Integrating fish scale and bone isotopic compositions for 'deep time' retrospective studies

Area of Science:

• Paleoecology
• Isotope Geochemistry
• Aquatic Ecosystem Analysis

Background:

• Archived fish scales offer long-term ecological insights but often miss pre-industrial periods.
• Archaeological fish bones provide a crucial temporal link to the Pleistocene, capturing earlier environmental conditions.
• Collagen, present in both scales and bones, is a key tissue for isotopic analysis.

Purpose of the Study:

• To establish the comparability of isotopic compositions (δ¹³C and δ¹⁵N) between fish scale and bone collagen.
• To lay the groundwork for integrating isotopic data from historical scales and archaeological bones.
• To enable the construction of millennium-scale isotopic time series for aquatic ecosystem research.

Main Methods:

• Controlled diet experiments were conducted on fish.
• Isotopic analysis (δ¹³C and δ¹⁵N) was performed on collagen extracted from various fish tissues, including scales and bones.
• Inter-tissue offsets in isotopic values were quantified and compared.

Main Results:

• No significant difference was found in δ¹³C values between scale and bone collagen.
• A very slight, but potentially meaningful, inter-tissue offset (<0.3‰) was observed in δ¹⁵N values.
• The observed δ¹⁵N offset is often smaller than analytical uncertainty, suggesting high comparability.

Conclusions:

• Fish scale and bone collagen exhibit directly comparable δ¹³C values.
• The small δ¹⁵N offset between scale and bone collagen is generally negligible for many studies.
• Isotopic data from modern, historical (scales), and archaeological (bones) fish collagen can be integrated, enhancing long-term ecological and anthropogenic impact studies.