Small Tails Tell Tall Tales--Intra-Individual Variation in the Stable Isotope Values of Fish Fin

Area of Science:

• Ecology
• Isotope analysis
• Ichthyology

Background:

• Fish fin is a common non-lethal sample for stable isotope studies.
• Fin tissues (ray and membrane) have heterogeneous stable isotope values.
• Sampling location within a fin can influence ecological interpretations.

Purpose of the Study:

• To quantify intra-fin variability in stable isotope values.
• To assess variation in carbon, nitrogen, hydrogen, and oxygen isotopes.
• To provide recommendations for accurate fish ecological studies.

Main Methods:

• Analyzed stable isotopes (δ13C, δ15N, δ2H, δ18O) in Atlantic salmon and brown trout caudal fins.
• Sub-sectioned fins into tip, mid, and base.
• Further divided sections into ray and membrane tissues.

Main Results:

• Significant isotope variation (δ13C, δ15N, δ2H, δ18O) observed between fin ray and membrane tissues.
• δ13C and δ2H varied longitudinally, with base sections depleted/enriched relative to tips.
• δ18O showed enrichment in base/ray sections compared to tips/membranes; δ15N variation linked to ontogeny.

Conclusions:

• Intra-fin variability necessitates careful sampling strategies.
• Recommendations include analyzing muscle tissue for calibration, standardizing sampling to fin tips, or homogenizing fins.
• Accurate stable isotope analysis is crucial for reliable fish ecology research.