Evaluation of New Approaches to Estimate Ecstall Chum Escapement

Historically, the chum escapement in the Ecstall was believed to represent between 50 and 75% of the total reported for the Skeena–the Ecstall River is considered the largest chum spawning system in the Skeena watershed and has been identified as a priority for enumeration. However, following 2002 there was an almost 10-year gap in escapement estimates for Ecstall chum, and recent estimates indicate a decline. As such, Skeena chum are currently a stock of concern and lack the stock assessment data necessary to monitor trends in spawning abundance. Management actions aimed to reduce exploitation of Skeena chum have been initiated in recent years, but these also act as a constraint on August fisheries in the Skeena River.
Opportunities for visual chum escapement enumerations in the lower Skeena chum spawning areas (mainstem slough and lower river glacial tributaries) are often constrained by poor visibility. As a consequence, the success of aerial surveys of the Ecstall has been intermittent. As well, Ecstall River surveys have not been completed in some years due to limitations on staff and helicopter availability, but remain a high priority for annual surveys. Currently, one helicopter survey is done at the estimated peak of chum spawning in early to mid-September; however, there are concerns regarding the accuracy of these estimates given the amount of riparian tree canopy combined with the fact that chum tend to spawn close to the shores of the river. An improved annual estimate for Ecstall chum would greatly increase the confidence in the Skeena chum escapement estimations and allow better monitoring of future trends of this stock of concern.
Therefore, the objective of this project is to find the most reliable and consistent index of escapement for Ecstall chum. This project evaluated whether ground surveys and/or a mark recapture program are feasible as a more consistent alternative to aerial surveys.