Spatial and Temporal Species Associations with the Topeka Shiner (Notropis topeka) in Missouri

ABSTRACT

Causes for the decline of the federally endangered Topeka shiner (Notropis topeka) are unclear. I used a database of fish community samples in Missouri, dating from 1938 to the present, to investigate spatial and temporal patterns of species occurring within the range of N. topeka. I used what is known about other species associated with N. topeka to provide falsifying evidence for the alternative hypotheses for the decline of N. topeka. Seven species showed a strong decline and four showed a strong expansion over time. Strongly declined species were Ameiurus melas, Carpiodes carpio, Hybognathus placitus, Lepomis humilis, N. topeka, Phenacobius mirabilis, and Pimephales promelas. Strongly expanded species were Fundulus notatus, Lepomis macrochirus, Micropterus salmoides, and Semotilus atromaculatus. Notropis topeka retreated to small, high-gradient streams over time, but this was not a general pattern among other species. In the 1990s, declined species were generally less abundant than expanded species. Declined species were negatively associated with three of the expanded species: F. notatus, L. macrochirus, and M. salmoides. Declined species were not associated in general, but the same three expanded species were positively associated. Information from the literature showed declined species to be generally tolerant of physical/chemical stress but intolerant of species interactions. Information from this longterm data set and current knowledge of these species generally contradicted the physical/chemical hypotheses but not the species interaction hypotheses for the decline of N. topeka.