Short overall opinion
The idea is technically plausible and worth testing, especially as a solar USV + drifting/electronic FAD. The most promising near-term product is probably not “a self-propelled FAD that always overpowers the ocean,” but rather:
- a robust solar USV that can navigate, monitor fish, report by Starlink/cellular/satellite, and survive offshore;
- a low-drag FAD package it can tow slowly or reposition occasionally;
- route planning that uses currents/eddies rather than fighting them continuously;
- a service model selling fish-presence information and rendezvous scheduling to local fishers.
At 0.25 mph / 0.22 knots / 0.112 m/s, tow power for a well-designed artisanal FAD can be very low. The hard parts are not average propulsion power; they are reliability, fouling, storms, current uncertainty, legal approval, avoiding conflicts with fishers, and demonstrating that fish aggregation is commercially useful.
Have self-relocating solar/thruster FADs been made before?
There is extensive prior art for electronic FADs: satellite GPS buoys, echo sounder buoys, biomass estimates, temperature sensors, and fleet-management systems. Commercial examples include tuna purse-seine dFAD buoys from companies such as Satlink, Marine Instruments, Zunibal, and others.
There are also many autonomous ocean vehicles, including Saildrone, Liquid Robotics Wave Glider, ASVs/USVs, and solar boats. However, a small solar-powered FAD that actively relocates itself using thrusters appears to be uncommon as a commercial product. The closest existing categories are:
- Drifting dFADs with electronics — GPS/sonar, but generally not self-propelled.
- Moored artisanal FADs — common in Caribbean/island fisheries, but not mobile.
- Oceanographic drifters/gliders/USVs — mobile platforms, but not usually designed as FADs.
- Research concepts combining FADs with telemetry or autonomous vehicles.
So the concept is not “from nowhere,” but the specific combination of solar USV + towable artisanal FAD + fish sonar + scheduled local-fisher access may be novel enough to justify field experiments.
Estimated towing force at 0.25 mph
At 0.25 mph, hydrodynamic drag is small because drag scales with velocity squared. The basic estimate is:
Force = 0.5 × seawater density × Cd × area × velocity²
At 0.112 m/s, the dynamic pressure is only about 6.4 N/m², or about 1.44 lbf per m² of CdA.
| FAD type | Estimated tow force at 0.25 mph | Comments |
|---|---|---|
| Very clean low-drag FAD: streamlined float, vertical line, small attractor strips | 1–5 lbf | Likely achievable if designed specifically for towing. |
| Good “easy tow” artisanal FAD with rope streamers, modest palm/frond/sargassum-like attractor | 3–12 lbf | Probably the best target range for your USV. |
| Typical hand-deployed artisanal FAD, not optimized for towing | 5–25 lbf | Very dependent on rope diameter, knots, floats, netting, and biofouling. |
| Bulky net/brush/palm-frond FAD with lots of exposed area | 20–50+ lbf | Still possible at 0.25 mph, but power and steering margin suffer. |
If speed doubles to 0.5 mph, tow force becomes roughly 4× higher. If speed increases to 1 mph, force becomes roughly 16× higher. This is why slow relocation is practical but fast towing of a large FAD is not.
The best practical test is simple: put a waterproof load cell or spring scale in the towline and tow candidate FAD packages at 0.1, 0.25, 0.5, and 1.0 mph. This will give better data than any spreadsheet.
Can 0.25 mph control an unanchored FAD?
Sometimes, but not reliably by itself. 0.25 mph is only about 0.22 knots. Offshore currents around islands and eddies can easily be 0.2–1.0+ knots, and windage on the USV/FAD can also matter.
A 0.25 mph through-water capability is useful for:
- fine control inside favorable eddies;
- biasing drift direction over days;
- keeping a FAD in a useful current lane;
- slowly bringing it toward a planned rendezvous if currents help.
But it is probably not enough for guaranteed station-keeping or guaranteed weekly return to within 40 miles of Anguilla. To make the system commercially dependable, design for:
- 0.5–1.5 knots emergency/relocation capability for the bare USV or low-drag mode;
- a retractable drogue/sea anchor for quiet drifting;
- current forecasts and route optimization;
- a “give up and return” mode before the vehicle gets too far away.
Will the 1:4 scale seastead itself act as a FAD?
