Ship noise now dominates the soundscape of the world’s oceans, and the Salish Sea is no exception. Ocean noise can mask signals that fish, marine mammals, and even invertebrates use to communicate, navigate, find mates, and search for food. There has been so much amazing work done by many scientists and researchers to measure noise in the Salish Sea and to understand the impact of that noise on Southern resident killer whales (SRKWs). But how much noise is too much? How much mitigation is enough? And how will we know?
We are pleased to share this paper written by Oceans Initiative’s Chief Scientist Dr. Rob Williams along with Dr. Cindy Elliser and Ginny Broadhurst from the Salish Sea Institute, Western Washington University. This paper focuses on the critical question: How much is too much noise for Southern resident killer whales?
The Salish Sea Institute is publishing a series of white papers intended to stimulate discussion around urgent questions and transboundary cooperation of our shared Salish Sea. Together, Oceans Initiative and Salish Sea Institute hope to convince funders and managers of the urgent need for a carrying capacity study to try to estimate how much vessel noise is acceptable to SRKWs, and how much mitigation it will take to help the whales recover. If we don’t have a shared vision of our target destination for sound seas, we’ll never get there.
We tend to think of the air-water interface as a barrier to noise. Planes fly over the ocean all the time, but conventional wisdom tells us that most of the sound bounces off the surface of the ocean, and has little impact on the whales and dolphins that swim beneath the surface. A classic paper from 1972 tells us we only need to worry about airplane noise in a narrow cone under the flight path.
Planes fly pretty quickly of course, so any noise exposure is fleeting. But during the busiest periods, we recorded planes taking off every 3 minutes! Below is a map of runways, with coastal runways (<10 m above sea level) in red.
We conducted this study during Nyepi, the Balinese Day of Silence. We did not expect to be able to hear airplane noise over background conditions, but we got lucky. Did you know that fish have a chorus of song, just like the dawn chorus of songbirds? Check out the sounds of fish singing below:
And this is the sound of a small boat passing by our hydrophone. In the last few seconds, you can hear the roar of a jet aircraft taking off from the nearby runway of Denpasar airport, Bali, Indonesia.
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Runways of the world, with coastal (<10m above sea level) marked in red
This summer, from mid-July to the end of September, we studied southern resident killer whale behavior under varying levels of boat and ship traffic. (This is an extension of our 2017 field season with OrcaSound). The Port of Vancouver has asked ships to slow down to less than 11 knots as they transit Haro Strait. Reducing ship speed can reduce shipping noise underwater, but slower speeds mean those ships take longer to transit the area. Working with Port of Vancouver and SMRU Consulting, we are exploring how whales navigate that trade-off between noise level and duration of exposure.
Do the whales find more salmon if they are exposed to a little bit of noise for long periods of time? Or is it better to get the noise over with quickly?
Reducing noise is especially important because endangered southern resident killer whales (SRKW) feed in Haro Strait in the summer, and our work has shown that vessel noise disrupts killer whale foraging. While missing one meal might not seem like it would have long-lasting or population-level effects, Haro Strait is a noisy place, which may result cumulatively in many lost meals for the killer whales. We had our team on the western hillsides of San Juan Island all summer to track killer whales in an effort to find out if and how their behavior changes with the slower, quieter ships.
A ship transits Haro Strait by a family of southern resident killer whales. (PC Toby Hall). The theodolite crosshairs allow us to convert horizontal and vertical angles to estimates of latitude and longitude, knowing the cliff height.
To track these whales, we used an instrument called a theodolite. You may have seen them on construction sites or traffic surveys. A theodolite has a telescopic lens that we use to track killer whale movement. After setting a constant reference point, the theodolite can determine the angle between the reference point and the whale we’re looking at. It gets the vertical angle from a gravity-referenced level vector. A computer connected to the theodolite can use those two angles (along with the precise location and elevation of the theodolite) to estimate distances and fixed positions of objects on the ocean’s surface (whales, ships, etc). Your geometry teacher was right—this math does have real-world applications. And we can get all of this fine-scale information noninvasively, without another research boat confounding the effect we are trying to measure. This year, the developer of Pythagoras software generously shared code to let us integrate extremely high-resolution AIS data on the movement of ships, so we could automagically collect precise and accurate data on the ships, while having our expert observers concentrate on measuring the whales’ behavior.
