Albion-based Estimate of Total Fraser River Chum Escapement Using GSI and Estimate of Chilliwack River Chum Escapement

The Fraser River supports two Wild Salmon Policy chum salmon Conservation Units; however, the Fraser River chum is managed as a single stock and total chum salmon escapement to the Fraser River is not enumerated. Currently, only the Harrison and Stave River chum are surveyed annually and escapement enumerated; other significant contributors, such as Chilliwack River spawners, have not been enumerated for many years. Chilliwack River Chum have historically contributed significantly to the abundance of the Fraser River Chum aggregate: it is estimated that from 1953 to 2001 (the last year spawning escapement to the Chilliwack River was assessed), Chilliwack chum ranged between 2% and 42%, and averaged approximately 20% of the Fraser River chum escapement. The range of Chilliwack contribution to the total Fraser escapement points to the need for an annual assessment to either estimate Chilliwack spawning escapement, or independently estimate the total Fraser River chum salmon spawning escapement to allow the assessment and determination of Fraser River chum status and productivity for both a domestic and international benefit. Fraser River chum salmon and its key component populations are significant drivers for the mixed stock chum salmon fisheries occurring in Johnstone Strait, US Areas 7 & 7A and in the Fraser River.
We propose to enumerate total Fraser River chum salmon escapement by conducting a high precision enumeration project on Chilliwack River escapement (e.g. mark-recapture or DIDSON) and combining the result with the ratio of Chilliwack chum to the total Fraser chum captured in the Albion test fishery. The proportion of Chilliwack chum at Albion will be determined using GSI on tissue from scale samples already collected during the test fishery.
This project will improve our ability to provide accurate spawning escapement estimates for Fraser River chum salmon. Accurate estimates are important to all aspects of Fraser River chum salmon management including annual stock run reconstruction, production forecasting, in-season terminal abundance estimates, the evaluation of management decisions/actions, and harvest sharing.