Yes, likely. A solar-covered floating structure with shade, three submerged legs, stabilizers, thruster pods, and underwater shadows should attract at least some baitfish, triggerfish, small jacks, mahi-mahi, and other species over time.
However, a bare USV may be a weaker FAD than a purpose-built FAD because many FADs work partly by providing:
- vertical structure extending several meters down;
- hanging ropes or fronds;
- biofouling habitat;
- shade plus shelter for small organisms.
A good compromise is to test three modes:
- Bare USV only — establishes baseline attraction.
- USV with low-drag vertical attractor — e.g., rope ladder/streamer line, biodegradable strips, small subsurface float.
- USV towing a dumb FAD — lets you compare fish aggregation versus towing penalty.
Thrusters, noise, and fish attraction while moving
Six Blue Robotics M200/T200-class thrusters should have much more static thrust than required for a low-speed FAD tow. At 0.25 mph, the hydraulic power for even a 10 lbf tow load is only about:
10 lbf × 0.112 m/s ≈ 5 watts hydraulic
With propulsion inefficiencies, electronics, steering losses, and sea state, actual electrical power may be tens of watts, still very manageable with solar.
Fish can follow drifting FADs moving with currents, and 0.25 mph is slow enough that movement itself should not prevent aggregation. Thruster noise may matter for some species, so test these operating modes:
- continuous very-low-RPM propulsion;
- intermittent “pulse and drift” propulsion;
- quiet drifting with a drogue deployed;
- night-light mode with no thrusters except station corrections.
Underwater lights at night
Underwater lights can attract plankton, squid, baitfish, and sometimes predators. They are worth testing. Use controllable intensity and color rather than always-on maximum brightness.
Suggested test setup:
- green/blue underwater LEDs, dimmable;
- automatic shutoff when battery state-of-charge is low;
- camera/sonar logging before, during, and after lights;
- alternating light/no-light nights to measure effect.
Check local fisheries rules first. In some places, lights used to aggregate fish may be regulated.
How long until fish aggregate?
| Time after deployment | Likely observations |
|---|---|
| Hours | Curious small fish, bait, triggerfish/filefish-type species, if present nearby. |
| 1–3 days | More reliable small-fish association; possible mahi-mahi, jacks, small tuna depending on area. |
| 3–14 days | Better chance of a useful pelagic aggregation. |
| 2+ weeks | Often stronger FAD effect, especially if biofouling and small prey community develop. |
If the USV/FAD already has fish and then begins moving slowly, many associated fish may remain with it, especially if the motion is comparable to normal drift. If it accelerates hard, makes noise, or enters unsuitable water, fish may leave.
Will fish follow a FAD into shallow water?
Some fish may follow for a while, but oceanic pelagics generally prefer offshore/deep-water conditions, edges, drop-offs, current lines, and prey concentrations. If the FAD moves onto shallow shelf water, especially less than about 100 feet, many tuna/mahi-type fish may peel off.
Your better strategy is probably not to bring the FAD all the way to shallow water. Instead:
- bring it to a predictable offshore rendezvous area;
- use the NE Anguilla drop-off if it is accessible and legal;
- target locations 10–20 miles from harbor rather than 2–5 miles if deep-water species are the goal;
- collect data on depth, temperature, currents, sonar biomass, and catch results.
Legal and community issues in Anguilla
You should treat this as a fisheries-management project, not just a robotics project. Work directly with Anguilla Fisheries, maritime authorities, and local fishers before deployment.
I cannot give Anguilla-specific legal advice, but in many jurisdictions:
- owning a FAD does not automatically give exclusive fishing rights around it;
- the device itself may be private property, but fish in public waters may remain a common resource;
- deployment may require permits, markings, lights, AIS or other tracking, and removal obligations;
- lost FADs may be treated as marine debris or navigation hazards;
- using movement to deny access to other fishers could create conflict or regulatory concern.
A cooperative model may work better: approved smart FADs, public safety tracking, and paid access to fish-presence data or scheduled fishing windows for licensed local fishers.
