Population structure and ontogenetic habitat use of Micropogonias furnieri in the southwestern Atlantic Ocean inferred by otolith chemistry

Abstract

The whitemouth croaker Micropogonias furnieri is a demersal sciaenid fish widely distributed in Atlantic coasts and estuaries from Mexico to Argentina. In the South Atlantic (33°- 41 °S), there are two stocks: Río de la Plata (RDP) and El Rincón (ER), respectively. Studies based on genetic, age and size structure data suggested that RDP stock would be composed of two different populations, one estuarine-dependent (estuarine type) and the other with oceanic spawning sites (oceanic type). The hypothesis of segregation between the estuarine and oceanic types, and between these and the ER stock was tested by using the otolith chemistry in the edge (adult stage) and core (early stage) of fish. Li/Ca, Na/Ca, Mn/Ca, Cu/Ca, Ba/Ca, and Pb/Ca ratios were determined by LA-ICP-MS. Several ratios were significantly different between sampling sites for edge and core (p < 0.05). For edge, PERMANOVA showed significant differences (p < 0.05) between all sampling sites, while the quadratic discriminant analyses showed a mean jackknifed classification of 83 % (87 % for Uruguay, 76 % for RDP, and 86 % for ER). This supports the hypothesis of differentiation of the RDP stock into oceanic and estuarine-dependent groups. The non-metric multidimensional scaling and cluster analysis based on the core chemistry suggested that there would be at least two large chemical signatures in the early stage. The elemental ratio time series showed a potential endogenous effect on the incorporation of various elements (e.g. Ba, Mn, Li) in the early stages, while Sr/Ca time series suggested a general migratory behavior between estuarine and marine habitats throughout ontogeny.