Smart Mobile FAD (eFAD) Analysis — Anguilla Seastead Project

Notes on the 1:4 scale seastead concept used as a solar-powered, relocatable Fish Aggregating Device for Anguilla artisanal fishing support.

1. Has anyone built solar/thruster-relocatable FADs?

There are research prototypes and a few startups moving in this direction, but truly commercialized "mobile eFADs" are still rare:

Satlink, Marine Instruments, Zunibal — make instrumented (echo-sounder + GPS + satellite) drifting FADs widely used by tuna purse-seine fleets. These drift; they do not self-propel.
Saildrone, Open Ocean Robotics, AutoNaut — long-range solar/wind USVs, used mostly for surveying. Not marketed as FADs but technically capable.
Academic work (e.g., IFREMER, IRD, SPC in the Pacific) has explored "smart drifting FADs" with two-way comms, but propelled FADs are mostly conceptual.

So your idea — a solar USV that also aggregates fish and can be relocated — appears to be a genuinely novel niche, especially at artisanal scale.

2. Force needed to tow an artisanal FAD at 0.25 MPH

A typical artisanal FAD has a surface buoy, ~20–30 m of hanging palm fronds / netting / rope streamers, and the long anchor line. Detached from the anchor and just towing the aggregating "tail":

0.25 MPH ≈ 0.11 m/s — very slow, drag scales with v².
Wetted/projected area of streamers ≈ 5–10 m² with high drag coefficient (Cd ≈ 1.0–1.5 for trailing fronds).
Drag F = ½ ρ Cd A v² ≈ 0.5 × 1025 × 1.2 × 7 × 0.11² ≈ ~50 N ≈ 11 lbf

Practical estimate including rope and surface buoy drag: 15–25 lbf to tow a normal artisanal FAD at 0.25 MPH.

A streamlined "easy-tow FAD" (bundled fronds in a fairing, retractable streamers, smaller cross-section while underway) could plausibly cut this to 3–8 lbf at 0.25 MPH. That's well within the capability of a few hundred watts of solar.

3. Can 0.25 MPH + known eddies give useful control?

Yes — barely, but yes. Caribbean mesoscale eddies typically move at 0.1–0.4 m/s (0.2–0.9 MPH). At 0.25 MPH your USV moves slower than many currents, so you cannot fight a strong current head-on, but:

You can bias your drift — pick which eddy/streamline to ride.
Over a week, 0.25 MPH × 168 h ≈ 42 nautical miles of "steering authority" — enough to nudge your position by tens of miles.
Combined with HYCOM/Copernicus current forecasts, getting within 40 miles of Anguilla weekly is feasible most of the time, but expect occasional weeks where strong eddies push you off-plan. Plan for a 4-knot "sprint" mode for recovery.

4. Is the 1:4 seastead alone a useful FAD?

Quite possibly yes. A 1:4 model still has:

Triangle footprint ~17.5 ft on the long sides — significant shade.
3 vertical foils + 3 stabilizer "airplanes" submerged — lots of structure, edges, and shadow lines.

Fish (dolphinfish/mahi, small tuna, jacks, triggerfish) are attracted to shade, structure, and biofouling. Within 2–4 weeks of deployment biofouling alone will host small baitfish, and pelagics will follow. You likely do not need additional streamers for the model to function as a FAD, though adding ~5 m of frond bundles will accelerate aggregation substantially.

5. Will 6× Blue Robotics M200 thrusters at 0.25 MPH scare fish?

No. M200s at low RPM are quiet and gentle. At 0.25 MPH each thruster is drawing only a few watts — barely turning. Fish associate with slow-moving structures all the time (whale sharks, sargassum mats, drifting logs). The acoustic signature at low RPM is far below what spooks pelagics. 0.25 MPH should retain aggregated fish.

A retractable drogue / parachute sea anchor is an excellent idea — lets you sit nearly motionless without thruster noise, and dramatically reduces wind drift.

6. Underwater lights at night

Strongly recommended. Green LEDs at 5–20 W are standard for attracting baitfish (squid, sardines), which in turn pull in predators. With surplus solar by day stored in batteries, running 50–100 W of underwater light all night is easy and proven to accelerate aggregation.

