Stock structure of Atlantic spadefish Chaetodipterus faber from Southwest Atlantic Ocean inferred from otolith elemental and shape signatures

The Atlantic spadefish, Chaetodipterus faber, is an economically important species along the Southwest Atlantic Ocean, especially in the southeastern-south Brazil. Despite this, knowledge about stock structure is scarce and, at present, is no formal management strategy to ensure the long-term sustainability of the C. faber fishery in Brazil. In order to understand the stock structure of C. faber in the Southwest Atlantic, a total of 100 individuals ranging from 30 to 40 cm total length were collected from the five main fishery regions of Brazil [Espirito Santo (ES), Rio de Janeiro (RJ), Sao Paulo (SP), Parana (PR), and Santa Catarina (SC)], between December 2015 and March 2016. The shape outline of each otolith was assessed using Elliptic Fourier descriptors (EFD). Multi-Elemental signatures (MES) of whole otoliths were obtained using inductively coupled plasma mass spectrometry. Data were analyzed through uni- and multivariate statistics. Canonical analysis of principal coordinates indicated that spatial differences were mainly driven by Sr/Ca ratios, Ba/Ca ratios and EFD 14. Combining data from both techniques (EFD and MES), the leave-one-out classification re-assigned individuals to their region of origin with an accuracy of 100% (ES), 85% (RJ), 80% (SP), 85% (PR), and 65% (SC). The hereby results indicate that the connectivity between the local population of C. faber in the ES region (20 degrees S) with the southern populations (> 22 degrees S) is limited; moreover, data suggest the presence of spatially structured semi-discrete groups between 23 degrees S and 27 degrees S. Despite the possibility of intermixing C. faber populations in the Brazilian Southwest Atlantic coast, local populations should be regarded as different stocks for fisheries management purposes. However, at present, the degree of intermixing and the contribution that each local population receive from distant recruitment sources is unknown and demands further studies.