Loading...
HomeMy WebLinkAboutSuWa271Alaska Resources Library & Information Services Susitna-Watana Hydroelectric Project Document ARLIS Uniform Cover Page Title: SuWa 271 River productivity study (Study 9.8), Fish diet sample size sufficiency analysis technical memorandum Author(s) – Personal: Author(s) – Corporate: University of Alaska Fairbanks and R2 Resource Consultants, Inc. AEA-identified category, if specified: December 17, 2014 technical memorandum filings AEA-identified series, if specified: Series (ARLIS-assigned report number): Existing numbers on document: Susitna-Watana Hydroelectric Project document number 271 Published by: Date published: [Anchorage, Alaska : Alaska Energy Authority, 2014] December 2014 Published for: Date or date range of report: Prepared for Alaska Energy Authority Volume and/or Part numbers: Final or Draft status, as indicated: Attachment B Document type: Pagination: Technical memorandum ii, 4 p. Related work(s): Pages added/changed by ARLIS: Cover letter to this report: Susitna-Watana Hydroelectric Project, FERC Project no. 14241-000; Filing of additional information in response to October 2014 Initial Study Plan Meetings. (SuWa 269) Attachment A (SuWa 270) Added cover letter (2 pages) Notes: All reports in the Susitna-Watana Hydroelectric Project Document series include an ARLIS- produced cover page and an ARLIS-assigned number for uniformity and citability. All reports are posted online at http://www.arlis.org/resources/susitna-watana/ December 17, 2014 Ms. Kimberly D. Bose Secretary Federal Energy Regulatory Commission 888 First Street, N.E. Washington, D.C. 20426 Re: Susitna-Watana Hydroelectric Project, Project No. 14241-000 Filing of Additional Information in Response to October 2014 Initial Study Plan Meetings Dear Secretary Bose: By letters dated January 28, 2014 and October 3, 2014, the Federal Energy Regulatory Commission (Commission or FERC) modified the procedural schedule for the preparation and review of the Initial Study Report (ISR) for the proposed Susitna- Watana Hydroelectric Project, FERC Project No. 14241 (Project).1 As required by the Commission’s January 28 letter, the Alaska Energy Authority (AEA) filed the ISR with the Commission on June 3, 2014 and conducted ISR meetings on October 15, 16, 17, 21, 22, and 23, 2014. As required by the Commission’s October 3 letter, AEA will be conducting additional ISR meetings on January 7 and 8, 2015. In response to the October ISR meetings, AEA and licensing participants identified two technical memoranda that AEA would file with the Commission in December 2014, ahead of the January ISR meetings. In accordance, AEA is filing and distributing the following technical memoranda: • Attachment A: Study of Fish Distribution and Abundance in the Upper Susitna River (Study 9.5) - Evaluation of 2014 Study Modifications in the Black River Technical Memorandum. This technical memorandum describes how the modifications to the Study of Fish Distribution and Abundance in the Upper Susitna River (Study 9.5) outlined in the ISR were applied to the Black River during the 2014 study year. • Attachment B: River Productivity Study (Study 9.8) - Fish Diet Sample Size Sufficiency Analysis Technical Memorandum. This technical memorandum describes an analysis of stomach contents samples conducted after field 1 Letter from Jeff Wright, FERC Office of Energy Projects, to Wayne Dyok, Alaska Energy Authority, Project No. 14241-000 (issued Jan. 28, 2014); Letter from Jeff Wright, FERC Office of Energy Projects, to Wayne Dyok, Alaska Energy Authority, Project No. 14241-000 (issued Oct. 3, 2014). 2 sampling was completed to determine whether the sample size targets and the actual sample sizes were sufficient to meet the Study Plan objectives. Additionally, AEA notes that data collected during the Study Plan implementation, to the extent they have been verified through AEA’s quality assurance and quality control (QAQC) procedures and are publicly available, can be accessed at http://gis.suhydro.org/isr_mtg. On December 17, 2014, AEA posted the following data to this website: • Baseline Water Quality Data (Study 5.5), 2014 QAQC water quality data and DVRs per the Quality Assurance Project Plan. Finally, AEA notes that it has posted the agenda and PowerPoint presentations for the upcoming January ISR meetings to the Project website (http://www.susitna- watanahydro.org/meetings/ ). AEA appreciates the opportunity to provide this additional information to the Commission and licensing participants, which it believes will be helpful in determining the appropriate development of the 2015 study plan as set forth in the ISR. If you have questions concerning this submission please contact me at wdyok@aidea.org or (907) 771-3955. Sincerely, Wayne Dyok Project Manager Alaska Energy Authority Attachments cc: Distribution List (w/o Attachments) Susitna-Watana Hydroelectric Project (FERC No. 14241) River Productivity Study (Study 9.8) Fish Diet Sample Size Sufficiency Analysis Technical Memorandum Prepared for Alaska Energy Authority Prepared by University of Alaska Fairbanks and R2 Resource Consultants, Inc. December 