High plasticity in habitat use of Lycengraulis grossidens (Clupeiformes, Engraulididae)

In this study, we analyzed the Sr:Ca and Ba:Ca ratios of the otoliths of 139 Lycengraulis grossidens individuals sampled along the southwestern Atlantic Ocean, including two freshwater areas, to describe patterns of habitat use and their latitudinal organization. Otolith sections were analyzed by laser ablation inductively coupled plasma mass spectrometry along core-to-edge transects. Otolith edge analysis revealed significant differences in Sr:Ca and Ba:Ca ratios between fish from freshwater habitats and those from estuarine/marine habitats, indicating that these ratios may be used to describe habitat use patterns. Lifetime transects of Sr:Ca and Ba:Ca indicate at least four distinct habitat use patterns: freshwater residents, estuarine/marine residents, and two distinct diadromous/nomadic types. Most individuals (88.6%) sampled at northern latitudes in sheltered marine bays and the coastal ocean were estuarine/marine residents, whereas at southern latitudes, most individuals were diadromous (72.5%). We also identified landlocked populations in the Uruguay River and in Mirim Lagoon. These results suggest that L. grossidens exhibits flexible habitat use strategies and may use freshwater, estuarine and marine environments throughout their lifetime.