Gail Tang: HARPs and Hearts, August 25, 2023

NOAA Teacher at Sea

Gail Tang

Aboard NOAA Ship Oscar Elton Sette

August 4, 2023 – September 1, 2023

Mission: Hawaiian Islands Cetacean and Ecosystem Assessment Survey (HICEAS)

Geographic Area of Cruise: Hawaiian archipelago

Date: Aug 25, 2023

Science and Technology Log

Visually surveying for marine mammals has its limitations because they spend so much time underwater. To account for these limitations, a number of acoustic techniques are used to study cetaceans (whales and dolphins). There are four main passive acoustic instruments used by the Pacific Islands Fisheries Science Center’s Cetacean Research Program during ship surveys: towed arrays, drifting acoustic spar buoy recorders (DASBR), high-frequency acoustic recording packages (HARP), and sonobouys. Each instrument has its pros and cons so the data from each instrument provide a fuller picture of what’s under the sea.

On board the ship, every morning just before sunrise the acousticians deploy the towed array of hydrophones, which streams 300 m behind the ship. ​​The towed array provides real-time information on calls and clicks of the whales and dolphins. Each section of the towed array has three hydrophones and a depth sensor (see picture below). The design comes from the National Marine Fisheries Service and are all built by Lead Acoustician Jennifer McCullough (to read more about Jennifer, see my previous post). While the towed array can pick up sounds from the cetaceans around the ship in real-time, it also picks up the sounds of the ship, thus obfuscating other calls. As such, autonomous recorders (DASBRs, HARPs, and sonobouys) are used to collect more data, as well as match species data collected from the towed arrays.

view of the array resting on deck - it looks like curled up plastic tubing (with some purple sections) connected to a cable
A section of the towed array with three hydrophones (seen in purple). Photo credit: NOAA Fisheries/Gail Tang
on deck, Jennifer stands at a large spool in the center while Alexa leans over a coiled pile of cable attached to the plastic tubing that contains the hydrophones. Erik stands near the railing to help guide the array to the water.
Acoustician team Jennifer McCullough, Alexa Gonzalez, and Erik Norris deploy the towed array. Photo Credit: NOAA Fisheries/Gail Tang
illustration of the ship at the surface of the water (depicted by a horizontal line) with the array towed behind at a depth of about 10 meters. an inset box shows a larger illustration of the two arrays - one "end array" and one "inline array" with 20 m baseline cable in between. the three hydrophones in each array are spaced 1  m apart from each other.
A depiction of array towed behind a ship. Photo Credit: Barkley et al. (2021 p. 1122)

The HARP is a long-term acoustic recorder that sits on the seafloor at depths of 650-900 m depending on the site. Developed by the Whale Acoustics Lab at Scripps Institute of Oceanography, they are site-specific and sit out for one to two years. The one we retrieved during Leg 2 was deployed August 2022. The HARPs provide 1) time-series data that help with understanding seasonal occurrence of cetaceans and other marine life, 2) periodic data on the presence of animals that pass through the site, and 3) ocean noise reference points. The latter is important in measuring the potential impact of ship and construction noise on marine mammal behavior. For example, slowly over time, blue whales are shifting their call types to a lower frequency to compensate for the rise of ocean noise in their natural call range (Rice at al., 2022).

Matt, wearing a blue hard hat, a life vest, and gloves, stands on deck, tethered to something on deck by a yellow strap hooked into the back of his life vest. We are looking down at him as he faces away from the camera, hands raised in the air to guide a large yellow piece of equipment as a crane lifts it back on deck. Matt grasps a line (rope) connected to the crane's hook with his left and uses the right to steady the equipment.
Matt Benes (Able-bodied Seaman) retrieves HARP. Photo Credit: NOAA Fisheries/Suzanne Yin

