Nonlethal Fin Sampling of North American Freshwater Fishes for Food Web Studies Using Stable Isotopes

Abstract

Food web investigations using stable isotope analyses inform management strategies by quantitatively describing interactions among species. Fin tissue is a nonlethal alternative to white muscle tissue for obtaining stable isotope ratios of fish. However, the relationship between fin and muscle values must be evaluated before fin tissue can be substituted for muscle tissue. We examined the relationships between fin and muscle carbon (δ 13 C) and nitrogen (δ 15 N) isotope ratios in 15 species of North American freshwater fish using linear regression for multispecies models and species-specific models, and compared the performance of our models against models developed for European and Australian freshwater fishes. Fin and muscle isotope ratios differed but covaried with good explanatory power (R 2 δ 13 C = 0.74-0.99; R 2 δ 15 N = 0.45-0.99). Useful conversions of fin isotope values were provided by our species-specific models (δ 13 C error = 0.27‰; δ 15 N error = 0.22‰), and to a lesser extent our multispecies models (δ 13 C error = 0.51‰; δ 15 N error = 0.35‰) and the European models (δ 13 C error = 0.57‰; δ 15 N error = 0.42‰). Models developed for Australian fishes gave less precise conversions when applied to North American freshwater species (δ 13 C error = 0.78‰; δ 15 N error = 0.82‰). We recommend using species-specific conversion models when available, but in their absence, multispecies models may be adequate. Our study contributes to a growing literature seeking fin-muscle conversion models, which should serve to reduce the lethal take of individuals.

Aquatic food web expansion and trophic redundancy along the Rocky Mountain–Great Plains ecotone

“…We used data from 2016 to 2018 to assess community structure and data from 2016 to 2017 for stable isotope analysis. When possible, at least 15 specimens of each species were collected to characterize the range of trophic ecologies and body sizes present within a species at a site (Maitland & Rahel, 2021; Vinson & Budy, 2011).…”

Ecological outcomes of hybridization vary extensively in Catostomus fishes

“…We chose to use fin tissue because it can be sampled non-lethally and has a relatively slow turnover time, on the order of several months (comparable to muscle, a more frequently used tissue; Jardine, 2011;Thomas & Crowther, 2015). Recent work confirms that δ 13 C and δ 15 N are highly correlated in muscle and fin in C. commersonii and C. catostomus (Maitland & Rahel, 2021), confirming that use of fin is appropriate for these study species. Dried fin samples were analyzed for δ 13 C and δ 15 N ratios the University of Wyoming Stable Isotope Facility (UW-SIF) via high temperature oxidation in a Costech 4010 elemental analyzer interfaced to a Finnigan DeltaPlus XP mass spectrometer.…”

Inter-tissue variability in the stable isotope values of European perch (Perca fluviatilis) and pumpkinseed (Lepomis gibbosus)

“…Stable isotope analysis (SIA) is an alternative method for reconstructing trophic relationships that provides temporally integrated dietary perspectives (Trueman et al, 2012). Dorsal muscle is generally the main tissue analysed in fish SI studies, with its sampling also tending to be destructive, especially in smaller fishes (Hette-Tronquart et al, 2012;Maitland and Rahel, 2021;Boardman et al, 2022). However, other fish tissues (e.g.…”

“…in metaanalyses), data generated from different tissues can be encountered. Providing knowledge is available on the extent to which the SI values vary between the tissues then correction factors and/ or conversion equations can be applied to standardise all values to dorsal muscle equivalents (Maitland and Rahel, 2021;Roberts et al, 2021).…”