Are Fat Reserves Adequate in Migrant Silver American Eels of a Large-Scale Stocking Experiment in the St. Lawrence/Lake Ontario System ?

An experimental stocking program in the St. Lawrence River/Lake Ontario system provided a unique opportunity to compare fitness of migrant silver American eels Anguilla rostrata from the stocking program (SM) and wild migrants (WM), that have grown in the same location, and were captured in the St. Lawrence River Estuary. SM were smaller than WM and of similar length than silver eels from their site of original capture, in the Maritimes. A bio-energetic model was used to estimate costs of migration and reproduction and duration of migration. The adequacy of the measured lipid reserves to meet these energetic costs was assessed. Compared to WM, SM had lower initial muscle fat reserves and higher estimated energetic requirements for migration as a consequence of their smaller size. It was estimated that 57% of the WM and none of the SM would have adequate fat reserves for migration and reproduction. SM would take 1.6 times longer to reach the spawning grounds than WM. Thus, SM are less likely to complete successfully spawning migration than WM. These results support the recommendation to source and stock eels at sites where they have similar life strategies to increase the likelihood of successful silver eel escapement.