DASBRs are floating acoustic recorders deployed from the ship and retrieved sometime between 1-30 days later depending on their location from the ship. The DASBR collects acoustic data away from the ship and at a depth deeper in the water column than the towed array (about 150 m from the surface). This means there’s no noise from the ship that may disturb the animals and no surface noise from crashing waves or rain. A clear advantage of the DASBR is its ability to record beaked whale vocalizations, super high-frequency echolocation clicks.  Beaked whales are only vocal during the lower portions of their foraging dives, which last for about 60-90 mins. On the ship with the towed array, we don’t spend enough time to capture their vocalizations. The DASBR on the other hand has time to capture an entire dive cycle of a beaked whale. Depending on the frequency and amplitude of the animal, the distance at which the DASBR can detect animals (or detection range) varies by species. For example, Kogia (pygmy and dwarf sperm whales) need to be near the sensor and facing it to pick up their calls, while the baleen whales have a larger detection range. To give you an idea of the overall advantages of the DASBR, it can pick up about 10 times more cetaceans than the towed array and help us learn more about their vocalizations and study their habitat range.

Matt, wearing a hard hat, life vest, gloves, and a harness, tethered by a yellow strap to something on deck for safety, looks away from the camera, into the dark of the ocean at night. a spotlight extending from an upper deck highlights the location of the DASBR in glowing blue light.
With grapple hook in hand and eyes on the DASBR, Matt Benes (Able-bodied Seaman) prepares for retrieval. Photo Credit: NOAA Fisheries/Marie Hill
screenshot from Google Earth of the Hawaiian Islands showing segmented lines outlining a path north of the islands. some segments are labeled with dates from Aug 26 to Sept 1 (back at Honolulu). a short yellow arrow and a green parabola show the locations of DASBR 4 and 3 respectively.
This map shows the tracklines where we surveyed, as well as the DASBR paths. Photo Credit: NOAA Fisheries/Marie Hill

There are many recorded calls for which there is no visual match, so sonobouys are deployed after the visual team identifies a particular baleen whale species. Because the ship masks the very low frequency sounds made by most baleen whales, sonobouys are deployed to evaluate their call types. The hydrophones in the sonobouys are set at 90 ft from the ocean’s surface and they collect data for up to 8 hours.

I like the idea that these four instruments work in concert towards a shared goal, each with its strengths and weaknesses.

Career Log

The information above was provided by the acoustics team. I will focus on a couple in particular, Yvonne Barkley (Cruise Lead in Training) and Erik Norris (Acoustician), who met on NOAA Ship Oscar Elton Sette 13 years ago!

Eirk and Yvonne on deck; Yvonne is seated in an observation chair and Erik is holding his right arm out to take the selfie
Erik Norris (Acoustician) and Yvonne Barkley (Cruise Lead-in-Training)

Yvonne Barkley first went to University of California, San Diego and then transferred to Santa Barbara City College for a pipeline into University of California, Santa Barbara (UCSB). At UCSB, she studied aquatic biology.  A friend told her about a temporary job as an acoustic analyst for a local research firm invested in mitigating the impact of oil companies on the bowhead whale migration through the Beaufort Sea. It is at that job that she received her first acoustic training. On a path towards marine mammals, Yvonne’s cousin alerted her to an internship at the US Navy’s Marine Mammal Program in Pt. Loma, California prepping dolphin food, cleaning, etc. The program itself trained bottlenose dolphins to be swimmer detectors and California sea lions to be sea mine detectors! For example, bottlenose dolphins are used at different naval bases and combat zones to detect anomalous scuba divers. Yvonne was accepted into the internship where a seminar given by a NOAA Fisheries representative piqued her interest about marine mammal research. She found an acoustic analyst internship at the Southwest Fisheries Science Center (one of NOAA’s six science centers). There, she learned about field projects to collect cetacean data at sea for months at a time. In contact with Erin Oleson (HICEAS 2023 Chief Scientist), she embarked on her first mission from Hawaii to Guam in 2010 on the very ship we are currently on! That cruise brought Yvonne and Erik together, but more on that later.

