The archetypal proceedings of the exertion ‘SharkGuard’ reduced the bycatch of bluish sharks and pelagic rays by arsenic overmuch arsenic 91 per cent, but didn't interaction the tuna fishers were targeting.
Technology 21 November 2022The SharkGuard instrumentality is small, but it’s a large deterrent against sharks and rays that hazard becoming bycatch Rob Enever
An electrical pulse-emitting, pinkie-finger-sized instrumentality attached to sportfishing hooks appears to dramatically trim the accidental drawback of sharks and rays successful archetypal tract tests. The technology, called “SharkGuard”, could alteration fishers to harvest people taxon similar tuna portion limiting unintentional bycatch deaths of sharks astir the world.
Since 1970, the planetary abundance of sharks and rays has declined by 71 per cent. A large origin of this has been accidental snags connected longline sportfishing hooks, which dwell of a horizontal main enactment with hundreds oregon thousands of hooks trailing below.
The SharkGuard instrumentality hitches a thrust connected this aforesaid sportfishing cogwheel and is affixed a fewer centimetres supra a hook. The instrumentality – astir the size and signifier of a AA artillery – works by emitting a pulsing electrical complaint that creates an electromagnetic tract astir the SharkGuard’s position.
Sharks and rays person electrosensory organs successful their tegument that observe subtle changes successful underwater electrical fields. So, the purpose of the pulsing instrumentality is to “overwhelm the senses” says Phil Doherty astatine the University of Exeter successful the UK. Like a quality lasting excessively adjacent to a talker blasting music, “it’s overstimulating”, helium says.
To trial the technology, Doherty and his colleagues deployed SharkGuard connected 2 sportfishing vessels disconnected the coastline of confederate France implicit 11 antithetic trips successful the summertime of 2021. Each vas was equipped with 22 longlines with much than 9000 hooks. On some ships, fractional of the hooks were secured with a SharkGuard instrumentality successful an alternating signifier to spot if determination was a quality successful shark bycatch betwixt pulsing and non-pulsing hooks. SharkGuard reduced the bycatch of bluish sharks (Prionace glauca) and pelagic stingrays (Pteroplatytrygon violacea) by 91 and 71 per cent, respectively. Bluefin tuna (Thunnus thynnus), which deficiency electrosensory organs, appeared unbothered.
Doherty was impressed by however good the instrumentality performed successful the field.
“I was rather shocked, particularly astatine the bluish shark… I mean, that’s huge.”
Though SharkGuard shows archetypal promise, the results should beryllium taken with caution, says Nicholas Dulvy astatine Simon Fraser University successful Canada who was not progressive successful the work. The instrumentality whitethorn person varying effectiveness betwixt antithetic shark oregon ray species, arsenic each has a unsocial configuration of electrosensory organs.
“It would beryllium truly absorbing to spot however this works in, say, hammerhead and silky sharks,” says Dulvy.
Outfitting a longline sportfishing vas with SharkGuard costs astir $20,000 and the devices person a artillery beingness of 65 hours, thing developer Fishtek Marine is presently moving to extend. Still, the upfront outgo and effort could beryllium offset by allowing fishers to haul successful much of the people species.
Journal reference: Current Biology, DOI: 10.1016/j.cub.2022.09.003
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