Efficacy of Portable PIT Detectors for Tracking Long‐Term Movement of Colorado River Cutthroat Trout in a Small Montane Stream

Abstract

AbstractWe evaluated the efficacy of portable PIT detectors for tracking long‐term fish movement in an open stream environment. In June and October of 2012, we PIT‐tagged a total of 190 Colorado River Cutthroat Trout Oncorhynchus clarkii pleuriticus (CRCT) in a 1.7‐km segment of a small, montane stream. In the summers of 2012–2013 (15 total occasions), we relocated PIT‐tagged trout using portable PIT detectors. The maximum detection distance of 23‐mm PIT tags ranged from 6 to 56 cm and varied with detector, detection plane, and tag orientation. Of the CRCT tagged, 38% were never detected and 43% were detected on two or more occasions. Mean detection efficiencies of PIT‐tagged trout were 34% and 45% in 2012 and 2013, respectively, and were generally lower than in evaluations of closed systems and less mobile fishes. We observed a smaller range of CRCT than has been observed by others using radiotelemetry, a difference that could be explained by the spatial and temporal limitations of portable PIT detection we encountered. We conclude that portable PIT detector surveys have value but also drawbacks for tracking the movement of relatively mobile fishes in montane streams.Received September 27, 2014; accepted January 21, 2015