Analysis of the Spatial Distribution of Satellite-Tagged Sperm Whales (Physeter macrocephalus) in Close Proximity to Seismic Surveys in the Gulf of Mexico

摘要

Sperm whales (Physeter macrocephalus) in thethe northern Gulf of Mexico were tagged with Argos satellite-monitored radio tags during June to August of 2002 to 2005. Locations from 51 tagged whales were compared with locations of active airgun arrays from seismic surveys to determine if there was evidence of horizontal avoidance of the arrays. Only whale locations in close proximity (within 50 km) to an active survey were considered under the assumption that avoidance patterns would be more detectable closer to the sound source. A total of 122 locations from 26 whales occurred during or within 30 min of seismic survey lines with a calculated minimum distance of 5 km from an array. The distribution of the whale locations, relative to the airgun arrays, was analyzed to determine possible departures from complete spatial randomness. A test for bivariate uniformity (p > 0.10) and a modified quadrat count test (p = 0.85) produced no evidence of departures from complete spatial randomness. There was no evidence of directedness of orientation of the whale to the airgun array heading (Rayleigh test, p > 0.70). This analysis suggests that distances and orientations between whales and active seismic vessel airgun arrays at this scale appear to be randomly distributed with no evidence of horizontal avoidance. This is the first study to systematically examine the spatial distribution of sperm whales in relation to seismic survey activity from a satellite-tracking perspective. Additional studies using higher resolution data are needed to better understand how sperm whales may respond at finer scales.