Magnetic, E+ metals, electrical deterrents

The use of permanent magnets, electropositive rare earth metals (EPREM) and other electrical measures has been trialled as a means of deterring sharks from approaching baited hooks. Permanent magnets are made from magnetised material and create their own persistent magnetic field. EPREM react with seawater to create such fields.
 
Elasmobranch fishes (sharks, skates and rays) are able to detect the Earth's geomagnetic field using their ampullae of Lorenzini. Electropositive metals or magnets appear to generate an aversion response in some species of sharks through an overstimulation of their ampullae, which are sensitive electroreceptors. Research has shown that different shark species respond differently to magnets and metals. Tuna and swordfish do not have electroreceptors and are not repelled by magnets or EPREM.
 
Recent studies have evaluated the effects of incorporating magnets and rare earth metals into longline and rod and reel fishing gear. In some instances, magnets and/or metals have been incorporated directly into fishing hooks, while at other times they have been added to the line (e.g. as metal discs) at varying distances from the hook. Magnets and EPREM have been trialled individually and in tandem.
 
Results have been promising, but more investigation and large-scale trials are required.
 
Commercially available 'Smart Hooks' combine both a magnetic and a galvanic repellent. Note that the inclusion of this link is for information only, and does not signify endorsement by WCPFC.
References
  1. Brill, R., Bushnell, P., Smith, L., Speaks, C.,  Sundaram, R., Stroud, E. and Wang,J. 2009. The repulsive and feeding-deterrent effects of electropositive metals on juvenile sandbar sharks (Carcharhinus plumbeus). Fishery Bulletin 107(3): 298-307.
  2. Kaimmer, S. and Stoner, A.W. 2008. Field investigation of rare-earth metal as a deterrent to spiny dogfish in the Pacific halibut fishery. Fisheries Research 94(1): 43-47.
  3. Marcotte, M.M. and Lowe, C.G. 2010. Behavioral responses of two species of sharks to pulsed, direct current electrical fields: testing a potential shark deterrent. Marine Technology Society Journal 42(2): 53-61.
  4. O'Connell, C.P., Abel, D.C., Gruber, S.H., Stroud, E.M. and Rice, P.H. 2011. Response of juvenile lemon sharks, Negaprion brevirostris, to a magnetic barrier simulating a beach net. Ocean and Coastal Management 54(3):225-230.
  5. O'Connell, C.P., Abel, D.C., Rice, P.H., Stroud, E.M. and Simuro, N.C. 2010. Responses of the southern stingray (Dasyatis americana) and the nurse shark (Ginglymostoma cirratum) to permanent magnets. Marine and Freshwater Behaviour and Physiology 43(1):63-73.
  6. Rigg, D.P., Peverell, S.C., Hearndon, M. and Seymour, J.E. 2009. Do elasmobranch reactions to magnetic fields in water show promise for bycatch mitigation? Marine and Freshwater Research 60(9): 942?948.
  7. Robbins, W.D., Peddemors, V.M. and Kennelly, S.J. 2011. Assessment of permanent magnets and electropositive metals to reduce the line-based capture of Galapagos sharks, Carcharhinus galapagensis. Fisheries Research 109(1):100-106.
  8. Spaet, J.L.Y., Kessel, S.T. and Gruber, S.H. 2010. Learned hook avoidance of lemon sharks (Negaprion brevirostris) based on electroreception and shock treatment. Marine Biology Research 6(4):399-407.
  9. Tallack, S. M. L. 2009. Do rare-earth metals deter spiny dogfish? A feasibility study on the use of electropositive 'mischmetal' to reduce the bycatch of Squalus acanthias by hook gear in the Gulf of Maine. ICES Journal of Marine Science 66(2): 315-322.