Is attempting to change marine mammal behaviour a generic solution to the bycatch problem? A dugong case study

Published source details Hodgson A.J., Marsh H., Delean S. & Marcus L. (2007) Is attempting to change marine mammal behaviour a generic solution to the bycatch problem? A dugong case study. Animal Conservation, 10, 263-273.
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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 controlled study in 2002 and 2005 at a pelagic site in Moreton Bay, Queensland, Australia (Hodgson et al. 2007) found that active acoustic devices of two types deployed to simulate a fishing net had similar numbers of dugongs Dugong dugon passing between them compared to inactive acoustic devices, and dugong orientation and feeding behaviour were also similar. The number of dugongs passing between two acoustic devices was similar when the devices were active or inactive (data reported as statistical model results). The proportion of dugongs oriented towards the acoustic devices and the number of dugongs feeding within 100 m of them also did not differ significantly when the devices were active or inactive. Two acoustic devices (either 4 kHz or 10 kHz ‘BASA’ devices) were deployed 50–55 m apart at depths of 1 m below the water surface to simulate a fishing net. The devices were attached to a research vessel and an anchored floating tube close to dugong herds. Each trial comprised three 10-minute sequential treatments with both devices inactive (silent), active (emitting pulses at 4-second intervals), and inactive (silent). Ten trials were carried out in August 2002 with 10 kHz devices. Sixteen trials were carried out in July 2005 with 4 kHz devices. Dugong behaviour and feeding plumes (disturbed sediment) were recorded with a video camera attached to a balloon during each of the 26 trials.

(Summarised by: Anna Berthinussen)