The first of three papers included here (Sanderson et al., 2023a) has been published and measures the detection efficiency of acoustic tags in Minas Passage – a prerequisite for estimating fish-turbine encounter using these technologies. Acoustic tags are commonly programmed to emit a pulse position modulation (PPM; 69 kHz, 180 kHz) signal or high-residency (HR; 170 kHz) signal.

Although a useful technology under many conditions, the PPM signal is spaced over an extended period of time (usually > 30 seconds) and could remain undetected by an acoustic receiver in Minas Passage if the PPM tag is swept by at high current speeds. This could lead to the incorrect conclusion that a tagged fish was not present when in fact it was, but simply remained undetected.

Alternatively, HR technology emits signals much more frequently and may be better suited for detecting tagged fish across the range of tidal current speeds experienced at the FORCE site. Sanderson et al. (2023a) conducted a detection range experiment using tags moored near the seafloor at the FORCE site to determine how efficiently 170 kHz HR acoustic transmissions were detected as a function of range (distance between signal source and receiver) and tidal current speed. The study reveals that the detection density (efficiency) of these signals is high (> 90%) for ranges out to 150 m and current speeds up to 3 m/sec, but drops off quickly for higher current speeds.