MAGNETIC ELASMOBRANCH DETERRENT TECHNOLOGY

Scientific Research Summary & Peer-Reviewed Studies

Prepared for Rock-It Surf

Elasmobranchs — the class of cartilaginous fishes that includes sharks, skates, and rays — possess a unique sensory organ known as the Ampullae of Lorenzini. These gel-filled pores, distributed around the head and snout, allow sharks to detect extremely weak electric fields generated by the muscular contractions of prey animals. The detection range of this organ is effective only at close range (within inches), making it central to the final stage of prey capture.

SharkDefense Technologies LLC — a scientific research and development company based in Oak Ridge, NJ — has found that the magnetic flux per unit area of certain permanent magnets, particularly Neodymium-Iron-Boride (NdFeB) and Barium-Ferrite (BaFe₂O₄) magnets, corresponds closely with the detection range of the Ampullae of Lorenzini. A properly specified permanent magnet is hypothesized to overstimulate this organ, creating an aversive response — making it a selective, non-harmful shark deterrent.

Crucially, the magnetic field generated by these magnets decreases at the inverse cube of the distance from the magnet. At a few meters away, the field is weaker than the Earth’s background magnetic field. Animals that lack the Ampullae of Lorenzini — including bony fish, marine mammals, and sea turtles — do not display aversive behavior, making this technology species-selective and environmentally sound.

SharkDefense Technologies LLC was founded in September 2001 by Eric and Jean Stroud. The company is the world’s leading researcher of chemical, electrochemical, and magnetic shark repellents. Its primary mission is the development of shark bycatch reduction devices for commercial fisheries; its secondary mission includes shark repellents for rescue operations, aquaculture, and alternatives to shark netting. The company is an SAM vendor and is in good standing in the state of New Jersey, USA.

Research is conducted with strict animal welfare protocols, including IACUC compliance in the United States and Bahamian research permits for field testing. The SharkDefense team works closely with the College of the Florida Keys, Seton Hall University, Dr. Samuel Gruber, and the Bimini Biological Field Station.

Key Team Members

DR. ERIC M. STROUD – Managing Partner & Senior Chemist

Dr. Stroud is an entrepreneurial organic chemist, life sciences consultant, and co-founder of SharkDefense. His research interests span chemical alarm signals, magnetic repellents, Schreckstoffs, magnetoreception, and time-release delivery systems. Notable recognition includes:

•       2013 – Seton Hall University Petersheim Award (most outstanding graduate student)

•       2011 – New Jersey Inventor’s Hall of Fame, Graduate Student Award

•       2006 – WWF SmartGear Competition, Grand Prize: “Deterring Sharks with Magnets”

DR. PATRICK H. RICE – Partner, Senior Marine Biologist, Chief Science & Research Officer, College of the Florida Keys

Dr. Rice is a certified scientific diver with NSF/Monbusho fellowships in aquaculture and marine biology. He serves on the advisory board of the Wyland Foundation and has chaired science and technology task forces for the Florida Keys Environmental Coalition. Dr. Rice is a principal investigator on many of the studies cited in this document and has co-authored numerous peer-reviewed publications on magnetic elasmobranch deterrence.

SharkDefense’s work has been supported by competitive grants from NOAA, the National Science Foundation (SBIR Phase 1 and 1B awards), Save Our Seas Foundation, the Great Lakes Fishery Commission, and the Saltonstall-Kennedy Grant Program, among others.

The Ampullae of Lorenzini

The ampullae are small vesicles and pores that form a subcutaneous sensory network around the head of sharks and rays. Each pore is connected to a gel-filled canal lined with sensory cells. When an electric potential difference exists between the canal opening and the sensory cell layer, an action potential is generated and transmitted to the brain via afferent neurons. This system allows detection of fields as weak as 5 nanovolts per centimeter.

Electromagnetic Induction

When a shark swims through the Earth’s magnetic field, electromagnetic induction generates a small electric field around the shark’s body. Minute differences in the Earth’s field at different locations create minute differences in the induced electric field that the shark’s highly sensitive Ampullae of Lorenzini can detect. SharkDefense researchers hypothesize that the shark’s body — particularly the Ampullae of Lorenzini — acts as a conductor moving through either the Earth’s magnetic field or the permanent magnet’s field, registering the induced EMF (electromotive force).

