The majority of coho salmon enter the lake as smolts in May and June. The primary predator of juvenile salmonids in Lake Washington is cutthroat trout. The majority of known bass predation on juvenile salmonids occurs in the Ship Canal. Smallmouth bass are the primary predator, preying most heavily on chinook juveniles due to their small size relative to sockeye and coho yearlings. Bass are structurally oriented for both spawning and foraging, and smallmouth bass may prefer artificial structures such as piles for nest sites.
Piers are structurally simple, lacking the complexity necessary to function as prey-refuge habitat.
Thus, they confer an advantage to predatory fish and birds over vulnerable juvenile salmonids. Bulkheads are also structurally simple relative to undisturbed shorelines. Bulkheads waterward of OHW eliminate shallow-water refuge and foraging habitat of juvenile salmonids. Bulkheads with large interstitial spaces provide concealment habitat for sculpin, which prey upon juvenile chinook. Chinook fry appear to avoid bulkheads, which may affect their dispersal.