Population structure of the Brazilian sardine (Sardinella brasiliensis) in the Southwest Atlantic inferred from body morphology and otolith shape signatures

The Brazilian sardine (Sardinella brasiliensis) sustains the most important pelagic fishery off Brazilian waters. The present study evaluated the existence of distinct population-units inferred from body geometric morphometrics and otolith shape analyses using two and three-year-old individuals collected in Rio de Janeiro and Santa Catarina, the two main Brazilian fishery grounds. Univariate and multivariate statistics were performed for the entire dataset and separated by age groups. Re-classification success for combined ages achieved an overall re-classification rate of 84% and 89% for body and otolith signatures, respectively. Moreover, the combination of both techniques improved the overall re-classification success to 93%. However, when both techniques were conducted by age group, it allowed to unravel a more detailed population structure scenario, and a complete group separation (100% re-classification success) was obtained using otolith shape analyses for two-year-old individuals. Both techniques indicated the existence of two different population-units considering the Brazilian geographical extremes of the species' fishing area. Such regional differences are probably related to distinct oceanographic conditions affecting the feeding regime and fish growth. This study clearly shows that S. brasiliensis caught off southeast-south Brazil corresponds to two distinct population-units, and recommends a finer regional fishery management for the species.

Automated summary

The study evaluated distinct population-units of Brazilian sardine inferred from body geometric morphometrics and otolith shape analyses. It revealed the existence of two different population-units in the Brazilian fishing area, likely due to varying oceanographic conditions and fish growth patterns.