This web application uses cookies and other tracking technologies to ensure you get the best experience.
SC/69A/HIM/08
Download this file1.2 MB |
Download |
View directly in browser1.2 MB |
View in browser |
| Additional files | |
SC_69A_HIM_08.pdf1.2 MB |
Download |
| View in browser | |
Resource ID
20012
Access
Open
Document Number
SC/69A/HIM/08
Full Title
PearlNet - Passive acoustic reflectors to reduce odontocete bycatch in gillnets – update 2023
Author
Daniel Stepputtis, Isabella M.F. Kratzer, Hannah Schartmann, Thomas Noack, Ingo Schäfer, Arne Stoltenberg, Sabri Bilgin, Süleyman Özdemir, Lotte Kindt-Larsen, Finn Larsen
Authors Summary
The need to minimize bycatch of toothed whales (odontocetes) in gillnets has long been recognized. It is likely that a key to achieving this goal is the improvement of gillnet acoustic visibility, because these species use underwater sonar for orientation. Previous work on increasing gillnet detectability for echolocating animals by making the nets more recognizable has been based on trial and error, without understanding the fundamental acoustic properties of the tested modifications. Consequently, these studies have produced mixed and sometimes contradictory results. We systematically identified small, passive reflective objects that can improve the visibility of gillnets at a broad range of frequencies, i.e., for many odontocete species world wide. We used a combination of simulations and experimental verification to identify ideal, single objects that have a strong echo (or technically target strength), but are very small. To further verify the improved acoustic visibility of the modified gillnets, we took sonar images of a gillnet equipped with the identified objects and compared to sonar images of a conventional gillnet. Additionally, two commercials field trials were conducted. One field pilot trial in the commercial turbot fishery in the Black Sea gathered first information on bycatch reduction potential, while a second trial in commercial Baltic gillnet fishery focused on the target species catch efficiency. In this report, we re-iterate and summarize the past work (Kratzer et al., 2022, 2021, 2020) and update it with recent results and focus on next steps.
Publisher
IWC
Publication Year
2023
Abstract
The paper/presentation describes the current status of the development and test of the "PearlNet". An innovative approach to improve the acoustic visibility of gillnets in order to reduce the bycatch of thoothed whale species around the world.