Increases in Colored Terrestrial Dissolved Organic Carbon (t-DOC) Concentrations Reduce Panfish Fecundity in a Cross Lake Survey

Widespread increases in water color due to associated t-DOC concentrations have been observed over the past few decades in northern hemisphere freshwaters which may have important implications for the productivity of affected ecosystems and their consumers. A reduction of fish production has been observed in lakes with high DOC concentrations but few solid mechanisms for this have been tested. It is possible that a reduction in basal resources and thermocline/oxycline depth lead to a habitat squeezing effect in darker lakes which may lead to reduced growth rates and reproductive output in fishes. In this study, we investigate if a reduction in panfish productivity in dark lakes is due primarily to a reduction in fecundity and size at maturity. If fish in dark lakes are maturing earlier, at smaller sizes, this could have implications in maintaining viable recreational fisheries in the light of increasing DOC concentrations.