On February 25, 2010, NOAA Fisheries requested ISAB assistance with a question related to a low flow transportation proposal for the spring 2010 juvenile salmon outmigration. Current river forecasts predict a low flow year for 2010, prompting NOAA Fisheries to propose maximizing the transport of Snake River juvenile steelhead and spring/summer Chinook in the month of May. The ISAB's review is attached.
- Multi-species Perspective
Based on ecological principles and considering the uncertainties of the data, using combinations of transport and in-river migration with spill spreads the risk across species, stocks, and the ecosystem, while offering an approach that can shed light on uncertainties in the longer-term dataset.
- Operational Changes – Lessons Learned
The ISAB concluded (ISAB 2008-5) that a mixed strategy of spill and transport during the critical spring migration period allows learning from spill conditions and supports potential advances in knowledge to improve decision-making in the future. This conclusion remains as valid in 2010 as in 2008. A mixed strategy in low-flow conditions provides an important opportunity to learn from the concurrent spill and transport mix of recent years.
- Addressing Uncertainties – Lamprey
There remains a gap in knowledge of the effects of various spill-transport operations on downstream juvenile Pacific lamprey migration. Development of a suitable means of tracking migrating juvenile lamprey is a critical need. Information on Pacific lamprey response to hydrosystem operations, including spill-transport, would be vastly improved if mark-recovery methods were available for juveniles.
- Addressing Uncertainties – Sockeye
Studies to examine the relative benefits of spill and transport for sockeye were initiated in 2009 and anticipated to continue in 2010. These studies could provide important additional information to reduce uncertainties relevant to sockeye juvenile migration.
- Addressing Uncertainties – Straying
Out-of-basin straying remains a concern for some steelhead stocks. The reports that steelhead transported from the Snake River on barges have a higher straying rate and lower homing rate than fish migrating in-river adds to the concern. Information is needed to inform efforts to minimize the number of out-of-basin strays spawning in Lower Columbia tributaries.
- Spill as the Baseline – Ecological and Evolutionary Considerations
The premise that spill more closely mimics natural situations and ecological processes than maximum transportation leads to a mixed strategy of concurrent spill and transport to conserve diversity and future potential of the ecosystem.
Thus, the ISAB conclusion is the same now as it was in 2008. From a scientific standpoint, a mixed strategy for spill and transport is best supported by the available science. Ecological and evolutionary considerations provide an important framework in support of this strategy.
NOAA Fisheries request for ISAB review
On February 25, 2010 NOAA Fisheries requested ISAB assistance with a question related to a "low flow" transportation proposal for the spring 2010 juvenile migration. These are review materials leading to the completed ISAB review:
For 2010, the Columbia River Basin appears to be facing a very low water year. The latest river forecasts estimate flow at The Dalles Dam to be only 71 percent of the 30-year average. The current flow forecast for the Snake River is approximately 65 kcfs. NOAA Fisheries believes new information in a 2010 Northwest Fisheries Science Center Report demonstrates there is significant benefit to maximizing the transport of Snake River juvenile steelhead and spring/summer Chinook under low flow conditions in the month of May. Information from 2007 (the most recent low flow year) is generally consistent with transport data used to structure transport operations under the 2008 FRCRPS Biological Opinion.
The ISAB recommended, in their Snake River Spill-Transport Review (ISAB 2008-5), that “whenever river conditions allow during the late April-May period, a strategy allowing for concurrent transportation and spill is prudent.” Taking into account the ISAB’s recommendation, NOAA Fisheries looked at the data from the 2007 low-flow year and determined that if flow conditions in 2010 were similar to 2007 (i.e., <65 kcfs), it would not be “prudent” to continue spilling water in May at the three collector projects as in 2007.
NOAA's question to the ISAB: Has NOAA Fisheries correctly interpreted the ISAB’s recommendation? If not, please further explain your reasoning in the 2008 recommendation.
The ISAB intends to complete its review by early April in time to inform management decision for the salmon migration season.