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.