Use of otolith microchemistry to identify subbasin natal origin and use by invasive Lake Trout in Yellowstone Lake

Abstract

Nonindigenous lake trout (Salvelinus namaycush) expansion in Yellowstone Lake has led to a large decline in the native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) population. We assessed whether otolith microchemistry could be used to identify subbasin natal origins and long-term use by lake trout as a potential tool for optimizing removal efforts. 87Sr:86Sr and Sr:Ca ratios in otolith cores were used to assess natal origins and 87Sr:86Sr ratios in otolith transects were used to assess movement patterns. Water chemistry was similar throughout the lake, ranging from 0.70634 to 0.70642 and 3.94 to 4.38\xa0mmol/mol for 87Sr:86Sr and Sr:Ca ratios, respectively. Lake trout otoliths also showed little variation in 87Sr:86Sr and Sr:Ca ratios of the natal region and 87Sr:86Sr across otolith transects. Thus, we found that microchemical differences among Sr isotope and Sr:Ca elemental ratios in otoliths were insufficient to detect the natal origin or extensive within-lake movement that has been established from telemetry investigations. Detailed analysis of other elements or isotopes in hard-part microchemistry, in combination with other tools for detecting movement, may improve detection of natal origin and life history movement among fishes within freshwater lentic systems.