Results/Implications

Results

• Aerial surveys of tagged fish from November-April indicated that trout overwinter in the mainstem Susitna and Talkeetna Rivers, clustered near the mouths of tributaries. Fish moved up to 51 km away from the tributary of origin. Trout appeared to be seeking out areas of open water and deep pools.

• On-the-ground tracking in May 2014 showed that trout moved out of the Susitna River and into Willow Creek. Most then traveled up Deception Creek to spawn. Several also spawned in Little Willow Creek.

• During the pre-salmon feeding season (June-early July) trout were spread throughout lower tributary reaches. In the late feeding season (mid-July-early September), as Chinook salmon entered the creek, most of our tagged fish moved upstream and were concentrated near spawning salmon aggregations to take advantage of egg and flesh food subsidies. However, several fish remained in lower reaches and did not respond to the presence of the migrating salmon.

• In September and October, fish began to move downstream towards mainstem overwintering areas in the Susitna or Talkeetna Rivers with dropping temperatures and waning salmon spawning activity in the tributaries.

• Inter-tributary movement was seen in tagged fish from all tributaries at a low proportion, except for in the Kashwitna River sample (more migratory). There was no evidence of differential seasonal or annual movement between males and females in Willow Creek in 2013-2014. Trout appeared to select habitats with higher water volume and presence of salmon in Willow Creek in 2014. Across various seasons and basin-wide, mean annual flow, gradient, sinuousity, and Chinook salmon spawning potential were selected for by rainbow trout.

• Interestingly, the percentage of hooking scars (deformities likely due to catch-and-release angling) was highest in Willow and Montana Creeks, which generally see the most angling pressure. Deformities ranged from minor crossbite and scarred maxilla to dysfunctional eyes and serious lesions. See below figure for additional results:

Other interesting observations:

-A Willow Creek trout was tracked to a bald eagle nest in 2014, assumed predation

-Roughly 1/2 of fish caught in Willow Creek in 2013-2014 were > 400 mm fork length

-Females outnumbered males in the 2013-2014 Willow Creek trout samples

-Illicit harvest of adult rainbow trout (>16 inches in length) was observed in Willow Creek

-The farthest a fish traveled between seasons was 101 km (Kashwitna River)

-The farthest a fish traveled over the course of a year was 190 km (Kashwitna River)

-Rainbow trout and Arctic grayling tended to segregate longitudinally in Willow Creek

Conclusions