Discussion

Streams tributary to the Hudson River are significant habitats for some Hudson River fishes and may be significant for more species than we have been able to document. However, not all tributaries are equally valuable primarily due to variation in accessibility.

The distance of the Fall Line from the tidal Hudson River varies along the length of the Hudson. There are some areas, like in the Hudson Highlands, where tributary streams are naturally impassable for fishes because of very steep gradients at their mouths. These streams, like Highland Brook (RKM 82), Breakneck Brook (RKM 90), and Philipse Brook (RKM 85) have probably been inaccessible to Hudson River fishes since the glacial lakes filling the Hudson Valley drained (ca. 12,000 years ago; Connelly and Sirkin, 1973).

Degraded water quality can limit access to tributary streams. Great progress has been made in the past several decades in reducing or eliminating municipal and industrial pollutants from Hudson River tributaries. Most of the fishes that enter tributaries do so in the springwhenwe canexpecthigher water volumes and reduction of pollution effects. There are still some Hudson River tributaries where we think water pollution limits fish use, however, so this task of cleaning up water is incomplete in the Hudson Valley. The worst case we observed was Mill Creek (Rensselaer - RKM 231.5).

Through the history of European settlement in the Hudson Valley, tributary streams often have been dammed. Dams have provided power to run mills, processing water for industry, drinking water for communities, and recreational opportunities. Currently, half of the tributaries to the Hudson River have dams (or other obstructions) that limit fishes' access to the streams. Depending on where the dams are placed, they have decreased or eliminated access to nontidal stream habitats. Recently, the first dam on Furnace Brook (RKM 62.5) washed out and TRL observed potamodromous fishes already using the newly available stream bed in spring 2000. We have seen anadromous and potamodro-mous fishes aggregating below dams, such as the Eddyville Dam on Rondout Creek (RKM 146.5). We have no doubt that fishes would use the stream habitat upstream of these dams if access were provided.

In the Hudson Valley, we have no facilities available for helping fishes gain access to aquatic habitat above dams. Some dams are so large, like the dam on Murderers Creek (RKM 190), that designing fish passage would be prohibitively expensive -thus that tributary is essentially extinct as far as Hudson River fishes are concerned. Other Hudson River tributaries have barriers that canbe bypassed, breached, or removed. We think that providing access to tributary streams can only enhance the populations of Hudson River fishes.

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