Rules of thumb for artisanal FAD spacing, mass, biomass, and catch
Values vary enormously by island, depth, current, species, season, and fishing method. The following are rough planning ranges, not guarantees.
| Question | Rule-of-thumb range | Notes |
|---|---|---|
| Spacing between artisanal FADs | 5–20 nautical miles | Closer spacing may work near productive features, but too many FADs can dilute fish and increase conflicts. |
| Mass of ropes/floats/attractors, excluding deep mooring line | 50–300 lb | Your estimate of about 100 lb for a hand-handled local FAD is plausible. |
| Total moored FAD system mass including long anchor/mooring | hundreds to thousands of lb | Deep moorings are the heavy/expensive part; your mobile concept avoids this. |
| Biomass associated with an artisanal FAD | 50 kg to several tonnes | Can be near zero some days; can be very high when tuna/mahi schools associate. |
| Catch per local fishing visit | 20–300 lb | Your default of 80 lb/visit is reasonable for an economics sensitivity case. |
| Revisit interval | 2–7 days | Depends on distance, weather, catch rates, and whether fishers rotate among FADs. |
Passive acoustics: can hydrophones count fish?
Hydrophones are useful, but they are unlikely to replace sonar for biomass estimation.
- Some fish vocalize strongly, especially reef fish, drums, groupers, croakers, etc.
- Many pelagic target species such as tuna are not easy to count acoustically from passive sound alone.
- Hydrophones are excellent for detecting boats, dolphins, rain, snapping shrimp, some spawning choruses, and general soundscape.
- Fish biomass around a FAD is better estimated with an echosounder/sonar, possibly combined with cameras and lights.
Best sensor package: GPS/AIS, weather, cameras above water, underwater camera, downward/side-looking fish sonar, hydrophone for context, and periodic manual validation by fishing results.
Recommended field-test plan
Phase 1: Platform survival and propulsion
- Run nearshore endurance tests: 24 hr, 72 hr, 1 week.
- Measure power budget, solar production, battery state, Starlink draw, fouling, leaks, corrosion.
- Measure bollard pull and towing force with a load cell.
- Test autonomous return-to-home and loss-of-comms behavior.
Phase 2: FAD attraction baseline
- Deploy bare USV at a fixed drift/loiter site for several days.
- Record sonar/camera/light data on a schedule.
- Compare day/night, lights/no lights, thrusters/no thrusters.
Phase 3: Low-drag FAD comparison
- Test 2–4 FAD appendage designs.
- Record tow force, fish aggregation, tangling, fouling, and retrieval difficulty.
- Choose the design with best fish-per-pound-of-drag, not maximum structure.
Phase 4: Fisher cooperative trial
- Work with a few trusted local fishers.
- Share location and fish-presence data.
- Record actual catch, travel distance saved, fuel saved, and revenue.
- Use results to refine the business model.
Interactive weekly economics calculator
This is a simple depreciation-and-revenue calculator. It does not include maintenance, Starlink subscription, insurance, permits, shore operations, fisher fuel costs, repairs, batteries, storms, theft, or downtime.
Results
| FAD visits per week | |
|---|---|
| Total fish catch value per week | |
| USV operator revenue per week | |
| USV loss/depreciation cost per week | |
| Dumb FAD loss/depreciation cost per week | |
| Total depreciation cost per week | |
| Estimated weekly profit/loss |
Formula: weekly operator revenue = FADs × 7 / days between visits × lbs/visit × price/lb × operator share. Weekly depreciation = USV cost / life weeks + total FAD cost / FAD life weeks. Uses 4.345 weeks/month.
Important design suggestions
- Use biodegradable FAD materials where possible to reduce ghost-gear risk.
- Avoid netting that can entangle turtles, sharks, rays, or marine mammals.
- Make everything retrievable: drogue, attractor line, towline, and emergency marker.
- Use AIS carefully: small unmanned vehicles may need appropriate markings/lights and may not always be allowed to transmit normal AIS unless approved.
- Build a kill/recovery mode: if batteries fall too low, retract appendages, reduce drag, and head home.
- Expect fouling: biofouling increases drag and can jam thrusters and moving parts.
- Collect real data: towline force, current, wind, fish sonar, camera images, catch results, and maintenance hours.
Bottom line
A smart mobile FAD based on your 1:4 scale seastead model is a credible experiment. At 0.25 mph, towing a purpose-built low-drag artisanal FAD may require only a few pounds of force, so the propulsion and solar budget are favorable. The business case depends less on raw thrust and more on fish behavior, reliable offshore operation, local permissions, fisher cooperation, and proof that the system increases catch or reduces search time.
The best first milestone is a measured demonstration: 30 days offshore, reliable tracking, controlled FAD appendage tests, sonar-confirmed fish aggregation, and at least a few validated fishing trips with local fishers.