Field investigation of rare-earth metal as a deterrent to spiny dogfish in the Pacific halibut fishery

Rare earth metals (made of cerium mischmetal) were compared with control treatments of standard circle hooks and inert steel above circle hooks on longline fishing gear to determine if bycatch reduction of spiny dogfish could be achieved. Results indicated a slight reduction in dogfish bycatch and a greater reduction in catch of longnose skate on hooks with mischmetal. Problems for using mischmetal commercially include its expense, hazardous nature, and rapid hydrolysis in seawater.
Field Studies:

Location	Fishing gear	Reduction technique	Bycatch species	Effect on bycatch species	Catch	Effect on target catch	Type
Alaska	Hooks-and-Lines	Rare earth magnets	Elasmobranchs	Slightly reduced bycatch of spiny dogfish but had a greater reduction on catch of longnose skate	Pacific halibut	Did not affect catch of halibut	In the wild