Estimating Escapement of Chilkat River Chinook Salmon Using Transgenerational Mark-Recapture

This project combined ADF&G’s traditional mark-recapture protocol with genetic sampling to estimate escapement of Chilkat River Chinook salmon abundance via tGMR). We compared the results from tGMR to the traditional mark-recapture estimates. tGMR is based on several assumptions, and so we used individual-based model simulations to determine the effects of violating those assumptions. Overall, we found that traditional and tGMR estimates were broadly similar and the tGMR estimate was a little (3%) more precise. The estimates produced by tGMR depended on whether mainstem or tributary samples were included. Results affirmed that tGMR can be a robust method to estimate salmon population sizes and provides a tool for evaluating potential biases in tGMR.



This project utilized funds from PCSRF award NA17NMF4380170. No funds from this award were used past its end date.

Accurate and efficient enumeration of salmon populations is essential for assessing the status of salmon populations, including monitoring declines as well as recovery. Since the listing of Chilkat Chinook as a “stock of management concern”, subsistence harvest has been severely restricted. This project develops methods that may enhance the efficiency, accuracy, and precision of abundance estimates for Chilkat Chinook. The project will also provide widely applicable benefits to many stocks of salmon by refining our understanding of the extent of, and how to mitigate for, potential biases in the tGMR method. Moreover, if the tGMR methodology can be validated, it could be used as a cost-effective tool to estimate spawning abundance on wild salmon populations in Southeast Alaska lacking robust assessment tools.