Palka, D.L., M.C. Rossman, A.S. VanAtten, and C.D. Orphanides.
2008. Effect of pingers on harbour porpoise (Phocoena phocoena)
bycatch in the US Northeast gillnet fishery. Journal of Cetacean
Research and Management 10(3):217-226.
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Harbour porpoise (Phocoena phocoena) bycatch in the US Northeast
gillnet fishery is managed under the Harbor Porpoise Take Reduction
Plan (HPTRP), which was implemented on 1 January 1999. The HPTRP
divides this fishery into management areas that are either completely
closed to all gillnets or closed only to gillnets that do not use
pingers. Questions about pingers that have arisen include: (1) would
pingers be as effective in an operational fishery as in controlled
scientific experiments; (2) would the fishery comply with these
regulations; and (3) would harbour porpoises habituate to pingers? To
investigate these questions, data from over 25,000 gillnet hauls
observed by the Northeast Fisheries Observer Program after the
implementation of the HPTRP, 1999-2007, were examined. In a 1994
controlled scientific experiment conducted in part of this fishery
that used 15cm mesh gillnets, the bycatch rate in pingered nets was
92% less than that in nets without pingers. In contrast, in the
operational fishery, the bycatch reduction in pingered nets was
50-70%, depending on the time, area and mesh size. In particular,
there was no observed bycatch in pingered nets that used the same mesh
size as used in the experiment. Thus, it seem that the apparent
decrease in pinger effectiveness in the operational fishery was
partially due to the type of gillnet used and lack of compliance.
Pinger usage started out high in 1999 (the first year required),
dropped substantially during 2003-05 and perhaps due to outreach
activities increased beginning in 2006. During years of high pinger
usage, 87% of the tested pingers were functional, while only 36% of
the tested pingers were functional during years of low pinger
usage. In general, as expected, observed bycatch rates in hauls
without pingers were greater than bycatch rates in hauls with the
required number of pingers. Unexpectedly, bycatch rates of observed
hauls with an incomplete set of pingers were higher that in observed
hauls without pingers. Confounding factors that could partially
explain this apparently contrary result are discussed. There was no
evidence for temporal trends in the bycatch rates, suggesting that
harbour porpoises had not habituated to the pingers. In conclusion, in
the US Northeast gillnet fishery, harbour porpoises do not appear to
have habituated to pingers, and pingers appear to have reduced the
bycatch rate, particularly when the required number of pingers were
used and in nets using mesh sizes of 15cm or less.
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Berrow, S., R. Cosgrove, R.H. Leeney, J. O'Brien, D. McGrath,
J. Dalgard, and Y. Le Gall. 2008. Effect of acoustic deterrents on the
behaviour of common dolphins (Delphinus delphis). Journal of Cetacean
Research and Management 10(3):227-233.
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Not all delphinids are similarly affected by acoustic deterrent
devices (pingers). At-sea trials were carried out to assess a range of
acoustic signals and deterrents on the behaviour of common
dolphins. In initial tests two acoustic deterrent devices, which
previously produced an evasive response by bottlenose dolphins, failed
to elicit any similar behaviour in common dolphins. A new signal
output device, which permitted a range of signals to be tested at
various source levels and characteristics was subsequently developed
but again no significant effects on the behaviour of common dolphins
were observed. Two commercially available acoustic deterrents, which
had deterred common dolphins in previous studies, produced an
occasional mild evasive response. Significant modification of the
signal type or source level may be more effective, but our results
suggest that pingers, at their current state of development, may not
provide a consistently effective deterrent signal for common
dolphins.
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