To ping or not to ping : the use of active acoustic devices in mitigating interactions between small cetaceans and gillnet fisheries

Active sound emitters (‘pingers’) are used in several gillnet fisheries to reduce bycatch of small cetaceans, and/or to reduce depredation by dolphins. Here, we review studies conducted to determine how effective these devices may be as management tools. Significant reductions in bycatch of harbour porpoise Phocoena phocoena, franciscana Pontoporia blainvillei, common Delphinus delphis and striped dolphin Stenella coeruleoalba, and beaked whales as a group have been demonstrated. For harbour porpoise this result has been replicated in 14 controlled experiments in North America and Europe, and appears to be due to porpoises avoiding the area ensonified by pingers. Two gillnet fisheries (California-Oregon driftnet fishery for swordfish; New England groundfish fishery) with mandatory pinger use have been studied for over a decade. Bycatch rates of dolphins/porpoises have fallen by 50 to 60%, and there is no evidence of bycatch increasing over time due to habituation. In both fisheries, bycatch rates were significantly higher in nets sparsely equipped with pingers or in which pingers had failed, than in nets without any pingers at all. Studies of pinger use to reduce depredation by bottlenose dolphins Tursiops truncatus generally show small and inconsistent improvements in fish catches and somewhat reduced net damage. Dolphin bycatch in these fisheries is rare, but still occurs in nets with pingers. Taken together, these studies suggest that the most promising candidates for bycatch reduction via pinger use will be gillnet fisheries in developed countries in which the bycaught cetaceans are generally neophobic species with large home ranges. We offer a set of lessons learned from the last decade of bycatch management.Publisher PDFPeer reviewe

To ping or not to ping:the use of active acoustic devices in mitigating interactions between small cetaceans and gillnet fisheries

Active sound emitters (‘pingers’) are used in several gillnet fisheries to reduce bycatch of small cetaceans, and/or to reduce depredation by dolphins. Here, we review studies conducted to determine how effective these devices may be as management tools. Significant reductions in bycatch of harbour porpoise Phocoena phocoena, franciscana Pontoporia blainvillei, common Delphinus delphis and striped dolphin Stenella coeruleoalba, and beaked whales as a group have been demonstrated. For harbour porpoise this result has been replicated in 14 controlled experiments in North America and Europe, and appears to be due to porpoises avoiding the area ensonified by pingers. Two gillnet fisheries (California-Oregon driftnet fishery for swordfish; New England groundfish fishery) with mandatory pinger use have been studied for over a decade. Bycatch rates of dolphins/porpoises have fallen by 50 to 60%, and there is no evidence of bycatch increasing over time due to habituation. In both fisheries, bycatch rates were significantly higher in nets sparsely equipped with pingers or in which pingers had failed, than in nets without any pingers at all. Studies of pinger use to reduce depredation by bottlenose dolphins Tursiops truncatus generally show small and inconsistent improvements in fish catches and somewhat reduced net damage. Dolphin bycatch in these fisheries is rare, but still occurs in nets with pingers. Taken together, these studies suggest that the most promising candidates for bycatch reduction via pinger use will be gillnet fisheries in developed countries in which the bycaught cetaceans are generally neophobic species with large home ranges. We offer a set of lessons learned from the last decade of bycatch management

Fine-scale behaviour of bottlenose dolphins around gillnets.

We studied the fine-scale behaviour of bottlenose dolphins Tursiops truncatus around gillnets in North Carolina, USA, during May and June 2002. We made observations from an overhead digital video camera, suspended from a helium-filled aerostat, tethered 70 m above a fishing vessel. We positioned the camera above a gillnet set for Spanish mackerel Scomberomorus maculatus. We observed frequent encounters (n = 36) and interactions (n = 27) between dolphins and the net, but no dolphins became entangled. Most dolphins diverted their course around the net, but on nine occasions we observed dolphins engaging in depredation. We conclude that interactions between dolphins and these gillnets are common, but that entanglement is rare

Diving behavior of Cuvier's beaked whales off Cape Hatteras, North Carolina

Behavior data from satellite-relayed Wildlife Computers Mk10 Splash tags deployed on Cuvier's beaked whales off Cape Hatteras, NC

Data from: Diving behavior of Cuvier's beaked whales (Ziphius cavirostris) off Cape Hatteras, North Carolina

Cuvier’s beaked whales exhibit exceptionally long and deep foraging dives. The species is relatively little studied due to their deep-water, offshore distribution and limited time spent at the surface. We used LIMPET satellite tags to study the diving behavior of Cuvier's beaked whales off Cape Hatteras, North Carolina from 2014 to 2016. We deployed 11 tags, recording 3,242 hours of behavior data, encompassing 5,926 dives. Dive types were highly bimodal; deep dives (>800m, n=1,408) had a median depth of 1,456 m and median duration of 58.9 min; shallow dives (50-800m, n=4,518) were to median depths of 280 m with a median duration of 18.7 min. Most surface intervals were very short (median 2.2 min), but all animals occasionally performed extended surface intervals. We found no diel differences in dive depth or percentage of time spent deep diving, but whales spent significantly more time near the surface at night. Other populations of this species exhibit similar dive patterns, but with regional differences in depth, duration, and inter-dive intervals. Satellite-linked tags allow for the collection of long periods of dive records, including the occurrence of anomalous behaviors, bringing new insights into the lives of these deep divers

The Effect of a Low-Frequency Sound Source (Acoustic Thermometry of the Ocean Climate) on the Diving Behavior of Juvenile Northern Elephant Seals, Mirounga angustirostris

Published by and copyright of AIP Publishing. The definitive version of this article is available at: http://scitation.aip.org/content/asa/journal/jasa/113/2/10.1121/1.1538248Changes in the diving behavior of individual free-ranging juvenile northern elephant seals,\ud Mirounga angustirostris, exposed to the acoustic thermometry of the ocean climate (ATOC) sound\ud source were examined using data loggers. Data loggers were attached to the animals and measured\ud swim speed, maximum depth of dive, dive duration, surface interval, descent and ascent rate, and\ud descent and ascent angle along with sound pressure level (SPL). The ATOC sound source was at a\ud depth of 939 m and transmitted at 195 dB re: 1??Pa at 1 m centered at 75 Hz with a 37.5-Hz\ud bandwidth. Sound pressure levels (SPL) measured at the seal during transmissions averaged 128 dB\ud and ranged from 118 to 137 dB re: 1 ??Pa for the 60???90 Hz band, in comparison to ambient levels\ud of 87???107 dB within this band. In no case did an animal end its dive or show any other obvious\ud change in behavior upon exposure to the ATOC sound. Subtle changes in diving behavior were\ud detected, however. During exposure, deviations in descent rate were greater than 1 s.d. of the control\ud mean in 9 of 14 seals. Dive depth increased and descent velocity increased in three animals, ascent\ud velocity decreased in two animals, ascent rate increased in one animal and decreased in another, and\ud dive duration decreased in only one animal. There was a highly significant positive correlation\ud between SPL and descent rate. The biological significance of these subtle changes is likely to be\ud minimal. This is the first study to quantify behavioral responses of an animal underwater with\ud simultaneous measurements of SPL of anthropogenic sounds recorded at the animal.This work was funded by the Office of Naval\ud Research (ONR N00014-94-1-0455) and the Scripps Institution\ud of Oceanography Acoustic Thermometry of Ocean Climate\ud program via subcontracts from grants ARPA MDA 972-\ud 93-1-003 and ONR N00014-94-1-0692