Exclusion Zones

EnerGeo Alliance supports the use of exclusion zones as part of effective, science-based mitigation for offshore seismic survey operations. Exclusion zones are intended to reduce the already low risk of auditory injury to marine mammals by triggering real-time mitigation measures, such as temporary shutdowns of the seismic source, when protected species are detected within a defined radius. 

However, exclusion zones should be risk-based and proportionate to the actual potential for impact in the relevant operating environment. A fixed 500-meter zone has become a common regulatory standard in many jurisdictions because it is practical to implement in the field under most environmental conditions. It should not be interpreted as the distance at which auditory injury occurs for all species or under all environmental conditions. Exclusion zones should be designed around demonstrated biological risk rather than generalized precaution alone, recognizing that mitigation measures should remain effective while avoiding unnecessary operational impacts that do not improve environmental protection. 

Marine seismic source arrays are engineered to direct acoustic energy downward into the subsurface, thereby reducing horizontal sound propagation relative to the downward-directed energy used for imaging. Seismic source pulses are short in duration, and most acoustic energy is concentrated at very low frequencies. At distances of approximately 500 meters, received sound pressure levels are well below marine mammal auditory injury thresholds, with levels often decreasing substantially within 300 meters, depending on source configuration and propagation conditions.  

EnerGeo does not support expanding exclusion zones beyond levels that are supported by the best available science. Larger precautionary zones may provide little or no additional protective value to individual marine mammals while creating unintended consequences, including more frequent shutdowns, longer survey durations, increased emissions, and potentially greater cumulative exposure across all species. 

EnerGeo also supports differentiated mitigation requirements for species groups based on their hearing capabilities and actual risk profile. Dolphins and other delphinids hear best at frequencies much higher than those produced by seismic sources and are at exceedingly low risk of auditory injury or biologically significant behavioral disturbance from seismic survey operations. Decades of protected species observer reports have not demonstrated consistent reductions in dolphin sightings or acoustic detections when seismic sources are active versus silent, and dolphins are frequently observed voluntarily approaching seismic survey vessels. 

Requiring shutdowns for dolphins and other delphinids may therefore extend operations without providing a corresponding conservation benefit. Mitigation measures should instead focus on species and circumstances where a plausible, documented potential for risk exists. 

EnerGeo strongly supports marine mammal mitigation measures that are grounded in sound science, operationally feasible, and proportionate to the potential risk in the relevant operating environment. Exclusion zones should be applied as practical tools for reducing real risk—not as one-size-fits-all measures that increase operational complexity without improving environmental outcomes.