Changes in Fish Catch Rates in the Presence of Air Gun Sounds in Prudhoe Bay, Alaska

Bill Streever,Anthony D Hawkins,Arthur N Popper,Katherine H Kim,Scott W Raborn

doi:10.14430/arctic4596

Abstract

Air guns used in oil industry seismic surveys have the capacity to change fish catch rates, but no previous work has demonstrated this effect in shallow water or in Arctic oilfields. Long-term monitoring of fish catches using four fyke nets allowed assessment of changes in catch rates during a 2014 seismic survey in Prudhoe Bay, Alaska. Fyke net locations were instrumented with both conventional hydrophones and vector sensors. Catch rates were generally within the range of those found in 27 previous sampling seasons. The effect of air guns on eight species was assessed using a modified Before-After/Control-Impact analysis, with historical data and 2014 data as the Before-After components of the analysis and days without and with air gun activity as the Control-Impact components. Results showed significant changes associated with air guns in catch rates at one or more nets at p < 0.1 for all eight species and at p < 0.05 for seven of the eight. Changes included both increased and decreased catch rates, perhaps reflecting displacement of fish in response to air gun sounds throughout the study area. Measured sound pressure levels associated with air gun pulses were low and usually undetectable close to the fyke nets, reflecting the loss of low frequencies in shallow water (~1.5 m). Attempts to measure particle velocities failed when wind-driven surface waves overwhelmed vector sensors. However, fish responses may have been related to changes in particle motion associated with air gun sounds.

Highlights

Offshore industrial activities generate underwater sounds with the potential to affect marine life, including fishes (Southall et al, 2007; Hastings, 2008; Popper and Hastings, 2009; Hawkins and Popper, 2014; Hawkins et al, 2014; Popper and Hawkins, 2016)
Air guns used in seismic surveys to map geological features, including features associated with oil and gas deposits, have drawn attention because of their output of high amplitude, lowfrequency sounds and their pervasive presence in the world’s offshore oilfields (Richardson et al, 1995; Southall et al, 2007; Nowacek et al, 2015)
Mortality has never been recorded under field conditions, inner ear damage has been documented in one fish species (McCauley et al, 2003), but not in several others (Song et al, 2008)

Summary

Introduction

Offshore industrial activities generate underwater sounds with the potential to affect marine life, including fishes (Southall et al, 2007; Hastings, 2008; Popper and Hastings, 2009; Hawkins and Popper, 2014; Hawkins et al, 2014; Popper and Hawkins, 2016). Seismic investigations in an area off western Norway showed that the acoustic abundance estimate for pelagic fish was higher outside than inside the seismic shooting area, indicating a long-term effect of the seismic activity (Slotte et al, 2004). Both the herring and blue whiting in that study were examined during a large-scale feeding migration. Very little is known about the detailed effects of air guns or other loud sound sources on fish behavior

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Results

Conclusion