UC Santa Cruz

Oxygen isotope ratios of fish biominerals reflect environmental growth conditions - specifically, the temperature and δ¹⁸O values of water. In Holocene ocean sediments, phosphate δ¹⁸O (δ¹⁸O_P) values of small pelagic fish bones and scales can be coupled with abundance data to study connections between past climate and population dynamics. This requires the detection of decadal scale climate variability via precise isotope measurements. To accomplish this, isotope data is best corrected by multiple regression methods that facilitate both instrumental monitoring and correction model optimization. Our measurements of δ¹⁸O values from bones, scales, and otoliths indicated that all three materials provide similar information about growth conditions, provided that each material's unique allometry is considered. For sardines cultured at controlled temperatures, δ¹⁸O_P values of scales were consistent with the fractionation equation proposed by Longinelli and Nuti (1973). These results support the use of δ¹⁸O_P to investigate the paleoecology of small pelagic fish.