Stephani Clark Barkalow¹, Martinique J. Chavez¹, Adam L. Barkalow², Phaedra Budy³, Peter Mackinnon³, Mark Mckinstry⁴

1. American Southwest Ichthyological Researchers LLC, 800 Encino Pl NE, Albuquerque, NM 87102
2. New Mexico Department of Game and Fish, 7816 Alamo Rd NW, Albuquerque, NM 87120
3. Utah Cooperative Fish and Wildlife Research Unit, 5210 Old Main Hill, Logan, UT 84321
4. Bureau of Reclamation, 125 South State St, Salt Lake City, UT 84138

Remote detection technologies have increasingly been used to estimate habitat use, movement metrics, passage efficiency, population dynamics, and demographic parameters in freshwater fishes. Stationary passive integrated transponder (PIT) tag antennas are valuable for tracking fish movement past discrete locations and may elucidate fragmentation effects, allude to timing of spawning migrations, and reveal critical responses to environmental conditions; however, they are unable to document the ultimate destination of tagged individuals or characterize the behavior of the fish that bypass the antennas or use areas of the river absent antennas. Floating PIT tag antennas, like Passive Integrated Transponder Portable Antenna SystemS (PITPASS), overcome many of the challenges associated with stationary antennas and traditional monitoring approaches, thus providing opportunities to study fishes across various spatial and temporal scales. Each raft-mounted PITPASS interrogation system has 6.0 m of antenna coverage and is capable of detecting tags at depths of up to 1.0 m. This innovative technology can detect fishes at similar rates to electrofishing and along a broader geographic extent than stationary antennas, while providing opportunities to collect fine-scale habitat use information. Further, longitudinal PITPASS surveys can be repeated in short succession to build a history of detection events and acquire fine-scale movement metrics.

Here, we demonstrate applications of PITPASS to evaluate life histories and movement patterns of Endangered Species Act listed species: Rio Grande Silvery Minnow (Hybognathus amarus), a relatively short-lived small-bodied species endemic to the Rio Grande basin, and Razorback Sucker (Xyrauchen texanus), a long-lived large-bodied species endemic to the Colorado River basin. Repeated longitudinal surveys were performed on both species using three PITPASS equipped rafts. Using PITPASS, we documented long-distance movements and passages through instream barriers in both species. In the Rio Grande, we documented longer distances moved by Rio Grande Silvery Minnow than ever previously recorded and had an extremely high resight rate, detecting 13,706 unique PIT-tagged Rio Grande Silvery Minnow out of the 37,215 released. Notably, we documented upstream passages through a diversion dam that is not equipped with fish passage. In the San Juan River, we implemented a novel application of PITPASS to identify Razorback Sucker spawning aggregates, subsequently detecting discrete spawning areas and a large reproducing population upstream of listed critical habitat. In both studies, the spatial resolution of fish detected by PITPASS would not otherwise have been achieved using traditional monitoring methods requiring physical capture of fish or by stationary PIT tag antennas. The demonstrated efficacy of PITPASS to detect imperiled fish species has crucial conservation applications and serves as an important model to inform future recovery efforts of native fishes.