Acoustic detectability of whales amidst underwater noise off the west coast of South Africa

Anthropogenic underwater noise has been shown to negatively affect marine organisms globally; yet little to no noise research has been conducted in most African waters including South Africa's. This study aimed to quan-titatively describe sources of underwater noise and effects of underwater noise on the acoustic detectability of Antarctic blue, fin, minke, humpback, and sperm whales off South Africa's west coast. Noise from vessel traffic (<35 km to the location of recorders) dominated the soundscape below 500 Hz while wind-generated noise increased with wind speed above 5 m s-1 and dominated the soundscape above 500 Hz. Acoustic detectability of humpback, minke and sperm whales decreased with increasing ambient noise levels whereas blue and fin whale acoustic detectability increased with the ambient noise levels. We provide baseline information on underwater noise sources and the effects of underwater noise on whale acoustic detectability off the west coast of South Africa.

Automated summary

This study quantitatively describes the sources of underwater noise and the effects of underwater noise on the acoustic detectability of different whale species off the west coast of South Africa. The study found that noise from vessel traffic dominated the soundscape below 500 Hz, while wind-generated noise dominated the soundscape above 500 Hz. The acoustic detectability of humpback, minke, and sperm whales decreased with increasing ambient noise levels, while the detectability of blue and fin whales increased with ambient noise levels.