Changes in American eel age structure and length at silvering in the St.Lawrence Estuary since 45yrs

Session: Poster session

Frederic Lecomte, Ministère des Forêts, de la Faune et des Parcs du Québec, [email protected]
Guy Verreault, Ministère des Forêts, de la Faune et des Parcs, [email protected]
Thomas Pratt, Fisheries and Oceans Canada, [email protected]
David Stanley, Ontario Power Generation, [email protected]
Scott Schlueter, USFWS, [email protected]
Paul Jacobson, EPRI, [email protected]

Abstract

In 2014, 674 seaward migrant eels (Anguilla rostrata) caught in the St. Lawrence estuary were assessed for age, sex, and length. This sample was composed exclusively of large maturing females measuring on average 870.1 mm (SD= 77.2). Age determination was performed on 626 eels; mean age was 12.7 y (SD= 3.3) and mean annual growth rate was 72.2 mm/y (SD= 16.1). These characteristics were compared to a large unpublished database consisting of 2,933 silver eels caught in the estuary in 1970 for which age was estimated. Since size at silvering increased significantly by more than 60 mm while mean age decreased by 4.1 years, the average growth rate increased by 47% compared to the situation observed in 1970. This dramatic change was confirmed by further sampling from 2014 to 2017. We hypothesized that modifications in age structure is linked with recruitment decline in upstream growing habitats and that such increase in growth rate could be related to a relaxation of density-dependent processes favoring the few eels remaining in the system. This new population dynamics, as well as the steadily decline in recruitment, urges managers to review recovery strategies for this population in the Upper St. Lawrence River and Lake Ontario.

1. Keyword
recruitment

2. Keyword
St. Lawrence River

3. Keyword
fish management

4. Additional Keyword
American eel

5. Additional Keyword
Growth Rate

6. Additional Keyword
Population dynamics