Sulfur stable isotopes as a tracer of insect migration and fish predation

Here we examined the utility of the stable isotope ratio of sulfur, δ34S, as a tracer of the seasonal migration of water boatmen (Hemiptera: Corixidae) between wetlands and rivers and the use of these insects as a dietary subsidy by riverine fish. We found that both corixids and other invertebrate taxa originating from wetland ecosystems typically exhibited lower δ34S values, as opposed to riverine taxa. Specifically, riverine taxa from the South Saskatchewan River were more depleted in 34S than those from the North Saskatchewan River. spring and summer, δ34S values were more negative for corixid feeders in fall. We conclude that δ34S has the potential to trace insect movement and consumer use between isotopically distinct freshwater systems.