Trace element and strontium isotopic analysis of Gulf Sturgeon fin rays to assess habitat use

Trace element and 87 Sr/ 86 Sr isotope analyses of fish pectoral fin rays offer non-destructive methods for determining habitat use. In this study, water and fin ray samples were analyzed for Gulf Sturgeon Acipenser oxyrinchus desotoi from the Choctawhatchee River Basin (FL and AL, USA) and compared with reference samples from Atlantic Sturgeon A. o. oxyrinchus held at controlled salinities (0, 10, 33 ppt). Samples were analyzed using inductively coupled plasma mass spectrometry, with a multi-collector for 87 Sr/ 86 Sr. In water, Sr, Ba, Mn and Zn differed between freshwater and saline habitats, with increases in Sr and decreases in Ba, Mn and Zn. 87 Sr/ 86 Sr decreased upstream to downstream with lowest values in saline habitats. In the reference study, water trace element concentrations and 87 Sr/ 86 Sr corresponded to those in pectoral fin rays. 87 Sr/ 86 Sr was higher in pectoral fin ray than water, due to influence of diet, which differed with salinity. In wild fish, trace elements in pectoral fin rays indicated freshwater emigration to saline habitats primarily occurred in the second to third growth zone with some heterogeneity in the population (4%