Fish passage through headwater stream road crossings monitored by radio frequency identification stations.

摘要

Road crossings on small streams typically alter stream hydrology and potentially fragment aquatic ecosystems. The Ouachita National Forest, Arkansas has thousands of road crossings which may hinder fish movement and contribute to genetic inbreeding or extirpation. To monitor the impacts of road crossings on fish movement, I used stationary antenna arrays to detect and record radio frequency identification tags (RFID, also known as PIT tags) in the Ouachita Mountains. From 2011-2013, I marked ∼3,800 fish (nine species) 85 mm or longer total length with 12-mm, half-duplex, RFID tags. I installed remotely-powered RFID detection stations in two streams with road crossings and two reference streams without road crossings to continuously monitor fish movements. The RFID stations included two, pass-through antennas transecting the stream, with one antenna upstream of the road crossing or reference reach and the other located downstream. The two-part antenna array was designed to precisely record timing and movement direction of each fish passage. The antennas lacked rigid in-stream structures, which may have affected fish movement and I developed a crossover antenna design to improve tag detection efficiency. I monitored associated stream depths and velocities to characterize hydrological conditions and road crossing hydraulics. Fish passed at higher rates across reference reaches than road crossings and at higher rates across a box-culvert than a vented-ford, where fish utilized high water events to bypass high velocity and low swimming depth barriers. Stream intermittency caused extensive stream dryness and exacerbated the hydraulic obstacles at road crossings, which reduced passage rates. Fish species and length had little impact on passage rates but Longear Sunfish did move significantly shorter distances than Creek Chub and Highland Stonerollers. The RFID stations monitored fish passage more efficiently than electrofishing recapture methods and should enhance future studies of aquatic organism passage and road crossing permeability.