Three-Species on the move: tracking movement patterns to inform conservation of three native fishes in the Dolores River basin

Authors: Reece Samuelson, Derek Houston, Russ Japuntich, Daniel Cammack, Hannah Carroll

Year: 2021

Abstract

The so-called ‘three-species’, (Flannelmouth Sucker, Catostomus latipinnis; bluehead sucker, C. discobolus; roundtail chub, Gila robusta), broadly co-inhabit the Dolores River basin of southwestern Colorado and eastern Utah. This basin, made up of the Dolores and San Miguel rivers, is unique in that it has relatively few human-made instream structures that impede connectivity, and it is still primarily dominated by native fish, despite being directly connected to the non-native dominated upper Colorado River. However, much of the basin is notoriously difficult to sample because of highly remote reaches and a severely modified flow regime due to a large impoundment in the Dolores River. Because of these issues, many reaches of the basin can only be sampled sporadically when flows allow, and the abundances and distributions of three-species are highly variable both spatially and temporally. Our goal was to gain a better understanding of three-species populations in the Dolores River basin and to guide conservation efforts by investigating movement patterns using passive integrated technology. Beginning in 2013, three-species individuals were implanted with passive integrated transponder (PIT) tags opportunistically during sampling efforts led by state and federal agencies in the Dolores, San Miguel, and Colorado Rivers. We analyzed stored detection data from 2014-2021 on two passive interrogation arrays (PIAs) located in the lower (river mile 11.5; Rio Mesa Array) and upper (river mile 131; Disappointment Creek Array) Dolores River. Detection magnitude and timing were compared among species and between arrays, site fidelity and connectivity were assessed, movement direction associated with each detection event was calculated, and dispersal from original capture location was evaluated. Despite the coarse spatial resolution of the study, over 1,000 individuals and 34% of the total three-species individuals tagged provided detection data on the PIAs. Timing of peak detections varied between PIAs and among species on each PIA. Site fidelity of detected individuals was generally high, and individuals of each species were detected three consecutive years on each PIA. Detection records illustrated the excellent connectivity both within the Dolores River basin and between the Dolores River basin and the Colorado River. High numbers of three-species tagged in the Colorado River and San Miguel River were detected on the Rio Mesa Array, with individuals of each species making the 120-mile movement between the two PIAs within the same year. Upstream movements were frequently observed at the Rio Mesa Array in the spring, while movement direction was more variable on the Disappointment Creek Array. We suggest these movement patterns indicate that many three-species use the Dolores River basin as a spawning tributary, and conclude that remaining flows and connectivity must be protected to conserve one of the last remaining three-species strongholds