In 2017, the killer whales were worryingly absent from the islands much of the summer, which left us with a small sample size. In fact, for the month of August 2017, the SRKWs were nowhere to be found. This year’s longer field season produced much more data. There were 29 days with whales present around San Juan Island. We had tracking stations set up in three locations along the west side of San Juan Island: County Park, Hannah Heights, and Cattle Point, which allowed us to get close to continuous tracks along Haro Strait. We are excited to analyze the data, which should allow us to determine more about killer whale behavior in the presence of these slower ships.
Video credit: Toby Hall
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This work felt profoundly important this year, in a season riddled with heartbreaking news about the endangered southern residents. J35’s calf died shortly after being born, and the mother mourned the loss of her offspring by pushing around the carcass for 17 days. J50, the youngest individual in the southern resident population, was found to be critically malnourished. NOAA launched the first attempt to supplement a southern resident killer whale’s diet with additional fish. Unfortunately she has not been seen since September 7 and is presumed dead. It is abundantly clear than additional conservation effort is needed, and our team worked hard to make this field season count, both in the field and on the Southern Resident Killer Whale Task Force.
This work wouldn’t have been possible without a super pod of a team. The Oceans Initiative team was led by Erin and Rob, and consisted of our employees Laurel Yruretagoyena, Natalie Mastick, and Laura Bogaard, as well as Toby Hall, Sarah Colosimo, Jess and Chris Newley, and Elizabeth Robinson, who provided additional field support.
Thank you, as always, for supporting our efforts to keep orca habitat clean, quiet, and full of salmon.
We need to recover Chinook salmon stocks throughout the whales’ range.
We support all efforts to do so. We support dam removal, where this will get more salmon into the environment. We applaud the recent announcement to reduce salmon fishing quotas until the whales recovery, which will reduce our competition with the whales. While we wait for those measures to take effect, we need your help to give the whales a fighting chance to find as many of those salmon as possible in a noisy ocean.
We need to give the whales a quiet place to hunt for salmon
A protected area can help the whales if we put it in the right place.
We have found that killer whales are more vulnerable to disturbance when they are feeding than when they are travelling from A to B. They also need more salmon. We have identified areas that whales use preferentially for feeding. (One is called Salmon Bank. We have a feeling the whales knew this before people did.) We need to bring together all dedicated datasets we can use to identify areas where the whales are finding salmon, so we can prioritize those for protection. Protecting key feeding areas is essential to protecting the whales.
Please support our efforts to keep orca habitat clean, quiet, and full of fat, wild salmon.
PS Thanks to our team, especially Toby Hall, for the great footage, and to our friends at SeaLegacy for help editing this video.
Southern resident killer whales in Haro Strait. Photo by Toby Hall
Southern resident killer whales are in decline. Our recent population viability analysis on southern resident killer whales predicted that, if threats remained constant, it should take several decades for the population to decline from 80 to 75 whales. In fact, that decline took only three years. We fear that the decline is accelerating, and we may be reaching a tipping point.
By studying killer whales from land, we can measure their responses to noise without adding the noise of a research boat to the equation. We use noninvasive techniques to measure swimming speeds, breathing rates, and other behavior. Our work on both northern and southern resident orca has shown us that the whales spend 18-25% less time feeding in the presence of boats than in their absence.
We recently joined an international, interdisciplinary study to understand the relative importance of the three main threats to recovery in the endangered killer whale population. The whales are facing a perfect storm of threats–not enough salmon, too much noise, and too many toxic chemicals in their bodies–but lack of prey is at the eye of the storm. This research shows it will take 30% more big, fatty, Chinook salmon than we’ve seen on average over the last 40 years for the population to reach our recovery goals. That will take time, but we have to start now. Meanwhile, reducing noise and disturbance can help make it a little bit easier for whales to find the salmon we have now. In the coming months, we will be revisiting our study on identifying critical foraging areas in the Salish Sea and strengthening their protection.
