The Effects of Electropositive Metals on Shark Catch Rates and Feeding Behavior

Bycatch of sharks in longline fisheries is one of several factors that have contributed to global declines of shark populations. Thus strategies to minimize the incidental capture of sharks are needed. One strategy is to exploit the unique electrosensory system of sharks.  Sharks and other elasmobranchs use their electrosensory system to detect changes in electric fields. Metals from the lanthanide series, specifically Neodymium (Nd) and Praseodymium (Pr) generate strong electric fields in water.  In this study we tested the effects of this E+ metal alloy on catch rates and feeding behaviors of several shark species impacted by longline fishing. We conducted several comparative assays using demersal longline fishing gear in Kaneohe Bay, Hawaii and pelagic longline fishing experiments in the Southern California Bight (SCB).  In addition a laboratory behavior experiment using juvenile scalloped hammerhead sharks (Sphyrna lewini) was performed.  Data from these experiments indicate that there are inter-specific differences in responses to electropositive metals.  These disparate results may be due to diverse feeding strategies and the way in which different sensory modalities are used for detecting and attacking prey.