Post-Fire Bonneville Cutthroat Trout Recovery in Strawberry Creek

This article was originally published in The Midden – Great Basin National Park: Vol. 24, No. 2, Winter 2024.

A beautiful Bonneville cutthroat trout about to be measured. NPS/ P. Brannon

By Parker Brannon, Biological Science Technician

On August 8th, 2016, a wildfire broke out in Strawberry Creek, burning 2,790 acres (41%) of the drainage in Great Basin National Park (GRBA), 1,769 acres of BLM land, and 97 acres of private land equaling 4,656 total acres. The fire was especially severe in the riparian area of the creek, negatively affecting local vegetation, fish, and wildlife. To help salvage the remaining population, 251 Bonneville Cutthroat Trout (Oncorhynchus clarkii utah) (BCT) were captured, transported, and released into nearby Silver Creek. An additional 27 BCT were captured and released in the headwaters of Strawberry Creek above the burn perimeter. This recovery was performed within days after the fire due to BCT susceptibility to changes in water chemistry, increased stream siltation, and potential flash flooding.

Before the fire, Strawberry Creek was considered the park’s most productive BCT stream. During a population survey in 2011, BCT were present at 8 of 9 survey sites with an average population density of 755 fish per mile and a max density of 1,867 fish per mile. Immediately after the fire, a set of population and habitat surveys were conducted. Only 2 of 9 sites contained BCT with an average population density of 114 fish per mile and a max density of 805 fish per mile. This represents a 75% decrease in distribution and 85% decrease in population. The 2016 General Aquatic Wildlife Survey (GAWS) produced a Habitat Condition Index (HCI) score of 48.6, which showed a 22% decrease from the last survey taken in 2009 (HCI=62.0).

Map of nine BCT survey sites in Strawberry Creek within NPS boundaries.

Post fire habitat restoration efforts have focused on increasing ground cover by seeding native vegetation and halting and reversing stream channel incision with beaver dam analogs (BDAs) and post-assisted log structures (PALS). Post-fire GAWS surveys were conducted in 2017 and 2018, which produced HCI scores of 53.4 and 60.3 respectively.

Number of Bonneville Cutthroat Trout captured during fisheries surveys from 2009-2024. The Strawberry Creek fire occurred in 2016.

Population surveys for BCT have occurred in Strawberry Creek in 2016-2018 and 2021-2024. Population numbers have varied but show a general increasing trend post-fire. This year, 2024, showed the highest number of sampled individuals since 2011 (136 BCT in 2024, 187 BCT in 2011). Site R2S4 had the highest number of BCT at 58 individuals while R2S1 did not contain any fish (BCT last observed at R2S1 in 2011). R4S1 only contained one individual but this is the first year that a BCT has been observed at that specific site since the fire occurred.

Our results and observations suggest that BCT populations are steadily increasing throughout Strawberry Creek and returning to areas that they occupied pre-fire. More evidence pointing towards successful recruitment include the observation of 7 young of year (YOY, <50mm) BCT as well as several juvenile fish (between 50 and 150mm). In 2024, BCT were present at 8/9 survey sites with an average population density of 511 fish per mile and a max density of 2,092 fish per mile. This is the highest estimate post-fire, and the second-highest estimate since we began Strawberry fisheries surveys in 2009.

Captured fish looked to be in good health. We primarily caught juvenile-adult fish ranging from 60-150 millimeters in length and 5-50 grams in weight, and we also observed multiple YOYs. The largest individual was seen at R3S1 weighing 300 grams with a total length of 293 millimeters (11.5 inches). Our smallest individual was seen at R2S4 weighing 0.45 grams with a total length of only 38 millimeters (1.5 inches).

Part of a series of articles titled
The Midden - Great Basin National Park: Vol. 24, No. 2, Winter 2024.

Previous:
Strawberry Fire Restoration Recap

Next:
Strawberry Creek Birds, Pre- and Post Fire

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