Premium
Effect of Pulsed DC Frequency on Capture Efficiency and Spinal Injury of Trout in Small Streams
Author(s) -
Chiaramonte Luciano V.,
Meyer Kevin A.,
Branigan Philip R.,
Reynolds James B.
Publication year - 2020
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1002/nafm.10440
Subject(s) - electrofishing , salvelinus , trout , fontinalis , pulse (music) , rainbow trout , zoology , duty cycle , fishery , environmental science , fish <actinopterygii> , streams , materials science , physics , biology , power (physics) , voltage , computer science , computer network , quantum mechanics
Electrofishing studies in the 1990s established that higher frequencies of pulsed DC (e.g., 60 Hz) generally result in more spinal injury to fish in comparison with lower pulse frequencies (e.g., 30 Hz). In response to those findings, some agencies adopted low pulse frequency standards to minimize fish injury. However, those earlier studies did not assess whether capture efficiency (CE) was also influenced by pulse frequency. We sampled small trout streams (1–6‐m average width; SE = 0.14 m) by backpack electrofishing with settings of 30 and 60 Hz to evaluate the effect of pulse frequency on both CE and spinal injury rates for Cutthroat Trout Oncorhynchus clarkii , Rainbow Trout O. mykiss , and Brook Trout Salvelinus fontinalis . Duty cycle was held constant at 24% and average power output was held at approximately 100 W. Using a four‐pass removal protocol, cumulative CE (all four passes) averaged 0.84 for 30‐Hz reaches and 0.94 for 60‐Hz reaches. Capture efficiency in pass 1 averaged 0.59 for 30‐Hz reaches and 0.75 for 60‐Hz reaches and declined with successive passes using both pulse frequencies. X‐ray images revealed vertebral compressions and misalignments for 4% of fish captured with 30 Hz ( n = 230) and 4% of those captured with 60 Hz ( n = 222); no fractured vertebrae were observed. No spinal injuries were observed in control fish that were captured via angling ( n = 92). Our results indicate that in small streams where trout are generally less than 300 mm TL, backpack electrofishing with 60 Hz will result in greater CE, improved trout occupancy and abundance estimates, and no increase in spinal injury.