Entanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa

dc.contributor.advisorGridley, Tess
dc.contributor.advisorReed, Cecile
dc.contributor.authorHenry, Maguiña Ramilo
dc.date.accessioned2023-03-07T11:20:08Z
dc.date.available2023-03-07T11:20:08Z
dc.date.issued2022
dc.date.updated2023-02-20T12:55:43Z
dc.description.abstractGlobal pollution is increasing, and marine mammals are commonly affected by the waste in the ocean. Endemic to the African continent, the pinniped species, Cape fur seal (Arctocephalus pusillus pusillus), are vulnerable to entanglement due to their curious nature and thick fur. Entanglement data were available from systematic photographic surveys of six colonies in South Africa (2019-2022) as well as opportunistic and citizen science records, photographs, aerial images and historical records from 1997 onwards. Overall, 314 cases of entangled seals were identified. As calculated from the systematic surveys, Baboon Point in Elands Bay (0.24% ± 0.78%, n = 7, with a 95% confidence interval) had the highest entanglement incidence. Seal Island in False Bay had the highest overall number of entanglements (50) and the highest mean number per survey (5.10 ± 0.46 number of entangled seals, n = 10), but this was also the largest colony assessed. Entanglement was observed the most in adults (61%, n = 189), with fishing materials being the primary cause of entanglements (40%, n = 59), specifically monofilament fishing lines (33%, n = 103). Although most entanglements were deemed ‘sight' (67%, n = 100), 28 cases (19%) were considered ‘severe,' likely impacting the health and welfare of affected individuals. Random Forest classification analysis identified the item of entangling material as an important predictor variable in terms of the severity level of the entanglement. The most common entangling material color was white (35%, n=82) followed by green (13%, n=30) and clear (7%, n=17) which may reflect the proportion of materials seals are exposed to, how they perceive them underwater, or their attraction to such colors. Aerial photographs showed higher efficiency in detecting entanglement cases than boat-based data where comparisons were possible. This is the first study to investigate entanglements of Cape fur seals in South Africa and highlights the need for correct disposal of waste, particularly that derived from the fishing industry, to mitigate its impacts on the welfare and conservation of marine fauna.
dc.identifier.apacitationHenry, M. R. (2022). <i>Entanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa</i>. (). ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/37318en_ZA
dc.identifier.chicagocitationHenry, Maguiña Ramilo. <i>"Entanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa."</i> ., ,Faculty of Science ,Department of Biological Sciences, 2022. http://hdl.handle.net/11427/37318en_ZA
dc.identifier.citationHenry, M.R. 2022. Entanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa. . ,Faculty of Science ,Department of Biological Sciences. http://hdl.handle.net/11427/37318en_ZA
dc.identifier.ris TY - Master Thesis AU - Henry, Maguiña Ramilo AB - Global pollution is increasing, and marine mammals are commonly affected by the waste in the ocean. Endemic to the African continent, the pinniped species, Cape fur seal (Arctocephalus pusillus pusillus), are vulnerable to entanglement due to their curious nature and thick fur. Entanglement data were available from systematic photographic surveys of six colonies in South Africa (2019-2022) as well as opportunistic and citizen science records, photographs, aerial images and historical records from 1997 onwards. Overall, 314 cases of entangled seals were identified. As calculated from the systematic surveys, Baboon Point in Elands Bay (0.24% ± 0.78%, n = 7, with a 95% confidence interval) had the highest entanglement incidence. Seal Island in False Bay had the highest overall number of entanglements (50) and the highest mean number per survey (5.10 ± 0.46 number of entangled seals, n = 10), but this was also the largest colony assessed. Entanglement was observed the most in adults (61%, n = 189), with fishing materials being the primary cause of entanglements (40%, n = 59), specifically monofilament fishing lines (33%, n = 103). Although most entanglements were deemed ‘sight' (67%, n = 100), 28 cases (19%) were considered ‘severe,' likely impacting the health and welfare of affected individuals. Random Forest classification analysis identified the item of entangling material as an important predictor variable in terms of the severity level of the entanglement. The most common entangling material color was white (35%, n=82) followed by green (13%, n=30) and clear (7%, n=17) which may reflect the proportion of materials seals are exposed to, how they perceive them underwater, or their attraction to such colors. Aerial photographs showed higher efficiency in detecting entanglement cases than boat-based data where comparisons were possible. This is the first study to investigate entanglements of Cape fur seals in South Africa and highlights the need for correct disposal of waste, particularly that derived from the fishing industry, to mitigate its impacts on the welfare and conservation of marine fauna. DA - 2022_ DB - OpenUCT DP - University of Cape Town KW - Africa KW - Entanglement KW - Marine Pollution KW - Pinniped LK - https://open.uct.ac.za PY - 2022 T1 - Entanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa TI - Entanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa UR - http://hdl.handle.net/11427/37318 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/37318
dc.identifier.vancouvercitationHenry MR. Entanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa. []. ,Faculty of Science ,Department of Biological Sciences, 2022 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/37318en_ZA
dc.language.rfc3066eng
dc.publisher.departmentDepartment of Biological Sciences
dc.publisher.facultyFaculty of Science
dc.subjectAfrica
dc.subjectEntanglement
dc.subjectMarine Pollution
dc.subjectPinniped
dc.titleEntanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationlevelMSc
Files
Original bundle
Now showing 1 - 1 of 1
Loading...
Thumbnail Image
Name:
thesis_sci_2022_henry magui a ramilo.pdf
Size:
3.38 MB
Format:
Adobe Portable Document Format
Description:
License bundle
Now showing 1 - 1 of 1
Loading...
Thumbnail Image
Name:
license.txt
Size:
0 B
Format:
Item-specific license agreed upon to submission
Description:
Collections