Phaedra Budy

A Comparison of Visual and Measurement-Based Techniques for Quantifying Cobble Embeddedness and Fine-Sediment Levels in Salmonid-Bearing Streams

Abstract Excess fine-sediment loading can strongly affect the performance of salmonids rearing in fluvial habitats. Consequently, there are multiple techniques for quantifying the biologically relevant aspects of streambed material quality. While similar methods should provide similar measurements for a given attribute, little information is available that validates this assumption. Nevertheless, there are ongoing efforts toward assembling and analyzing large-scale habitat databases using existing information collected via multiple techniques. For these reasons, we used regression to compare visual and measurement-based approaches for two commonly assessed substrate variables (cobble embeddedness and percent surface fines). For both embeddedness and percent fines, we found moderate to strong linear relationships (R 2 = 0.46–0.83) between estimates obtained by visual and measurement-based approaches. However, the fitted line differed significantly from a null 1:1 expectation for the percent fines and embed...