International eel symposium, 2003 - Quebec August 11, 2003
Poster Session

Age and Growth, by Migratory Contingent, of Silver American Eels from a Nova Scotia River

Jessop, B.M.* Department of Fisheries and Oceans, Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia, B2Y 4A2, Canada
Shiao, J.-C. Department of Zoology, College of Science, National Taiwan University, Taipei, Taiwan 10617, ROC
Iizuka, Y. Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, Taiwan 11529, ROC
Tzeng, W.-N. Department of Zoology, College of Science, National Taiwan University, Taipei, Taiwan 10617, ROC

Presenter email address: jessopb AT mar.dfo-mpo.gc.ca

Abstract Text: Concern exists about declines in river-specific stocks of, and perceived effects on the larger population of, American eels Anguilla rostrata and the subsequent production of sexually maturing (silver) eels. To test specific hypotheses, better information is needed on the temporal change in life-history characteristics of specific stocks under varying regimes of exploitation. Few studies have examined aspects of the annual growth rates for each sex and the age and sex composition at migration of unexploited populations of silver American eels. This study will examine the age composition and growth rates, for each sex, of silver American eels from an unexploited stock. The environmental history of fishes has been examined by analysis of the temporal pattern of Sr:Ca ratios in their otoliths. Tsukamoto et al. (2002) hypothesized that marine/estuarine residency of Anguilla spp. should occur more frequently at high latitudes. We determined that 64% of 64 silver eels examined showed evidence of a history of freshwater-estuarine migration as yellow eels. No comparative data exists from more southern stocks. We also examine the hypothesis that such a migratory contingent will show differences in annual growth rates reflective of their relative residence times in fresh and estuarine waters.