Spatial and temporal patterns of Pecos River fish assemblage

Authors: Megan G. Bean, Timothy H. Bonner, Preston T. Bean

Year: 2010 (xlii)

Abstract

We examined spatial and temporal patterns in the fish assemblage and habitat associations of fishes of the lower Pecos River, Texas at five sites seasonally between Red Bluff Reservoir and the confluence of the Pecos River and the Rio Grande at Amistad International Reservoir. A distinct dissimilarity between upstream and downstream sites’ fish assemblages was observed and reflected differences among sites in relative contribution of groundwater. Upstream sites were characterized by greater conductivity and finer substrates and the fish assemblage was dominated by sheepshead minnow, Cyprinodon varigatus, and gulf killifish, Cyprinodon variegatus, rainwater killifish, Lucania parva, and inland silverside, Menidia beryllina. Downstream sites were characterized by lower conductivity, reflecting a high degree of spring influence, and larger substrates. Spring associated fishes including Proserpine shiner, Cyprinella proserpina, and manantial roundnose minnow, Dionda argentosa, were common at downstream sites and species tolerant of high conductivity were low in abundance or not present. The contribution of groundwater to stream flow appears to have a large influence on the occurrence and abundance of several species endemic to the Rio Grande drainage.