scholarly journals Intensified environmental and density-dependent regulation of white perch recruitment after an ecosystem shift in the Hudson River Estuary

2018 ◽  
Vol 75 (1) ◽  
pp. 36-46 ◽  
Author(s):  
Brian K. Gallagher ◽  
David H. Secor

Long-term monitoring data were used to test whether the invasion of zebra mussels (Dreissena polymorpha) in the Hudson River Estuary in 1991 altered the influence of density dependence and environmental conditions on life-stage transitions, growth, and partial migration in white perch (Morone americana). During the post-invasion period (1992–2013), we estimated standing stocks of white perch eggs, yolk-sac larvae (YSL), post-yolk-sac larvae (PYSL), young-of-the-year (YOY), and adults as well as indices of YOY growth and spatial distribution. A series of linear and nonlinear functions were employed to model life-stage transitions, while the effects of six environmental and density-dependent variables on YOY growth and partial migration were quantified. Comparisons to pre-invasion observations (1974–1991) indicated that egg–YSL, PYSL–YOY, and YOY–yearling transitions changed significantly after the invasion, while PYSL abundance developed a stronger negative effect on YOY growth. The PYSL–YOY transition became more sensitive to density dependence and freshwater flow from 1992 to 2013, which is consistent with diminished abundance and increased environmental sensitivity of the forage base in the Hudson River Estuary reported after the zebra mussel invasion.

1993 ◽  
Vol 50 (9) ◽  
pp. 1976-1985 ◽  
Author(s):  
Michael L. Pace ◽  
Stephen B. Baines ◽  
Hélène Cyr ◽  
John A. Downing

Annual abundances of eggs, yolk-sac larvae (YSL), post-yolk-sac larvae (PYSL), and young-of-the-year (YOY) stages of Morone americana and Morone saxatilis are summarized from a 17-yr monitoring program in the Hudson River Estuary. Variability in temperature and freshwater flow in the Hudson River explained little of the interannual variation of early life stages of either species. Year class strength as indicated by the abundance of early life stages does not appear to be strongly influenced by environmental conditions. YSL were positively related to the abundance of eggs, but these relationships were weak, reflecting the high uncertainty in egg abundance estimates. There were positive relationships between the abundances of YSL and PYSL for both species. Our analysis implies that interannual variability in mortality is less important in determining recruitment to PYSL than the abundance of the prior life stages. There was no relationship, however, between the abundance estimates of PYSL and YOY. Differential mortality among years during the larval stage may result in juvenile recruitment being independent of larval abundance. A second possibility is that YOY are poorly sampled so that the monitoring programs currently provide inadequate estimates of the abundance of YOY.


1999 ◽  
Vol 56 (2) ◽  
pp. 275-287 ◽  
Author(s):  
Jeffrey A Buckel ◽  
David O Conover ◽  
Nancy D Steinberg ◽  
Kim A McKown

We measured bluefish (Pomatomus saltatrix) weights, densities, and prey sizes during the summers of 1992 and 1993 and diets over a 4-year period (1990-1993) in the Hudson River estuary. This information was used to estimate the loss of young-of-the-year (YOY) striped bass (Morone saxatilis) resulting from YOY bluefish predation. We then compared this predation mortality with the total loss of striped bass in the system. Data from sampling surveys conducted since the mid-1970's were used to examine relationships between bluefish abundance and striped bass recruitment levels. YOY striped bass, bay anchovy (Anchoa mitchilli), Atlantic silverside (Menidia menidia), and Alosa spp. dominated YOY bluefish diets. There were ontogenetic and interannual differences in YOY bluefish diets. Bluefish avoided striped bass at low densities but selected for them at high densities, suggesting a density-dependent feeding response. In the early summer of 1993, bluefish predation accounted for 50-100% of the total estimated loss of YOY striped bass. A significant negative correlation exists between the relative magnitude of striped bass recruitment and bluefish abundance. We conclude that YOY bluefish are important predators of estuarine fish and can have a substantial impact on their recruitment.


1996 ◽  
Vol 53 (5) ◽  
pp. 1143-1149 ◽  
Author(s):  
D L Strayer ◽  
J Powell ◽  
P Ambrose ◽  
L C Smith ◽  
M L Pace ◽  
...  

1998 ◽  
Vol 34 (2-3) ◽  
pp. 214-222 ◽  
Author(s):  
M. G. Menon ◽  
R. J. Gibbs ◽  
A. Phillips

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