2014 TECHNICAL MEMORANDUM FISH DIET SAMPLE SIZE SUFFICIENCY ANALYSIS Susitna-Watana Hydroelectric Project Alaska Energy Authority FERC Project No. 14241 Page i December 2014 TABLE OF CONTENTS 1. Background ........................................................................................................................1 2. Analysis Methods ...............................................................................................................1 3. Results and Interpretation ................................................................................................2 4. Plans for Further Analysis ................................................................................................2 5. Literature Cited .................................................................................................................3 6. Figures .................................................................................................................................4 LIST OF FIGURES Figure 1. Cumulative prey curves for Chinook salmon, coho salmon, and rainbow trout sampled during 2013. ............................................................................................................................ 4 TECHNICAL MEMORANDUM FISH DIET SAMPLE SIZE SUFFICIENCY ANALYSIS Susitna-Watana Hydroelectric Project Alaska Energy Authority FERC Project No. 14241 Page ii December 2014 LIST OF ACRONYMS AND SCIENTIFIC LABELS Abbreviation Definition AEA Alaska Energy Authority FA Focus Area ISR Initial Study Report RSP Revised Study Plan TM Technical Memorandum TECHNICAL MEMORANDUM FISH DIET SAMPLE SIZE SUFFICIENCY ANALYSIS Susitna-Watana Hydroelectric Project Alaska Energy Authority FERC Project No. 14241 Page 1 December 2014 1. BACKGROUND The River Productivity Study Revised Study Plan (RSP) (AEA 2012) proposed to conduct a trophic analysis to describe the food web relationships within the current riverine community within the Susitna River. To achieve this objective, the RSP proposed to sample the stomach contents of juvenile Chinook salmon, juvenile coho salmon, and two size classes of rainbow trout. The RSP established a target sample size (n) of eight fish per species and size class, within each sampling site, during each season. This sample size target was selected because estimates of the diet composition of salmonids often stabilize between n = 7-12 stomach content samples (Beauchamp et al. 2007, Vinson and Budy 2011). We selected n = 8, at the low end of this range, because the study objectives were focused on quantifying the broad dietary patterns (e.g., distinguishing among aquatic invertebrates, terrestrial invertebrates, and marine derived food such as salmon eggs) across a large number of sampling sites, rather than comprehensively identifying all prey taxa within any given site. Further, the study also included a stable isotope analysis to provide a complementary estimate of diet composition. One advantage of stable isotope analysis is the ability to quantify diet composition with relatively few samples, because each sample integrates the food assimilated into the consumer’s tissue over a period of weeks to months (Fry 2006, Hanisch et al. 2010). The River Productivity Study collected stomach contents and stable isotope samples from the same individual fish, which is an especially effective approach to quantify dietary patterns (McIntyre et al. 2006, Vinson and Budy 2011). This technical memorandum (TM) describes an analysis conducted after field sampling was completed to determine whether the sample size targets and the actual sample sizes were sufficient to meet the objectives. Field sampling during 2013 did not collect the full eight samples for each species during many sampling events, as described in the Initial Study Report (ISR) (AEA 2014). This was due both to logistical difficulties that prevented all sites from being sampled and also to the apparent absence or very low densities of the study species at some sites that were sampled, especially in the main channel. To determine whether this dataset was sufficient to quantify fish diet composition, we analyzed the 2013 stomach content data using cumulative prey curves. Field sampling during 2014 achieved the sample size target at many more sites with a total of 449 additional fish collected. However, the stomach content data were in the early quality control stage during the preparation of this TM, so they are not included here. In response to the October 2014 ISR meetings, AEA informed the licensing participants that AEA would be filing this TM with the Federal Energy Regulatory Commission ahead of the January 2015 ISR meetings. 