Sharks and other elasmobranchs (e.g. rays and skates) are critical to the resilience of marine ecosystems. Shark bycatch is a worldwide conservation problem that is devastating shark populations, with an estimated 63 to 273 million sharks bycaught annually in commercial fisheries. Shark populations are at crisis point, with over a third of shark species now threatened with extinction.
Sharks are sometimes deliberately targeted in legal and illegal fisheries, but more usually caught unintentionally and then discarded. Pelagic longlining for high-value tuna and bill fish, mainly in sub-tropical and temperate regions is known to have particularly high bycatch rates. Many species are in major decline due to overfishing. Blue shark (Prionace glauca) is the most encountered bycatch species in pelagic longline fisheries.
Sharks and other elasmobranchs have acute sensitivity to electrical fields in water through the use of a unique sensory organ the ‘ampullae of lorenzini’. They use these electroreceptors to detect weak voltages to navigate and detect prey, but they will actively avoid much higher voltages. These insights have been key to developing, prototyping and successfully testing SharkGuard.
The SharkGuard Mark V is a tiny cylinder that is attached above a baited hook which creates a powerful, short-range, 3-D electric pulse at short intervals. The field is enough to deter sharks and other elasmobranchs, without affecting target species. We have designed a setting bin with 340 induction charged devices allowing for easy deployment and recharging during setting and hauling.
In 2022, the University of Exeter led the publication of a paper which described the results of trials in the Mediterranean. Working with tuna fishers in the Mediterranean coast of France the trials tested the impact of the shark guard, where the device achieved a remarkable reduction of 91% for blue shark and 71% for pelagic stingray. Our research is ongoing and we are working towards a more comprehensive research publication from two years of data gathering with fleets in New Caledonia.
|
Paper |
Location | Product/model used | Effect | Species |
Gear Type |
| FISHTEK MARINE LED | |||||
| Efficacy of a novel shark bycatch mitigation device in a tuna longline fishery (Doherty et al., 2022) | Mediterranean, France | Fishtek’s SharkGuard MK.IV | 91% bycatch reduction
71% bycatch reduction |
Blue shark (Priomace glauca)
Pelagic stingrays (Pteroplatytrygon violacea) |
Pelagic Longline |