Fin spine metals by LA-ICP-MS as a method for fish stock discrimination of Genidens barbus in anthropized estuaries

Abstract

Metal:Ca ratios (Li:Ca, Cu:Ca, Fe:Ca, Na:Ca, Rb:Ca, Pb:Ca and Zn:Ca) in fin spines of Genidens barbus, an endangered catfish species, were used as possible habitat markers from three Southwestern Atlantic sampling areas (Paranaguá estuarine complex, Brazil; Paraná River Delta, Argentina-Uruguay; and Negro River, Patagonia). Significant differences (p < 0.05) among sites for metal:Ca ratios support the utility of two prospective indicators: (1) habitat – outer 45 μm of spine edge and, (2) fish stock – outer ∼600 μm of spine. Multivariate analysis (MANOVA and PERMANOVA, p < 0.05) and lineal discriminant function analysis (LDA) proved relatively effective for discriminating both habitat (classification rate: 73%) and fish stock (classification rate: 66%) between sampling sites. Classification success improved to 85% (habitat) and 96% (fish stock) when LDAs incorporating Sr:Ca, Ba:Ca, Mg:Ca and Mn:Ca) from previous research (same samples) were performed. These results support the use of metal:Ca ratios in G. barbus fin spines as a non-lethal tool for discriminating habitat use and stocks of this endangered catfish. This approach may be applicable to other vulnerable species in polluted habitats.