Study

Acoustic alarms reduce porpoise mortality

  • Published source details Kraus S.D., Read A.J., Solow A., Baldwin K., Spradlin T., Anderson E. & Williamson J. (1997) Acoustic alarms reduce porpoise mortality. Nature, 388, 525.

Actions

This study is summarised as evidence for the following.

Action Category

Use acoustic devices on fishing gear

Action Link
Marine and Freshwater Mammal Conservation
  1. Use acoustic devices on fishing gear

    A randomized, controlled study in 1994 of a pelagic site in the North Atlantic Ocean, off the coast of New Hampshire, USA (Kraus et al. 1997) found that using active acoustic devices on fishing nets resulted in fewer harbour porpoise Phocoena phocoena entanglements compared with using inactive acoustic devices. The probability of at least one porpoise being entangled was lower in nets with active acoustic devices (0.0027) than in nets with inactive acoustic devices (0.025). Two harbour porpoises were entangled in nets with active devices, whereas 25 were entangled in nets with inactive devices. Catches of target cod Gadus morhuai and pollock Pollachius virens were similar in nets with active and inactive devices (data not reported). Commercial gill net fishers deployed a total of 844 net strings (each comprising 12 nets, 92 m long x 4 m deep, stretched mesh size 15 cm) with acoustic devices attached at 92 m intervals. The acoustic devices on each net string were randomly assigned as active (emitting 300 ms sounds every 4 seconds at 10 kHz; total 421 net strings) or inactive (silent; total 423 net strings). Net strings were submerged for 24 h. Onboard observers and fishers recorded porpoise entanglements and fish catches during daily hauls in October–December 1994.

    (Summarised by: Anna Berthinussen)

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