Underwater shipping noise in the Salish Sea is likely making it difficult for endangered southern resident killer whales to find food and could threaten their survival, according to a team of U.S. scientists.
A new, two-year study, published in the academic journal Peer J, used underwater microphones to take 3,000 noise measurements as 1,600 individual ships passed through the Washington State side of Haro Strait.
The study site is in the middle of critical habitat for the fish-eating southern resident killer whales and researchers found shipping noise extended to middle and high frequencies used by killer whales to echo-locate prey. Killer whales emit a series of clicking sounds and then listen for the bounce-back echoes in order to find fish.
The researchers found the growth in commercial shipping has raised the intensity of low-frequency noise almost 10-fold since the 1960s and there is growing evidence that it is affecting the communication ability of baleen whales, such as humpbacks, gray whales and right whales.