Diet overlap of top-level predators in recent sympatry: bull trout and nonnative lake trout
Journal of Fish and Wildlife Management
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Abstract
The establishment of nonnative lake trout Salvelinus namaycush in lakes containing lacustrine–adfluvial bull trout Salvelinus confluentus often results in a precipitous decline in bull trout abundance. The exact mechanism for the decline is unknown, but one hypothesis is related to competitive exclusion for prey resources. We had the rare opportunity to study the diets of bull trout and nonnative lake trout in Swan Lake, Montana during a concomitant study. The presence of nonnative lake trout in Swan Lake is relatively recent and the population is experiencing rapid population growth. The objective of this study was to evaluate the diets of bull trout and lake trout during the early expansion of this nonnative predator. Diets were sampled from 142 bull trout and 327 lake trout during the autumn in 2007 and 2008. Bull trout and lake trout had similar diets, both consumed Mysis diluviana as the primary invertebrate, especially at juvenile stages, and kokanee Oncorhynchus nerka as the primary vertebrate prey, as adults. A diet shift from primarily M. diluviana to fish occurred at similar lengths for both species, 506 mm (476–545 mm, 95% CI) for bull trout and 495 mm (470–518 mm CI) for lake trout. These data indicate high diet overlap between these two morphologically similar top-level predators. Competitive exclusion may be a possible mechanism if the observed overlap remains similar at varying prey densities and availability.
Suggested Citation
Guy, C.S., McMahon, T., Fredenberg, W.A., Smith, C.J., Garfield, D.W., and Cox, B.S., 2011, Diet overlap of top-level predators in recent sympatry: bull trout and nonnative lake trout: Journal of Fish and Wildlife Management, v. 2, no. 2, p. 183-189, https://doi.org/10.3996/012011-JFWM-004.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Diet overlap of top-level predators in recent sympatry: bull trout and nonnative lake trout |
| Series title | Journal of Fish and Wildlife Management |
| DOI | 10.3996/012011-JFWM-004 |
| Volume | 2 |
| Issue | 2 |
| Year Published | 2011 |
| Language | English |
| Publisher | U.S. Fish and Wildlife Service |
| Publisher location | Arlington, VA |
| Contributing office(s) | Montana Cooperative Fishery Research Unit |
| Description | 7 p. |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Fish and Wildlife Management |
| First page | 183 |
| Last page | 189 |
| Country | United States |
| State | Montana |
| Other Geospatial | Swan Lake |