7. How fast do fish aggregate? Do they stay if you move?

Typical timelines around new artisanal FADs:

Hours to 1 day: small baitfish, triggerfish
1–2 weeks: jacks, small tuna, mahi begin visiting
3–8 weeks: mature aggregation, larger pelagics

If you then move at 0.25 MPH, most resident fish will follow — this is well documented. Faster than ~1.5 knots and pelagics often disengage. So your 0.25 MPH "lead-them-home" speed is in the sweet spot.

8. Will fish follow into shallow (<100 ft) water?

Pelagic species (mahi, tuna, wahoo) generally stop following once depth drops below ~150–200 m (500–650 ft). They tend to peel off at the shelf break. Anguilla's NE drop-off is therefore an ideal "delivery zone": bring the FAD to just outside the drop-off (5–6 miles NE) and let the fishermen come to that staging point. Don't expect to drag mahi into 100 ft water — but you don't need to. Staging at the shelf break ~12 miles from Island Harbour is realistic and useful.

9. Legal protections for FAD owners in Anguilla

Anguilla, like most Eastern Caribbean states, does not grant exclusive fishing rights around a privately owned FAD by default. The Fisheries Protection Act and regulations administered by the Department of Fisheries & Marine Resources require permits to deploy FADs, and registered FADs may have customary respect, but legally any licensed fisherman can fish nearby. Practical protection comes from:

Information asymmetry (only you know via Starlink when fish are there)
"Sprint mode" to scatter fish if a non-customer approaches
Community agreement with Island Harbour cooperatives

Worth formalizing an MOU with the Department of Fisheries before deployment.

10. Artisanal FAD rules of thumb

11. Acoustic fish detection

Parameter	Typical Value
Spacing between FADs	5–10 nautical miles (closer reduces per-FAD aggregation)
Total mass (excl. main anchor line)	50–150 lbs of rope, fronds, floats
Biomass around mature FAD	500 – 5,000 lbs (highly variable; mahi school dominates)
Catch per visit (small boat, hand line/troll)	30 – 200 lbs; 80 lbs is a fair average
Revisit frequency	Every 2–5 days when productive
Productive lifespan	6–18 months (until lost/storm-damaged)

Some species (groupers, drums, croakers, snappers) are very vocal — passive acoustic monitoring (PAM) can identify them and even estimate abundance. Pelagic schoolers (tuna, mahi) make less species-specific noise but a school still generates measurable swim/feeding sounds. Combined with a low-cost down-looking echo-sounder (e.g., Deeper, or a Cerulean Sonar unit), you can get a strong "fish-here-now" signal. Hydrophone + ML classifier is an active research area and very feasible at hobbyist scale.

12. Overall assessment

The concept is genuinely promising for these reasons:

It solves a real problem (deep water makes anchored FADs expensive).
It pairs cleanly with your seastead R&D — testing the platform while generating revenue.
The information-asymmetry business model (sell tip-offs, not fish) avoids fisheries-licensing complications.
Anguilla is small, sheltered enough, with a real artisanal fleet that already understands FAD fishing.

Main risks: storms (hurricane season), theft/vandalism of FADs, regulatory friction, and the biological reality that pelagic aggregations are patchy. Start with 2 units and iterate.

13. Interactive Economics Calculator

Cost of USV ($):
Cost of one dumb FAD ($):
Dumb FADs per USV:
Months till loss of USV:
Months till loss of dumb FADs:
Days between FAD visits:
Lbs fish caught per FAD visit:
Price of fish ($/lb):
% of fish sales to USV operator:

Weekly gross revenue (all FADs): —

Weekly revenue to operator: —

Weekly equipment depreciation: —

Weekly profit / loss: —

Note: This calculator covers depreciation only. Add maintenance, comms (Starlink ~$150/mo), insurance, and labor for a fuller picture.

14. Suggested next steps

Document generated for the Anguilla Seastead / eFAD project. Estimates are order-of-magnitude; refine with field measurements.

Smart Mobile FAD (eFAD) — Analysis & Calculator