Abstract
In the late 1970s, studies on the population structure of S. brasiliensis suggested the existence of two stocks, considering distinct regional somatic growth rates and spawning areas (23–25° S and 26–28° S). This scenario was further confirmed by geochemical signatures of whole otoliths combined with basic biological data regarding 2-year-old sardines collected in SW-S Brazil. However, information about sardine movements and connectivity between their main juvenile recruitment areas and the adult fishing grounds is currently limited. In this study, natal otolith elemental fingerprints (core section) of young-of-year (age 0+) and adult (age 2+) individuals were collected, respectively, in the main spawning areas (2019) and fishing grounds (2021) and evaluated. Elemental signatures of recruits were compared with those of adult fish from the same cohort to estimate connectivity between juvenile recruitment areas (RJ-22° S, SP-23° S and SC-26° S) and regional adult populations captured in the major fishing grounds (22–23° S, 24–25° S and 26–27° S). Uni- and multi-elemental chemical signatures showed significant differences for age 0+ and for age 2+. Pairwise comparisons associated age 0+ and age 2+ with the northern distribution area (RJ + SP) and differentiated them from those of SC. The leave-one-out reclassification matrix combining chemical fingerprints and reassigned the individuals to their original areas with moderate-to-high accuracy: RJ 0+ (85%), SP 0+ (80%), SC 0+ (85%), and from RJ 2+ (80%), SP 2+ (70%), SC 2+ (75%). This variability was driven by Ba/Ca, Fe/Ca, Mg/Ca, Mn/Ca, and Sr/Ca ratios. Maximum likelihood analysis suggested for the 2019 cohort that replenishment of adult populations of S. brasiliensis along the Brazilian coast was mostly derived from the northern recruitment area (RJ + SP = 64%). Nonetheless, an important contribution from the southern counterparts to the northern stock was detected (36%), supporting the hypothesis of meta-population structure.
Author Contributions
Conceptualization, R.S. (Rafael Schroeder) and A.T.C.; Statistical analysis, R.S. (Rafael Schroeder); Investigation, R.S. (Rafael Schroeder), A.T.C., P.R.S., A.M.V.-d.-S.; Fish Sampling, R.S. (Richard Schwarz), F.A.D., T.P.F. and N.T.H.; Analytical analysis, R.S. (Rafael Schroeder), A.T.C., A.M.-V. and J.P.C.; Writing—original draft preparation, R.S. (Rafael Schroeder); writing—review and editing, R.S. (Rafael Schroeder) and A.T.C.; Supervision, A.T.C.; Funding acquisition, A.T.C. and P.R.S. All authors have read and agreed to the published version of the manuscript.
Funding
Rafael Schroeder received a PhD scholarship from the Coordination for the Improvement of Higher Education Personnel (CAPES). Alberto T. Correia was supported by national funds through FCT—Foundation for Science and Technology within the scope of UIDB/04423/2020 and UIDP/04423/2020. This study was also funded by the Brazilian Biodiversity Fund (FUNBIO).
Institutional Review Board Statement
Not applicable (seafood product).
Informed Consent Statement
Not applicable.
Data Availability Statement
Not available. Only upon request.
Conflicts of Interest
The authors declare no conflict of interest.
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