Monitoring of sockeye salmon smolt abundance and inriver distribution using sonar on the Kvichak, Egegik, and Ugashik rivers in 2011 Prepared for Bristol Bay Science and Research Institute Box 1464, Dillingham, AK 99576 October 2012 Monitoring of sockeye salmon smolt abundance and inriver distribution using sonar on the Kvichak, Egegik, and Ugashik rivers in 2011 by Guy D. Wadea, Don J. Deganb, Michael R. Linka, and Matthew J. Nemetha aLGL Alaska Research Associates, Inc. 1101 East 76th Avenue, Suite B Anchorage, Alaska 99518 bAquacoustics, Inc. P.O. Box 1473 Sterling, AK 99672-1473 for Bristol Bay Science and Research Institute Box 1464, Dillingham, AK 99576 October 2012 Smolt monitoring on the Kvichak, Egegik and Ugashik rivers, 2011 Suggested format for citation: Wade, G. D., D. J. Degan, M. R. Link, and M. J. Nemeth. 2012. Monitoring of sockeye salmon smolt abundance and inriver distribution using sonar on the Kvichak, Egegik, and Ugashik rivers in 2011. Report prepared by LGL Alaska Research Associates, Inc., Anchorage, AK, and Aquacoustics, Inc. Sterling, AK, for the Bristol Bay Science and Research Institute, Dillingham, AK, 64p. ii Smolt monitoring on the Kvichak, Egegik and Ugashik rivers, 2011 ABSTRACT We operated up-looking sonar systems on the Kvichak, Egegik, and Ugashik rivers in 2011 to estimate the hourly, daily, and seasonal abundance of sockeye salmon (Oncorhynchus nerka) smolts migrating from the watersheds. Smolt numbers can provide data needed to evaluate freshwater production, set biological escapement goals, and forecast adult returns. Two independent sonar systems were operated on each river and used to generate separate abundance estimates. Each sonar array consisted of a single row of pods placed along the river bottom, perpendicular to the bank. Smolt densities were estimated using echo integration stratified by pod and water depth. Kvichak River sonar systems were operated 3.5 rkm (Site 1, operated from 21 May to 12 June) and 7.0 rkm (Site 2, operated from 21 May to 13 June) downstream of Lake Iliamna. Total sockeye salmon smolt abundance was estimated to be 48.8 million (95% confidence interval of 45.5 – 52.0 million) at Site 1 and 41.7 (39.3 – 44.2 million) at Site 2. Run timing data indicates both sites operated for the entirety of the smolt out migration. Egegik River sonar systems were both 4.5 rkm downstream from the outlet of Lake Becharof, and each operated from 17 May through 11 June; sockeye salmon smolt abundance was estimated to be 9.9 million (8.8 – 11.1 million) at Site 1 and 8.9 (7.7 – 10.0 million) at Site 2. Ugashik River sonar systems were deployed approximately 80 m downstream of the outlet of Lower Ugashik Lake on 12 May (Site 1) and 15 May (Site 2). High water velocity (> 3.0 m/s) washed both Ugashik River arrays downstream on 24 May, preventing abundance estimates in 2011. When water conditions allowed, the sonar systems described here effectively estimated smolt abundance and behavior. Ice and water conditions affect fish behavior and sonar operation, and must be accounted for when using this technology to estimate smolt abundance. Unusual ice conditions in 2011 may have accounted for some differences in seasonal and diel timing of smolt migration between the Kvichak and Egegik rivers, and among years on the Kvichak River. Smolts were distributed through more of the water column on the Egegik River than on the Kvichak River. The effectiveness of this approach in future years will depend on the ability to maintain operation at times of abnormally high or variable water and ice conditions, and to describe associations between water velocity and smolt swimming speed. iii Smolt monitoring on the Kvichak, Egegik and Ugashik rivers, 2011 TABLE OF CONTENTS ABSTRACT ............................................................................................................................. iii LIST OF TABLES .....................................................................................................................v LIST OF FIGURES ................................................................................................................. vi LIST OF PHOTOS ................................................................................................................. vii APPENDIX A ........................................................................................................................ viii INTRODUCTION .....................................................................................................................1 Background and history of the project .................................................................................. 1 Current project operation ...................................................................................................... 2 OBJECTIVES ............................................................................................................................2 STUDY AREA ..........................................................................................................................3 Kvichak River ....................................................................................................................... 3 Egegik River ......................................................................................................................... 3 Ugashik River ....................................................................................................................... 4 METHODS ................................................................................................................................4 Sonar System Design ............................................................................................................ 4 Sonar Pod...........................................................................................................................4 Control Box ........................................................................................................................5 Power Requirements ..........................................................................................................5 Sonar Specifications for up-looking sonar pods ................................................................5 Sonar Calibration ..............................................................................................................6 Sonar Deployment and Operation ......................................................................................... 6 Kvichak Sonar Deployment and Operation .......................................................................6 Egegik Sonar Deployment and Operation .........................................................................7 Ugashik Sonar Deployment and Operation .......................................................................8 Sampling Smolt for Age, Weight, and Length ..................................................................... 8 Environmental Data ............................................................................................................ 10 Sonar Data Analysis ............................................................................................................ 11 Data Pre-processing ........................................................................................................11 Requirements for a Reliable Abundance Estimate ............................................................. 11 Smolt Abundance Estimates ............................................................................................... 12 RESULTS ................................................................................................................................14 Kvichak River ..................................................................................................................... 14 Data Pre-processing ........................................................................................................14 Abundance Estimate.........................................................................................................14 Smolt Distribution ............................................................................................................14 Run Timing .......................................................................................................................15 Sampling Smolt for Age, Weight, and Length ..................................................................15 Egegik River ....................................................................................................................... 15 Data Pre-processing ........................................................................................................15 Abundance Estimate.........................................................................................................16 Smolt Distribution ............................................................................................................16 Run Timing .......................................................................................................................16 Ugashik River ..................................................................................................................... 16 iv Smolt monitoring on the Kvichak, Egegik and Ugashik rivers, 2011 Abundance Estimate.........................................................................................................16 DISCUSSION ..........................................................................................................................17