Comparing Pectoral Fin-Clip and Dorsal Muscle Tissue in an Investigation of Lake Sturgeon Trophic Ecology Using Stable Isotope Analysis

Stable isotope analysis has become a commonly used method for obtaining time-integrated feeding relationships in food web studies. Recently, there has been emphasis on developing non-lethal sampling methods. Because lake sturgeon (Acipenser fulvescens) are threatened in many aquatic ecosystems, we evaluated the feasibility of using pectoral fin clips as an alternative to dorsal muscle tissue in stable isotope studies. Because lipid content can affect stable isotope ratios, we also determined whether lipid extraction affected the relationship between fin-clip and muscle tissue signatures. Significant, positive relationships were observed between fin and muscle tissues for both δ¹⁵N (r²=0.63) and δ¹³C (r²=0.34). Lipid extraction significantly reduced the among-individual variation, and improved the δ¹³C relationship significantly (r²=0.76). The strong relationships between fin-clip and muscle tissue signatures demonstrate that fin-clips will allow trophic studies to accurately adjust for the effect of differential lipid accumulation and for lake sturgeon can effectively limit the need for invasive sampling. We further investigated the carbon sources and trophic position of lake sturgeon in Rainy River, ON to assess their role in the food web which can be used as a baseline for investigating changes in trophic structure due to introduction of invasive species and/or anthropogenic stressors.