Spatial variability in strontium to calcium in the Caspian Sea: Recognition of starry sturgeon stocks from the pectoral fin spine chemistry

One of the fundamental hypotheses in aquatic ecology deals with the recognition of fish stocks. The present study tested the spatial dynamics of starry sturgeon stocks across environmental gradients by spatial variability in strontium to calcium in the pectoral fin spine. Forty samples of starry sturgeon were collected from the north and south of the Caspian Sea. A quantitative method was used to examine stocks using digested pectoral fin spine, reflecting habitat characters of fish. Parts of pectoral fin spines from adult starry sturgeon were separated and analyzed using Inductively Coupled Plasma- Mass Spectrometry (ICP-MS). Comparisons of Sr/Ca ratios in digested spines of the fish from north and south of the Caspian Sea demonstrated that Sr/Ca varied in the region and this significance was reflected in the spine as well. Our results for starry sturgeon support the use of spine Sr/Ca as a proxy for ambient levels throughout their life-history, confident interpretation of life history from spine Sr/Ca chronologies, however likely require matching time series of ambient Sr/Ca in the water bodies of interest.