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Magnets & EPREM

WHAT ARE MAGNETS & EPREM METALS?

Some species of elasmobranch (sharks, skates and ray) are deterred by certain permanent magnets and electropositive rare earth metals (EPREM), due to the highly sensitive electroreceptors in their noses, which are able to detect Earth’s magnetic field. Permanent magnets create their own magnetic fields, whilst EPREM create such fields when reacting to seawater, both of which are detectable by most elasmobranchs.

CURRENT RESEARCH & USE

Studies have incorporated magnets and metals into longlines and gill nets, either directly into the hooks or added to lines as metal discs, and onto the ropes of pots and traps. A 2018 study in an ocean fish trap fishery targeting snapper in New South Wales, Australia indicated that the addition of permanent magnets to traps reduced elasmobranch bycatch by over a third.

However, overall results vary, with studies highlight that elasmobranchs’ responses to magnets and metals depend on the specific species. Furthermore, there are concerns over the possibility of sensory habituation to magnetic fields with longlines, as this gear is soaked for long intervals.

 

Metals and magnets have still not been proven to be an effective and consistent elasmobranch bycatch mitigation technique. Most recently, a 2023 lab-based study concluded that rare-earth metal magnets had only a weak deterrent effect on four species of elasmobranchs found in Australian waters, with the study’s authors recommending that the focus of future mitigation trials shift from magnets to electrical fields which show could be more effective.

This page was last updated on 25.05.24.

Interested in how this and other measures could mitigate bycatch in your fishery? Get in touch with us to collaborate or take part in a study.

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