Sound “Waves”: How Acoustic Deterrent Devices Increase Sound in the Ocean

Featured Scientist: Charlotte Findlay (she/her/hers), PhD (2021). Currently a Postdoctoral Research Fellow in the Department of Biology at Aarhus University in Denmark.

Dr. Findlay is sitting on an island staring out to sea. She is looking for harbor porpoises as part of a scientific survey during a rainstorm. She is soaking wet from being rained on, but a rainbow has formed in the background as the sun has finally started to come out.
Dr. Findlay Watching for harbor porpoises as the rain finally stopped at our survey site on the Isle of Mull, Scotland.

Hometown: I have lived in a lot of different places, but I would say my hometown is Oban, Scotland (United Kingdom).

My Research: I study different types of human-made noises in the ocean. I study how these sounds affect the behavior and physiology of marine animals.

Research Goals: I hope to continue to understand and assess the impacts of human-made underwater noises on marine ecosystems. My goal is to help provide solutions that can reduce the impacts on marine wildlife.

Career Goals: I hope to continue to be able to do science which helps to protect the environment.

Hobbies: I enjoy wild swimming, surfing, sea kayaking, snowboarding, and spending time with my partner and two cats!

Favorite Thing About Science: I like that I am constantly learning and that every day brings a new challenge or activity so it’s never boring.

Scientist Upbringing: I’ve always been fascinated by the natural world. When I was younger, I would sit for hours watching Animal Planet or reading books about different animals to learn as much as I possibly could. I also loved swimming and being in the ocean, so when I realized I could combine my love of animals and the ocean I think marine biologist became an obvious choice! I decided to go to the University in Glasgow in Scotland to study Marine and Freshwater Biology and I never looked back.

My Team: I am the joint first author on this publication along with Hayden Ripple. This paper is formed in part from my master’s degree thesis at the University of St Andrews and Scottish Association for Marine Science. My advisors Dr. Denise Risch, Dr. Steven Benjamins and Professor Ben Wilson helped me come up with the project, Hayden Ripple assisted with data analysis and mapping, other co-authors were involved in collecting the line-transect data as part of surveys conducted by the Hebridean Whale and Dolphin Trust (HWDT), and everyone helped in writing and editing the publication.

Field of Study: Aquatic Ecology

What is Aquatic Ecology? Ecology is the study of how organisms interact with their environment. Aquatic ecology focuses on aquatic species.

Organism of Study: I study marine mammals and have so far focused on harbour porpoises (Phocoena phocoena) and harbor seals (Phoca vitulina).

A picture of a harbour porpoise with its face sticking out of the water.
Harbour porpoise
A picture of a harbor seal with only its face above the water.
Harbor seal

Check Out My Original Paper: “Mapping widespread and increasing underwater noise pollution from acoustic deterrent devices”

A QR code that links to the original publication.
QR code to the original publication

Citation: Findlay, C.R., Ripple, H., Coomber, F., Froud, K., Harries, O., Van Geel, N., . . . Wilson, B. (2018). Mapping widespread and increasing underwater noise pollution from acoustic deterrent devices. Marine Pollution Bulletin, 135, 1042-1050.

Article written by Milan (He/Him, Sophomore, Pre-Medicine), Luis Martinez (Senior, Biology Major), Jesly (She/Her, Junior, Biology major), Adriana Botero (She/Her, Senior, Biology Major), and Audrey (She/Her, Senior, Biology major), undergraduate students at Texas Tech University during the Spring 2023 semester.

Research At A Glance: An Acoustic Deterrent Device (ADD) is a loud underwater device that can be heard by aquatic animals and that is used to deter them from approaching an area. ADDs are used by aquaculture farmers to prevent carnivorous animals, like seals, from damaging fish farming sites. Fish farming has become popular in recent years in Scotland and has led to an increase in the use of ADDs. Despite the wide use of ADDs, there has not been a lot of research about how ADDs contribute to noise pollution in marine ecosystems. In this study, the authors investigated the presence and distribution of ADDs across the Scotland coast over a 10-year period. The goal of the study was to determine how ADDs were distributed and how often ADDs were added or removed from the west coast of Scotland over time. The authors worked with the Hebridean Whale and Dolphin Trust (HWDT), an organization that seeks to protect whales, dolphins, and porpoises, to sail along the west coast of Scotland. The authors collected data for 10 years between the months of March and October on a boat named the RV Silurian.

