Population structure and habitat connectivity of Genidens genidens (Siluriformes) in tropical and subtropical coasts from Southwestern Atlantic

Abstract

We use otolith trace element-to-calcium element concentraton ratios (Ba:Ca, Cu:Ca, Mg:Ca, Mn:Ca, Ni:Ca, Sr:Ca and Zn:Ca) and shape to evaluate the degree of segregation and presence of different nursery areas and fish stocks of Genidens genidens in the Brazilian coastal area. Otolith core (juvenile stage) and edge (adult stage) element:Ca fingerprints (N = 89), as well as otolith elliptic Fourier descriptors (N = 147) were compared between four estuaries. Several element:Ca ratios were significantly different between estuaries for otolith core and edge (p < 0.05). MANOVA, PERMANOVA, linear and quadratic discriminant analyses based on Fourier descriptors (12 harmonics) and microchemistry were effective for discriminating between all sampling sites (p < 0.05), except Itapanhaú River and Paranaguá Bay (p > 0.05). The discriminant analyses showed jackknifed classification from 54.1% to 100% considering young (core microchemistry) and adult life stages (edge microchemistry and shape). When otolith microchemistry and shape were combined, the jackknifed classification increased in relation to the separates methods, ranged from 89.5 to 100% (mean 95.2%). The high degree of segregation (low connectivity) in juvenile and adult stages between the estuaries is consistent with the presence of isolated populations, and advocates for estuary-specific management strategies.