Fisheries Research 131–133 (2012) 45–51 Contents lists available at SciVerse ScienceDirect Fisheries Research jou rn al hom epage: www.elsevier.com/locate/fishres The effects of a lanthanide metal alloy on shark catch rates Melanie Hutchinson a,∗ , John H. Wang b,1 , Yonat Swimmer c,2 , Kim Holland a,3 , Suzanne Kohin d,4 , Heidi Dewar d,4 , James Wraith d,4 , Russ Vetter d,4 , Craig Heberer e,5 , Jimmy Martinez f,6 a University of Hawaii, Department of Zoology, Hawaii Institute of Marine Biology, 46-007 Lilipuna Rd., Kaneohe, HI 96744, United States b Joint Institute for Marine and Atmospheric Research, University of Hawaii, 1000 Pope Rd., Honolulu, HI 96822, United States c Pacific Islands Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822, United States d Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Dr., La Jolla, CA 92037, United States e National Marine Fisheries Service, Southwest Region, Sustainable Fisheries Division, 6010 Hidden Valley Rd., Carlsbad, CA 92011, United States f Jefe de los Planes de Acción Nacional para la Conservación y Manejo de los Tiburones y el Dorado (mahimahi), y del Proyecto de Reducción de Bycatch, Subsecretaria de Recursos Pesqueros del ECUADOR, Avenida 4 entre calle 12 y 13, Edif Pinoargotty, Manta, Manabí, América del Sur, Ecuador a r t i c l e i n f o Article history: Received 2 March 2012 Received in revised form 9 July 2012 Accepted 11 July 2012 Keywords: Shark bycatch Longline Lanthanide metal CPUE a b s t r a c t Bycatch of sharks in longline fisheries has contributed to declines in shark populations and prompted the need for exploring novel technologies to reduce the incidental capture of sharks. One potential strategy is to exploit the unique electrosensory system of sharks, used to detect weak electric fields. Metals from the lanthanide series, made up of neodymium (Nd) and praseodymium (Pr), produce strong electric fields in water. In this study, we tested the effects of an Nd/Pr alloy on shark catch rates. Using longline fishing gear, we compared the catch rates of baited hooks affixed with either a block of the metal alloy (experimental) or a lead weight (control). Four experiments were conducted in different regions of the Pacific Ocean. Two bottom longline experiments were conducted inside and offshore of Kaneohe Bay, Hawaii. One of these experiments targeted young of the year scalloped hammerhead sharks (Sphyrna lewini), while the other targeted sandbar (Carcharhinus plumbeus) and tiger sharks (Galeocerdo cuvier). In the Southern California Bight (SCB), pelagic longlines were deployed to target mako (Isurus oxyrinchus) and blue sharks (Prionace glauca) and longlines targeting pelagic sharks were set in the Eastern Tropical Pacific (ETP) off Ecuador. There was a significant reduction in juvenile hammerhead sharks caught on hooks with the lanthanide metal compared to the controls. In contrast, there was no difference in the catch rates for experiments targeting sandbar sharks in Hawaii or those conducted in the SCB and Ecuador. These results suggest that there are inter-specific differences regarding the effects of lanthanide metals on catch rates. This may reflect the diverse feeding strategies and sensory modalities used by shark species for detecting and attacking prey. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Many shark populations are in a state of decline due to fishery interactions (Camhi et al., 2009; Dulvy et al., 2008) such as directed shark fisheries (Beerkircher et al., 2002), the shark fin trade (Clarke et al., 2006), and the unintended bycatch of shark species in a range of commercial gear types (Bonfil, 1994; Stevens et al., 2000). Shark populations are particularly vulnerable to fisheries exploitation ∗ Corresponding author. Tel.: +1 808 236 7401; fax: +1 808 236 7443. E-mail address: melanier@hawaii.edu (M. Hutchinson). 1 Tel.: +1 808.983.3714; fax +1 808.983.5300. 2 Tel.: +1 808 983 5300; fax: +1 808 592 7013. 3 Tel.: +1 808 236 7401; fax: +1 808 236 7443. 4 Tel.: +1 858 334 2800; fax: +1 858 546 5651. 5 Tel.: +1 760 431 9440x303. 6 Tel.: +593 5 2611410. because of their low intrinsic rebound potential (Frisk et al., 2005; Smith et al., 1998). Currently, 16 of 20 pelagic shark species are now classified as threatened or near threatened with endangerment by the IUCN (International Union for the Conservation of Nature) as a result of their life history traits coupled with heavy fishing pressure (Dulvy et al., 2008; IUCN, 2010). Several shark species, including the scalloped hammerhead shark (Sphyrna lewini), have also been evaluated for listing under the United States Endangered Species Act (http://www.nmfs.noaa.gov/pr/species/fish, accessed December 2011). In addition, a global review of the biological and trade status of sharks conducted by the Convention on Inter- national Trade in Endangered Species of Wild Fauna and Flora resulted in the listing of three pelagic shark species (Daves and Nammack, 1998; www.CITES.org, accessed December 2011). Developing strategies to minimize and mitigate shark bycatch in fisheries is important for the sustainable management of shark pop- ulations and has become a priority for fishers, fishery managers by 0165-7836/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fishres.2012.07.006