Salmon Escapement into Chester Creek Before and After Habitat Restoration - Rusty Myers , Environmental Science Department, Alaska Pacific University (co-authors: none)

ABSTRACT

Chester Creek once supported significant fish populations. Davis and Muhlberg estimated the coho salmon (Oncorhynchus kisutch) population at 217 fish per stream mile in 1974 and 34 per stream mile in 2001. A significant impact on salmon passage into and out of Chester Creek occurred in 1971 when the city of Anchorage constructed a dam at the mouth of Chester Creek to create Westchester Lagoon. The dam included a concrete weir with two 7-foot diameter outlet pipes that dropped approximately 60 m through an elevation change of 6.5 m to Knik Arm at low tide. The dam also included a fish ladder constructed of a 6-foot diameter corrugated metal pipe running 25 m from the dam-weir structure to Westchester Lagoon. While the fish ladder was constructed to assist fish passage between the Knik Arm and Westchester Lagoon, it was largely ineffective. The Chester Creek Ecosystem Aquatic Habitat Restoration Project was a multi-million dollar effort to restore free passage of salmon from Knik Arm to Chester Creek via Westchester Lagoon. A major component of the project was to replace the culvert-weir system with a box culvert and new channel allowing salmon free passage between marine and freshwater systems. The last year in which salmon had to move upstream though the weir to escape into Westchester Lagoon was 2008 and in 2009 salmon moved freely into and out Westchester through the new channel. Visual counts conducted in 2008 indicated 497 cohos escaped into Westchester, while corresponding counts from video footage indicated 388 cohos escaped. In 2009 using a replicated systematic sample design the estimated number of coho and pink salmon (Oncorhynchus gorbuscha) entering Westchester was 1,938 with a standard deviation of 436. Video monitoring in 2009 was largely ineffective due to several factors including vandalism, technical difficulties, and turbidity. In addition to work done at the mouth of Westchester during 2008 and 2009, several other components of our work included a habitat survey to estimate Chester Creek’s carrying capacity for coho salmon, minnow trapping, and carcass surveys. Adult coho were observed as far as 14 kilometers upstream until a large beaver dam located in the vicinity of Windsong Park halted migration. Approximately 60 carcasses were found within a 50-m stretch just below the beaver dam in September of 2009.

Topic: Fish habitat