Population Biology | Zoology
We review three areas of recent research on Hudson River bay anchovy. One focus has been the along-estuary movement of early life stages. A cohort analysis of samples collected in a spatiotemporally extensive monitoring program has confirmed that early-stage anchovy migrate up-estuary, at an estimated rate of 0.6 km/d. Complementary fine-scale field sampling was designed to clarify behaviors that effect the migration. This work found that early-stage anchovy can show preferences for depth and can conduct periodic vertical migration. To determine whether these behaviors were sufficient to produce up-estuary migration, larval flux and velocity were estimated. These estimates were consistent with local retention rather than concerted migration. High priority should be given to examining individual migration histories through analysis of otolith microchemistry. A second focus of research on Hudson anchovy has been on local population structure, permitting comparison to anchovy in other locations. The demography of the Hudson River anchovy appears to be unique. Anchovy that spawn in the Hudson River are larger than those spawning in the Chesapeake Bay region and are mostly two years old, whereas yearlings predominate in other estuaries. Batch fecundity was lower and egg mortality higher in Hudson River than in Chesapeake Bay. A key issue arising from these recent findings is the degree to which the Hudson anchovy pool is connected with other large anchovy pools, such as Narragansett Bay and Chesapeake Bay. A third focus of research on Hudson anchovy has been analysis of interannual variability in early-stage abundance. A >20 year time series of juvenile bay anchovy abundance shows that juvenile abundance has varied over one order of magnitude. There has been no significant change in abundance over the entire time series, but abundance has declined 10-fold since a peak in the late 1980s. Anchovy abundance was negatively associated with the abundance of early-stage striped bass, and positively associated with the abundance of early-stage tomcod. We suggest that these associations reflect direct interactions among the species and urge further work on the ecological role of striped bass in the estuary.
Schultz, Eric T.; Lwiza, Kamazima M. M.; Young, John R.; Hartman, Kyle J.; and Tipton, R. C., "The Dynamics of Bay Anchovy in the Hudson River Estuary: Process-oriented Studies and Long-term Changes" (2005). EEB Articles. 34.