Subtle shift in groundfish depth distribution within the impact range of seismic surveying along a continental slope

The impact of an industry-based 3D seismic airgun survey on fish and zooplankton was investigated on offshore commercial fishing grounds in Newfoundland and Labrador, Canada. Seismic surveying was conducted for 100 consecutive days by Petroleum GeoServices using the Ramform Titan seismic vessel during summer 2021. A seabed moored autonomous multichannel acoustic recorder measured sound levels while a wideband autonomous transceiver equipped with 38 and 333 kHz transducers measured fish and zooplankton backscatter in the water column. The distance between the seismic survey vessel and the instruments ranged from 0 to 152 km and was tracked continuously. Fish between depths of 50 m and 350 m exhibited a response to seismic surveying, descending to greater depths when the seismic vessel was within 60 km and when average sound pressure levels (SPL, using a 60-sec average over the band of 8.9-8900 Hz) were >122 dB re 1μPa². Conversely, no discernible effect on zooplankton abundance or behavior was measured between 250 m and 340 m depths. These findings suggest that the effects of seismic surveying in offshore environments are mainly impacting fish behaviour when sound levels are high, and impacts were observed at greater distances than previously reported. 

Methods
Data was collected using Autonomous Multichannel Acoustic Recorder and upward-looking Wideband Autonomous Transceiver coorrdinating with commercial seismic surveying