Magnetite-Based Magnetoreception

A second theory involves thousands of small magnetic crystals (magnetite, Fe₂O₃) linked to neurons via glycoproteins. When an ambient magnetic field orients the magnetite, it may block ion channels on the nerve cell membrane, generating action potentials that convey positional information to the brain. Magnetite-based magnetoreception has been documented in yellowfin tuna, rainbow trout, sea turtles, and spiny lobster. The precise mechanism in elasmobranchs remains under investigation, and both electromagnetic induction and magnetite-based pathways remain active areas of research.

The underlying magnetic deterrent technology is protected under:

•       United States Patent No. 9,084,415 — “Devices and methods for repelling elasmobranchs with high-pull-force magnets, including devices and methods for reducing by-catch in commercial fisheries and protecting humans from attacks by elasmobranchs.”

•       Australia Patent No. AU2006223291 (additional international territories pending)

The following studies have been conducted and published by researchers at SharkDefense Technologies LLC, its academic partners, and independent scientific institutions. Studies involving SharkDefense team members Dr. Patrick H. Rice and/or Dr. Eric M. Stroud are noted.

Great White Shark (Carcharodon carcharias)

Evaluating the Shark Deterrent Effects of the Novel Exclusion Barrier in Comparison to the Rigorously Tested Sharksafe Barrier Technology
O’Connell CP, Crews J, King A, Gressle J
Journal of Marine Science and Engineering, 10(5), 634 (2022)

Effects of the Sharksafe barrier on white shark (Carcharodon carcharias) behavior and its implications for future conservation technologies
O’Connell CP, Andreotti S, Rutzen M, Meyër M, Matthee CA, He P
Journal of Experimental Marine Biology and Ecology, 460, 37–46 (2014)

The use of permanent magnets to reduce elasmobranch encounter with a simulated beach net. 2. The great white shark (Carcharodon carcharias)
O’Connell CP, Andreotti S, Rutzen M, Meyer M, He P
Ocean & Coastal Management, 97, 20–28 (2014)

Bull Shark (Carcharhinus leucas)

Evaluating the effects of a SharkSafe Barrier™ shoreline deployment on bull shark (Carcharhinus leucas) behaviour
O’Connell CP, Gressle J, Crews J, King AA, He P
Aquatic Conservation: Marine and Freshwater Ecosystems, 32(1), 55–65 (2022)

The use of permanent magnets to reduce elasmobranch encounter with a simulated beach net. 1. The bull shark (Carcharhinus leucas)
O’Connell CP, Hyun S-Y, Gruber SH, O’Connell TJ, Johnson G, Grudecki K, He P
Ocean & Coastal Management, 97, 12–19 (2014)

Sandbar Shark (Carcharhinus plumbeus)

Sharks can detect changes in the geomagnetic field
Meyer CG, Holland KN, Papastamatiou YP
Journal of the Royal Society Interface, 2(2), 129–130 (2005)

Aversive responses of captive sandbar sharks Carcharhinus plumbeus to strong magnetic fields
Siegenthaler A, Niemantsverdriet PRW, Laterveer M, Heitkönig IMA
Journal of Fish Biology, 89(3), 1505–1515 (2016)

Lemon Shark (Negaprion brevirostris)

Behavioral modification of visually deprived lemon sharks (Negaprion brevirostris) towards magnetic fields
O’Connell CP, Guttridge TL, Gruber SH, Brooks J, Finger JS, He P
Journal of Experimental Marine Biology and Ecology, 453, 131–137 (2014)

Response of juvenile lemon sharks, Negaprion brevirostris, to a magnetic barrier simulating a beach net — Rice & Stroud co-authors
O’Connell CP, Abel DC, Gruber SH, Stroud EM, Rice PH
Ocean & Coastal Management, 54(3), 225–230 (2011)

Great Hammerhead Shark (Sphyrna mokarran)

Effects of barium-ferrite permanent magnets on great hammerhead shark Sphyrna mokarran behavior and implications for future conservation technologies
O’Connell CP, Hyun S-Y, Gruber SH, He P
Endangered Species Research, 26(3), 243–256 (2015)

Southern Stingray (Hypanus americanus) & Nurse Shark (Ginglymostoma cirratum)

Responses of the southern stingray (Dasyatis americana) and the nurse shark (Ginglymostoma cirratum) to permanent magnets — Rice & Stroud co-authors
O’Connell CP, Abel DC, Rice PH, Stroud EM, Simuro NC
Marine and Freshwater Behaviour and Physiology, 43(1), 63–73 (2010)

An Evaluation of the Behavioral Responses of Cownose Rays (Rhinoptera bonasus) to Permanent Magnets and Electropositive Alloys — Stroud & Rice co-authors
Fisher RA, Stroud EM, Herrmann MM, Rice PH
Virginia Institute of Marine Science, Marine Resource Report No. 2006-12 / VSG-06-14 (2006)
Technical report — available through VIMS library (no public URL)

