abstract The objectives of this chapter are to summarize our observations of fishes in Hudson River tributaries and to document the significance of tributaries to them. Currently alewife is the only anadromous fish that extensively uses Hudson River tributaries. Several potamodromous species depend on tributaries for reproduction (at least smallmouth bass and white sucker) or reproduce in several areas including tributaries (white perch). In many cases, the data available are not adequate to determine how significant tributary spawning is in these species. Young-of-year fishes present in tributary mouths are also abundant in other habitats in the tidal Hudson River, which is also true for those species considered resident in the tributary mouths. Too few tributaries have been examined thoroughly enough to determine whether tributaries are significant for either of these groups of fishes.
Introduction
The tidal Hudson River has at least seventy-nine small to large tributary streams in addition to the Upper Hudson and Mohawk Rivers, which enter the tidal Hudson at the Troy Dam, the upstream limit of tidal influence. There are also an unknown number of smaller, often ephemeral, streams that contribute water to the tidal Hudson River. These tributaries (other than the Upper Hudson/Mohawk) contribute about 20 percent of the freshwater input to the Hudson River (Cooper, Cantelmo, and Newton, 1988). Various researchers have considered these tributaries as sources of important materials such as carbon, sediments (Howarth et al., 1991; Howarth, Schneider, and Swaney, 1996; Swaney, Sherman, and Howarth, 1996), and contaminants (Hirschberg et al., 1996).