korman, Ecometric Research, Inc., personal communications, 2015). | ||
− | We believe the best long term and ecologically appropriate solution to controlling trout densities is to increase invertebrate diversity and manage Grand Canyon Dam flows to avoid excessive trout spawning and recruitment (see recommendations related to the aquatic food base and equalization flows). We are concerned about the collateral damage that TMFs could have on other resources especially the aquatic food base and native fish. TMFs may be especially useful when spring HFE's are implemented or in years when high equalization flows are required. | + | We believe the best long term and ecologically appropriate solution to controlling trout densities is |
+ | to increase invertebrate diversity and manage Grand Canyon Dam flows to avoid excessive trout spawning | ||
+ | and recruitment (see recommendations related to the aquatic food base and equalization flows). We are concerned about the | ||
+ | collateral damage that TMFs could have on other resources especially the aquatic food base and native | ||
+ | fish. TMFs may be especially useful when spring HFE's are implemented or in years when high equalization flows are required. | ||
− | TMF's should only be implemented in a carefully designed experimental framework that includes quantified criteria for success (for managing trout recruitment and improving the humpback chub population) and the impacts to other resources, especially the aquatic food base, are fully assessed. TMF's should only be used when the rainbow trout population is stable and includes a healthy abundance of all size classes of rainbow trout. Mitigation measures such as emergency stocking of trout need to be in place prior to the implementation of TMFs in case of catastrophic loss to the fishery (see recommendations on Trout Stocking). In conclusion, the experimental evaluation of TMFs needs to recognize the trout fishery as a highly valued asset. The AZGFD should have a seat at the table along with Federal agencies on any discussion and decisions related to implementation of TMFs. | + | TMF's should only be implemented in a carefully designed experimental framework that includes quantified |
+ | criteria for success (for managing trout recruitment and improving the humpback chub population) and the | ||
+ | impacts to other resources, especially the aquatic food base, are fully assessed. TMF's should only be used when the | ||
+ | rainbow trout population is stable and includes a healthy abundance of all size classes of rainbow trout. | ||
+ | Mitigation measures such as emergency stocking of trout need to be in place prior to the implementation of TMFs in case of | ||
+ | catastrophic loss to the fishery (see recommendations on Trout Stocking). In conclusion, the experimental | ||
+ | evaluation of TMFs needs to recognize the trout fishery as a highly valued asset. The AZGFD should have a seat at the | ||
+ | table along with Federal agencies on any discussion and decisions related to implementation of TMFs. | ||
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− | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;"> | + | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Descriptions of Trout Management Flows in LTEMP</h2> |
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− | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;"> History of GCDAMP's Assement of "CRe Turbidity Managment" to Conserve Native Fish </h2> | + | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">History of GCDAMP's Assement of "CRe Turbidity Managment" to Conserve Native Fish</h2> |
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TMFs were modeled in LTEMP to reduce the rainbow trout recruitment rate to 0.1 and 0.5. | TMFs were modeled in LTEMP to reduce the rainbow trout recruitment rate to 0.1 and 0.5. | ||
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Revision as of 10:35, 28 March 2019
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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 their affects are largely unknown. |
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