Barbara Maichak de Carvalho

Nursery areas and connectivity of the adults anadromous catfish (Genidens barbus) revealed by otolith-core microchemistry in the south-western Atlantic Ocean

The anadromous catfish, Genidens barbus, is a commercial and vulnerable species from South America. The aims of the present study were to assess whether the nursery areas can be discriminated by using microchemical signatures of lapillus otoliths, to assess the accuracy of classifying fish in relation to natal nursery area and to discuss the possibility of existence of homing behaviour. Thus, the otolith-core chemical signatures (barium (Ba):calcium (Ca), lithium (Li):Ca, magnesium (Mg):Ca, manganese (Mn):Ca, strontium (Sr):Ca, and zinc (Zn):Ca ratios) of adult fish were compared among different estuaries (De La Plata River in Argentina, and Patos Lagoon, Paranagua Bay and Guanabara Bay in Brazil). PERMANOVA analysis showed significant differences in the multi-element signatures of the otolith core among sampling sites for all cohorts (2002, 2003, 2006 and 2007), indicating that the technique has considerable potential for use in future assessments of population connectivity and nursery areas of G. barbus. Via quadratic discriminant function analysis, fish were classified to natal nursery areas with 80–100% cross-validation classification accuracies. These results suggested that a high level of spatial segregation exists in adult catfish life and homing behaviour could not be ruled out on the basis of our data.

Displacements of Anchoa tricolor (Spix & Agassiz, 1829) in a subtropical estuary revealed by the otolith microchemistry

This study aimed to describe the displacements of anchovy ( Anchoa tricolor ) in a subtropical estuary in South America, using the otolith microchemistry. We analyzed 198 specimens of A. tricolor in the Paranagua Estuarine Complex (Brazil) and data of salinity and rainfall. The biological and environmental data were grouped into sectors (internal, intermediate and external) and periods (early and late rainy and dry periods). The concentrations of Ca, Ba and Sr were determined using an ICP-OES. The Sr: Ca ratio indicated the existence of two groups of probably different origins that use the estuary at the same time but occupy different sectors of the estuary. In the other periods and sectors, we observed that part of the A. tricolor population used the estuary for feeding and growth, with an increase in the Sr: Ca ratio. The Ba: Ca ratio did not differ groups of use in the estuary, but rather, revealed low values suggesting that this species does not use freshwater environments. However, this ratio showed a high variation in the rainy period, indicating greater availability of barium in the estuarine regions affected by river discharge. Considering our results, it is possible to classify A. tricolor as an estuarine migrant species that uses estuaries for feeding and growth. Also, Sr: Ca and Ba: Ca ratios can be indicative of spatial and temporal displacement, respectively.