American eel slipping between our hands: Unexpected results from stocking programs
Ann Arbor, MI — Could stocking help to restore a fish species experiencing a dramatic continent-wide decline? For the first time in North America, stakeholders and resources managers undertook a large-scale experimental stocking program with the American eel (Anguilla rostrata) in 2005. Caught in river mouths flowing on the Atlantic seaboard, young wild baby eels were marked with tetracycline (OTC) and transferred to large lakes as a mean to increase population and ultimately adult spawner numbers.
"American eel has a complex life history," said Guy Verreault, Fisheries scientist with the Quebec Ministry of Natural Resources and Wildlife. "Young eels are born in the Atlantic Ocean and migrate to continental waters of North America where they settle for more than two decades in the northern part of their distribution range," he explained. "As they become large (±900 mm or about 3 feet) and mature, they migrate back to marine spawning grounds to reproduce and die thereafter."
In October 2009, scientists sampled unusually small mature eels in the St. Lawrence estuary. They all exhibited a fluorescent OTC mark, proof they originated from the stocking operation done in 2005. Their young age (4 years old) and small size (±615 mm or about 2 feet long) is very unusual for migrating eels in the St. Lawrence River system. This first direct observation documents one of the main uncertainties surrounding eel stocking programs: stocked individuals can find their way out en route to the salt water spawning grounds.
This study is not a final answer to the debate surrounding eel stocking as a conservation measure. It advocates seizing this opportunity to increase our knowledge in order to measure the real output and impacts on population level.
Original Publication Information
Results of this study, "First record of migrating silver American eels (Anguilla rostrata) in the St. Lawrence Estuary originating from a stocking program," are reported by Guy Verreault, Pierre Dumont, Johanne Dussureault and Rémi Tardif in the latest issue (Volume 36, No. 4, pp. 625-632) of the Journal of Great Lakes Research, published by Elsevier, 2010.
Contacts
For more information about the study, contact Guy Verreault, Fisheries scientist with the Quebec Ministry of Natural resources and Wildlife, 186, rue Fraser, Riviere-du-Loup. G5R 1C8, Canada. Carolina Taraborelli, guy.verreault@mrnf.gouv.qc.ca, +418 862-8213 ext. 306.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
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