Echo Sounder Buoys: Upcycling Playbook

Annually, tens of thousands of drifting FAD buoys are deployed in the ocean. Let's upgrade them for cutting-edge marine research.

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Worldwide, Drifting Fish Aggregation Devices (𝗗𝗙𝗔𝗗𝘀) are used in fishing operations to attract fish for harvesting. 𝗗𝗙𝗔𝗗𝘀 are regularly left at sea due the cost of their recovery. These 𝗗𝗙𝗔𝗗𝘀 damage sensitive ecological habitats and contribute to ghost fishing and plastic pollution. Low-income coastal communities bear the burden of this practice.

Many 𝗗𝗙𝗔𝗗𝘀 are accompanied by a satellite connected echsounder buoy for detecting fish and locating the 𝗗𝗙𝗔𝗗 at sea. Here, we will convert used 𝗗𝗙𝗔𝗗 buoys into 3 different solar powered buoy installations:

• A reef camera
• A hydrophone
• A water quality monitor

Our goal is to motivate their recovery, decrease their impact, and provide the best open-source platform for marine reasearch.

The life cycle of a DFAD buoy

After the DFAD is launched from the fishing vessel, it will drift freely in the ocean until it either detects fish or runs ashore. In the Indian Ocean, a single purse-seining vessel is allowed to deploy 300 such DFADs a year depending on the region. Photo provided by Alex Hofford under the creative commons license.
The subsurface structure of the DFAD attracts marine life while its accompanying echo sounder buoy can remotely detect the prescence of tuna shoals. Photos provided by Alex Hofford under the creative commons license.
This a top view of the sub-surface structure of a DFAD. Many DFADs have structure that extends 50 meters below the FAD. Photo provided by Alex Hofford under the creative commons license.
While most are never recovered, here we see a crew of conservationists unentangling a DFAD that has grounded on a coral structure. Photo by Blue Safari Seychelles and is not for redistribution without their express consent.
Recovering a grounded DFAD with echo sounder buoy in view. Photo by Blue Safari Seychelles and is not for redistribution without their express consent.
Old, broken, or unused echo sounder buoys near a fishing port.

DFAD Shakedown:

Upcyling DFADs for Conservation & Research

While the commercial fishing industry has access to these mass produced buoys, the conservation and research sector does not have access to this level of remote technology at this price point. While DFADs are certainly an environmental hazard, they also represent untapped resource for coastal communities.

Furthermore, carbon credits and debt-for-nature swaps are creating a need for sustainable, cost-effective   monitoring globally, as more and more nations try to quantify the benefit their local environment contributes to global ecological health.

These three projects can help meet those needs while incentivizing larger scale reclamation and recycling programs.

Solar Powered Hydrophone

Listen here or see the deployment in the video below.

Solar Powered Video Buoy

Check out the video to see the deployment, or download the raw video footage here

The Technical Challenges

As we delve into the challenges of remote marine monitoring, it becomes evident that equipment cost, environmental hazards, post-processing, and delayed feedback are significant barriers to researchers and conservation workers.

Equipment Cost

The high equipment cost in marine monitoring arises from the harsh oceanic environment, limited demand, intensive service requirements, and limited suppliers. However, by managing our deployments personally and sourcing materials from recycled and open-source resources, the resulting systems is substantially below market price while providing modern features left missing on most off the shelf solutions.

Environmental Hazards

The extreme oceanic conditions can pose a design and testing challenge. However, by utilizing recycled materials - specifically, robust FAD buoys initially built for these conditions - we bypass many of these challenges, saving both time and resources.

Post Proceessing

The sheer volume of data generated from marine monitoring systems can be overwhelming. We address this by employing open-source tools like OpenCV and FFmpeg to post-process our data in parallel with data capture. This provides summary statistics and feature extraction that considerably reduce the time spent reviewing extensive video, audio, and numerical data.

Delayed Feedback

Traditional remote marine monitoring typically uses data loggers that require device retrieval which adds significantly operational costs. Additionally, the cumbersome access to results increases response time for both research and shrinks the window for meaningful action. By incorporating cell modems and iridium modems into our system, we provide real-time feedback on the status of the deployments

Want to build one but dont have access to old DFADs?...

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Zip Archive - 62.90 kB - 06/24/2023 at 18:50


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kbirkenmayer wrote 05/24/2023 at 18:56 point

Excellent project. Well thought through with great practical applications. FADs are a huge problem in the SWIO region; glad you're thinking of ways to do something useful with them! Looking forward to more build logs.

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Brett Smith wrote 04/14/2023 at 13:03 point

Yes I will take photos again next time I am the buoy graveyard.

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Alexey Vazhnov wrote 04/17/2023 at 12:19 point

It also would be nice to have some photos of disassembled devices on Wikimedia Commons.

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Alexey Vazhnov wrote 04/13/2023 at 09:22 point

I found there is no "Fish aggregating device" images at

Could you please upload some, under an opensource license? I can add category and include images into the main article

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Brett Smith wrote 06/24/2023 at 19:32 point

I added some photos, however I am not an active wikipedia contributor. Please let me know if you want me to send you something personally.

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Alexey Vazhnov wrote 06/24/2023 at 20:37 point

Amazing!!! Thank you very much! Now we have a dedicated category:

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