NOAA Teacher at Sea
Kiersten Newtoff
Aboard NOAA Ship Pisces
January 6 – January 29, 2025
Mission: Atlantic Marine Assessment Program for Protected Species (AMAPPS)
Geographic Area of Cruise: North Atlantic Coast
Date: January 15, 2025
Data from the Bridge: Currently standing still at 39°12’0″N, 74°24’0″W due to offshore weather. It’s 38°F with 26kt winds.
Team Spotlight: Hydrophone Heroes
It started as periodic clicking.
Click.
Click.
Click click.
Click click click.
Cliiiiiiiiiiiiiiiiiccccccccccccccckkkkkkkkkkkkkk.
And then nothing.
These series of clicks tell the story of a sperm whale attacking prey and feasting on its prize. This is just one of the many cool stories coming from the Hydrophone Heroes.
In Tandem, Eyes and Ears on the Ocean
All marine mammals are protected by the Marine Mammal Protection Act, and some are dually protected under the Endangered Species Act. These laws dictate that marine mammals cannot be hunted, harassed, taken, or killed; although some exclusions exist for scientific research among other things. You may recall from an earlier post that there are two marine mammal teams on the Pisces: the bioacoustics team and the visual observation team. Both teams are working toward a common goal: where are marine mammals, how are they behaving, what is the diversity, and how many are there? These surveys help NOAA propose new rules or develop new technologies to reduce the accidental bycatch or injuries from boats to preserve the species. By doing surveys periodically, we can better understand how populations are changing in response to the environment.
The sampling protocol differs between the visual and bioacoustics teams, as well as what they can and can’t detect. By combining their data together, a complete picture of marine mammal abundance can be made.
| Bioacoustics | Visual Observation | |
| Detection Range | Larger | Smaller |
| Water Depth to Operate | > 100m | Any |
| Weather Conditions | Any | Better the more clear |
| Species ID Confidence | Medium | High |
| Discerning Number of Individuals | Only when there is 1 or 2 | Any |
| Statistical Methods for Analyzing | Not well developed | Well developed and standardized |
The world of marine mammal bioacoustics is relatively new, starting in the 1960s but taking off in the late 1990s to early 2000s. Also, each species of marine mammal has a large ‘vocabulary’ that we are still learning. Because of this, the library of sounds of each species is limited. While it may be great to hear a click or whistle through the hydrophone, it means very little if there isn’t a visual confirmation from the observation team.
Science is the art of inquiry.
Annamaria
How Do Hydrophones Work?
As the name implies, a hydrophone is a listening device that is in the water. It can pick up frequencies higher and lower than what humans can hear and it can hear sounds from miles away. On the Pisces, the hydrophone array consists of multiple sensors and equipment in a long tube. There are three omnidirectional hydrophones in the array, and all three will pick up the same signals. However, the hydrophone that hears a sound first can give the team an idea of the direction the sounds are coming from: in front, in line, or behind the ship. This setup can’t identify starboard or port side, and that’s where the visual observation team comes in. As the ship moves and the hydrophone continues to pick up sounds, they can be triangulated to get an idea of how far away the sound is from the ship. The array setup can’t tell you how deep the sound is coming from, but some patterns of clicks of different species can give clues to if a cetacean is diving or at the surface.
The array is towed behind the ship in waters that are at least 100m deep. Although the hydrophone doesn’t actually sit that close to the bottom, it’s a fail safe for if the ship has to slow down or stop. This can cause the hydrophone array to sink and it is imperative that it does not touch the bottom. The equipment in the array is very sensitive (and very expensive!), so it’s crucial that it’s impossible for it to touch the bottom. You may be thinking “well, just tow it closer to the boat so that you can work in shallower waters”, but the problem is that the boat itself is making noise that the hydrophone will pick up. If the array is too close to the ship, the sound would be deafening, and you would miss many marine sounds. The hydrophone is set about 350m out from the ship, which does dampen the noise quite a bit. The hydrophone has a high pass filter, meaning only high frequency sounds are picked up. The auditory range of ship noise is much lower, so it gets filtered out, but unfortunately that also means filtering out some marine mammal sounds, particularly baleen whale songs.
There are six (!!) screens that the Hydrophone Heroes are monitoring when the array is out. They are:
- High frequency setup: this is focused on high frequencies such as from dwarf and pygmy sperm whales and is giving a bearing on where they are located.
- Diagnostic plots that characterize the incoming signals.
- A spectrogram that displays tonal signals like whistles.
- Data entry form to record each incoming sound.
- Map displays of the bearings of sounds as a way to localize and track them.
- Client computer which is synced with the visual team to match up sounds with visuals.
Perhaps some time in the future, machine learning can be used to automatically classify sounds picked up by a hydrophone. But in order for that to happen, we need a lot of matched acoustic and visual data to be used for training the machine learning models.
Do You Hear What I Hear? (by Bing Crosby and Kiersten)
Do you hear what I hear?
Said Rob to Annamaria
Do you see what I see?
(Do you see what I see?)
Visuals said to acoustics
Do you see what I see?
(Do you see what I see?)
A whale, a whale, leaping through the waves
With a tail as big as a kite
With a tail as big as a kite
Meet the Hydrophone Heroes
Annamaria is a research biologist from the Northeast Fisheries Science Center in Massachusetts. Her love of the ocean started early, and she pursued it more intently in her high school’s oceanography club and in the Quahog Bowl . From there she got a bachelor’s degree in marine biology, during which she did an internship with the U.S. Navy in their marine mammal monitoring program. It is through this internship that Annamaria learned about bioacoustics and left with the experience of managing 93 hydrophones! She really liked the internship, especially because she was able to apply the science with real time responses (and it was paid!). Post-graduation, she worked at the Bioacoustic Research Program at Cornell University and then went to Scotland to get her master’s degree. She volunteered with the Wood’s Hole Oceanographic Institution working in fish bioacoustics before landing a position at NOAA in 2014.
Rob is a biological science technician who has been working with NOAA for the past 4 years at the Pacific Island Fisheries Science Center in Honolulu. In college he studied marine and environmental science and afterwards he looked into fisheries science so he could be outside. He ended up at the California Fish and Wildlife Service (FWS) working with salmon and delta smelt and then moved to the Federal FWS. He finally moved into the Protected Species Division at NOAA where he learned about bioacoustics in cetaceans. Baby Rob’s dream was to do a cetacean cruise, and he made it!
Advice & Words of Wisdom
- Be curious – science is a never-ending process of asking more questions.
- When applying for jobs on USAJobs, cast a wide net (pun intended). There are lots more fisheries positions which can still be valuable to your career by developing transferable skills to cetaceans.
- If you are working with data, try to seek opportunities to see how that data is collected in the field. It can help you better understand the data which will be advantageous when running analyses.
- Internships are crucial and can really define your career. They also help with connections to other people in the industry.
- Be open to lots of career paths and gain skills to enable you to be a jack of all trades. If you have skills from multiple fields, you are more likely to find positions.
Here’s some additional pictures from setting out the array and working in the acoustics lab.
