Spatio-temporal genetic variation of juvenile smooth hammerhead sharks in South Africa

ABSTRACT

The smooth hammerhead shark Sphyrna zygaena is known to display a high degree of site fidelity to specific areas along the South African coastline. This species is vulnerable to overfishing and steep declines have been noted globally. In this study, a dual marker approach was used to investigate the spatial and temporal genetic variation of juvenile S. zygaena across the south and east coast of South Africa. Kinship of individuals was determined within and across cohorts from juvenile S. zygaena sampled in Mossel Bay, a putative pupping ground. Significant genetic differentiation (supported by F-statistics, multivariate analysis and Bayesian clustering) was evident between individuals sampled from the warm temperate south coast and the subtropical east coast, with asymmetric gene flow between regions. Distinct genetic composition was also revealed between sampling years, with different levels of relatedness within and among cohorts, indicating different temporal populations utilizing Mossel Bay annually. Based on these results, further investigation of S. zygaena populations across a wider region is warranted in order to make recommendations regarding conservation management of this vulnerable coastal shark.

KEYWORDS:

• Conservation management
• hammerhead shark
• kinship
• genetic structure
• Sphyrna zygaena

Acknowledgements

The authors are very grateful to everyone who assisted with collecting tissue samples including the crew and interns from White Shark Africa, Mossel Bay, South Africa.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Sabine Wintner http://orcid.org/0000-0001-7350-5999

Juliana D. Klein http://orcid.org/0000-0002-6741-9821

Aletta E. Bester-van der Merwe http://orcid.org/0000-0002-0332-7864

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This project was partly funded by the National Research Foundation of South Africa (TTK1206071101).