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SC/69A/HIM/01/Rev1
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Resource ID
20020
Access
Open
Document Number
SC/69A/HIM/01/Rev1
Full Title
Assessing effectiveness of upcycled plastic bottles to reduce franciscana dolphin (Pontoporia blainvillei) bycatch in bottom set trammel nets in southern Brazil: Preliminary results
Author
Federico Sucunza, Gabriel G Larre, Leonardo M Pinheiro, Daniel Danilewicz, Paulo H Ott, Lorenzo Von Fersen, Nick Tregenza, Per Berggren
Authors Summary
The purpose of this study was to evaluate the effectiveness of upcycled plastic drink bottles as echolocation reflectors and a low-cost mitigation method to reduce franciscana dolphin bycatch and their potential impact on target species catch in bottom set trammel nets, in southern Brazil. Observed trials with (treatment) and without (control) plastic bottles in trammels nets recording dolphin bycatch and target species catch were conducted between November 2020 and December 2022. A total of 108 sets (59 control and 49 treatment) resulted in bycatch of two franciscana dolphins and two bottlenose dolphins (Tursiops sp.) in control sets and no dolphin bycatch in treatment sets. GLM results showed a statistically non-significant negative effect on dolphin bycatch using plastic bottles (z-value = 0.007, p = 0.994) and a significant positive effect on target fish catch using plastic bottles (z-value = 2.824, p = 0.0047). Passive acoustic monitoring (using F-POD) was conducted on 44 sets (32 treatment and 12 control) and showed that franciscana dolphins and other cetaceans were present and that there was no difference in detection positive minutes per set for treatment and control sets. These preliminary results indicate that upcycled plastic bottles used as acoustic reflectors in bottom set trammel nets may reduce the bycatch of dolphins (including franciscana) and have a positive effect on target species catch compared to control sets. These preliminary results require continued trials with additional sets to confirm the trends.
Publisher
IWC
Publication Year
2023
Abstract
The purpose of this study was to evaluate the effectiveness of upcycled plastic drink bottles as echolocation reflectors and a low-cost mitigation method to reduce franciscana dolphin bycatch and their potential impact on target species catch in bottom set trammel nets, in southern Brazil. Observed trials with (treatment) and without (control) plastic bottles in trammels nets recording dolphin bycatch and target species catch were conducted between November 2020 and December 2022. A total of 108 sets (59 control and 49 treatment) resulted in bycatch of two franciscana dolphins and two bottlenose dolphins (Tursiops sp.) in control sets and no dolphin bycatch in treatment sets. GLM results showed a statistically non-significant negative effect on dolphin bycatch using plastic bottles (z-value = 0.007, p = 0.994) and a significant positive effect on target fish catch using plastic bottles (z-value = 2.824, p = 0.0047). Passive acoustic monitoring (using F-POD) was conducted on 44 sets (32 treatment and 12 control) and showed that franciscana dolphins and other cetaceans were present and that there was no difference in detection positive minutes per set for treatment and control sets. These preliminary results indicate that upcycled plastic bottles used as acoustic reflectors in bottom set trammel nets may reduce the bycatch of dolphins (including franciscana) and have a positive effect on target species catch compared to control sets. These preliminary results require continued trials with additional sets to confirm the trends.