The distribution of shallow water juvenile fishes in an urban estuary: The effects of manmade structures in the lower Hudson river

The objective of this study was to determine what effect, if any, large pile-supported platforms (piers) have on the habitat distribution and abundance of juvenile fishes. Trapping techniques were used in 1993 and 1994 under piers, in pile fields, and in open-water habitat types in shallow areas (<5 m) in the lower Hudson River estuary (40 degrees 44'N, 70 degrees 01'W). Nearly 1500 fishes, mostly juveniles, representing 24 species were collected in 1865 trap-days from May through October in the 2-yr study. The presence of relatively large numbers of young-of-the-year (YOY) fish during both years lends support to the idea that shallow areas in the lower Hudson River estuary currently function as nursery habitats for a variety of fishes. Two seasonal assemblages were apparent, but their composition varied somewhat between years. Microgadus tomcod and Pseudopleuronectes americanus YOY dominated an early summer assemblage (May-July) while large numbers of YOY Morone saxatilis were collected as part of a late summer assemblage (August-September). The effects of habitat type on fish assemblage structure were significant during both years. Fish abundance and species richness were typically low under piers; YOY fishes were rare and Anguilla rostrata accounted for a large proportion of the total catch. In contrast, YOY fishes dominated collections at pile field and open-water stations, where abundance and species richness were high. These results indicate that habitat quality under the platforms of large piers (>20,000 m(2)) is probably poor for YOY fishes when compared with nearby pile field and open-water habitat types.