Stability and resiliency of fish assemblages in an Ozark stream /

Abstract

Fish assemblages from main channel riffle habitats varied independently with little evidence of stability. Assemblages from backwater inlet and pool habitats varied seasonally with respect to stability and resiliency. Results were inconsistent across sites for inlet assemblages. In backwater pools, a consistent pattern of stable and resilient fish-assemblage structure was noted in summer and fall. The pattern corresponds with a predictable pattern of resource limitation, and suggests equilibrium structure based on occurrences of interspecific competition. However, the summer-fall period coincided with the period of post-larval recruitment. During this period pool assemblages were dominated by young-of-year of species that occurred across habitat types, suggesting that the pattern of stability and resiliency was dependent on ephemerally high abundances of fish recruits. Life history characteristics of the species considered here support an interpretation of the pattern as independent coexistences of species.

Predictions of alternative hypotheses of assemblage structure concerning equilibrium states were tested for fish assemblages from spatially repeated sets of habitats in an Ozark stream. Equilibrium characteristics (stability and resiliency) were elucidated through manipulation experiments conducted within habitats over a 15-mo period and Mantel tests for associations among the correlation patterns of the fish assemblages within habitats across sites.