Non-lethal efforts to deter shark predation of Hawaiian monk seal pups

Abstract

Joint Institute for Marine and Atmospheric Research, University of Hawaii at Manoa, 1000 Pope Rd, Bldg 312, Honolulu, HI 96822, USAABSTRACT1. More than adecade of shark predation onnursing and newly weaned pups of theendangered Hawaiian monkseal (Monachus schauinslandi) has significantly contributed to a steep decline of the French Frigate Shoals (FFS)subpopulation.2. In an effort to develop non-lethal methods of mitigating predation, the feasibility of deploying potential sharkdeterrents at FFS was examined, and then tests were done to see if any of the successfully deployed devices or acontinuous human presence deters shark predation of monk seal pups.3. During the feasibility trial, an underwater acoustic playback and a moored boat performed without issue. Afloat array proved hazardous to non-target wildlife and electronic diver devices functioned poorly; both wereomitted from further experimentation.4. The number of shark sightings and predation incidents at two pupping islets was compared across twoexperimental treatments: (1) acoustic playback and a moored boat, and (2) continuous human presence, versusa control. Sharks were sighted with a remote camera system; predation incidents were evident from bite woundsor the disappearance of pups.5. Observed shark activity was rare (12 sightings on video and six predation incidents) but similar to recentyears. The number of shark sightings and predation incidents did not differ significantly between the twotreatments and the control.6. The relative scarcity of shark activity in the shallows around the pupping islets made detecting a treatmenteffect challenging. Sharks’ wariness to humans is probably variable, unpredictable, possibly individualistic andunreliable at FFS. The acoustic playback as a deterrent could benefit from further testing and development.Other non-lethal or lethal approaches for mitigating predation should be investigated to protect monk seal pupsat FFS.Published 2012. This article is a U.S. Government work and is in the public domain in the USA.Received 20December2011; Revised 20June2012; Accepted 02July2012