Vessel Separation Distances
Various countries have proposed draft regulations requiring minimum separation distances or “buffer zones” between seismic survey vessels as a purported mitigation tool that would create corridors for marine mammals to travel. There is no evidence to support the assumption that marine mammals would utilize a “corridor” these separation distances are supposed to create. The erroneous supposition is that marine mammals will somehow understand they are “supposed” to use these “corridors” and thereby reduce their exposure to sound produced by seismic survey operations.
The best available scientific information does not support buffer zones for this purpose beyond 17.5 km if at all, which is consistent with standard industry practice. Vessel separation distance requirements must be based on the best available scientific information.
Modeling demonstrates that the typical exposure radius for the current threshold recognized by the U.S. National Marine Fisheries Service (NMFS) for the onset of behavioral disruption at 160 dBrms is 10 km. The largest observed exposure radius was 15 km, but this occurred in less than 10% of the modeled cases, while the lowest observed exposure radius was 5 km. Current technology has enabled operators to decrease typical exposure radii to 7 to 9 km.
The IAGC does not support a separation distance or buffer zone greater than industry standard practices, which is clearly not reasonable nor scientifically supported. Additionally, implementation of such a measure could indeed increase the possibility of exposure.
The industry encourages regulators to apply only those mitigation measures that are appropriate for the undertaking and that result in the least practicable adverse impact, as required by statute.