After collecting data that weren’t intended to be used in stock assessments, like a true scientist, Yvonne began to wonder, “How can we use these data?” This curiosity, the advancement of acoustic data collection methods, and the drive to uncover data gaps in the literature converged into a puzzle for Yvonne to solve. I listened in awe as Yvonne described the three main chapters of her doctoral thesis. The first one involved species classification for false killer whales (a priority species for HICEAS). Her research used whistle data to distinguish the whales acoustically at the population level. She found that the classification machine learning model yielded low accuracy rates. Access the paper here:

The next chapter focused on improving localizing methods for deep diving whales using sperm whale acoustic data. I was drawn to the research of this chapter because of the modeling components.  Probabilistic models are used to estimate the location of cetaceans. An ambiguity volume is an example of such a probabilistic indicator.  It is computed from source location estimates that are most accurate to the actual measured locations. As the number of different detections for the same whale at different positions from the ship increases, the ambiguity volume decreases, thereby narrowing down the possible location of the whale. The increased location accuracy is depicted in the figure below through the progression of subfigures a) – f); subfigure a) has fewer detections for the same whale than subfigure f). As we move to subfigure f), we can see that the margins of location estimates are much smaller, giving us a more accurate location estimate for the whale.

Six subfigures showing three dimensionsal plots. the Y axis shows depth, from zero to -3000 m below sea surface. the x and z axes are West-East km and North-South km. caption reads: "Fig 2. Cumulative ambiguity volumes [(a)-(f)] for detections of simulated echolocation clicks from a stationary whale located 1.2 km directly below the transect line (denoted by a white asterisk.) The product of all volumes results in a volume representing all possible location estimates for the whale (f). The color scale represents the ambiguity volume values ranging from 0 (white) as low probability to 1 (black) as high probability. The dotted lines (white or black) indicate the trackline traveling in the direction of the arrow."
Progression of ambiguity volumes as detection data points increase. Photo Credit: Barkley et al. (2022, p. 1122)

The final chapter used the ambiguity volumes for location estimates from the previous chapter and available environmental data from remotely sensed satellite data sets that lined up with those locations to learn about the habitat preferences of sperm whales. Check out the paper:

Erik Norris got his Bachelor’s degree at James Madison University in integrated science and technology. He was initially working with energy production and city planning, dredging company shipping channels up and down the east coast.  He left and traveled for a while. When I asked him to share one of his fondest memories, he mentioned his time in a small fishing village called Nomozaki, Japan. What struck him most about this village was the community-oriented nature of the villagers. At the end of the day, local fishermen took a portion of their catch of the day and shared it with the entire village. The whole community came out to have a big party together, enjoying the catch and the company. The expression of an economy focused on people rather than on profits really speaks to me. I am reminded of a couple of quotes from Braiding Sweetgrass by Robin Kimmerer:

“A gift comes to you through no action of your own…the more something is shared, the greater its value becomes. This is hard to grasp for society is steeped in notions of private property, where others are by definition excluded from sharing.”

(Kimmerer, 2013, p. 23 and 27, respectively)

While Erik worked on a boatyard, he saw people working on the escort vessel for the Hōkūle’a, a wa’a (voyaging canoe) that uses traditional Polynesian wayfinding techniques (no technology, not even a watch) to navigate the ocean. (The Hōkūle’a is currently on its 15th voyage. Follow along here: He approached the crew and volunteered to work on the escort vessel in-port. When the vessels were ready to commence their voyage, Erik had become so familiar with that vessel that they asked him to join, which turned into a 6-month journey. When I inquired about Erik’s attraction to the maritime industry, he quipped that he’s Moana from the Disney movie. For the sake of research, I had the ship’s movie DJ, Octavio De Menas (General Vessel Assistant), put on the movie. From what I gathered, this quote from Moana’s song “How Far I’ll Go” must represent his draw to the ocean:

“See the line where the sky meets the sea, it calls me.”


Through conversations with others on the ship, it seems like the ocean has a similar allure for many. Having been out here for three weeks, I get it. We first saw land last week and it felt like an intrusion. Enough about me, back to Erik!

