The Nocomis chub species (hereafter, “chubs”) are nest-building fish recognized for their importance to ecosystem health in eastern North America due to their indirect support of other fish species’ reproductive activities. Chubs construct mounded nests for spawning activity in gravel streams during the breeding season from late April through June. These nests are also critical breeding grounds for other species, including some species of concern. In this study, we examine the stability of mounded nests under a variety of flow conditions, and we present a method for predicting whether or not a nest can survive a particular flow event without sustaining detrimental amounts of erosion. The method is based on a series of laboratory experiments in which nests were constructed out of chub-selected stones from a local stream and subjected to a range of different slope and discharge values in a tilting flume. Throughout the experiments, the morphologic deformation of the nest and loss of mass was recorded and used to determine a critical stress beyond which the nest suffers substantial damage that would require rebuilding or lead to abandonment. Using the data, a method was developed to map local stress conditions at the nest to bulk reach-averaged flow conditions in the channel using an amplification factor. Doing so allows for nest stability to be determined using simple estimates of flow conditions and reach cross-sectional geometry without consideration of local topography around the nest. The developed method is then applied to a local stream and compared to visual observations of nest survival.
