Habitat quality for shallow water fishes in an urban estuary: the effects of man-made structures on growth

Caging experiments were conducted to determine the growth of juvenile fishes as a measure of habitat quality under large pile-supported platforms or piers, in pile fields and in open-water habitat types in shallow areas (average depth 1.1 to 3.9 m) in the Hudson River estuary in 1994. Three 10 d caging experiments were conducted in June and early July with recently settled winter flounder Pseudopleuronectes americanus (14.3 to 40.1 mm SL) and 3 experiments of similar duration in July and August with recently settled tautog Tautoga onitis (20.6 to 48.6 mm TL). For both species, within-experiment instantaneous growth rates in weight (G(w)(-1)) were significantly higher (3-way ANOVA, Tukey's pair-wise test, p < 0.05) in pile field and open-water habitats than under the piers where fish lost weight in all of the experiments. Growth rates for individual winter flounder and tautog reached Values as high as 0.09 d(-1) and 0.11 d(-1), respectively. in open water and pile field habitats. In addition, G(w) values for both winter flounder and tautog caged under piers were not significantly different (p > 0.017, 1-sided Dunnett test with Bonferroni correction) from those of conspecifics held concurrently in the laboratory without food. These results, as wen as related studies of fish distribution and abundance in the same habitats, indicate that habitat quality under the platforms of large piers (> 20 000 m(2)) is poor for juvenile fishes when compared with nearby pile field and open-water habitat types. As a result, the impacts of these structures should be considered when estuarine shorelines are developed or renovated.