Release Site Fidelity and Spawning Location of Adult Atlantic Salmon Translocated to Novel Headwater Habitat within the Penobscot Basin, Maine

We investigated adult salmon translocation to headwater habitat to improve spawning effectiveness and wild smolt recruitment.  Penobscot River headwater habitat is far more productive than downriver habitat but hatchery smolts are currently stocked (and inadvertently imprinted) downriver to avoid dam related mortality, cumulatively as high as 40%.  Returning adult salmon, originating from hatchery smolts, were captured at a head tide fishway, held at a USFWS hatchery, later trucked 156 km above head tide (bypassing seven dams) and released.  Release date was 10 days prior to the expected spawning date to minimize post-release roving and homing to the original smolt stocking site near head tide.  Translocations occurred in 2009 (female:male 57:47) 2010 (79:40) and 2011 (109:57).  Radio tags were implanted in 60% of female salmon to monitor post release movement and redd counts were conducted to assess spawning activity.  Most fish (87.5 ± 2.9%) moved downriver immediately after release but 45.7 ± 1.0% of fish remained in the novel habitat and spawned within 4.2 ± 1.9 km of the release location.  Apparent homing to head tide smolt stocking sites (24.5%, 2 year mean) increased to 40.5% when the interval between release and spawn dates was increased by three weeks in 2010.