Habitat use of the amphidromous catfish Genidens barbus: first insights at its southern distribution limit

Abstract

White sea catfish Genidens barbus is an endangered amphidromous species distributed between northeastern Brazil and northern Argentine Patagonia, whose migratory behaviour at the southern end of its range is unknown. Here, the migratory patterns of this species were studied including marine and freshwater (Patagonian stock) environments via otolith core-to-edge Sr/Ca and Ba/Ca profiles. Based on the Sr/Ca ratio, all specimens were classified as amphidromous with annual cycles of movement between waters of relatively low to high salinity occurring during spring. The core Sr/Ca ratio matched with the reference values for freshwater in all specimens. No evidence of resident freshwater or marine individuals was found. No evident antagonistic relationship was found between both Sr/Ca and Ba/Ca ratios. A Ba/Ca peak was observed followed by a drop coinciding with the core edge, highlighting the need to evaluate the potential transfer from the yolk, and to understand what factors are linked to the growth marks within the first year of life.