Natural chemical markers identify source and date of introduction of an exotic species: lake trout (Salvelinus namaycush) in Yellowstone Lake

• Published in: Canadian journal of fisheries and aquatic sciences 2005-01, Vol.62 (1), p.79-87
• Main Authors: Munro, Andrew R, McMahon, Thomas E, Ruzycki, James R
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Aquatic ecosystems; Biological and medical sciences; Chemical analysis; Environmental history; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fish migration; Fresh water ecosystems; Freshwater; Freshwater fish; Fundamental and applied biological sciences. Psychology; Genetic markers; Introduced species; Invasions; Invasive species; Lakes; National parks; Otoliths; Salmon; Salvelinus namaycush; Seawater; Streams; Synecology; Water analysis; Water chemistry; Water depth; Wildfires
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f04-174

Exotic species invasions pose a pervasive threat to aquatic ecosystems worldwide, yet fundamental questions about the geographic origin and timing of invasions or introductions are frequently difficult to answer. We used natural chemical markers (Sr:Ca ratios) in otoliths to identify probable source and date of introduction of exotic lake trout (Salvelinus namaycush) into Yellowstone Lake, Wyoming, USA. Otolith Sr:Ca ratios were significantly different among lake trout known to have reared in three different Yellowstone National Park lakes (Yellowstone, Heart, and Lewis lakes) and showed little variation along the otolith axis, indicating that lake trout within each lake experienced a similar, and consistent, environmental history. In contrast, suspected transplants showed a large and rapid increase in otolith Sr:Ca ratios indicative of a marked shift to water of differing chemistry. Timing of the abrupt change in Sr:Ca ratios indicated that some lake trout were introduced into Yellowstone Lake during the late 1980s, but more recent transplants also occurred. A discriminant model identified Lewis Lake as the likely source lake for lake trout transplanted into Yellowstone Lake. Our results demonstrate that chemical signatures within otoliths can serve as an important forensic tool for identifying the probable source and date of exotic fish introductions.