Annual Report: 1997 Sammamish River Sockeye Salmon Fry Production Evaluation PDF Format - [137KB] Acknowledgements The 1997 Sammamish River Sockeye Salmon Fry Production Evaluation was funded by the Lake Washington/Cedar River Forum. Forum Coordinator, John Lombard, facilitated funding for this work, as part of the Lake Washington Ecological Studies. The City of Bothell was instrumental in permitting and providing operational support for our trapping operation. In particular, we greatly appreciated the help of Mac McDonald, of the City of Bothell Public Works Department, who granted us use of an electrical connection. This improved worker safety during our nightly trapping operations. The National Marine Fisheries Service provided longterm moorage for the trapping barge after the season. Daily mean flow data was provided by USGS. The success of this project relies on the hard work of a number of dedicated permanent and temporary WDFW personnel. WDFW Fish Biologist Steve Wolthausen, and Scientific Technician Chuck Ridley worked long hours at night operating and maintaining the trap, marking and releasing fry, and enumerating catches. WDFW Wild Salmon Production & Survival Evaluation Unit biologists Mike Ackley and Pete Topping provided valuable logistical support.

<<< Return to Wild Salmon Population Monitoring Annual Report: 1997 Sammamish River Sockeye Salmon Fry Production Evaluation By: Dave Seiler and Lori Kishimoto November 1997 Introduction The numbers of adult sockeye salmon returning to the Lake Washington system are estimated as they pass the Ballard Locks, and as spawners in the Cedar River, primary tributaries to the Sammamish system, and on certain beaches. The majority of the spawning has occurred in the Cedar River, but in three recent years (1992, 1994, and 1996), biologists have estimated that a quarter to a third of the Lake Washington Basin sockeye have spawned in the Sammamish River Basin (Egan and Ames WDFW memo, 1997) . Over the other twelve of the last fifteen years for which escapement estimates are available for all areas, the Cedar River accounts for an average of 88% of the total spawners (range = 82% to 98%). This interannual variation may result from differential survival as a function of spawning and emergence timing relative to stream specific hydrology. In addition to run timing differences, recent electrophoretic analysis indicates that the sockeye which spawn in the Sammamish system are genetically distinct from the larger Cedar River population. In 1992, as part of a multi-agency effort to determine the cause(s) of the decline in the Lake Washington sockeye run, we began enumerating sockeye fry production from the Cedar River. Measuring the population at this lifestage and location separates freshwater survival into its two major components; spawning which takes place in the river and rearing which occurs in the lake. Over the past six broods, natural spawners in the Cedar River have produced fry populations to the lake of 0.7 to 27.1 million. We have determined that the severity of peak flows is the primary factor controlling survival from spawning to fry emigration in this system. Annual estimates of the numbers of fry entering the lake are also needed to understand the complex ecological relationships which regulate juvenile sockeye survival during their year in the lake. Because the Sammamish system may account for a significant portion of the fry entering Lake Washington in some years, an estimate of this production component is also needed to understand the dynamics of the combined population.