Spatiotemporal Dynamics of Stream Fish Assemblages Over Four Decades

Abstract

Fish assemblage structure was compared between 1974 and 2014 at 33 sampling locations in the Muddy Boggy River drainage, OK. The two main objectives for this comparison were to first quantify change in assemblage structure, and, second, to test for a relationship between compositional change and spatial scale. Spatial scale was manipulated by pooling assemblage data into groups ranging from K=33 pairs (i.e., local scale) to K=1 pair (i.e., global scale). Local assemblages varied in the degree of assemblage change over 4 decades (range=10-99% dissimilarity; mean=66%). The global assemblage remained quantitatively and qualitatively similar: most species persisted through time and those that did not were rare, and several diversity measures were not significantly different between time periods. Pooling assemblage data into consecutively larger groups and assessing the resultant compositional change revealed interesting patterns indicative of domains of spatial scaling. A discontinuity in the relationship between compositional change and spatial scale occurred at K=15, and this grouping is roughly the size of the headwater/tributary drainages of the Muddy Boggy system. This result suggests assemblages are more predictable when defined at scales larger than a stream reach, and a domain of higher predictability exists at a scale smaller than the entire drainage.