PNNL

Abstract

Albeni Falls Dam (AFD) on the Pend Oreille River is located within a critical migration route for fish passing between the upstream habitats of Lake Pend Oreille and downstream habitats of the Pend Oreille River and its tributaries. However, due to its presence as an upstream migration barrier, the potential effects of the dam on downstream migrating fish, and consequent to stipulations by the U.S. Endangered Species Act (ESA), 2000 Biological Opinion (BiOp, USFWS 2000), and other agreements, the U.S. Army Corps of Engineers (USACE), Seattle District (NWS) is working to develop a study plan to monitor both volitional and non-volitional fish entrainment through the turbines and spillway of AFD in conjunction with the USACE Walla Walla District (NWW), Bonneville Power Administration (BPA), the Kalispel Tribe of Indians (KTI), and the Pacific Northwest National Laboratory (PNNL). Consequently, the USACE contracted with PNNL to assist with the development of a study plan to evaluate the potential research alternatives to study downstream entrainment through AFD. Each methodology presented for evaluating fish entrainment at AFD has advantages and disadvantages. Quantifying fish entrainment through netting of turbine draft tubes or spillway gate wells is relatively time intensive and requires a significant amount of up-front engineering planning; however, it allows each fish to be handled to get exact size and species information. Hydroacoustics and acoustic imaging, although they do not provide species-specific information, would be a relatively inexpensive method for evaluating proportion of passage continuously (i.e,. 24 hours a day) throughout the study period. Acquiring behavioral data using acoustic imaging has demonstrated value to other hydroelectric entrainment studies as it provides information that can be used to determine dam operations that minimize entrainment, or direct entrainment to high-survival routes. A mark-recapture study using external tags or transmitters would provide useful information on the specific size and species entrained by the dam, and is considered a lower-cost option that could be implemented with limited funding, but would require a significant amount of labor. The recommended approach for evaluating fish entrainment at AFD is by using netting in combination with hydroacoustics. This combination of alternatives would provide the best estimate of entrainment route, magnitude, and species composition through AFD. Hydroacoustics would provide relatively inexpensive data on fish entrainment continuously (24 hours per day) through time (e.g., by diel period or seasons) and by passage route (i.e., 10 spill bays and 3 turbines). Netting would allow researchers to enumerate the size and species being entrained. Using these methods in tandem would also allow corroboration of entrainment data and extrapolation of species- and size-specific total-project entrainment. The exact method to be used to assess entrainment through the passage routes at AFD, whether a combination of hydroacoustics and netting, a phased approach, or a less-expensive mark-recapture study, would ultimately be determined in consultation between the USACE, BPA, KTI, and other stakeholders. However, final implementation should consider the guidelines suggested within this study plan to evaluate the advantages, disadvantages, and assumptions of each outlined alternative. Management goals for the resource should also be considered to ensure that the alternative chosen is able to sufficiently inform fisheries management and dam operations decision-making.