[MARMAM] Long-term effectiveness of acoustic pingers on marine mammal bycatch in gillnets

Jim Carretta jim.carretta at noaa.gov
Fri Dec 23 20:44:49 PST 2011

Dear colleagues,

A paper on the long-term effectiveness of acoustic pingers on marine mammal
bycatch in gillnets was recently published in the Marine Technology Society

Carretta, J.V. and J. Barlow.  2011.  Long-term effectiveness, failure
rates, and "dinner bell" properties of acoustic pingers in a gillnet
fishery.  Marine Technology Society Journal 45(5):7-19.


The long-term effectiveness of acoustic pingers in reducing marine mammal
bycatch was assessed for the swordfish and thresher shark drift gillnet
fishery in California. Between 1990 and 2009, data on fishing gear,
environmental variables, and bycatch were recorded for over 8,000 fishing
sets by at-sea fishery observers, including over 4,000 sets outfitted with
acoustic pingers between 1996 and 2009. Bycatch rates of cetaceans in sets
with ≥30 pingers were nearly 50% lower compared to sets without pingers (*p* =
1.2 × 10−6), though this result is driven largely by common dolphin (*Delphinus
delphis*) bycatch. Beaked whales have not been observed entangled in this
fishery since 1995, the last full year of fishing without acoustic pingers.
Pinger failure (≥1 nonfunctioning pingers in a net) was noted in 3.7% of
observed sets. In sets where the number of failed pingers was recorded,
approximately 18% of deployed pingers had failed. Cetacean bycatch rates
were 10 times higher in sets where ≥1 pingers failed versus sets without
pinger failure (*p* = 0.002), though sample sizes for sets with pinger
failure were small. No evidence of habituation to pingers by cetaceans was
apparent over a 14-year period of use. Bycatch rates of California sea
lions in sets with ≥30 pingers were nearly double that of sets without
pingers, which prompted us to examine the potential “dinner bell“ effects
of pingers. Depredation of swordfish catch by California sea lions was not
linked to pinger use—the best predictors of depredation were total
swordfish catch, month fished, area fished, and nighttime use of deck
lights on vessels.

This article appears in the Sep./Oct. 2011 general issue of Marine
Technology Society Journal, which can be purchased at
For pdf reprints of only the article itself, e-mail:
Jim.Carretta at noaa.gov<Kerri.Danil at noaa.gov>
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