New Zealand Study Demonstrates Ship Noise Concern
University of Auckland scientists have carried out the first-ever large scale investigation into the effects of ship noise in the waters of the Hauraki Gulf and found that at least two key species are affected.
The research adds to a growing body of data indicating a wide range of animals are affected around the world. For example, in December last year, NOAA scientists studying sounds made by Atlantic cod and haddock at spawning sites in the Gulf of Maine released evidence that vessel traffic noise is reducing the distance over which these animals can communicate with each other.
For the Auckland study, PhD candidate Rosalyn Putland and Associate Professor Craig Radford from the Institute of Marine Science combined sound recordings from four hydrophone listening stations over a nine month period with automatic ship tracking data to track underwater noise contributed by shipping. The study focused on two species which use sound to communicate, Bryde’s whales and the common reef fish, bigeye.
It found noise from cargo, container and tanker vessels overlapped their vocalizations up to 20 percent of the time. Every time a vessel passed within 10 kilometers (six miles) of a listening station, it reduced communication space for bigeyes by up to 61.5 percent and by up to 87.4 percent for Bryde’s whales. Research has shown bigeyes can communicate over distances of up to 31 meters (102 feet), so a passing ship would reduce this to less than 12 meters (40 feet).
The biggest impact from ship noise was at Jellicoe Channel, the most regularly used shipping lane into Ports of Auckland where vessel passages were recorded 18.9 percent of the time.
The concept of “communication space” can be likened to the hubbub of a cocktail party where the ability to hear what is going on is reduced the louder the party becomes, says Radford. “Communication space is the range at which two species can hear each other and this study has found the range at which bigeyes and Bryde’s whales can communicate is significantly reduced when a ship comes past.”
The reduction of communication space for marine species is becoming an increasing concern for scientists worldwide as more is learned about how sound is used among groups of species to ensure survival including finding a mate, defending territory and warning of predators.
This latest study provides further evidence that compliance with the 10-knot speed restriction within the Hauraki Gulf Marine Park area could benefit marine species, Rosalyn Putland says, as vessels traveling at lower speeds produce quieter levels of noise.
“The voluntary speed limit of 10 knots is fairly recent, but we believe is having a significant effect on helping reduce noise in the Gulf to allow species to hear each other,” she says. “Even so, when a ship is directly above marine animals, it reduces communication for those animals almost completely,” she says.
While this study focused on large commercial vessels, more than 130,000 recreational boats regularly use the Gulf and this number is expected to rise 40 percent in the next 20 years. Recreational boats produce sound that also overlaps fish and marine mammal vocalizations. Further research at the Leigh Marine Laboratory will focus on how recreational boat noise in the Gulf affects the communication space of fish and marine mammals.
The quest for both understanding and regulation continues to expand across the maritime space. The IMO published MEPC.1/Circ.833 Guidelines for the Reduction of Underwater Noise from Commercial Shipping to Address Adverse Impacts on Marine Life in 2014. Additionally, the IMO has made changes to onboard noise limits that are mandatory for vessels over 1,600 tons in resolution MSC.337(91). The noise limits provided in the Code on noise levels on board ships are now mandatory under SOLAS.
Other recent developments have seen NOAA in the U.S. publish a roadmap for addressing ocean noise, and the E.U. has completed several large projects looking into the effects of underwater noise in European waters.