N-mixture modeling for juvenile Rio Grande Blue Sucker in the Trans-Pecos region of the Rio Grande

Authors: Seiji Miyazono, Sarah Fritts, Timothy B Grabowski, Blake Grisham, Kevin Mayes, Preston Bean

Year: 2016 (xlviii)

Abstract

Blue Sucker Cycleptus elongatus is a state-listed threatened species in Texas and is considered vulnerable throughout its range. Once considered a single, wide-ranging species, blue suckers are now recognized as a complex of closely related, but genetically and morphologically distinct species within the genus Cycleptus, including an undescribed species within the Rio Grande Basin. Numerous factors are likely driving the decline of Blue Suckers in Texas, including flow alteration, water quality, habitat fragmentation, and changing land use patterns, but it is not clear how these factors interact to influence the abundance and distribution of blue suckers. We examined relationships between the abundance of juvenile Rio Grande Blue Sucker (RGBS), Cycleptus sp., and various abiotic variables in the Trans-Pecos region of the Rio Grande in Texas using N-mixture modeling. Pool area was the most important covariate for juvenile RGBS abundance. As pool area increased, the abundance of RGBS increased. The detection of RGBS decreased from April to June in 2016 possibly because RGBS grew larger and became less vulnerable to our sampling methodology (seining). We suggest that slow current areas could be important nursery habitat for juvenile RGBS i n the Rio Grande, and that changes in flow regime that affects the availability of this habitat type could significantly affect recruitment of RGBS.