Fish Communities of Environmentally Different Streams: Response to Drought, Tempo of Recovery, and "Loose Equilibrium"

Over a period of more than 40 years, we have studied the fish communities of Brier Creek, OK, and Piney Creek, AR. These creeks fall at opposite ends of a benign- harsh gradient with respect to environmental conditions. Brier Creek is subject to seasonal drying and has experienced several severe droughts over our study period. In contrast, Piney Creek is environmentally benign although there have been periods with occasional “no flow” in headwaters, but even the extraordinary drought of 2012 resulted in no substantial reduction in flow in the mainstem of this spring-fed system. Despite this difference, fish communities of both creeks exhibit a “loose equilibrium” of community structure, but with the scope of variation being greater in Brier Creek. We address mechanisms maintaining “loose equilibrium” based on studies of recolonization rates for individual fish species during and after drought, and studies of the resistance or recovery of various species from experimental droughts in large outdoor mesocosms.