Nass Chinook Mark-Recapture Project

Since 2009, the Pacific Salmon Commission (PSC) Chinook Technical Committee (CTC) has established a 15% coefficient of variation (CV) as an acceptable level of uncertainty for estimating Chinook Salmon populations that are used in managing US and Canadian Chinook Salmon fisheries. We are requesting funding support from the PSC Northern Fund to continue the Upper Nass Chinook Salmon mark-recapture (MR) program initiated in 2009 in order to achieve the PSC CTC data standard. Past funding from the PSC to the Nisga’a Fisheries and Wildlife Department (NFWD) supported increased marking and recovery efforts for generating accurate estimates of abundance for the Upper Nass Chinook Salmon aggregate population, meeting the CV data standard in six of the seven years that funding was provided. Overall, the Nass Chinook Salmon program has achieved the CV data standard in 15 of 24 (63%) years since the start of the Nisga’a Fisheries Program in 1992. The main factor determining CV has been the number of marked Chinook Salmon recovered at terminal spawning areas in the Upper Nass River. Achieving an adequate number of marked recoveries has required two conditions to be met: (1) a sufficient number of Chinook Salmon are marked (>1250) at the fishwheels and (2) sufficient effort is made on the spawning grounds for recovering marks such that >50 marks are recovered. Results from the past funded studies have indicated that these requirements can be met, even in low return years, by marking adult Chinook Salmon at both fishwheel marking locations (Gitwinksihlkw and Grease Harbour), examining fish throughout the run at Meziadin Fishway and the Kwinageese videocounting weir, and conducting carcass surveys at Damdochax Creek. These three Upper Nass spawning systems represent on average 39% of the aggregate spawning stock based on stock composition estimates and are geographically separated to be representative of all stocks that spawn above the marking sites.
The primary purposes of the proposed project are to: (1) continue to augment marking and recovery efforts, (2) improve methods for generating accurate and precise MR escapement estimates for the Upper Nass River Chinook Salmon aggregate stock, and (3) achieve unbiased population estimates that meet the PSC CTC data standard (CV – 15%).