Southern resident killer whales are an endangered population that are regularly targeted by the whale watching industry. The effects of vessels and the noise they produce has been identified as a risk to the recovery of the population. This new study provides some really interesting data on the noise levels that killer whales experience during these vessel interactions.
The Salish Sea (Washington State and British Columbia) includes critical habitat for killer whales. Since the 1980s, whale watching activities in this area have increased to 80 vessels, half a million tourists a year and is now worth more than $70 million annually to the economy of Washington State and British Columbia! To investigate how these vessels affect the southern resident killer whales in the study area, DTAGs were attached to 22 killer whales. These tags contain hydrophones that can record underwater sounds and ambient noise. The tagged whales were followed by the research boat to record the number of interactions the tagged killer whales had with vessels and to record data on vessel characteristics such as size, speed, number of propellers etc.
The results showed that vessel speed best predicted the noise levels received by the killer whales, where the faster the vessels the higher the received noise levels. Read the full publication here.
Why is this data important?
Current whale watching regulations in the US limit the distance of approach to the whales to 200 yards but do not limit the vessel speeds, while Canadian regulations are only voluntary and suggest a 100m minimum approach distance. The results of this study highlight that one key way to reduce noise exposure is to reduce the vessel speed when near the killer whales. These data could be used to help amend whale watching regulations to reduce pressures on the Southern resident killer whale population which could help it to recover from endangered status.
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