Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South Africa
Bather protection nets have been in place off the coast of KwaZulu-Natal (KZN), South Africa, since the 1950’s. Besides sharks, they also catch a number of other marine vertebrates, including dolphins, the majority of which are Indo-Pacific bottlenose dolphins Tursiops aduncus. Previous analyses of...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Frontiers Media S.A.
2020-12-01
|
| Series: | Frontiers in Marine Science |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/articles/10.3389/fmars.2020.542675/full |
| _version_ | 1818724465236770816 |
|---|---|
| author | Stephanie Plön Christine Erbe Sabine Wintner Sabine Wintner |
| author_facet | Stephanie Plön Christine Erbe Sabine Wintner Sabine Wintner |
| author_sort | Stephanie Plön |
| collection | DOAJ |
| description | Bather protection nets have been in place off the coast of KwaZulu-Natal (KZN), South Africa, since the 1950’s. Besides sharks, they also catch a number of other marine vertebrates, including dolphins, the majority of which are Indo-Pacific bottlenose dolphins Tursiops aduncus. Previous analyses of dolphin bycatch in the nets indicated the potential impacts on the local populations, but a lack of information on population structure has to-date hindered a more detailed assessment. A recent re-assessment of the status and population delineations of T. aduncus off South Africa prompted a re-examination of demographic, spatial, and temporal patterns of its catches in bather protection nets over a 36-year period (January 1980 to December 2015). In total, 1169 dolphins were caught, including a slightly greater number of females and juveniles than other sex-classes, raising concern about the potential long-term effects on population demographics. More dolphins were caught off the North than the South coast. Temporal trends indicate that the bycatch during June and July every year (peak Sardine Run period) as a percentage of overall dolphin bycatch has been steadily decreasing from 39.8% in 1980 to 13% in 2015. A large inter-annual fluctuation can be seen, probably as a result of the inter-annual intensity of the Sardine Run. Although our results do not indicate a long-term decline of the individual populations as previously predicted, revised abundance estimates and data on the demographics and movement patterns of the animals are urgently required to accurately assess the impact of bycatch on the Indo-Pacific bottlenose dolphin populations off KZN and to advise conservation and management decisions going forward. |
| first_indexed | 2024-12-17T21:26:51Z |
| format | Article |
| id | doaj.art-0da5b4348abd45f6814d0a3d04903061 |
| institution | Directory Open Access Journal |
| issn | 2296-7745 |
| language | English |
| last_indexed | 2024-12-17T21:26:51Z |
| publishDate | 2020-12-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Marine Science |
| spelling | doaj.art-0da5b4348abd45f6814d0a3d049030612022-12-21T21:32:01ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452020-12-01710.3389/fmars.2020.542675542675Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South AfricaStephanie Plön0Christine Erbe1Sabine Wintner2Sabine Wintner3Bayworld Centre for Research and Education (BCRE), Port Elizabeth, South AfricaCentre for Marine Science and Technology, Curtin University, Perth, WA, AustraliaKwaZulu-Natal Sharks Board, Umhlanga Rocks, South AfricaUniversity of KwaZulu-Natal, School of Life Sciences, Durban, South AfricaBather protection nets have been in place off the coast of KwaZulu-Natal (KZN), South Africa, since the 1950’s. Besides sharks, they also catch a number of other marine vertebrates, including dolphins, the majority of which are Indo-Pacific bottlenose dolphins Tursiops aduncus. Previous analyses of dolphin bycatch in the nets indicated the potential impacts on the local populations, but a lack of information on population structure has to-date hindered a more detailed assessment. A recent re-assessment of the status and population delineations of T. aduncus off South Africa prompted a re-examination of demographic, spatial, and temporal patterns of its catches in bather protection nets over a 36-year period (January 1980 to December 2015). In total, 1169 dolphins were caught, including a slightly greater number of females and juveniles than other sex-classes, raising concern about the potential long-term effects on population demographics. More dolphins were caught off the North than the South coast. Temporal trends indicate that the bycatch during June and July every year (peak Sardine Run period) as a percentage of overall dolphin bycatch has been steadily decreasing from 39.8% in 1980 to 13% in 2015. A large inter-annual fluctuation can be seen, probably as a result of the inter-annual intensity of the Sardine Run. Although our results do not indicate a long-term decline of the individual populations as previously predicted, revised abundance estimates and data on the demographics and movement patterns of the animals are urgently required to accurately assess the impact of bycatch on the Indo-Pacific bottlenose dolphin populations off KZN and to advise conservation and management decisions going forward.https://www.frontiersin.org/articles/10.3389/fmars.2020.542675/fullbycatchIndo-Pacific bottlenose dolphinTursiops aduncusSouth Africasustainability |
| spellingShingle | Stephanie Plön Christine Erbe Sabine Wintner Sabine Wintner Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South Africa Frontiers in Marine Science bycatch Indo-Pacific bottlenose dolphin Tursiops aduncus South Africa sustainability |
| title | Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South Africa |
| title_full | Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South Africa |
| title_fullStr | Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South Africa |
| title_full_unstemmed | Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South Africa |
| title_short | Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South Africa |
| title_sort | long term demographic and spatio temporal trends of indo pacific bottlenose dolphin tursiops aduncus bycatch in bather protection nets off kwazulu natal south africa |
| topic | bycatch Indo-Pacific bottlenose dolphin Tursiops aduncus South Africa sustainability |
| url | https://www.frontiersin.org/articles/10.3389/fmars.2020.542675/full |
| work_keys_str_mv | AT stephanieplon longtermdemographicandspatiotemporaltrendsofindopacificbottlenosedolphintursiopsaduncusbycatchinbatherprotectionnetsoffkwazulunatalsouthafrica AT christineerbe longtermdemographicandspatiotemporaltrendsofindopacificbottlenosedolphintursiopsaduncusbycatchinbatherprotectionnetsoffkwazulunatalsouthafrica AT sabinewintner longtermdemographicandspatiotemporaltrendsofindopacificbottlenosedolphintursiopsaduncusbycatchinbatherprotectionnetsoffkwazulunatalsouthafrica AT sabinewintner longtermdemographicandspatiotemporaltrendsofindopacificbottlenosedolphintursiopsaduncusbycatchinbatherprotectionnetsoffkwazulunatalsouthafrica |