Later, while talking to his friend’s dad who was a NOAA Corps Officer about his passion for the ocean, he joined the NOAA Corps himself. He met Yvonne as an Ensign on the Sette. He went on to become Lieutenant Junior Grade, and then “retired” from NOAA Corps as a Lieutenant because he was about to rotate from his land billet at Pacific Islands Fisheries Science Center (PIFSC) to another land billet which would have taken him away from Hawaii. He found a civilian job in Hawaii with PIFSC as a vessel operations coordinator in charge of small boats, fabrication and design, field logistics, and HARPs. He attributes his entry into the world of acoustics to Yvonne and HARPs. His current interests include using autonomous vehicles (e.g. sea glider) for a range of oceanographic environment missions.

I asked Yvonne and Erik the same questions separately and we laughed about the different approaches they took in their answers. Erik first noticed Yvonne because she was moving equipment and he was in charge of the equipment on the ship. Yvonne first noticed Erik’s sense of humor juxtaposed with her expectations from someone in the uniformed services. On their time at sea, they shared conversations over meals. Erik was captivated by the way Yvonne talked about her oma’s (grandmother’s) Indo-Dutch cooking. For more on Erik and Yvonne’s food connection, visit the Food Log below. Once in Guam, Yvonne was struck by Erik’s thoughtfulness in preceding her on a hike in the jungle so he could clear off all the spider webs; his distaste for spiders elevated Yvonne’s appreciation for his sacrifice. This is not the only time Erik put Yvonne before himself. Yvonne was really sick in Bali and ended up in a hospital in Malaysia. Erik took leave from work and (according to him) flew to comfort her and accompany her home. According to others, he rescued her. With a ring attached to the keyring on his swimming trunks, under a rainbow and surrounded by sea turtles, Erik proposed to Yvonne while surfing. They have been married since 2016. They currently live in their house, Gertrude, with their dog Sweetpea.

Personal Log with Career Highlight

I started teaching this week. Classes are going well! Shout out to my Abstract Algebra students who never cease to amaze me with their curiosity and courage. Brave Space–IYKYK! I told them our picture below looks like the Brady Bunch, which they did not understand so they have additional homework to watch the opening credits.

a screenshot of a zoom meeting between Gail (on the ship) and 9 students (two sharing a window), creating a 3 x 3 collage
University of La Verne’s Fall 2023 Abstract Algebra class!

Everyday, I try to do one thing I didn’t do the day before. I had two memorable events from this week. The first was during drills. We have weekly fire and abandon ship drills, so this week a few of us practiced the fire hose off the bow. Below you can see Yvonne assisting me as I cycled through the different spraying options.

view from an upper deck over the bow as Gail sprays the firehose over the railing and Yvonne help steady the hose
Gail Tang (Teacher at Sea) and Yvonne Barkley (Cruise Lead-in-Training) test out the fire hose during weekly drills. Photo Credit: NOAA Fisheries/Ernesto Vásquez

The second non-routine thing I enjoyed was helping Joe Roessler (Electronic Technician–ET) install a cable to the outdoor wifi antenna. Our work is the reason I can compose this blog post on the boat deck in my outdoor office, wind whipping my hair to the sounds of the ships’ wake. We worked in the trawl house to solder connector pins to cable ends. Joe’s approach to teaching is familiar. In my classrooms, I provide the tools for students to solve problems with very little instruction. If they need some, I am there to help answer questions. Joe set up the soldering station, provided the leatherman, rubber tape, the connectors, the cable and we went to work. There were many parallels in his methods and mine. We first attempted a connection to the cable, but the pins were not sitting right. Joe evaluated the situation and quickly thought of a different approach to connect the cables. Trying a solution and then pivoting when it doesn’t work out is a skill we try to develop in my classes!

