Nonlethal Sampling of Sunfish and Slimy Sculpin for Stable Isotope Analysis: How Scale and Fin Tissue Compare with Muscle Tissue

Abstract

We found that the sampling of tissues that do not result in the death of the fish, such as scale and fin tissue, may be substituted for muscle tissue in stable isotope analysis (SIA) of fishes. Comparisons were made between the values of δ¹³C and δ¹⁵N found in muscle tissue with the corresponding scale tissue of three sunfish species (bluegill Lepomis macrochirus, pumpkinseed L. gibbosus, and redbreast sunfish L. auritus) and with caudal fin tissue of slimy sculpin Cottus cognatus. The fish showed strong linear correlation in δ¹³C values between their nonlethally sampled scale or fin tissue and their muscle tissue (combined sunfish: r = 0.97; slimy sculpin: r = 0.84). Sunfish δ¹³C values were higher in scale tissue than in muscle tissue and required a correction factor for converting the scale values to the muscle values (regression equation: y = 1.1673x + 1.0531). Slimy sculpin δ¹³C fin and muscle values were similar and did not require a correction factor. The correlation of δ¹⁵N values between the tissues was also strong in both sunfish (r = 0.94) and slimy sculpin (r = 0.90). A correction factor was needed to convert δ¹⁵N values from scale to muscle in the three sunfish species (y = 0.8504x + 2.6698) and from fin to muscle in slimy sculpin (y = 1.2658x − 3.3234). Results of this study and other literature support the use of nonlethally sampled tissues for SIA of fish. These methods may be used for investigations of rare and endangered species and also allow for analysis of archived fish scales.