Reducing elasmobranch bycatch: laboratory investigation of rare earth metal and magnetic deterrents with spiny dogfish and Pacific halibut

Published source details Stoner A.W. & Kaimmer S.M. (2008) Reducing elasmobranch bycatch: laboratory investigation of rare earth metal and magnetic deterrents with spiny dogfish and Pacific halibut. Fisheries Research, 92, 162-168.
Share Tweet Email

Actions

This study is summarised as evidence for the following.

	Action	Category
	Attach an electropositive deterrent to fishing gear Action Link

Attach an electropositive deterrent to fishing gear

A replicated, paired, controlled study in 2006 in a laboratory in the USA (Stoner & Kaimmer 2008) found that the bait attacking behaviour of spiny dogfish Squalus acanthias (an unwanted catch species), but not commercially valuable Pacific halibut Hippoglossus stenolepis, was reduced in the presence of one of two potentially deterrent materials (mischmetal but not magnets), compared to inert metals. Overall, in the presence of mishmetal, both the times taken for dogfish to first bite the bait (mischmetal: 2–19 min, inert: 1–2 min) and the times taken to remove the bait (mischmetal: 4–30 min, inert: 2–4 min) were higher compared to the inert metals, irrespective of the period of food deprivation. Using magnets as the deterrent, overall bait attack and removal times by dogfish were not significantly different compared to the inert metals (magnet: 1–5 min, inert: 1–2 min). However, dogfish showed strong behavioural avoidance responses (flinch, disorientation) to both the deterrent materials, but not to the inert metals. For halibut, there were no responses to the either the deterrent materials or the inert metals, and bait removal times were similar (deterrents: <1–30 min, inert: <1–30 min). In 2006, two types of potential deterrents (non-magnetic mischmetal alloy and magnets) and an inert stainless steel/aluminium material were tested separately on 12 dogfish and 16 halibut held in indoor pools. Each material was suspended on a short section of twine above pieces of squid Loligo opalescens bait (no hooks). Deterrent/baits were presented simultaneously in pairs with the inert/bait material and behavioural responses recorded by video. Trials were done on dogfish (5 trials) and halibut (4 trials) deprived of food for periods of up to 4 d (16–20 trials/species/food deprivation period).

(Summarised by: Leo Clarke)