Trophic Relationships between Exotic Brown Trout (Salmo Trutta) and Native Bonneville Cutthroat Trout (Oncorhynchus Clarkii Utah) in the Logan River, Utah
Location
Eccles Conference Center
Event Website
http://water.usu.edu/
Start Date
3-27-2006 10:15 AM
End Date
3-27-2006 10:20 AM
Description
Cutthroat trout populations have declined throughout western North America due to the combined effects of habitat degradation and exotic trout invasion. In contrast to the well documented effects of brook and rainbow trout on cutthroat trout persistence, the role of exotic brown trout in cutthroat trout decline is less certain. Experimental analyses have illustrated that cutthroat trout are negatively affected by brown trout; however, the behavioral mechanism behind this competitive impact is not clearly understood. To help resolve this uncertainty, we performed a detailed evaluation of brown and cutthroat trout trophic relationships in a river where they co-occur (the Logan River, Utah) across two years (2003-2004). We quantified several aspects of fish diets using a combination of stable isotope (i.e., 13C and 15N) and stomach content analysis (e.g., prey composition and size structure). Further, we analyzed fish dietary patterns as an explicit function of ontogeny – as inferred from fish size – in order to identify life stages where interactions might be particularly intense. Our analysis of 13C signatures and prey composition demonstrates that brown and cutthroat trout generally consume a similar diet. However, across life stages, brown trout ingested significantly larger prey – including fishes – and occupied a higher trophic position (inferred from 15N) than did cutthroat trout. These results strengthen earlier conclusions that competition is an important mechanism via which brown trout impact cutthroat trout; however, our findings also suggest that a high potential exists for predation by brown trout on smaller cutthroat trout.
Trophic Relationships between Exotic Brown Trout (Salmo Trutta) and Native Bonneville Cutthroat Trout (Oncorhynchus Clarkii Utah) in the Logan River, Utah
Eccles Conference Center
Cutthroat trout populations have declined throughout western North America due to the combined effects of habitat degradation and exotic trout invasion. In contrast to the well documented effects of brook and rainbow trout on cutthroat trout persistence, the role of exotic brown trout in cutthroat trout decline is less certain. Experimental analyses have illustrated that cutthroat trout are negatively affected by brown trout; however, the behavioral mechanism behind this competitive impact is not clearly understood. To help resolve this uncertainty, we performed a detailed evaluation of brown and cutthroat trout trophic relationships in a river where they co-occur (the Logan River, Utah) across two years (2003-2004). We quantified several aspects of fish diets using a combination of stable isotope (i.e., 13C and 15N) and stomach content analysis (e.g., prey composition and size structure). Further, we analyzed fish dietary patterns as an explicit function of ontogeny – as inferred from fish size – in order to identify life stages where interactions might be particularly intense. Our analysis of 13C signatures and prey composition demonstrates that brown and cutthroat trout generally consume a similar diet. However, across life stages, brown trout ingested significantly larger prey – including fishes – and occupied a higher trophic position (inferred from 15N) than did cutthroat trout. These results strengthen earlier conclusions that competition is an important mechanism via which brown trout impact cutthroat trout; however, our findings also suggest that a high potential exists for predation by brown trout on smaller cutthroat trout.
https://digitalcommons.usu.edu/runoff/2006/AllPosters/10