The 100‐Watt Method: A Protocol for Backpack Electrofishing in Small Streams

Abstract

We present a 100‐Watt protocol for backpack electrofishing to capture salmonids in small streams. The protocol requires that electrofisher settings produce ~100 W of average power output. Since 2000, the protocol has been used in Idaho streams ranging in ambient conductivity from ~20–1,000 µS/cm and water temperatures from ~0–28°C, and results in satisfactory capture efficiency and desired fish response (i.e., taxis and immobilization) for pulse frequencies ranging from 30–60 Hz. Moreover, resulting spinal injuries are low (<5%) and similar between 30 and 60 Hz, contradicting past studies that show higher injury rates for salmonids at higher pulse frequencies. Despite significant variation in pulse frequency, fish size, and water conductivity, the 100‐W target works for salmonids in small streams because fish are especially vulnerable to electrofishing in small water volumes where boundary effects concentrate the electric field. Avenues of further research are highlighted that would more fully evaluate the 100‐W method.

Reach‐scale associations between introduced Brook Trout and juvenile and stream‐resident Bull Trout in Idaho

“…We estimated Bull and Brook Trout densities from multipass electrofishing depletion surveys, which IDFG uses to estimate stream fish abundance; surveys are conducted using a statewide protocol that standardizes electrofisher power output (Meyer et al. 2021). Surveyed reaches varied between 21 and 200 m in length, but the vast majority were 100 m long.…”

“…We removed Bull Trout × Brook Trout hybrids from all analyses because these individuals do not contribute to pure lineages of either parent species and rarely produce fit offspring (e.g., post-F 2 hybrids have never been documented; Kanda et al 2002;DeHaan et al 2010). We estimated Bull and Brook Trout densities from multipass electrofishing depletion surveys, which IDFG uses to estimate stream fish abundance; surveys are conducted using a statewide protocol that standardizes electrofisher power output (Meyer et al 2021). Surveyed reaches varied between 21 and 200 m in length, but the vast majority were 100 m long.…”

Comparing growth and body condition of wild and hatcheryMYYbrook trout in streams and alpine lakes

“…Fish were sampled in streams via backpack electrofishing in July of 2020 and 2021. Electrofisher settings were 60 Hz and 25% duty cycle, and voltage was adjusted until the electrofishing unit produced approximately 100 watts of average power output, to optimize capture of salmonids in small streams (Meyer et al, 2021).…”

Effects of elevated water temperature on cutthroat trout angler catch rates and catch‐and‐release mortality in Idaho streams

“…Post-release survival was evaluated by recapturing tagged fish on August 25-27, 2020, using a single-backpack electrofishing pass through each stream reach where angling occurred. Electrofishers were set at 60 Hz, 25% duty cycle and enough volts to emit about 100 watts of average power output, which is efficient for capturing stream-dwelling salmonids (Meyer et al, 2021). Captured fish were identified to species, examined for anchor tags and adipose fin clips (no recaptured fish lost their tag), measured in total length (TL = cm) and released.…”