Area-under-the-curve (AUC) methods are employed to estimate escapement at the majority of Chum Salmon spawning sites in the Fraser River where escapement is enumerated. The AUC methodology requires visual counts of Chum Salmon on the spawning grounds and an estimate of the time (in days) Chum Salmon are available to be visually counted during these surveys. This time is termed survey residence time or survey life (SL). Currently, there is very little SL information specific to Fraser River Chum Salmon populations (Grant el at. 2007; Wenman et al. 2014). As a result, an average literature value for the Region is used for AUC estimates of lower Fraser River Chum Salmon spawning populations. It is not known if using the average literature value biases these AUC generated estimates although limited work suggest the literature value currently used is biased high (Grant el at. 2007; Wenman et al. 2014). We propose to accurately and precisely estimate SL for select lower Fraser River Chum Salmon spawning populations in 2019 and to determine a more appropriate SL value to use for all Fraser Chum Salmon escapement estimates using the AUC methodology.
Accurate and precise spawning escapement estimates are important to all aspects of Fraser River Chum Salmon management including annual stock run reconstruction, production forecasting, in-season terminal abundance estimates (Albion Chum Model), the evaluation of management decisions/actions, and harvest sharing. The ability to correct a SL bias in over 20 years of AUC spawning ground estimation in the lower Fraser River will be incredibly valuable to the work of the Chum Technical Committee.