Behavioral reactions of free-ranging harbor porpoises Phocoena phocoena encountering standard nylon and BaSO4 mesh gillnets and warning sound
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Published source details
Koschinski S., Culik B.M., Trippel E.A. & Ginzkey L. (2006) Behavioral reactions of free-ranging harbor porpoises Phocoena phocoena encountering standard nylon and BaSO4 mesh gillnets and warning sound. Marine Ecology Progress Series, 313, 285-294.
Published source details Koschinski S., Culik B.M., Trippel E.A. & Ginzkey L. (2006) Behavioral reactions of free-ranging harbor porpoises Phocoena phocoena encountering standard nylon and BaSO4 mesh gillnets and warning sound. Marine Ecology Progress Series, 313, 285-294.
Actions
This study is summarised as evidence for the following.
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Use acoustically reflective fishing gear materials Action Link |
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Use acoustic devices on fishing gear Action Link |
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Use acoustically reflective fishing gear materials
A controlled study in 2003 in a fjord in the Fortune Channel, Vancouver Island, Canada (Koschinski et al. 2006) found that fishing nets made from an acoustically reflective material (barium sulfate) were approached to similar distances and for similar durations by harbour porpoises Phocoena phocoena compared to conventional nets, but porpoises used fewer echolocation clicks at barium sulfate nets. Harbour porpoises approached to similar distances and spent similar amounts of time within 50 m of barium sulfate nets (average 18 m; 24 seconds) and conventional nets (average 18 m; 20 seconds). At barium sulfate nets, echolocating porpoises used fewer clicks (average 23 clicks/interaction) and had longer click intervals (average 51 ms) than at conventional nets (average 56 clicks/interaction; click interval: 45 ms). Two surface gill nets (one barium sulfate, one conventional; both 45 x 9 m, 0.62 mm diameter mesh) were deployed in August 2003. Barium sulfate nets were a mix of high-density barium sulfate and nylon dyed green. Conventional nets were semi-transparent blue nylon. A theodolite was used to track porpoises during six deployments (14 h over four days) with the barium sulfate net and nine deployments (26.5 h over eight days) with the conventional net. A click detector suspended in the middle of each net at a depth of 4.5 m recorded echolocation activity.
(Summarised by: Anna Berthinussen)
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Use acoustic devices on fishing gear
A controlled study in 2003 in a fjord in the Fortune Channel, Vancouver Island, Canada (Koschinski et al. 2006) found that using an acoustic device at a float line did not reduce the approach distances or time spent near the line by harbour porpoises Phocoena phocoena. Closest approach distances of harbour porpoises and time spent within 50 m of float lines did not differ significantly between lines with an acoustic device (average 25 m; 32 seconds) or without (average 28 m; 17 seconds). In August 2010, a float line was deployed on one occasion (total 2.8 h) without an acoustic device and on three occasions (total 12.5 h) with an acoustic device. The acoustic device (a CD player with an underwater transducer at a depth of 4.5 m) emitted 0.3 second pulses at 2.5 kHz. Porpoises within 50 m of the float line were tracked with a theodolite during each of the four deployments.
(Summarised by: Anna Berthinussen)
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