Predicting impacts of urbanized stream processes on biota: high flows and river chub (Nocomis micropogon) nesting activity

Abstract

This study quantified the impact of high stream flows on reproductive activities of river chub (Nocomis micropogon). Using observed relationships between flow and reproductive activities, the number of predicted damaging flow events was compared between streams with extant river chub populations and urbanized streams. Monitoring the survivorship of river chub nests during 2013–2014 (N = 101) revealed consistent relationships between interval peak flow measured at flow gauges and the integrity of river chub nests within sites. Flow-mediated disruption of nests was frequent, and interval peak flows were significantly correlated with nest erosion rates. Logistic regression between fate of river chub nests and standardized peak flow (Qs) during monitoring intervals identified thresholds of peak flow corresponding to complete and partial destruction of river chub nests. Observed thresholds were used to predict the frequency of potentially damaging flows in urbanized versus river chub study streams, based on archival flow monitoring data. Repeated measures analysis revealed that the frequency of flows predicted to result in the loss of all nests was significantly higher in urbanized streams (F = 122.2; df = 1; P < 0.001 ). While key life history information needs to be determined to fully understand the impacts of high flows on river chub population dynamics, results indicate the disruption of nests through frequent high flows as a mechanism for the reduction of this important species in urbanized areas. Improved understanding of the interactions between stream processes and biota will aid in the design of specific stream protection and restoration strategies.