Joe got his amateur radio license at 13! At that time, kids were particularly into shortwave radio because of the US human moon landing. As a young adult he went to the Navy for naval aviation aircraft maintenance. After he was discharged from active duty, Joe continued working in the Naval Reserve and also at private sector companies where he tested robotic equipment. Later, he joined the Civil Service as an aircraft electrician at a naval air rework facility in San Diego. He then transferred to the Army at Dugway Proving Ground in Utah where he returned to the position of an ET. Joe worked with a biological integrated detection system for weapons of mass destruction, in biological warfare defense, with instrumentation and testing equipment and research development. He took a short 4-year detour a businessman and realized it was not what he wanted to do. NOAA had openings in Seattle so he applied and was hired! His first season was on NOAA Ship Rainier in Alaska. Having had enough of the cold weather, he asked for a relocation to Hawaii. He worked on our very ship, the Sette, installing equipment before its very first mission! He met his wife in Samoa and has been working for NOAA 22 years! 

Joe, wearing a hard hat and sunglasses, stands for a photo in the middle of his office, surrounded by electrical boxes and wires. He is wearing a t-shirt that reads: Don't fear the beard. He has a beard.
Joe Roessler (Electronic Technician) in his office! Photo Credit: Gail Tang

Food Log

This week Chef Chris Williams [see previous blog post for more about Chris] made some yummy meals, my favorite pictured below!

When Erik first mentioned Yvonne’s Oma’s Dutch-Indo cooking, I was intrigued because I haven’t had much of either, let alone their fusion. Though Erik insisted that all of Yvonne’s dishes are his favorite dish, after much encouragement he narrowed it down to Oma’s croquette recipe. It’s a fried potato dish with meat inside, best when served with Chinese or Dijon mustard. Yvonne’s favorite dish is her oma’s lemper ayam. The moment she mentioned that it’s sticky rice stuffed with chicken inside I asked if it’s wrapped in any type of leaf. After researching some recipes, I found that it’s traditionally wrapped with banana leaves. 

photo of sticky rice stuffed with chicken wrapped in banana leaves
Lemper. Photo Credit: Wikipedia

I am going to search for lemper when I get home because I have a certain fondness for food wrapped in leaves. I am particularly tickled by the similarities in leaf-wrapped food across different cultures. For example, there’s law mai gai (wrapped in lotus leaf with Chinese origins), zong (wrapped in bamboo leaf also with Chinese origins), dolmas (wrapped in grape leaves with origins in the Levant), tamale (wrapped in corn husk with Aztec origins), and cochinita pibil (wrapped in banana leaves with Mayan origins). This may be a stretch, but I also like onigirazu/handrolls/onigiri (wrapped in seaweed with Japanese origins) and gimbap (wrapped in seaweed with Korean origins).

There is even a Hawaiian version of a leaf-wrapped food called lau lau! It was the second thing I tried when I landed in Honolulu. Usually lau lau consists of pork and salted butterfish first wrapped in kalo (taro) leaves, which are edible, and then in ki (ti) leaves, which are not edible. Finally, traditionally it is steamed in an imu pit (underground pit). It can be found in restaurants and served at luaus. Though it was new to me, it felt so wonderfully familiar.

While searching for the history of lau lau, I found a beautifully written memory that describes lau lau as an embodiment of the beach, the valleys, and the mountains through the ingredients of butterfish, kalo/ki, and pig. Not only does the final product connect these landscapes, but the preparation connects families and friends.

“Early Hawaiians lived in valleys that provided them protection and food. Villages were organized by families and by land divisions, which, in old Hawaii, were divided from the beach to the mountains. That meant that each village and family had complete accessibility to the beach and the mountains and all their offerings. Lau Lau represents these familial land divisions because its ingredients come from the beach, the valleys, and the mountains. The preparation was always my favorite part, because we’d be together for hours sharing stories, laughing, and having fun. Wrapping Lau Laus was where we all became familiar with who we were.”

 Chad Schumacher,

Did you know?

The Big Dipper points to the North Star and the angle of elevation from the horizon to the North star is your latitude! This tip was brought to you by Erik Norris, himself.

Leave a Reply

%d bloggers like this: