While the effects of pingers in reducing cetacean by-catches in nets is considerable, figures indicate that the results are not as good as researchers had expected, as by-catch reduction is put at 54%.
The Norwegian Institute of Marine Research has published a new report examining the effectiveness of pingers, which emit sonic alerts at specific frequencies to discourage porpoises from approaching static fishing gears. These have been mandatory in particular areas since 2020.
‘The effects of pingers are still substantial, but not as large as we previously thought,’ said marine mammal researcher André Moan.
Previous research in 2018 to 2020 showed that pingers reduce by-catches by 95%, so the question is whether marine mammals simply get used to the sound and ignore it.
‘It’s possible that exposure over time has caused the porpoises in the area to become accustomed to the sound from the pingers, and that the sound signals therefore have less effect now than before,’ André Moan said.
Insufficient data is another possible explanation for the large difference. The most recent study has a smaller scope (four months and 308 fishing trips) while the previous study took place over 24 months and 735 fishing trips.
‘It has now also become common practise to put the pingers in bait bags and attach them to the nets. So it is possible that the bait bags may have dampened the sound signals,’ he said.
‘The new study shows that further research is needed. At the same time, the study also shows that the pingers still prevent a lot of porpoise by-catch.’
