Research Document 2021/032

Stock-wide assessment framework for American eel: review of trends and approaches to assessment

By Cornic, M., Zhu, X., Cairns, D.K.

Abstract

American eel population status in Canada was last assessed in 2012 and 2014. The present report re-assessed American eel abundance indices and investigated temporal trends in relative abundance in five management regions. Assessment included fishery-dependent and -independent data; however, the lack of data in several regions and/or for different life stages limited our ability to fully evaluate American eel population trends in Canada.

Between 1874 and 2016, reported American eel landings in Canada varied between 200.6 and 1411.7 tons. From the 1880s to 1990 reported landings fluctuated without an overall trend, but showed relative stability in the 1970s and 1980s. Since about 1990 reported landings have steadily decreased.

Fishery-independent indices, updated since the last assessment, were developed using generalized linear mixed models including temporal, environmental, and effort variables to account for changes in catchability. Overall, 12 fishery-independent datasets were evaluated of which 9 reflected yellow eel abundance. Trend analysis indicated that American eel abundance was stable (6 surveys), declining (4 surveys) or increasing (2 surveys). The 25^th percentile reference point when compared to the initial year indicated 8 downward trends; however, when the 25^th percentile reference point in the terminal year was compared to those in 2012 an increase in abundance was observed for 5 surveys over the last 5 years.

Reference points for defining the stock status of American eel in Canada were not estimated as further data and analysis are needed. However, trends in relative abundance are similar to the last stock assessment in 2012 and recovery plan in 2014. Commercial landings and fisheries-independent surveys suggest that American eel abundance has been stable since 2000 but at low abundance and the downward trend in several surveys remains a concern for the recovery of the population in Canada. Therefore, the American eel population is similar to 2012 and its stock continues to be at risk. We recommend continued monitoring and data gathering in order to better evaluate American eel status in Canada.

Research Document 2021/032 (PDF, 5,339 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.