Demographic attributes of yellow-phase American eels (Anguilla rostrata) in the Hudson River estuary

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Abstract:

Management of American eels (Anguilla rostrata) requires an understanding of how demographic attributes vary within large estuaries. Yellow-phase American eel length and age structure, growth, dispersal, nematode infestation rates, loss rate (natural mortality and emigration), and production were measured at six sites throughout the tidal portion of the Hudson River. Short-term dispersal was low, with >70% of eels at all sites captured <1 km from their original tagging area. Length was similar among sites (total length = 45.7 ± 0.3 cm), whereas age was substantially lower for brackish-water sites (8 ± 4 years) than for freshwater sites (17 ± 4 years). Growth was higher for brackish-water sites than for freshwater sites (8.0 cm·year–1 and 3.4 cm·year–1, respectively). From 1997 to 2000, infestation by the exotic nematode Anguillicola crassus increased dramatically in mean intensity as well as prevalence. Annual loss rates measured for the six sites varied between 9% and 24%, with no statistical difference between freshwater and brackish-water sites. Estimated eel production was higher in a brackish-water habitat (1.10–1.77 kg·ha–1·year–1) than in a freshwater location (0.21–0.58 kg·ha–1·year–1). The results of this study support a recent proposal to establish freshwater areas as exploitation reserves.

La gestion des anguilles d'Amérique (Anguilla rostrata) exige une compréhension de la variation des caractéristiques démographiques à l'intérieur des grands estuaires. Nous avons mesuré la structure en longueur et en âge, la croissance, la dispersion, le taux d'infection par les nématodes, les taux de perte par mortalité naturelle et par émigration, ainsi que la production chez des anguilles jaunes à six sites situés dans la section du fleuve Hudson affectée par les marées. La dispersion à court terme est réduite et >70 % des anguilles à tous les sites sont recapturées à <1 km de leur point original de marquage. La longueur est la même à tous les sites (longueur totale = 45,7 ± 0,3 cm), alors que l'âge est considérablement plus bas aux sites d'eau saumâtre (8 ± 4 ans) qu'aux sites d'eau douce (17 ± 4 ans). La croissance est plus forte en eau saumâtre qu'en eau douce, respectivement de 8,0 cm/an et de 3,4 cm/an. De 1997 à 2000, l'infection par le nématode exotique Anguillicola crassus a augmenté de façon spectaculaire, tant en intensité qu'en prévalence. Les taux de pertes annuelles aux six sites varient de 9 à 24 %, sans qu'il n'y ait de différence statistique entre les sites d'eau douce et d'eau saumâtre. La production estimée des anguilles est plus forte dans l'habitat d'eau saumâtre (1,10–1,77 kg·ha–1·an–1) qu'en eau douce (0,21-0,58 kg·ha–1·an–1). Les résultats de notre étude appuient la suggestion récente de l'établissement des zones d'eau douce comme réserves d'exploitation.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: December 1, 2003

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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