Salish Sea Marine Survival (Steelhead) - Early Marine Survival of Puget Sound Steelhead

The primary objectives of this study are to estimate a predation rate by harbor seals on steelhead smolt in Puget Sound, and determine whether predation by harbor seals differs by region. Nisqually River steelhead will be acoustic tagged, and 12 - 18 seals will be fitted with GPS/acoustic receiver instrument packs. Tag detection capabilities will be expanded by i) monitoring harbor seals in South and Central Puget Sound and Admiralty Inlet, ii) placing stationary receivers at seal haulouts and at random locations not frequented by harbor seals, iii) conducting mobile tracking to locate tags remaining in Puget Sound after the smolt outmigration period. Seal time at depth and locations will be quantified in such a manner that estimates the amount of time seals spend at haulout locations to estimate the probability that a tag consumed by a harbor seal would be defecated near a haulout site. Data on harbor seal abundance, behavior, steelhead tag locations, and smolt abundance will be combined to estimate the predation rate and total number of smolts consumed by harbor seals.
In addition, recent fish health assays indicate high infection prevalence (87-100%) and intensity (800-2500 cysts/fish) of Nanophyetus salmonica in steelhead outmigrating from Central (Green) and South (Nisqually) Puget Sound Rivers. South and Central Puget Sound steelhead populations generally experience lower early marine survival rates than those from North Puget Sound rivers, where Nanophyetus infections in assayed steelhead were absent. High infection intensity among freshwater outmigrants could contribute to rapid mortality shortly after seawater entry. This study will use acoustic telemetry to evaluate differences in the early marine survival (near river mouth to Pacific Ocean) of specific pathogen-free (SPF) and Nanophyetus-infected Puget Sound steelhead smolts. This approach will help us understand effects of Nanophyetus infection at different stages of the steelhead smolt migration through Puget Sound.
Steelhead smolt locations.