Every year, the migration of gray whales passing by the Oregon coast to and from warmer waters draws whale watchers to coastal towns like Newport, just to observe the animals on their journey.
However, the potential installation of new wave energy devices in the ocean could pose problems for these creatures, and researchers at Oregon State U.’s Marine Mammal Institute are planning to test an acoustic device in December that may help prevent foreseeable injury from occurring by directing whales away from danger.
“We don’t have any tools right now to keep the animals out of harm’s way if there’s an issue,” said Bruce Mate, director of the MMI. “In the event of an oil spill or other calamity, we’re hoping this device can be used widely. And if it’s successful, it’s likely to be effective with other whale species as well.”
The functionality of the system is fairly straightforward. According to Mate, the device will emit a one-second noise three times a minute, which amounts to 18 cumulative minutes of noise daily, given that the device will only be utilized for six hours a day. The noise will not be emitted at night, and there will also be a control period during the day to determine how the whales behave when the signal is off.
“We have come to this plan by virtue of consulting with five of the best acoustic experts in the world, including people from Cornell, Scripps, private consultants and people here in Oregon,” Mate said. “Ideally, the noise will influence the movements of the whales by having them avoid this device by 750 meters, which is less than half a mile.”
The idea for the whale-deterring device first cropped up in 2007 during a workshop held at the Hatfield Marine Science Center, in which marine scientists held discussions regarding the ecological effects of wave energy development and how marine mammals might be impacted. Considering the large percentage of gray whales that pass by the Oregon coast, scientists felt that the issue needed to be addressed.
“A 2007-2008 study monitoring gray whales provided some accurate location information, and from that work, they found out that 61 percent of gray whales are passing within three nautical miles of the Oregon shore,” said Barb Lagerquist, a senior faculty research assistant for the MMI. “With animals traveling through an area where wave energy is being proposed, there’s the potential for future encounters in those areas, and they may become injured by colliding with mooring cables that will be holding these devices in place in the water.”
Lagerquist explained that the wave energy devices will be held down with four- to six-inch-thick cables, and it is difficult to know if the whales would be able to detect them in time. A large animal like a whale moving three to four miles per hour through the water could experience significant harm by running into these cables.
The pinging of the whale-deterring device seems to be a viable solution to the problem, one that was widely discussed and openly considered at a town hall meeting in Newport last Wednesday. The meeting started with a talk by David Mellinger, associate professor at OSU’s Cooperative Institute for Marine Resources Studies and authority on marine mammal acoustics.
“There are a lot of different zones of influence, as to whether or not a sound is going to affect a marine mammal,” Mellinger said. “There’s a definite difference between sound in water and sound in air, and it’s hard to compare the two. Of course, what everyone wants to do is know if it’s as loud as a rock band or something like that, but it’s not a simple comparison.”
According to Mellinger’s presentation, gray whales have been shown to respond to low frequency sonar. However, the acoustic deterring device is at a signal intensity that is much too low to cause any hearing damage to the whales, and it will only affect their behavior for about a half of a mile within the target area of avoidance.
In simpler terms, the device will affect the whales only minimally, while keeping them away from dangerous areas.
“An animal potentially lined up to go straight through any cables that is then deterred by the device will only increase its migration .001 percent, so it’s a trivial energetic change that we would make in the animal’s path,” Mate said.
According to Lagerquist, the study will start in December and last until mid-April, which is during the southbound migration of the gray whale population, and also the beginning of the northbound migration. The observation will be entirely visual with no boats or tags that might affect behavior.
“What it amounts to is that we’ve done our homework,” Mate said. “We want people to understand that we aren’t doing the same thing as naval sonar, and what we’re really attempting to do is use sound in a way that will ultimately be very good for whales and everyone involved.”