La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Tracking cohorts: Analysis of migration in the early life stages of an estuarine fish
Auteurs :	E. T. Schultz, Auteur ; J. Young, Auteur ; J. M. Martin, Auteur ; K. M. M. Lwiza, Auteur
Type de document :	Article
Dans :	Estuaries (28(3) JUN 2005)
Article en page(s) :	394-405
Résumé :	Larvae and juveniles are often most abundant at some distance from where spawning occurs. Such apparent distribution shifts can be the result of larval migration, seasonal shifts in the distribution of spawners, or spatial heterogeneity in mortality. In the present study, a cohort-based method was adopted to test for larval migration of bay anchovy (Anchoa mitchilli) and to estimate its rate and timing. A spatially and temporally extensive series of ichthyoplankton samples was collected in the lowest 122 kin of the Hudson River in summer 1998. Bay anchovy eggs and young-of-year individuals were abundant (mean density = 1.6 m(-3) and 0.95 m(-3), respectively). Daily age used to define cohort membership was determined from otoliths. Age and length were strongly related (R(2) = 0.74). The age-length relationship varied over the season such that early-season bay anchovy hatched in June grew more rapidly than later-season anchovy hatched in August. Cohorts were defined as week-long birth-date classes, and net migration patterns of

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