Application of non-lethal stable isotope analysis to assess feeding patterns of juvenile pallid sturgeon Scaphirhynchus albus: a comparison of tissue types and sample preservation methods

Abstract

Summary Traditional techniques for stable isotope analysis (SIA) generally require sacrificing animals to collect tissue samples; this can be problematic when studying diets of endangered species such as the pallid sturgeon Scaphirhynchus albus. Our objectives were to (i) determine if pectoral fin tissue (non‐lethal) could be a substitute for muscle tissue (lethal) in SIA of juvenile pallid sturgeon, and (ii) evaluate the influence of preservation techniques on stable isotope values. In the laboratory, individual juvenile pallid sturgeon were held for up to 186 day and fed chironomids, fish, or a commercially available pellet diet. Significant, positive relationships (r² ≥ 0.8) were observed between fin and muscle tissues for both δ15N and δ13C; in all samples isotopes were enriched in fins compared to muscle tissue. Chironomid and fish based diets of juvenile pallid sturgeon were distinguishable for fast growing fish (0.3 mm day−1) using stable δ15N and δ13C isotopes. Frozen and preserved fin tissue δ15N isotopes were strongly related (r2 = 0.89) but δ13C isotopes were weakly related (r2 = 0.16). Therefore, freezing is recommended for preservation of fin clips to avoid the confounding effect of enrichment by ethanol. This study demonstrates the utility of a non‐lethal technique to assess time integrated food habits of juvenile pallid sturgeon and should be applicable to other threatened or endangered species.

Similarities and differences in 13 C and 15 N stable isotope ratios in two non-lethal tissue types from shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820)

“…Andvik et al. () reported that diet differences of pallid sturgeon became detectable in both fin clips and muscle tissue after approximately 6 months. The length of time required for diet changes to become detectable by SIA must be considered when measuring temporal variation in diet as well as determining timing of diet ontogeny.…”

“…MacNeil et al (2006) found that the length of time to detect diet changes using d 15 N varied among tissues, with more metabolically active tissue (i.e., liver) reflecting diet changes more rapidly than less metabolically active tissue (i.e., cartilage) in freshwater stingrays (Potamotrygon motoro). Andvik et al (2010) reported that diet differences of pallid sturgeon became detectable in both fin clips and muscle tissue after approximately 6 months. The length of time required for diet changes to become detectable by SIA must be considered when measuring temporal variation in diet as well as determining timing of diet ontogeny.…”

Non‐lethal sampling of walleye for stable isotope analysis: a comparison of three tissues

“…Different storage methods may alter the isotopic signatures of the scale tissue, necessitating the need to identify the impacts of preservation techniques (Kelly et al. 2006a; Andvik et al. 2010).…”

“…Scale envelopes were not used in this study, but this is a common practice when removing and cataloguing scales for ageing purposes. Different storage methods may alter the isotopic signatures of the scale tissue, necessitating the need to identify the impacts of preservation techniques (Kelly et al 2006a;Andvik et al 2010). Overall, because of the disparities in isotopic signatures between the different tissue types, it is recommended to use muscle tissue whenever available, unless a small subset of organisms can be sacrificed for tissue comparisons.…”

Walleye Sander vitreus and smallmouth bass Micropterus dolomieu interactions: an historic stable‐isotope analysis approach

“…Previous studies have relied upon stable‐isotope values in muscle and fin tissue to reconstruct fish trophic position (Overman & Parrish, 2001; Dalerum & Anjerbjörn, 2005; Sanderson et al , 2009; Andvik et al , 2010). Research demonstrates, however, that scale tissue provides a reliable isotopic indication of trophic position (Wainright et al , 1993; Perga & Gerdeaux, 2003; Pruell et al , 2003; Jardine et al , 2005; Grey et al , 2009).…”