During the period of performance of this contract (October 14, 2015 – September 30, 2016), Pacific Northwest National Laboratory (PNNL) staff will determine presence/absence, determine density estimates, and size classes of larvae rearing general vicinities of fish screening facilities located at Roza and Wapato diversion dams on the Yakima River.  PNNL will utilize the Deepwater Electrofishing Platform (DEP) either deployed from a motorboat.   The area will be divided into grid/transects to conduct sub-sampling within the overall reservoir in a time efficient manner.

BACKGROUND INFORMATION: The decline of Pacific Lamprey is well documented within the Columbia River Basin and irrigation diversions within the basin pose a potentially serious threat to the species. According to sampling conducted by the Yakama Nation Fisheries, irrigation diversions within the Yakima Basin, a subbasin of the Columbia River, entrain many thousands of larval/juvenile Western Brook Lamprey (Lampetra richardsoni), with a smaller portion being Pacific Lamprey (Entosphenus tridentatus) each year. The vast majority of lampreys (91.4%) were found in two large scale diversions: Wapato Diversion (upstream of fish screens) and Sunnyside Diversion (downstream of fish screens).  Based on a mark-recapture study, conservative estimates of entrained lamprey were 7,200 and 11,667 for Wapato and Sunnyside diversions, respectfully. At Wapato Diversion, the highest density of larval lamprey and habitat (fine sediment) were found upstream of the fish screens, . Also, there is larval lamprey habitat upstream of these diversion intake, potentially harboring thousands of lamprey ready to move into these diversions. Although Pacific Lamprey upstream of Roza Dam are functionally extinct, Roza diversion entrains a large number of Western Brook Lamprey and fine sediment. In addition, Roza Dam reservoir contains an abundance of larval lamprey habitat (34,251 m2), some of which is dewatered rapidly in the fall season. Lamprey use of this reservoir is unknown. The goal for this project will be to assess lamprey presence/absence, density, size classes, and habitat characteristics of these key locations (Sunnyside Diversion headgate and fish screen area, Wapato Diversion headgate and fish screen area, and Roza Dam reservoir).

APPROACH: To determine lamprey presence and to estimate relative abundance,  PNNL will utilize the DEP which has been lab and field tested and shown to be an extremely effective tool at determining present/absence of larval lamprey.  Utilizing image analysis software and post processing of video data, estimates can be made of lamprey lengths.  In addition to determining lamprey presence, the DEP can be used to characterize the physical habitat parameters and obtain water quality data in regions where lamprey are found. DEP system components include:

• integrated sled for use in large rivers at depths up to 75 feet
• ultra low light color optical camera
• paired lasers for scaled measurements
• high-definition multi-format recording system
• onboard remote electroshocking controller with customized settings
• infrared/white-light modules
• water velocity meter