The effects of pulse pressure from seismic water gun technology on Northern Pike

We examined the efficacy of sound pressure pulses generated from a water gun for controlling invasive Northern Pike Esox lucius. Pulse pressures from two sizes of water guns were evaluated for their effects on individual fish placed at a predetermined random distance. Fish mortality from a 5,620.8-cm³ water gun (peak pressure source level = 252 dB referenced to 1 μP at 1 m) was assessed every 24 h for 168 h, and damage (intact, hematoma, or rupture) to the gas bladder, kidney, and liver was recorded. The experiment was replicated with a 1,966.4-cm³ water gun (peak pressure source level = 244 dB referenced to 1 μP at 1 m), but fish were euthanized immediately. The peak sound pressure level (SPL_peak), peak-to-peak sound pressure level (SPL_p-p), and frequency spectrums were recorded, and the cumulative sound exposure level (SEL_cum) was subsequently calculated. The SPL_peak, SPL_p-p, and SEL_cum were correlated, and values varied significantly by treatment group for both guns. Mortality increased and organ damage was greater with decreasing distance to the water gun. Mortality (31%) by 168 h was only observed for Northern Pike exhibiting the highest degree of organ damage. Mortality at 72 h and 168 h postexposure was associated with increasing SEL_cum above 195 dB. The minimum SEL_cum calculated for gas bladder rupture was 199 dB recorded at 9 m from the 5,620.8-cm³ water gun and 194 dB recorded at 6 m from the 1,966.4-cm³water gun. Among Northern Pike that were exposed to the large water gun, 100% of fish exposed at 3 and 6 m had ruptured gas bladders, and 86% exposed at 9 m had ruptured gas bladders. Among fish that were exposed to pulse pressures from the smaller water gun, 78% exhibited gas bladder rupture. Results from these initial controlled experiments underscore the potential of water guns as a tool for controlling Northern Pike.