modifications to the harbor porpoise take reduction plan - Northeast ...

compliance, thus increasing the effectiveness of the HPTRP. Expanded pinger areas provide
potential benefits over expanded closure periods by preventing potential increased economic
effects, or by avoiding the shift of effort and bycatch into adjacent open areas. However, the
option to expand pinger requirements into the Mid-Atlantic, even when the discussion was
limited to the Waters off New Jersey, was not favorably received by HPTRT members. The
effectiveness of pingers for reducing harbor porpoise bycatch in Mid-Atlantic waters has not
been evaluated. However, limited testing has taken place in North Carolina on the effects of
acoustic devices on bottlenose dolphins. The dolphins observed during recent studies reacted
differently to pingers than harbor porpoises do in that their initial reactions are relatively small
and the pingers do not appear to deter them from the vicinity of the nets (Cox et al., 2003).
Rather, it is possible that pingers alert bottlenose dolphins to the presence of the nets. In a recent
study involving bottlenose dolphin depredation in the Spanish mackerel gillnet fishery, a new
type of acoustic deterrent device called the SaveWave was tested to determine its effects on
bottlenose dolphins. While a very low amount of depredation was observed during the study, the
results indicated that the SaveWave devices did not deter the dolphins from the nets. Rather, the
devices appeared to alert dolphins to the presence of the net (the researchers observed increased
echolocation in the presence of active SaveWave devices), which could help reduce
entanglement risk but could also increase depredation as the devices did not seem to deter the
dolphins away from the nets (Read et al., 2006).
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