During the sampling period, trained volunteers would perform a ‘listening event’ every 15 minutes where they would listen to the sound of the ocean for 1 minute through a hydrophone. A hydrophone is a device that is placed underwater to detect and record sounds from all directions. The volunteers would rate the intensity of the sound from 0 (quiet) to 5 (loud) and determine the source of the sound. For example, the sound might come from an animal, a ship, or an ADD. To determine if ADDs were the cause of noise pollution, the researchers used spectrograms. Spectrograms are used to measure the strength of a sound, or how loud it is. The authors found that the presence and distribution of ADDs across Scotland had increased over the 10 year period: 1,371 of the 19,601 listening events detected ADDs. The authors detected three types of ADDs and all of them contributed to noise pollution. This research is important as it helps describe ADDs and their influence on noise pollution in aquatic environments. With the increase of fish farming in Scotland, the dependence on ADDs has increased as a non-lethal way to deter animals. This could negatively impact aquatic species around the coastal areas because it forces them to move into unfavorable habitats, creates barriers for migration or movement, and damages their hearing. The scientists argue that there should be more specific ADD reporting by fish farms, such as the type of ADD, how many are present, and their locations.

Highlights: One of the most important parts of this paper was the listening events with trained volunteers. To listen to the ocean, a hydrophone was placed 20 meters underwater. ADDs can be heard by humans because they transmit sound frequency ranges of 2 to 40 kHz, and humans can hear from 20 Hz to 20 kHz. The volunteers were able to listen to the hydrophone and score the sound intensity from 0 (not heard or quiet) to 5 (very loud). The location of these sounds were measured using Logger software. Logger software is a program that automatically collects GPS data and stores it in a database. The Logger software allowed the researchers to pinpoint the location of the ADDs in relation to the fish farms.

After finding where the ADDs were located, the authors wanted to determine if they were detecting more ADDs over time. To answer this question, they used a beta regression model. A beta regression model is a statistical technique that can be used to analyze the relationship between one dependent variable and one independent variable. In this case, the dependent variable was the amount of ADDs that were detected and the independent variable was time in years. The authors found that the presence of ADDs increased over time (Figure 1).

A data figure that shows the percentage of ADDs detected by listening event over time. In 2006, it started nears zero, but by 2016 it's closer to ten.
Figure 1. The relationship between the amount of ADDs detected over time. The data on the y-axis shows the percentage of ADDs that were detected relative to the total number of listening events. The x-axis shows the year that the data were collected. Figure adapted from Findlay et al. 2015.

What The Science Looks Like: Volunteers were a very important part of this research. During a trip on the coast of Scotland, these trained volunteers were on board the vessel RV Silurian. They had the hydrophone attached to the boat, dangling 20m below the water level. Every 15 minutes of sailing, the boat would slow to a stop. During the 1 minute listening event, the sound waves from an ADD, ambient underwater noise, or animals, are picked up by the hydrophone. The volunteers would listen to the sounds, rate the noise level, determine what was making the sound, then continue to sail for another 15 minutes. This was the cycle used to gather data on underwater noise.

A graphic that shows the listening events. On the left, there is a boat with a hydrophone in the water detecting an ADD. There is arrow that points to another boat on the right labeled "15 Minutes of Sailing". On the right, there is a boat with a hydrophone in the water detecting a seal.
In this diagram, the first listening event shows the hydrophone detecting ADD sound waves. At the second stop, the hydrophone detects the sounds of a seal. At each stop, different sounds can be picked up by the hydrophone and rated by the volunteers. Icons from the Noun Project.

The Big Picture: There are many sources of noise pollution in the ocean, such as commercial shipping, military sonar, and oil and gas exploration. Noise pollution can be beneficial to science discovery. For example, different sound waves can be used to determine how deep the water is and get information about the structure of the ocean floor. Aquaculture is a part of the fishing industry and is expanding across the world. Fishermen and ocean predators both rely on fish and this can lead to conflict. One way to deter the marine mammals from approaching fish farming areas is through devices, like ADDs. However, the method of using loud and unpleasant sounds to scare away animals disrupts the balance of marine ecosystems. Whales, seals, and many other sea organisms experience hearing loss due to the high intensity noise that ADDs produce. In addition, animals close to ADDs are forced to migrate to other areas that may not be as suitable, which can lead to reduced survival and reproduction. Aquaculture plays a large role in how we gather food. It is important to find ways to protect our fish farms from marine predators, while also protecting ocean life. This study locates ADDs, measures the intensity of the sound waves that they produce, and records how frequently they can be found on the Coast of Scotland. Research like this can help us understand how noise pollution might affect marine animals and help us find ways to reduce harm in marine environments.

