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ISAB Reviews Fish Passage Memos On Long-Standing Issue Of Delayed Mortality In Migrating Salmon
Posted on Friday, October 14, 2011 (PST)

Fish Passage Center technical memorandums that say the rigors of negotiating Columbia and Snake River dams dampens salmon survival “are reasonable and scientifically defensible based on the data used,” according to a review of the analysis by the Independent Scientific Advisory Board.


“However, other reasonable conclusions could also be reached, and issues remain concerning the data used,” the ISAB wrote in its Sept. 16 memorandum to the FPC Oversight Board.


Researchers must dig deeper to resolve the long-debated issue of whether or not, and/or to what degree, migrating juvenile salmon suffer from latent/delayed mortality as a result of dam passage or barge transportation downstream, the science panel says.


“Based on our review, the studies and analyses cited in these technical memos do not provide an adequate base of reliable information to support a ‘weight of evidence’ conclusion on the strength of a relationship between multiple bypass passage and latent mortality of juvenile chinook and steelhead,” the ISAB memo says. “That is, the relationships observed between latent mortality and bypass passage are confounded with other factors that obscure unambiguous interpretation.”


The FPC was created through the Northwest Power and Conservation Council’s fish and wildlife program with the charge of providing technical assistance and information to fish and wildlife agencies in particular, and to the public in general, on matters related to water management, spill and other fish passage measures. The Oversight Board is made up of representatives of the Council, NOAA Fisheries Service, state fish and wildlife agencies, basin tribes and the public.


The program also calls for the Oversight Board to ensure that the FPC’s functions are implemented consistent with the program. To do this, the Council program specifies that the board will work with the FPC and the ISAB to organize a regular system of independent and timely science reviews of the center’s analytical products. The ISAB was created to provide scientific advice to the Council, NOAA Fisheries and basin tribes.


Review guidelines for the ISAB when it is reviewing FPC materials include whether new or novel analyses are introduced; new conditions or data bring old analyses into question; and/or consensus cannot be reached in the region on the science involved in the product. Three FPC technical memos on the topics of latent mortality and effects on in-river survival were identified as meeting that criteria for review. The three memos address latent mortality of in-river migrants due to route of dam passage.


The three FPC technical memoranda, with associated links, reviewed by the ISAB are:


1)         Memo #134-10 dated Oct. 5, 2010, “Delayed/latent Mortality and Dam Passage”


2)         Memo #135-10 dated Oct. 6, 2010, “Delayed/latent Mortality and Dam Passage, Fish Passage Operations Implications” and


3)         Memo #08-11 dated Jan. 19, 2011, “Effects of Passage through Juvenile Powerhouse Bypass Systems at Mainstem Dams on the Snake and Columbia Rivers.”



The FPC memorandums cited numerous studies as supporting the conclusion that delayed/latent mortality does indeed occur.


“Our overall conclusion is that there is a broad range and scope of evidence indicating that powerhouse passage and the transportation/collection/bypass systems at mainstem dams results in significant delayed/latent mortality of juvenile salmonids, which reduces adult return,” according to an Oct. 6, 2010, memo from FPC manager Michele DeHart to Ed Bowles, Oregon Department of Fish and Wildlife Fish Division Administrator. “In addition, these data and analyses have implications for fish passage management operations.”


Bowles had earlier request that the FPC staff review available information regarding delayed mortality and dam passage and the implications for fish passage operations.


A similar review was issued Oct. 5, 2010 in response to a request from the Columbia River Inter-Tribal Fish Commission’s Rob Lothrop.


The third memo, also to CRITFC, comes to the same conclusion.


The FPC memos, and research cited, leave many possible mitigating factors unexplored, the ISAB said.


“The issue of possible bypass selectivity for less-fit fish, for example injured, diseased, less advanced in the smoltification process, smaller, or with lower energy reserves, rendering them less likely to survive to return remains unresolved and is in need of evaluation,” the ISAB memo said, as an example.


The complex issue of the relationships among descaling, disease resistance, osmoregulation capability, and survival (See Zydlewski et al. reference above) is another issue in need of investigation,” the ISAB memo says. “These largely unexamined biological and ecological factors potentially affecting SARs have not been thoroughly evaluated. The memos use analytical approaches taking SARs at face value without discussing these unexamined factors.”



Those ISAB memorandum can be found at the Council’s web site:


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