Abstract Title

Cutthroat Competition: How Does Ketotestosterone Differ in the Brains of Competitive Brook and Cutthroat Trout?

Additional Funding Sources

The project described was supported by NSF Award No. OIA-1757324 from the NSF Idaho EPSCoR Program and by the National Science Foundation.

Abstract

Cutthroat trout (Oncorhynchus clarkia), native to the western united states, are being displaced from their native range by a variety of invasive species, including brook trout (Salvelinus fontinalis). One mechanism by which brook trout are displacing cutthroat trout is by outcompeting the native fish for resources. In many vertebrates resource competition is correlated with high androgen expression. The potent fish androgen, 11-Ketotestosterone (11-KT), affects growth and aggression in a variety of organisms. Our goal is to investigate the difference in brain 11-KT between invasive brook trout and native cutthroat trout during food competition. We made predictions on how brain 11-KT may correlate with individual and specific competitive success. These predictions are based on a previous study’s data that examined how brook trout and cutthroat trout compete for food under different light conditions (Whitworth 2021). In that study 42 young wild juvenile trout (21 cutthroat, 21 brook) were captured from Idaho streams via backpack electrofishing. Fish were size matched by mass, and placed into an arena for food competition trials. This was done by introducing blood worms to the arena every ten seconds over a five minute trial under both high and low light conditions. We found that cutthroat trout weighing under five grams had greater food capture rates in high light than brook trout. However, brook trout weighing over five grams had greater food capture rates in high light than cutthroat trout. There was no significant difference between species in low light. We predict that brain 11-KT concentrations will positively correlate with both individual and specific competitive success. We expect that within each trial, individuals that outcompeted their opponent will have the higher brain 11-KT concentration. We also expect that species will exhibit higher brain 11-KT concentration under conditions that they tended to outcompete the other species. If correct, these findings will give us insight into the physiological mechanisms of interspecies competition and how invasive species may be assisted by hormonal expression.

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Cutthroat Competition: How Does Ketotestosterone Differ in the Brains of Competitive Brook and Cutthroat Trout?

Cutthroat trout (Oncorhynchus clarkia), native to the western united states, are being displaced from their native range by a variety of invasive species, including brook trout (Salvelinus fontinalis). One mechanism by which brook trout are displacing cutthroat trout is by outcompeting the native fish for resources. In many vertebrates resource competition is correlated with high androgen expression. The potent fish androgen, 11-Ketotestosterone (11-KT), affects growth and aggression in a variety of organisms. Our goal is to investigate the difference in brain 11-KT between invasive brook trout and native cutthroat trout during food competition. We made predictions on how brain 11-KT may correlate with individual and specific competitive success. These predictions are based on a previous study’s data that examined how brook trout and cutthroat trout compete for food under different light conditions (Whitworth 2021). In that study 42 young wild juvenile trout (21 cutthroat, 21 brook) were captured from Idaho streams via backpack electrofishing. Fish were size matched by mass, and placed into an arena for food competition trials. This was done by introducing blood worms to the arena every ten seconds over a five minute trial under both high and low light conditions. We found that cutthroat trout weighing under five grams had greater food capture rates in high light than brook trout. However, brook trout weighing over five grams had greater food capture rates in high light than cutthroat trout. There was no significant difference between species in low light. We predict that brain 11-KT concentrations will positively correlate with both individual and specific competitive success. We expect that within each trial, individuals that outcompeted their opponent will have the higher brain 11-KT concentration. We also expect that species will exhibit higher brain 11-KT concentration under conditions that they tended to outcompete the other species. If correct, these findings will give us insight into the physiological mechanisms of interspecies competition and how invasive species may be assisted by hormonal expression.