Abstract

Knowledge about the demographic histories of natural populations helps to evaluate their conservation status, and potential impacts of natural and anthropogenic pressures. In particular, estimates of effective population size obtained through molecular data can provide useful information to guide management decisions for vulnerable populations. The spotted ragged-tooth shark, Carcharias taurus (also known as the sandtiger or grey nurse shark), is widely distributed in warm-temperate and subtropical waters, but has suffered severe population declines across much of its range as a result of overexploitation. Here, we used multilocus genotype data to investigate the demographic history of the South African C. taurus population. Using approximate Bayesian computation and likelihood-based importance sampling, we found that the population underwent a historical range expansion that may have been linked to climatic changes during the late Pleistocene. There was no evidence for a recent anthropogenic decline. Together with census data suggesting a stable population, these results support the idea that fishing pressure and other threats have so far not been detrimental to the local C. taurus population. The results reported here indicate that South Africa could possibly harbour the last remaining, relatively pristine population of this widespread but vulnerable top predator.

Details

Title
A globally threatened shark, Carcharias taurus, shows no population decline in South Africa
Author
Klein, Juliana D 1 ; der Merwe Aletta E Bester-van 2 ; Dicken, Matthew L 3 ; Emami-Khoyi Arsalan 4 ; Mmonwa, Kolobe L 5 ; Teske, Peter R 4 

 Stellenbosch University, Molecular Breeding and Biodiversity Group, Department of Genetics, Stellenbosch, South Africa (GRID:grid.11956.3a) (ISNI:0000 0001 2214 904X); University of Johannesburg, Centre for Ecological Genomics and Wildlife Conservation, Department of Zoology, Auckland Park, South Africa (GRID:grid.412988.e) (ISNI:0000 0001 0109 131X) 
 Stellenbosch University, Molecular Breeding and Biodiversity Group, Department of Genetics, Stellenbosch, South Africa (GRID:grid.11956.3a) (ISNI:0000 0001 2214 904X) 
 KwaZulu-Natal Sharks Board, Umhlanga Rocks, South Africa (GRID:grid.11956.3a); Nelson Mandela University, Department of Development Studies, School of Economics, Development and Tourism, Port Elizabeth, South Africa (GRID:grid.412139.c) (ISNI:0000 0001 2191 3608) 
 University of Johannesburg, Centre for Ecological Genomics and Wildlife Conservation, Department of Zoology, Auckland Park, South Africa (GRID:grid.412988.e) (ISNI:0000 0001 0109 131X) 
 KwaZulu-Natal Sharks Board, Umhlanga Rocks, South Africa (GRID:grid.412988.e) 
Publication year
2020
Publication date
2020
Publisher
Nature Publishing Group
e-ISSN
20452322
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2471500903
Copyright
© The Author(s) 2020. This work is published under http://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.