In addition to their ability to echolocate, cetaceans have a great capacity for learning. This raises some concern that acoustic alarms will become less effective over time as animals in a particular area become accustomed to the sounds and are no longer deterred. This process is called habituation.

Scientists are currently investigating whether cetaceans become habituated and if pinger design can address this problem. It may be possible to extend the effectiveness of pingers by varying their bandwidth, frequency or other features.

(Culik et al. 2001, Goodson et al. 1997, Kraus 1999)

Interactions between fisheries and cetaceans are not completely addressed by the use of acoustic alarms, and pingers should only be applied as one element of a larger effort to reduce bycatch.

In many regions of the world, large areas are covered by gillnets or aquaculture pens. Reliance on pingers in all of these coastal habitats could exclude dolphins, porpoises and whales and leave few options for alternative habitat.

(Carlstrom 2003, Culik et al. 2001, Johnston 2002)

Pingers are not reliable solutions for reducing bycatch of critically endangered species (such as the vaquita or North Island Hector's dolphin). With few animals remaining, bycatch is so rarely observed that the species could go extinct before scientific testing of pingers can be carried out.

(J. Barlow, pers.comm.)

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