Australian Elasmobranch Species

(Scalloped hammerhead, Australian blacktip shark, Grey reef shark, Milk shark, Bizant river shark)

Do elasmobranch reactions to magnetic fields in water show promise for bycatch mitigation?
Rigg DP, Peverell SC, Hearndon M, Seymour JE
Marine and Freshwater Research, 60(9), 942–948 (2009)

Catshark (Scyliorhinus canicula) & Thornback Skate (Raja clavata)

The effects of neodymium-iron-boron permanent magnets on the behaviour of the small spotted catshark (Scyliorhinus canicula) and the thornback skate (Raja clavata)
Smith LE, O’Connell CP
Ocean & Coastal Management, 97 (2013)

Galapagos Shark (Carcharhinus galapagensis)

Assessment of permanent magnets and electropositive metals to reduce the line-based capture of Galapagos sharks (Carcharhinus galapagensis)
Robbins WD, Peddemors VM, Kennelly SJ
Fisheries Research, 109(1–3), 100–106 (2011)

Spiny Dogfish (Squalus acanthias)

Effects of the SMART™ (Selective Magnetic and Repellent-Treated) hook on spiny dogfish catch in a longline experiment in the Gulf of Maine — Rice & Stroud co-authors
O’Connell CP, He P, Joyce J, Stroud EM, Rice PH
Ocean & Coastal Management, 97, 38–43 (2014)

Commercial & Recreational Fisheries — Bycatch Reduction

Analysis of permanent magnets as elasmobranch bycatch reduction devices in hook-and-line and longline trials — Stroud & Rice co-authors
O’Connell CP, Abel DC, Stroud EM, Rice PH
Fishery Bulletin, 109(4), 394–401 (2011)

Permanent magnets reduce bycatch of benthic sharks in an ocean trap fishery
Richards RJ, Raoult V, Powter DM, Gaston TF
Fisheries Research, 208, 16–21 (2018)

Map-like use of Earth’s magnetic field in sharks
Keller BA, Putman NF, Grubbs RD, Portnoy DS, Murphy TP
Current Biology, 31(13), 2881–2886 (2021)

The emerging field of electrosensory and semiochemical shark repellents: Mechanisms of detection, overview of past studies, and future directions — Stroud co-author
O’Connell CP, Stroud EM, He P
Ocean & Coastal Management, 97 (2014)

A large-scale field analysis examining the effect of magnetically-treated baits and barriers on teleost and elasmobranch behavior
O’Connell CP, He P
Ocean & Coastal Management, 96, 130–137 (2014)

Shark Deterrent and Incidental Capture Workshop (NOAA Technical Memorandum NMFS-PIFSC-16)
Swimmer Y, Wang JH, McNaughton L
NOAA, U.S. Dept. of Commerce (2008)

How Do Sharks and Rays Use Electricity to Find Hidden Prey? (Deep Look — PBS/KQED, video)
Kajiura S, Cassidy J, Singer G
KQED Inc. (2015)

The following studies involve direct product-level testing and field assessments. Dr. Patrick H. Rice of SharkDefense Technologies is a co-author on each study.

Response of Bull Sharks (Carcharhinus leucas) to Magnetic Deterrents — Bimini, Bahamas 2018 — Rice co-author
Garrison NR, Rice PH, Mersereau DG, Nelson T
Independent analysis by Dept. of Marine Science, Coastal Carolina University (2018)

Responses of Australian shark species to fishing tackle deterrents to reduce shark depredation and increase catch rate — Exmouth, Western Australia — Rice co-author
Garrison NR, Nelson T, Mersereau DG, Rice PH
Exmouth, Western Australia field study (2020)

Preliminary results from WA Government (DPIRD) study on the effectiveness of magnetic deterrents to reduce shark depredation in WA fisheries — Rice co-author
WA DPIRD, Garrison NR, Mersereau DG, Nelson T, Rice PH
WA Dept. of Primary Industries and Regional Development (2021)

Discouraging Confrontational Behaviors: Efficacy of Permanent Magnets for Shellfish Grow-Out (Publication Pending)
Jones L, Rojas Corzo A, Ajemian M
Florida Atlantic University (FAU) (2024)

Effectiveness of a Magnetic Shark Deterrent (Thesis, Publication Pending)
Jones L
Charles E. Schmidt College of Science, Florida Atlantic University (2024)