The repulsive and feeding-deterrent effects of electropositive metals on juvenile sandbar sharks (Carcharhinus plumbeus)
Reducing shark bycatch and depredation (i.e., damage causedby sharks to gear, bait, and desired fish species) in pelagic longline fisheries targeting tunas and swordfish isa priority. Electropositive metals (i.e., a mixture of the lanthanide elements lanthanum, cerium, neodymium, andpraseodymium) have been shown to deter spiny dogfish (Squalus acanthias, primarily a coastal species) fromattacking bait, presumably because of interactions with the electroreceptive system of this shark. We undertook todetermine the possible effectiveness of electropositive metals for reducing the interactions of pelagic sharks withlongline gear, using sandbar sharks (Carcharhinus plumbeus, family Carcharhinidae) as a model species. The presence of electropositive metal deterred feeding in groups of juvenilesandbar sharks and altered the swimming patterns of individuals in the absence of food motivation (these individuals generally avoided approaching electropositive metal closer than ~100 cm). The former effect was relativelyshort-lived however; primarily (we assume) because competition with other individuals increased feedingmotivation. In field trials with bottom longline gear, electropositive metal placed within ~10 cm of the hooksreduced the catch of sandbar sharks by approximately two thirds, compared to the catch on hooks in the proximity of plastic pieces of similar dimensions. Electropositive metalstherefore appear to have the potential to reduce shark interactions in pelagic longline fisheries, althoughthe optimal mass, shape, composition, and distance to baited hooks remain to be determined.
| Main Authors: | , , , , , , |
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| Format: | article biblioteca |
| Language: | English |
| Published: |
2009
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| Subjects: | Biology, Ecology, Fisheries, |
| Online Access: | http://hdl.handle.net/1834/25435 |
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