Measured Redd Imposition by Summer Chinook to Quantify Impacts on Spring Chinook

Inter- and intra-specific competition and use of spawning habitat has been commonly observed in salmonids. While spawning surveys have documented such cases, no technique for measurement has been suggested to quantify the amount and to what extent this shared use of spawning habitat has on the progeny. This study was designed to examine the extent of redd superimpostion that occurs between two runs of Chinook salmon. Reviews of published methods for redd measurement and superimposition will be presented, leading into this studies utilization of a Survey Grade Total Station. Specific measurements on area of redds, maximum excavation depth, volume of displaced gravel, percent of area superimposed and location of superimposition were all recorded. Data was then used to answer 1) total percent of summer Chinook redds superimposed on spring Chinook redds, 2) statistical differences between the two runs excavation depths, area and gravel displacement, and 3) location of superimposition (i.e. within the pit, hump or tailings). The ultimate goal of presenting this method is to aid other researchers on how to measure redd superimposition.