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 fishe s as a measure of habitat quality under large pile-supported platforms or p iers, in pile fields and in open-water habitat types in shallow areas (aver age depth 1.1 to 3.9 m) in the Hudson River estuary in 1994. Three 10 d cag ing experiments were conducted in June and early July with recently settled winter flounder Pseudopleuronectes americanus (14.3 to 40.1 mm SL) and 3 e xperiments of similar duration in July and August with recently settled tau tog Tautoga onitis (20.6 to 48.6 mm TL). For both species, within-experimen t 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-wat er habitats than under the piers where fish lost weight in all of the exper iments. Growth rates for individual winter flounder and tautog reached Valu es as high as 0.09 d(-1) and 0.11 d(-1), respectively. in open water and pi le field habitats. In addition, G(w) values for both winter flounder and ta utog caged under piers were not significantly different (p > 0.017, 1-sided Dunnett test with Bonferroni correction) from those of conspecifics held c oncurrently in the laboratory without food. These results, as wen as relate d 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-wat er habitat types. As a result, the impacts of these structures should be co nsidered when estuarine shorelines are developed or renovated.