Otolith δ18O and microstructure analyses provide further evidence of population structure in sardine Sardinops sagax around South Africa

Tatsuya Sakamoto, Carl D. Van Der Lingen, Kotaro Shirai, Toyoho Ishimura, Yonela Geja, James Peterson, Kosei Komatsu

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Sardine Sardinops sagax is an ecologically and economically important Clupeid found off the entire South African coast that includes both coastal upwelling and western boundary current systems. Although the management of the sardine fisheries historically assumed a single, panmictic population, the existence of three, semi-discrete subpopulations has recently been hypothesized. We conducted otolith δ18O and microstructure analyses to investigate nursery habitat temperatures and early life growth rates, respectively, of sardine collected from three biogeographic regions around South Africa's coast to test that hypothesis. Analyses indicated that for both summer- and winter-captured adults and summer-captured juveniles, fishes from the west coast grew significantly slower in water that was several degrees cooler than those from the south and east coasts. This suggests that mixing of sardines between regions, particularly the west and other coasts, is relatively limited and supports the hypothesis of semi-discrete subpopulations. However, the west-south differences disappeared in the results for winter-captured juveniles, suggesting that differences in early life conditions between regions may change seasonally, and/or that all or most winter-captured juveniles originated from the west coast. Further elucidating the interactions between South African sardine subpopulations and the mechanisms thereof is important for sustainable harvesting of this species.

Original languageEnglish
Pages (from-to)2669-2680
Number of pages12
JournalICES Journal of Marine Science
Volume77
Issue number7
DOIs
Publication statusPublished - Dec 1 2020
Externally publishedYes

Keywords

  • South African sardine
  • coastal upwelling
  • otolith microstructure
  • otolith δ18O
  • population structure
  • western boundary current

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Ecology

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