Desert Fishes Council, Death Valley, CA, November 1997.

Water limits the occurrence of fishes, but what limits the occurrence of water?

P.J. Unmack

Surface water is typically abundant in more mesic areas in a diversity of forms (streams, lakes, marshes), and persistence of some sort of aquatic habitat during drought is assured from a fish's perspective by water's commo nness and general distribution. As climate becomes increasingly xeric, however, geomorphology becomes increasingly important in determining the presence and persistence of surface water.

This presentation considers geomorphic constraints on persistence of surface water, and thus fishes in both Australia and North America. An understanding of how geomorphology affects water permanance allows past, present, and future pre dictions regarding persistence of aquatic biota in isolated basins under different climatic regimes. Baseline information on dynamics and persistence of water also is critical to management for conservation of any aquatic biota.