Behavioral responses of bottlenose dolphins, Tursiops truncatus, to gillnets and acoustic alarms

Published source details Cox T.M., Read A.J., Swanner D., Urian K. & Waples D. (2003) Behavioral responses of bottlenose dolphins, Tursiops truncatus, to gillnets and acoustic alarms. Biological Conservation, 115, 203-212.
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This study is summarised as evidence for the following.

	Action	Category
	Use acoustic devices on fishing gear Action Link

Use acoustic devices on fishing gear

A randomized, controlled study in 2001 at a coastal site in the North Atlantic Ocean, off the coast of North Carolina, USA (Cox et al. 2003) found that fishing nets with active acoustic devices were approached within 100 m by fewer common bottlenose dolphin Tursiops truncatus groups than nets with inactive devices, although the number of dolphin groups observed within 300 m of the nets and average closest approach distances were similar. Fewer dolphin groups approached within 100 m of nets with active acoustic devices (2 of 25 groups, 8%) than inactive devices (7 of 15 groups, 47%). The average number of dolphin groups observed within 300 m of the nets and average closest approach distances did not differ significantly with active (0.4 groups/h; 47 m) or inactive (0.6 groups/h; 38 m) acoustic devices. A gill net was deployed on random days with three active acoustic devices attached (Dukane NetMark 1000, emitting regular interval pulses at 10 kHz; total 13 days) or three inactive (silent) acoustic devices (total nine days). The net (200 m long, stretched mesh size 76 mm) was deployed 300 m from a beach perpendicular to the shore in water 3–6 m deep. Two observers tracked 40 dolphin groups from the shore using a theodolite over 22 days in April–May 2001.

(Summarised by: Anna Berthinussen)