2. ANALYSIS METHODS Cumulative prey curves were used to determine whether sample sizes were sufficient. This approach plots the cumulative number of randomly pooled stomach content samples on the x- axis, with the cumulative number of prey types on the y-axis. The point at which the curve stabilizes indicates the minimum number of stomach content samples necessary to characterize diet composition (Cortes 1997, Chipps and Garvey 2007). Cumulative prey curves were generated for each study species, at each sampling site, in each season. The order of stomach TECHNICAL MEMORANDUM FISH DIET SAMPLE SIZE SUFFICIENCY ANALYSIS Susitna-Watana Hydroelectric Project Alaska Energy Authority FERC Project No. 14241 Page 2 December 2014 content samples was randomized. Prey types were categorized following the methods of the overall diet composition analysis. Prey types were identified to the family level for invertebrates and to species level for fish when possible. Fish eggs were counted as a separate prey item. Due to the large number of curves representing every combination of sites and seasons, all curves were combined into a single figure for each species, and each curve was adjusted slightly up or down to show overlapping data points. To aid in interpreting the multiple curves per species, the mean increase in prey types per additional sample was also calculated. 3. RESULTS AND INTERPRETATION The cumulative prey curve analysis indicated the sample size target of n = 8 was likely sufficient to adequately quantify diet composition in this study (Figure 1). Overall, the number of prey types stabilized as sample sizes approached eight for all three species. Some individual curves stabilized at lower sample sizes, suggesting that smaller samples sizes (n = 4-7) may have been adequate at certain sites during certain seasons. Individual curves stabilized at different numbers of prey types, ranging from 2-16, suggesting that diet breadth differed between sites and seasons. The mean increase in cumulative prey types (indicated by the red lines in Figure 1) fluctuated due to random variability but approached zero as the number of samples approached n = 8, providing further support for the adequacy of this sample size to achieve the study objectives. These cumulative prey curves were interpreted with caution because the target sample sizes were not met during several sampling events in 2013. Repeating this analysis with the more complete 2014 dataset will be important to confirm these findings. However, based on the data currently available, the study design was likely adequate to achieve the objectives of the River Productivity Study, especially considering the additional information provided by the stable isotope analysis. 4. PLANS FOR FURTHER ANALYSIS A similar cumulative prey curve analysis will be conducted using the 2014 stomach content data and included in the Updated Study Report. The USR will also include a comprehensive evaluation of the adequacy of the combined stomach contents and stable isotope datasets to meet the study objectives. TECHNICAL MEMORANDUM FISH DIET SAMPLE SIZE SUFFICIENCY ANALYSIS Susitna-Watana Hydroelectric Project Alaska Energy Authority FERC Project No. 14241 Page 3 December 2014 5. LITERATURE CITED Alaska Energy Authority (AEA). 2012. Revised Study Plan: Susitna-Watana Hydroelectric Project FERC Project No. 14241. December 2012. Prepared for the Federal Energy Regulatory Commission by the Alaska Energy Authority, Anchorage, Alaska. http://www.susitna-watanahydro.org/study-plan. Alaska Energy Authority (AEA). 2014. Initial Study Report: Susitna-Watana Hydroelectric Project FERC Project No. 14241. June 2014. Prepared for the Federal Energy Regulatory Commission by the Alaska Energy Authority, Anchorage, Alaska. http://www.susitna-watanahydro.org/type/documents. Beauchamp, D.A., D. Wahl, and B.M. Johnson. 2007. Predator-prey interactions. Pages 765- 842 in C.S. Guy and M.L. Brown, editors. Analysis and Interpretation of Freshwater Fisheries Data. American Fisheries Society, Bethesda, Maryland. Chipps, S.R. and J.E. Garvey. 2007. Quantitative assessment of food habits and feeding patterns. Pages 473-514 in C. S. Guy and M. L. Brown, editors. Analysis and Interpretation of Freshwater Fisheries Data. American Fisheries Society, Bethesda, Maryland. Cortes, E. 1997. A critical review of methods of studying fish feeding based on analysis of stomach contents: Application to elasmobranch fishes. Canadian Journal of Fisheries and Aquatic Sciences 54:726-738. Fry, B. 2006. Stable isotope ecology. Springer Verlag. 320 pp. Hanisch, J.R., W.M. Tonn, C.A. Paszkowski, and G.J. Scrimgeour. 2010. δ13C and δ15N signatures in muscle and fin tissues: Nonlethal sampling methods for stable isotope analysis of salmonids. North American Journal of Fisheries Management 30:1-11. McIntyre, J.K., D.A. Beauchamp, M.M. Mazur, and N.C. Overman. 2006. Ontogenetic trophic interactions and benthopelagic coupling in Lake Washington: Evidence from stable isotopes and diet analysis. Transactions of the American Fisheries Society 135:1312- 1328. Vinson, M.R. and P. Budy. 2011. Sources of variability and comparability between salmonid stomach contents and isotopic analyses: study design lessons and recommendations. Canadian Journal of Fisheries and Aquatic Sciences 68:137-151. TECHNICAL MEMORANDUM FISH DIET SAMPLE SIZE SUFFICIENCY ANALYSIS Susitna-Watana Hydroelectric Project Alaska Energy Authority FERC Project No. 14241 Page 4 December 2014 6. FIGURES Figure 1. Cumulative prey curves for Chinook salmon, coho salmon, and rainbow trout sampled during 2013.