Total mercury concentrations in sharks, skates and rays along the South African coast

• Published in: Marine pollution bulletin 2022-11, Vol.184, p.114142-114142, Article 114142
• Main Authors: Erasmus, J.H., Smit, N.J., Gerber, R., Schaeffner, B.C., Nkabi, N., Wepener, V.
• Format: Article
• Language: English
• Subjects: Bioaccumulation; Biomagnification; Elasmobranchs; Mercury; Trophic position
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2022.114142

Global declines in elasmobranch populations resulting from several stressors raises conservation concern. Additionally, apex predators bioaccumulate high concentrations of total mercury (THg), due to biomagnification. Although South Africa is considered one of the top ten contributors of Hg emissions globally, information on Hg concentrations in elasmobranchs is limited. The aim of this study was to evaluate the THg concentrations in 22 species of elasmobranchs along the South African coastline. Concentrations ranged between 0.22 and 5.8 mg/kg in Haploblepharus pictus (dark shysharks) and Rostroraja alba (white skates) on the south coast, respectively. Along the east coast it ranged between 0.21 and 17.8 mg/kg in Mobula kuhlii (shortfin devil rays) and Sphyrna lewini (scalloped hammerheads), respectively. Mercury concentrations on the east coast were in the same range or higher compared to the same species sampled between 2005–10 from the same region, with generally higher concentrations compared to the same species sampled globally. •East coast THg concentrations are higher than the south coast of South Africa.•Higher trophic position elasmobranchs exhibit higher THg concentrations.•Foraging depth did not play a significant role in THg bioaccumulation.•Current THg concentrations are higher than those reported in 2005–10.•Highest THg concentrations for Sphyrna lewini reported globally