Decoding the Language:

Acoustic Deterrent Device (ADD): An ADD is an underwater device that can make sounds that deter certain species.

Aquaculture: Aquaculture refers to the breeding of aquatic organisms, like fish, in a stable environment so that people can eat them in the future.

Beta regression model: A beta regression model is a statistical test that looks at the relationship between one dependent variable and one independent variable. People usually choose to use the this model when their data is in the form of a fraction or a percentage. In this study the authors used this approach to determine if there were more ADDs over time.

Hebridean Whale and Dolphin Trust (HWDT): The HWDT is a charity that believes in conserving whales, dolphins, and porpoises in western Scotland. Their research has helped people understand more about the species that visit seasonally or are residents in the islands off the northwest coast of Scotland. The HWDT is using their research to protect marine life. HWDT does education programs highlight the importance of marine environments. These programs reach over 20,000 people each year.

Hydrophone: A hydrophone is a device that is used underwater to detect and record ocean sounds from all directions.

Logger software: Logger software records and tracks information over time. The software automatically collects GPA data and stores it in a database. For this specific study, the authors used a type of logger software developed by the International Fund for Animals.

Noise pollution: Noise pollution refers to sounds that affect the health and well-being of humans and other organisms. Sound is measured in decibels.

Spectrogram: A spectrogram is a visual representation of sound. It shows the strength of a signal, or how “loud” it is, at different time points.

Learn More:

A report from the University of Saint Andrews Mammal Research Unit on the negative effects of seals on fish farms.

An article from The Consortium for Wildlife Bycatch Reduction that describes ADDs and how they function. The article also provides real-life examples about ADD use across the world and how they affect marine organisms.

A YouTube video produced by The University of Maine that describes aquaculture and why it is important.

A YouTube video produced by the Sustainable Aquaculture Innovation Centre that describes aquaculture in Scotland. It details the marine organisms that are most farmed as well as the methods of farming/aquaculture that are primarily used in Scotland. It also explains the importance of aquaculture in providing jobs and helping with the economy in Scotland.

An article produced by a scuba diving company that shares fun facts about seals.

Synopsis edited by Rosario Marroquín-Flores, PhD 2022, Texas Tech University

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Meet The Authors

Luis Martinez is a current Senior at Texas Tech University majoring in Biology with a minor in Psychology. Coming from a military-oriented family, Luis lived much of his life in Yokosuka, Japan, where he got to experience and travel much of the Far East. Upon entering Freshman year, Luis moved back to the U.S. and resided in Virginia Beach, VA, until graduation in 2019. Luis enjoys his time doing strength training and swimming as he hopes to aspire to commission as an Officer in the United States Navy after graduation in August 2023.

Adriana Botero is a current undergraduate Senior at Texas Tech University (TTU) majoring in Biology with a minor in Chemistry. She was born and raised in the Austin, Texas area. In her free time, she likes to draw and volunteer. Her artwork has been on display in the TTU Office of International Affairs for the “Structures of the World Exhibit” and other museums. Adriana hopes to work in a field where she can combine creativity, science, and communication. She is set to graduate in August, 2023.

Jesly Quintero is currently a junior at Texas Tech University majoring in Biology with a double minor in Health Professions and Chemistry. She was born and raised in Dallas Texas. She is actively involved in leadership with the American Chemical Society organization at Texas Tech University and aspires to become a travel nurse.

Audrey Batista is currently a Senior at Texas Tech University majoring in Biology with a minor in Chemistry. She is a female Latina that was born and raised in El Paso, TX. In her free time, she is shadowing and interning at Covenant Hospital with Interventional Radiologists. She also enjoys getting involved with fitness platforms influencing others to better their lifestyles in health.

Milan Maheshwari is currently a sophomore at Texas Tech University on the pre-medicine track. In his free time, he enjoys making music using the software program known as FL studio. He also enjoys practicing mindfulness and loves being outdoors.

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