Title

Effects of Wildfire on Terrestrial Subsidies to Diets of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi)

Presentation Type

Poster

Abstract

Western United States forest wildfire frequency and severity have dramatically increased in recent decades and are predicted to continue to increase with climate change. However, few studies have addressed, how wildfire may influence the aquatic-terrestrial ecosystem connectivity. Therefore, we investigated the decadal influences of wildfire on the diet composition of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi). We examined fish diets in four burned and unburned streams to evaluate three alternative hypotheses (1) terrestrial invertebrate (TI) consumption will be greater in burned sites due to the influence of the vegetation’s earlier successional stage on insect production, (2) TI consumption will be similar between treatments, or (3) TI consumption will be lower due to the lack of overhanging/canopy vegetation. We captured fish using a backpack electrofishing unit, identified them, and measured their total length. Additionally, we sampled stomach contents of fish using gastric lavage and returned samples to the lab for identification. Finally, we described fish size distributions and densities across sites and burn treatments. Initial results did not demonstrate differences in consumption of TI between treatments. However, we detected differences in taxa consumed between treatments; specifically, we found more Ephemeroptera (mayfly) and Hemiptera (true bug) in fish diets from burned sites, and more Lepidoptera (butterfly and moth) in diets at unburned sites. There was no difference in the size range or density of trout between treatments. As landscapes warm and resulting wildfire regimes change, it is critical to investigate how these changes to riparian structure may be having lasting impacts on terrestrial-aquatic linkages and subsequently stream food webs and fisheries resources.

Category

Physical Sciences

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Apr 17th, 3:00 PM Apr 17th, 4:00 PM

Effects of Wildfire on Terrestrial Subsidies to Diets of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi)

South UC Ballroom

Western United States forest wildfire frequency and severity have dramatically increased in recent decades and are predicted to continue to increase with climate change. However, few studies have addressed, how wildfire may influence the aquatic-terrestrial ecosystem connectivity. Therefore, we investigated the decadal influences of wildfire on the diet composition of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi). We examined fish diets in four burned and unburned streams to evaluate three alternative hypotheses (1) terrestrial invertebrate (TI) consumption will be greater in burned sites due to the influence of the vegetation’s earlier successional stage on insect production, (2) TI consumption will be similar between treatments, or (3) TI consumption will be lower due to the lack of overhanging/canopy vegetation. We captured fish using a backpack electrofishing unit, identified them, and measured their total length. Additionally, we sampled stomach contents of fish using gastric lavage and returned samples to the lab for identification. Finally, we described fish size distributions and densities across sites and burn treatments. Initial results did not demonstrate differences in consumption of TI between treatments. However, we detected differences in taxa consumed between treatments; specifically, we found more Ephemeroptera (mayfly) and Hemiptera (true bug) in fish diets from burned sites, and more Lepidoptera (butterfly and moth) in diets at unburned sites. There was no difference in the size range or density of trout between treatments. As landscapes warm and resulting wildfire regimes change, it is critical to investigate how these changes to riparian structure may be having lasting impacts on terrestrial-aquatic linkages and subsequently stream food webs and fisheries resources.