Synchronous multidecadal fish recruitment patterns in Chesapeake Bay, USA

Multispecies fish recruitment patterns within Chesapeake Bay were investigated in four fishery-independent survey data sets (one primary and three ancillary data sets) that together span the years 1968-2004. These independently conducted surveys record interannual recruitment variability for 15 ecologically and economically important fish species of the Northeast US Continental Shelf Large Marine Ecosystem. Principal component analyses revealed that the strongest multispecies recruitment pattern (first principal component) present in each data set describes a negative recruitment relationship between anadromous and coastal shelf-spawning species. Among the data sets, the first principal component accounted for 31%-42% of multispecies variance. Locally weighted regression modeling revealed that the decadal-scale variability accounted for 62% of the variance in the primary data set's first principal component's (annual) scores, whereas interannual variability accounted for only 38%. Despite strong differences in sampling methods, sampled habitats, and sampling locations, this pattern of antagonistic recruitment between Chesapeake Bay anadromous and shelf-spawning (CBASS) species was synchronously correlated among data sets at both decadal and interannual scales. The CBASS pattern has tended to persist in one mode for periods lasting longer than a decade and tends to reverse sign rather within only 2-3 years. A statistically significant regime shift occurred in 1992, when recruitment in anadromous fishes became favored at the expense of recruitment of shelf-spawning estuarine-dependant fishes. Nous avons etudie les patrons de recrutement multispecifiques des poisons de la baie de Chesapeake dans quatre ensembles de donnees d'inventaire independants des peches commerciales (un ensemble de donnees primaire et trois ensembles accessoires) qui conjointement couvrent les annees 1968-2004. Ces inventaires menes de facon independante recensent la variabilite du recrutement chez 15 especes de poisons d'importance ecologique et economique du grand ecosysteme marin de la plate-forme continentale du nord-est des E.-U. Les analyses en composantes principales indiquent que le patron le plus evident de recrutement multispecifique (premiere composante principale) present dans chaque ensemble de donnees decrit une relation negative de recrutement entre les poisons anadromes et ceux qui fraient sur la plateforme continentale. Dans ces ensembles de donnees, la premiere composante principale explique 31-42% de la variance multispecifique. Une modelisation loess de la premiere composante principale de l'ensemble de donnees primaire montre que la variabilite a l'echelle de la decennie explique 62 % de la variance des cotes (annuelles) de PC1, alors que la variabilite interannuelle explique le 38% qui reste. Malgre d'importantes differences dans les methodes d'echantillonnage, les habitats inventories et les sites echantillonnees, ce patron des poisons anadromes ou frayant sur la plate-forme de la baie de Chesapeake (CBASS) est correle en synchronie dans les ensembles de donnees, tant a l'echelle de la decennie qu'a l'echelle interannuelle. Le patron CBASS a eu tendance a persister dans un meme mode durant des periodes de plus dune decennie et il tend a changer de signe plutot sur une periode de 2-3 ans. Un changement statistiquement significatif de regime s'est produit en 1992, lorsque le recrutement des poisons anadromes a ete favorise au depends du recrutement des poisons qui fraient sur la plateforme et qui sont dependants des estuaires. [Traduit par la Redaction]
Introduction Understanding mechanisms responsible for the high variability observed in annual fish recruitment is essential for the development and implementation of multispecies and ecosystem-based fisheries management. Potentially important causal mechanisms [...]