Ships Voluntarily Slow Down For Underwater Noise Reduction Trial
A majority of large ship operators are cooperating with a request to temporarily slow down in the shared border waters between Victoria and San Juan Island. The Port of Vancouver in British Columbia is running an experiment there to reduce underwater noise that bothers whales.
This is week four of the two month long voluntary vessel slowdown trial in Haro Strait. Those waters are a prime summer feeding ground for endangered orca pods and a "hotspot" for disturbance from ship noise. A series of underwater microphones is measuring the drop in decibels.
Krista Trounce of the Port of Vancouver says so far more than half of piloted cargo ships have agreed to slow to eleven knots going down the strait. Trounce manages the slowdown trial within the port's ECHO Program, a project to manage and mitigate threats to endangered whales from shipping.
"We had hoped for a minimum of 50 percent participation for good statistics on the data," Trounce said. "We're encouraged that we're going to get enough participation that we'll be able to see if there is a good solid trend between slower vessels and reduced underwater noise."
If the slowdown trial gives scientists enough evidence to say threatened whales would benefit, policymakers could set a mandatory vessel speed limit. Trounce said ship operators that opted out of the trial said they needed to meet a schedule or were concerned about incurring additional costs.
In the first week of the slowdown trial, total tracked vessel participation was 59 percent. In the second week, the participation rate rose to 68 percent and this past week it dropped to 55 percent, likely due in part to unfavorable, strong tidal currents.
Trounce has been working with the cruise line and shipping industry for more than a year to get buy-in on the slowdown, which started on August 7 and lasts to early October. The slowdown zone is roughly 15-16 nautical miles in length.
“We haven’t seen much of the southern resident killer whales this year in this area,” Trounce said of an unanticipated wrinkle for observation purposes. She said low salmon numbers might be a cause.
The suggested eleven knot speed limit is close to half speed for a fast container or cruise ship, but not much a slowdown at all for the average bulk carrier. Eleven knots equates to about 12.6 miles per hour.
The population of resident killer whales in the shared border waters of Western Washington and southwestern British Columbia has dwindled to 78 individuals. These endangered orcas primarily use sound -- including echolocation -- to hunt for food, to orient and communicate. Ship noise can mask the whale calls, effectively blinding the mammals whose ears in a lot of ways are their eyes. Canadian and American government agencies have identified physical and acoustic disturbance as one of the key threats to survival of the endangered killer whales.
You can listen to the underwater soundscape of Haro Strait through a live-streaming hydrophone at Lime Kiln Lighthouse via the SeaSound Remote Sensing Network.